Silicon Laboratories SI2494/39 User's Manual

Silicon Laboratories SI2494/39 User's Manual
AN93
Si2493/57/34/15/04 (Revision D) and Si2494/39
Modem Designer ’s Guide
1. Introduction
The Si2494/93/57/39/34/15/04 ISOmodem chipset family consists of a 38-pin QFN (Si2494/39) or 24-pin TSSOP
(Si2493/57/34/15/04) or 16-pin SOIC (Si2493/57/34/15/04) low-voltage modem device, and a 16-pin SOIC lineside DAA device (Si3018/10) connecting directly with the telephone local loop (Tip and Ring). This modem solution
is a complete hardware (controller-based) modem that connects to a host processor through a UART, parallel or
SPI interface. Parallel and EEPROM interfaces are available only on the 38-pin QFN or 24-pin TSSOP package
option. Refer to Table 4, “ISOmodem Capabilities,” on page 10 for available part number, capability and package
combinations. Isolation is provided by Silicon Laboratories’ isolation capacitor technology, which uses high-voltage
capacitors instead of a transformer. This isolation technology complies with global telecommunications standards
including FCC, ETSI ES 203 021, JATE, and all known country-specific requirements.
Additional features include programmable ac/dc termination and ring impedance, on-hook and off-hook intrusion
detection, Caller ID, loop voltage/loop current monitoring, overcurrent detection, ring detection, and the hookswitch function. All required program and data memory is included in the modem device. When the modem
receives a software or hardware reset, all register settings revert to the default values stored in the on-chip
program memory. The host processor interacts with the modem controller through AT commands used to change
register settings and control modem operation. Country, EMI/EMC, and safety test reports are available from
Silicon Laboratories representatives and distributors.
This application note is intended to supplement the Si2494/39 Revision A, Si2493 Revision D, and the Si2457/34/
15/04 Revision D data sheets. It provides all the hardware and software information necessary to implement a
variety of modem applications, including reference schematics, sample PCB layouts, AT command and register
reference, country configuration tables, programming examples and more. Particular topics of interest can be
easily located through the table of contents or the comprehensive index located at the back of this document.
XTI
C1
UART
Interface
CS
WR
RD
A0
D0-D7
Parallel
Interface
SDI
SDO
SCLK
SS
SPI
Interface
INT
RESET
Data Bus
DAA
Interface
C2
Si3018/10
EEPROM
Interface
DSP
EESD
EECLK
EECS
RXD
TXD
CTS
RTS
DCD
ESC
RI
Controller
CLKOUT
XTO
PLL
Clocking
To Phone
Line
AOUT
AOUTb
ROM
Program Bus
RAM
Si3000
Interface
FSYNC
SDO
SDI
MCLK
Figure 1. Functional Block Diagram
Rev. 1.3 8/11
Copyright © 2011 by Silicon Laboratories
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This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
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Rev. 1.3
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TABLE O F C ONTENTS
Section
Page
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1. Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2. Modem (System-Side) Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1. Resetting the Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.1. Reset Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.2. Reset Strapping: General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.3. Reset-Strap Options for 16-Pin SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.4. Reset-Strap Options for 24-Pin TSSOP Package . . . . . . . . . . . . . . . . . . . . . . 13
2.1.4.1. Reset Strapping Options for TSSOP-24 with UART-Interface . . . . . . . . . 14
2.1.4.2. Reset Strapping Options for TSSOP-24 with Parallel-Interface. . . . . . . . 14
2.1.4.3. Reset Strapping Options for TSSOP with SPI-Interface . . . . . . . . . . . . . 15
2.1.5. Reset Strapping Options for QFN Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1.5.1. Reset Strapping Options for QFN Parts with UART Operation . . . . . . . . 15
2.1.5.2. Reset Strapping Options for QFN Parts with SPI Operation . . . . . . . . . . 16
2.1.5.3. Reset Strapping Options for QFN Parts with Parallel Operation . . . . . . . 16
2.2. System Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2.1. Interface Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2.2. Interface Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.3. UART Interface Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.3.1. UART Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.3.2. Autobaud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.3.3. Flow Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2.4. Parallel and SPI Interface Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.4.1. Hardware Interface Register 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2.4.2. Hardware Interface Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2.4.3. Parallel Interface Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.2.4.4. SPI Interface Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.2.4.5. Interface Communication Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3. Isolation Capacitor Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4. Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.1. Power-Down Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.2. Wake-on-Ring Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.3. Sleep Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.5. SSI/Voice Mode (24-Pin TSSOP and 38-Pin QFN Only) . . . . . . . . . . . . . . . . . . . . . . 30
2.6. EEPROM Interface (24-Pin TSSOP and 38-Pin QFN Only) . . . . . . . . . . . . . . . . . . . . 31
2.6.1. Supported EEPROM Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.6.2. Three-Wire SPI Interface to EEPROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.6.3. Detailed EEPROM Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.6.4. Boot Commands (Custom Defaults). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.6.5. AT Command Macros (Customized AT Commands) . . . . . . . . . . . . . . . . . . . . 34
2.6.6. Firmware Upgrades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.6.6.1. Boot Command Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
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2.6.6.2. AT Command Macro Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.6.6.3. Autoloading Firmware Upgrade Example . . . . . . . . . . . . . . . . . . . . . . . . 35
2.6.6.4. Combination Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3. DAA (Line-Side) Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.1. Hookswitch and DC Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2. AC Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3. Ringer Impedance and Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.4. Pulse Dialing and Spark Quenching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.5. Line Voltage and Loop Current Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.6. Legacy-Mode Line Voltage and Loop Current Measurement . . . . . . . . . . . . . . . . . . . 42
3.7. Billing Tone Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4. Hardware Design Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1. Component Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.1. Power Supply and Bias Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.2. Hookswitch and DC Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.3. Clocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.4. Ringer Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.1.5. Optional Billing-Tone Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.2. Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.3. Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.4. Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.4.1. ISOmodem Layout Check List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.4.2. Module Design and Application Considerations . . . . . . . . . . . . . . . . . . . . . . . . 53
4.4.2.1. Module Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.4.2.2. Motherboard Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.5. Analog Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.5.1. Interaction between the AOUT Circuit and the
Required Modem Reset Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.5.2. Audio Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5. Modem Reference Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.1. Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.2. DSP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.3. Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.4. AT Command Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.5. Extended AT Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.6. S Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.7. U Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.7.1. U-Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.7.2. U00–U16 (Dial Tone Detect Filter Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.7.3. U17–U30 (Busy Tone Detect Filter Registers) . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.7.4. U31–U33 (Ringback Cadence Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.7.5. U34–U35 (Dial Tone Timing Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.7.6. U37–U45 (Pulse Dial Registers). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5.7.7. U46–U48 (DTMF Dial Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.7.8. U49–U4C (Ring Detect Registers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.7.9. U4D (Modem Control Register 1—MOD1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.7.10. U4E (Pre-Dial Delay Time Register). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
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5.7.11. U4F (Flash Hook Time Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.7.12. U50–U51 (Loop Current Debouncing Registers) . . . . . . . . . . . . . . . . . . . . . 105
5.7.13. U52 (Transmit Level Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.7.14. U53 (Modem Control Register 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.7.15. U54 (Calibration Timing Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.7.16. U62–U66 (DAA Control Registers). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.7.17. U67–U6A (International Configuration Registers) . . . . . . . . . . . . . . . . . . . . 108
5.7.18. U6C (Line-Voltage Status Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
5.7.19. U6E–U7D (Modem Control and Interface Registers) . . . . . . . . . . . . . . . . . . 111
5.7.20. U80 (Transmit Delay for V.22 Fast Connect) . . . . . . . . . . . . . . . . . . . . . . . . 119
5.7.21. U87 (Synchronous Access Mode Configuration Register) . . . . . . . . . . . . . . 120
5.7.22. UAA (V.29 Mode Register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.7.23. UIDA Response and Answer Tone Delay Register . . . . . . . . . . . . . . . . . . . 121
5.8. Firmware Upgrades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.8.1. Method 1 (Fastest) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
5.8.2. Method 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.8.3. Method 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.9. Escape Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.9.1. +++ Escape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.9.2. “9th Bit” Escape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.9.3. “Escape Pin” Escape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.10. Data Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
5.11. Error Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
5.12. Wire Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
5.13. EPOS (Electronic Point of Sale) Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.13.1. EPOS Fast Connect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.13.2. EPOS V.29 Fast Connect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.14. Legacy Synchronous DCE Mode/V.80 Synchronous Access Mode . . . . . . . . . . . . 125
5.15. V.80 Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6. Programming Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
6.1. Quick Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
6.2. Country-Dependent Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.2.1. DC Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
6.2.2. Country Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
6.2.2.1. Country Initialization Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
6.2.2.2. Country-Setting Register Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
6.2.2.3. Special Requirements for India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
6.2.2.4. Special Requirements for Serbia and Montenegro . . . . . . . . . . . . . . . . 147
6.2.3. Blacklisting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
6.3. Caller ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.1. Force Caller ID Monitor (Always On) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.2. Caller ID After Ring Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.3. UK Caller ID with Wetting Pulse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.4. Japan Caller ID. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.3.5. DTMF Caller ID. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
6.4. SMS Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
6.5. Type II Caller ID/SAS Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
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6.6. Intrusion/Parallel Phone Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.6.1. On-Hook Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.6.1.1. Line Not Present/In Use Indication (Method 1—Fixed) . . . . . . . . . . . . . 161
6.6.1.2. Line Not Present/In Use Indication (Method 2—Adaptive). . . . . . . . . . . 162
6.6.2. Off-Hook Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
6.7. Modem-On-Hold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
6.7.1. Initiating Modem-On-Hold. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
6.7.2. Receiving Modem-On-Hold Requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
6.8. HDLC: Bit Errors on a Noisy Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
6.9. Overcurrent Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
6.10. Pulse/Tone Dial Decision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
6.10.1. Method 1: Multiple Off-Hook Transitions . . . . . . . . . . . . . . . . . . . . . . . . . 169
6.10.2. Method 2: Single Off-Hook Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
6.10.3. Method 3: Adaptive Dialing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
6.10.4. Automatic Phone-Line Configuration Detection . . . . . . . . . . . . . . . . . . . . . . 170
6.10.5. Line Type Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
6.11. Telephone Voting Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
6.12. V.92 Quick Connect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
7. Handset, TAM, and Speakerphone Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.1. Software Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.1.1. AT Command Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.1.2. AT+ Extended Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.1.3. <DLE> Commands (DTE-to-DCE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
7.1.4. <DLE> Events (DCE-to-DTE). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
7.1.4.1. Simple Event Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
7.1.4.2. Complex Event Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
7.1.5. U Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
7.2. Voice Reference—Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
7.3. Si3000 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.1. Microphone and Speaker Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.2. Register Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3. System Voice Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.1. TAM Hands-Free . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.2. TAM Handset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.3. Speakerphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.4. Handset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
7.3.3.5. TAM PSTN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
7.4. Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
7.5. Handset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
7.5.1. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
7.5.2. Handset Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
7.5.3. Call – Automatic Tone Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
7.5.4. Call – Manual Off-Hook Tone Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
7.5.5. Call – Automatic Pulse Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
7.5.6. Answer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
7.5.7. Terminate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
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7.5.8. Speakerphone Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
7.6. Telephone Answering Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
7.6.1. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
7.6.2. TAM Hands-Free—Idle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
7.6.2.1. Record OGM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
7.6.2.2. Review OGM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.2.3. Record Local ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.2.4. Review ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.2.5. Speakerphone Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.2.6. Handset Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.3. TAM Handset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.3.1. Record OGM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
7.6.3.2. Review OGM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
7.6.3.3. Record Local ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
7.6.3.4. Review ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
7.6.4. TAM PSTN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
7.6.4.1. Normal Answer – OGM Playback with ICM Record. . . . . . . . . . . . . . . . 208
7.6.4.2. Interrupted Answer – OGM Playback with DTMF Menu Entry. . . . . . . . 210
7.6.4.3. Speakerphone Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.6.4.4. Handset Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.7. Speakerphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.7.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.7.2. Simplex Speakerphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.7.3. External Microphone/Speaker Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
7.7.3.1. Transmit Gain Calibration—Speakerphone Disabled . . . . . . . . . . . . . . 213
7.7.3.2. Receive Gain Calibration—Speakerphone Disabled . . . . . . . . . . . . . . . 216
7.7.3.3. Speakerphone Calibration—AEC Gain Calibration . . . . . . . . . . . . . . . . 217
7.7.4. Speakerphone Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
7.7.5. Simplex Speakerphone Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
7.7.6. Call—Automatic Tone Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
7.7.7. Call—Manual Off-Hook Tone Dial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
7.7.8. Call—Automatic Pulse Dial. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
7.7.9. Answer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
7.7.10. Handset Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
7.7.11. Termination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
7.8. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
7.9. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
8. Security Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
8.1. Implementing the SIA Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
8.1.1. Modem-Specific Implementation Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
8.1.1.1. Listen-In and V-channel Periods (Voice Pass-Through) . . . . . . . . . . . . 224
8.1.1.2. Inserting a V.32bis period (e.g., SIA Level-3 Video Block Support). . . . 224
8.1.1.3. Considerations when Disconnecting the Session . . . . . . . . . . . . . . . . . 225
8.2. Implementing the Ademco® Contact ID Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
8.2.1. Modem Specific Implementation Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
8.2.1.1. Handshake Tone Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
8.2.1.2. Session Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
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9. Chinese ePOS SMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
9.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
9.2. SMS AT Command Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
9.2.1. SMS User Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
9.2.2. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
9.2.2.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
9.2.2.2. Response 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
9.2.2.3. Response 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
9.2.2.4. Response 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
9.3. Example Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
10. Testing and Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1. Prototype Bring-Up (Si3018/10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1.1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1.2. Visual Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1.3. Basic Troubleshooting Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
10.1.4. Host Interface Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
10.1.5. Isolation Capacitor Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
10.1.6. Si3018/10 Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
10.1.7. Component Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
10.2. Self Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
10.3. Board Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
10.4. Compliance Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
10.4.1. EMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
10.4.2. Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
10.4.3. Surges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
10.5. AM-Band Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
10.6. Debugging the DTE interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
Appendix A—EPOS Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
VISA II (7E1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Recommendation V.80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
The ISOmodem in EPOS Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
A V.29 FastPOS Sample Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
Appendix B—Line Audio Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
When to Use Audio Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Times When Audio Recording May Not Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Audio Playback and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
Examples of Line Impairments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
Appendix C—Parallel/SPI Interface Software Implementation . . . . . . . . . . . . . . . . . . . . . 290
Software Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
Compiler Option: Dot Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
Modem Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
Modem Interrupt Service Sample Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
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1.1. Selection Guide
Tables 1 through 3 list the modulations, protocols, carriers, tones and interface modes supported by the Si2494/39
and Si2493/57/34/15/04 ISOmodem family. The Si2493 supports all modulations and protocols from Bell 103
through V.92. The Si2457 supports all modulations and protocols from Bell 103 through V.90. The Si2434 supports
all modulations and protocols from Bell 103 through V.34. The Si2415 supports all modulations and protocols from
Bell 103 through V.32bis. The Si2404 supports all modulations and protocols from Bell 103 through V.22bis.
Table 1. Modulations
Modulation
V.92*
Data Rates (bps)
48k, 40k, 32k, 24k
V.90*
56k, 54.6k, 53.3k, 52k, 50.6k,
49.3k, 48k, 46.6k, 45.3k, 44k,
42.6k, 41.3k, 40k, 38.6k,
37.3k, 36k, 34.6k, 33.3k, 32k,
30.6k, 29.3k, 28k
33.6k, 31.2k, 28.8k, 26.4k, 24k,
21.6k, 19.2k, 16.8k, 14.4k, 12k,
9600, 7200, 4800, 2400
14.4k, 12k, 9600, 7200, 4800
PCM


TCM



TCM
TCM
QAM
QAM






V.29FC*
9600
9600, 4800
9600


V.23
1200
FSK
V.22bis
2400, 1200
QAM
V.22
1200
DPSK
Bell 212A
1200
DPSK
V.21
300
FSK
Bell 103
300
FSK




























V.34*
V.32bis*
V.32*
Modulation Si2494/93 Si2457 Si2439/34 Si2415 Si2404
PCM

*






*Note: With the Si3018 DAA only.
Table 2. Protocols
Protocol*
Function
Si2494/93
Si2457
Si2439/34
Si2415
Si2404
V.44
Compression
V.42bis
Compression
V.42
Error Correction











MNP5
Compression




MNP2-4
Error Correction





*Note: The Si2494/93/57/39/34/15/04 family allows any supported protocol combined with any modulation.
Rev. 1.3
9
AN93
Table 3. Carriers and Tones
Specification
Transmit Carrier
(Hz)
Receive Carrier
(Hz)
Answer
Tone (Hz)
Carrier Detect (Acquire/
Release)
V.92
Variable
Variable
per ITU-T V.92
V.90
Variable
Variable
per ITU-T V.90
V.34
Variable
Variable
per ITU-T V.34
V.32bis
1800
1800
2100
per ITU-T V.32bis
V.32
1800
1800
2100
per ITU-T V.32
V.29
1700
1700
V.22bis, V.22
Originate/answer
1200
2400
2400
1200
2100
–43 dBm/–48 dBm
–43 dBm/–48 dBm
V.21
Originate/answer (M/S)
1180/980
1850/1650
1850/1650
1180/980
2100
–43 dBm/–48 dBm
–43 dBm/–48 dBm
Bell 212A
Originate/answer
1200
2400
2400
1200
2225
–43 dBm/–48 dBm
–43 dBm/–48 dBm
Bell 103
Originate/answer (M/S)
1270/1070
2225/2025
2225/2025
1270/1070
2225
–43 dBm/–48 dBm
–43 dBm/–48 dBm
per ITU-T V.29
Table 4. ISOmodem Capabilities
Part Numbers
Package
UART
Si2493/57/34/15/041
SOIC-16

Si2493/57/34/15/041
TSSOP-24

2


QFN-38




Si2494/39
EEPROM
SPI
Parallel

Notes:
1. Die Revision D or later
2. The EEPROM interface option is available only when the UART or SPI interface is selected.
10
SSI/Voice
Rev. 1.3

AN93
2. Modem (System-Side) Device
The Si24xx ISOmodem system-side devices contain a controller, a DSP, program memory (ROM), data memory
(RAM), UART, SPI and parallel interfaces, a crystal oscillator, and an isolation capacitor interface. The following
sections describe the reset sequence, the host interface, the isolation interface, low-power modes, SSI/voice mode
and the EEPROM interface.
2.1. Resetting the Device
Reset is required after power-on or brownout conditions (the supply dropping to less than the data sheet minimum).
The supply must be stable throughout the minimum required reset time described here and thereafter. A reset is
also required in order to come out of the power down mode.
Some operational choices, including the crystal oscillator frequency used and the command interface used (e.g.
UART vs SPI), is made during the reset time according to pull-down resistors placed on some modem pins. These
pins are modem output lines, but, during reset, the modem places them into a high-impedance mode with weak
internal pull-ups, then reads the user's strapping choices. It is important that the resultant state changes of these
pins during reset are not misinterpreted by the host.
For example the INT output pin of the modem (and perhaps others) can be strapped low with a 10 k resistor to
request SPI operation. If that mode is chosen, the host should take care not to enable this interrupt input before the
modem reset since the INT signal will transition from high to low and back up during reset in this case and can
generate an unexpected interrupt.
If an external clock signal is provided instead of a crystal attached to the modem, it is important that this external
clock signal be stable before the reset ends.
2.1.1. Reset Sequence
After power-on, the modem must be reset by asserting the RESET pin (low) for the required time then waiting a
fixed 300 ms before sending the first AT command. The reset recovery time of 300 ms is also applicable if the reset
is a SW triggered event, such as an ATZ command.
If a 4.9152 MHz crystal or an external 27 MHz clock is used, the reset must be asserted for 5 ms, and a wait of
300 ms duration must happen before an AT command is issued. If a 32 kHz crystal is used, the reset pulse must be
500 ms long and followed by the same 300 ms duration wait as that used for higher frequency clocks.
This is adequate to reset all the on-chip registers. Note that 16 µs after the customer-applied reset pulse starts, the
I/O pins will be tri-stated with a weak pull-up, and, 16 µs after the end of this reset pulse, the IO pins will switch to
inputs or outputs as appropriate to the mode indicated by the pull-down strapping. This 16 µs delay is for newer
revs of the modem parts (those parts that introduce a 32 kHz crystal and SPI operation); older revs exhibit a delay
of only nanoseconds.
The reset sequence described above is appropriate for all user modes of the modem including UART, SPI, and
Parallel bus operation.
A software reset of the modem can also be performed by issuing the command ATZ or by setting U-register 6E bit
4 (RST) high using AT commands. After issuing a software or hardware reset, the host must wait for the reset
recovery time before issuing any subsequent AT commands.
There is no non-volatile memory on the ISOmodem other than program ROM. When reset, the ISOmodem reverts
to the original factory default settings. Any set-up or configuration data and software updates must be reloaded
after every reset. This is true whether the reset occurs due to a power-down/power-up cycle, a power-on reset
through a manual reset switch, by writing U6E [4] (RST) = 1, or by executing ATZ.
A suggested reset sequence is as follows:
1. Apply an active-low pulse to the RESET pin; write RST bit or ATZ<CR>.
2. Wait at least the reset recovery time.
3. Load firmware updates (if required).
4. Set non-default DAA interface parameters—DCV, ACT, ILIM, OHS2, OHS, RZ, RT, (U67), LIM, (U68).
5. Set non-default cadence values—Busy Tone, Ringback, Ring.
Rev. 1.3
11
AN93
6. Set non-default frequency values—Ring.
7. Set non-default filter parameters.
8. Set non-default S-register values.
The modem is now ready to detect rings, answer another modem, call, or dial out to a remote modem.
Some key default settings for the modem after reset or powerup include the following:













V.92 and fall-backs enabled (Si2494/93)
V.90 and fall-backs enabled (Si2457)
V.34 and fall-backs enabled (Si2439/34)
V.32bis and fall-backs enabled (Si2415)
V.22bis and fall-backs enabled (Si2404)
V.42/42bis enabled
+++ escape sequence enabled
Answer-on-ring is disabled
Speaker off
DTE echo enabled
Verbal result codes enabled
CTS only enabled
FCC (US) DAA and call progress settings
2.1.2. Reset Strapping: General Considerations
The different options available in the Si24xx ISOmodem family are selected by means of 10 k pulldown resistors
placed at certain pins. During power-on or pin reset, the ISOmodem’s signal pins are read and the option resistors
are taken into account to determine the required configuration. After reset, the ISOmodem assumes the
functionality selected by the corresponding combination of pulldown resistors.
Below is a summary of reset-strap options. Not all options are available on all part number or packages. Refer to
Table 4, “ISOmodem Capabilities,” on page 10 for details.

Host interface: UART, parallel or SPI
Input clock frequency: 32 kHz, 4.9152 MHz or 27 MHz
 Autobaud mode or fixed-rate UART communication (when UART interface is selected). Disabling the autobaud
feature at reset sets the rate to 19,200 baud.
 EEPROM interface
 Three-wire EEPROM or four-wire EEPROM when EEPROM interface is selected
Refer to "2.6. EEPROM Interface (24-Pin TSSOP and 38-Pin QFN Only)" on page 31 for more details on the
various ISOmodem EEPROM options.

The next few sections describe the various reset options that must be selected for each package. In all the tables,
the following conventions apply:


12
0 means a 10 k pulldown resistor to ground.
1 means the pin is left open. If a pin is left open, the internal pullup resistor is normally sufficient as long as the
pin is not driven externally during reset. If there is noise or special power-sequencing situations, then an
external pullup resistor may be needed.
Rev. 1.3
AN93
2.1.3. Reset-Strap Options for 16-Pin SOIC Package
The clock frequency and interface on the 16-pin SOIC package are selected according to Table 5 below. The
parallel interface, EEPROM and autobaud options are not available in the 16-pin SOIC package.
Table 5. SOIC-16 Reset-Strap Options
Mode
Reset-Strap Pins
Interface
Input Clock
Pin 3
RI
Pin 5, RXD/MISO
Pin 7, CTS/SCLK
Pin 11
INT
Pin 15
DCD
UART
32 kHz
0
X
1
1
X
4.9152 MHz
1
X
1
1
1
27 MHz
1
X
1
1
0
32 kHz
1
1
X
0
1
4.9152 MHz
0
1
X
0
X
27 MHz
1
1
X
0
0
SPI
2.1.4. Reset-Strap Options for 24-Pin TSSOP Package
The pin-strapping options for the 24-pin TSSOP package are described in the three subsections below, depending
on the interface mode selected.
Rev. 1.3
13
AN93
2.1.4.1. Reset Strapping Options for TSSOP-24 with UART-Interface
UART-interface options for the 24-pin TSSOP package are shown in Table 6 below.
Table 6. TSSOP-24 UART-Interface Options
Mode
Reset-Strap Pins
Input Clock
Autobaud
Disabled?
Three-Wire
EEPROM
Interface?
Pin 4
FSYNC
32 kHz
No
No
1
Yes
Yes
4.9152 MHz
No
Yes
27 MHz
No
Yes
Pin 11, CTS
Pin 15, AOUT
Pin 16, INT
Pin 17
RI
Pin 18
SDI/EESD
Pin 23
DCD
1
0
1
X
0
1
0
1
X
No
1
1
0
0
X
Yes
0
1
0
0
X
No
1
1
1
1
1
Yes
0
1
1
1
1
No
1
1
1
0
1
Yes
0
1
1
0
1
No
1
1
1
1
0
Yes
0
1
1
1
0
No
1
1
1
0
0
Yes
0
1
1
0
0
2.1.4.2. Reset Strapping Options for TSSOP-24 with Parallel-Interface
Parallel-interface options for the 24-pin TSSOP package appear in Table 7 below. The EEPROM and autobaud
options are not available when the parallel interface is selected.
Table 7. TSSOP-24 Parallel-Interface Options
Mode
14
Reset-Strap Pins
Input Clock
Pin 9, RD
Pin 10, WR
Pin 11
SCLK
Pin 15
INT
27 MHz
1
0
0
4.9152 MHz
1
1
0
Rev. 1.3
AN93
2.1.4.3. Reset Strapping Options for TSSOP with SPI-Interface
Table 8 lists the SPI-interface options for the 24-pin TSSOP package.
Table 8. TSSOP-24 SPI-Interface Clock-Frequency Options
Mode
Reset-Strap Pins
Input Clock
Three-Wire
EEPROM
Interface?
Pin 4
FSYNC
32 kHz
No
1
Yes
4.9152 MHz
27 MHz
Pin 9, RXD
Pin 11, SCLK
Pin 15, AOUT
Pin 18, SDI/EESD
Pin 16
INT
Pin 17
RI
Pin 23
DCD
1
0
1
1
0
1
0
1
1
No
1
1
0
0
X
Yes
0
1
0
0
X
No
1
1
0
1
0
Yes
0
1
0
1
0
2.1.5. Reset Strapping Options for QFN Parts
2.1.5.1. Reset Strapping Options for QFN Parts with UART Operation
Table 9 lists the reset strapping options for QFN parts with UART operation.
Table 9. Reset Strapping Options for QFN Parts with UART Operation
Input Clk
Auto-Baud
Disable
Three-Wire
EEPROM
Interface
FSYNCH
Pin 2
32 kHz
No
Yes
4.9152 MHz
No
Yes
27 MHz
No
Yes
CTS
AOUT
EECLK
Pin 21 Pin 15
Pin 13
INT
RI
SDI
Pin 35 Pin 19 Pin 8
DCD
Pin 28
No
1
1
1
1
1
1
1
1
Yes
0
1
1
1
1
1
1
1
No
1
1
1
1
1
1
0
1
Yes
0
1
1
1
1
1
0
1
No
1
1
1
1
1
0
1
X
Yes
0
1
1
1
1
0
1
X
No
1
1
1
1
1
0
0
X
Yes
0
1
1
1
1
0
0
X
No
1
1
1
1
1
1
1
0
Yes
0
1
1
1
1
1
1
0
No
1
1
1
1
1
1
0
0
Yes
0
1
1
1
1
1
0
0
Rev. 1.3
15
AN93
2.1.5.2. Reset Strapping Options for QFN Parts with SPI Operation
Table 10 lists the reset strapping options for QFN parts with SPI operation.
Table 10. Reset Strapping Options for QFN parts with SPI Operation
Input Clk
Three-Wire
EEPROM
Interface
32 kHz
4.9152 MHz
27 MHz
FSYNCH
AOUT
EECLK
INT
RI
SDI
DCD
MISO
Pin 2
Pin 15
Pin 13
Pin 35
Pin 19
Pin 8
Pin 28
Pin 22
No
1
1
1
0
1
1
1
1
Yes
0
1
1
0
1
1
1
1
No
1
1
1
0
0
1
X
1
Yes
0
1
1
0
0
1
X
1
No
1
1
1
0
1
1
0
1
Yes
0
1
1
0
1
1
0
1
2.1.5.3. Reset Strapping Options for QFN Parts with Parallel Operation
Table 11 lists the reset strapping options for QFN parts with parallel operation.
Table 11. Reset Strapping Options for QFN Parts with Parallel Operation
Input Clk
32 kHz
4.9152 MHz
27 MHz
16
CS
AOUT
EECLK
RD
Pin 21
Pin 15
Pin 13
Pin 22
1
0
1
1
1
0
1
1
1
0
0
1
1
0
0
1
0
0
1
1
0
0
1
1
Rev. 1.3
AN93
2.2. System Interface
The ISOmodem can be connected to a host processor through a UART, SPI or parallel interface. Connection to the
chip requires low-voltage CMOS signal levels from the host and any other circuitry interfacing directly. The
following sections describe the digital interface options in detail.
2.2.1. Interface Selection
The interface is selected during reset, as described in "2.1. Resetting the Device". Tables 12, 13, and 14 show the
functions of the affected pins for possible interface modes for 16-, 24- and 38-pin packages, respectively.
Table 12. Pin Functions vs. Interface Mode (SOIC-16)
Pin #
UART Mode
SPI Mode
3
RI
RI
5
RXD
MISO
6
TXD
MOSI
7
CTS
SCLK
11
INT
INT
14
ESC
ESC
15
DCD
DCD
16
RTS
SS
Table 13. Pin Functions vs. Interface Mode (TSSOP-24)
Pin #
UART Mode
SPI Mode
Parallel Mode
2
FSYNC (SSI)
FSYNC (SSI)
D6
3
CLKOUT (SSI)
CLKOUT (SSI)
A0
8
RTS
SS
D7
9
RXD
MISO
RD
10
TXD
MOSI
WR
11
CTS
SCLK
CS
15
AOUT
AOUT
INT
16
INT
INT
D0
17
RI
RI
D1
18
SDI (SSI)
SDI (SSI)
D2
22
ESC
ESC
D3
23
DCD
DCD
D4
24
SDO (SSI)
SDO (SSI)
D5
Rev. 1.3
17
AN93
Table 14. Pin Functions vs. Interface Mode (QFN-38)
18
Pin #
UART Mode
SPI Mode
Parallel Mode
35
INT
INT
INT
34
GPIO18
GPIO18
D0
33
GPIO17
GPIO17
D1
32
GPIO16
GPIO16
D2
31
GPIO23
GPIO23
D3
30
GPIO24
GPIO24
D4
29
ESC
D5
28
DCD
D6
24
RTS
SS
D7
23
TXD
MOSI
WR
22
RXD
MISO
RD
21
CTS
SCLK
CS
20
GPIO11
GPIO11
A0
19
RI
Rev. 1.3
AN93
2.2.2. Interface Signal Description
The following tables describe each set of UART, parallel and SPI interface signals:
Table 15. UART-Interface Signals
Signal
Direction
Description
TXD
Input
Data input from host TXD pin
RXD
Output
Data output to host RXD pin
RTS
Input
CTS
Output
Active-low request-to-send input for flow control
Clear to send: Si2493 is ready to receive data on the TXD pin (active low)
Table 16. SPI-Interface Signals
Signal
Direction
Description
SCLK
Input
Serial data clock
MISO
Output
Serial data output
MOSI
Input
Serial data input
SS
Input
Chip select (active low)
INT
Output
Interrupt (active low)
Table 17. Parallel-Interface Signals
Signal
Direction
Description
A0
Input
Register selection (address input)
CS
Input
Chip select (active low)
RD
Input
Read enable (active low)
WR
Input
Write enable (active low)
D[7:0]
INT
Bidirectional Parallel data bus
Output
Interrupt (active low)
2.2.3. UART Interface Operation
The UART interface allows the host processor to communicate with the modem controller through a UART driver.
In this mode, the modem is analogous to an external “box” modem. The interface pins are 5 V tolerant and
communicate with TTL-compatible, low-voltage CMOS levels. RS232 interface chips, such as those used on the
modem evaluation board, can be used to make the UART interface directly compatible with a PC or terminal serial
port.
2.2.3.1. UART Options
The DTE rate is set by the autobaud feature after reset. When autobaud is disabled, the UART is configured to
19.2 kbps, 8-bit data, no parity and 1 stop bit on reset. The UART data rate is programmable from 300 bps to
307.2 kbps with the AT\Tn command (see Table 42, “Extended AT\ Command Set,” on page 81). After the AT\Tn
command is issued, the ISOmodem echoes the result code at the old DTE rate. After the result code is sent, all
subsequent communication is at the new DTE rate.
The DTE baud clock is within the modem crystal tolerance (typically ±50 ppm), except for DTE rates that are
uneven multiples of the modem clock. All DTE rates are within the +1%/–2.5% required by the V.14 specification.
Table 18 shows the ideal DTE rate, the actual DTE rate, and the approximate error.
Rev. 1.3
19
AN93
The UART interface synchronizes on the start bits of incoming characters and samples the data bit field and stop
bits. The interface is designed to accommodate character lengths of 8, 9, 10, and 11 bits giving data fields of 6, 7,
8, or 9 bits. Data width can be set to 6, 7, or 8 bits with the AT\Bn command. Parity can be set to odd, even, mark,
or space by the AT\Pn command in conjunction with AT\B2 or AT\B5. Other AT\Bn settings have no parity.
Table 18. DTE Rates
MARK
Ideal DTE Rate (bps)
Actual DTE Rate (bps)
300
300
600
600
1200
1200
2400
2400
7200
7202
9600
9600
12000
12003
14400
14400
19200
19200
38400
38400
57600
57488
0.2
0.01
0.02
115200
115651
0.4
230400
228613
0.8
245760
245760
307200
307200
START
BIT
SPACE
Approximate Error(%)
D0
D1
D2
D3
D4
D5
D6
D7
STOP
BIT
BIT TIMES
BIT SAMPLING
MARK
SPACE
START
BIT
D0
D1
D2
D3
D4
D5
D6
D7
D8
STOP
BIT
BIT TIMES
BIT SAMPLING
Figure 2. Asychronous UART Serial Interface Timing Diagram
2.2.3.2. Autobaud
When set in UART interface mode, the ISOmodem includes an automatic baud rate detection feature that allows
the host to start transmitting data at any standard DTE rate from 300 bps to 307.2 kbps. This feature is enabled by
default. When autobaud is enabled, it continually adjusts the baud rate, and the ISOmodem always echoes result
codes at the same baud rate as the most recently received character from the host. Autobaud can be turned off
using AT commands \T0 through \T15, and \T17. Host software should disable autobaud operation once the DTE
rate has been established. This prevents transients on TXD to cause inadvertent baud rate changes.
Autobaud is off when dialing, answering, and in data mode. When autobaud mode is off, the baud rate is set to the
most recently-active baud rate prior to entering one of these states. When autobaud mode is on, autoparity is
performed when either “at” or “AT” is detected. Autoparity detects the formats listed in Table 19.
20
Rev. 1.3
AN93
:
Table 19. Serial Formats Detected in Autobaud Mode
Symbol Data bits
Parity
Stop bits
7N1
7
None (mark)
1
7N2
7
None (mark)
2
7S1
7
None (space)
1
7O1
7
Odd
1
7E1
7
Even
1
8N1
8
None (mark)
1
8E1
8
Even
1
8O1
8
Odd
1
9N1
9
None (mark)
1
Note: For 7N1, the modem is programmed to 7 data bits, mark parity and one stop bit. This may be changed with the AT\P and
AT\B commands. In autobaud mode, 7N1 is properly interpreted and echoed, but the AT\P and AT\B commands must be
sent prior to dialing in order to lock the parity and format to 7N1. Otherwise, the ISOmodem locks to 7 bits, mark parity
and two stop bits (7N2).
2.2.3.3. Flow Control
The ISOmodem supports flow control through RTS/CTS and XON/XOFF. RTS (request-to-send) is a control signal
from the terminal (DTE) to the modem (DCE) indicating data may be sent from the modem to the terminal. CTS
(clear-to-send) is a control signal from the modem (DCE) to the terminal (DTE) indicating data may be sent from
the terminal to the modem for transmission to the remote modem. This arrangement is typically referred to as
hardware flow control. There is a 14-character FIFO and a 1024 character elastic transmit buffer (see Figure 3).
CTS goes inactive (high) when the 1024 character buffer reaches 796 characters, then reasserts (low) when the
buffer falls below 128 characters. There is no provision to compensate for FIFO overflow. Data received on TXD
when the FIFO is full are lost.
XON/XOFF is a software flow control method in which the modem and terminal control the data flow by sending
XON characters (^Q/0x11) and XOFF characters (^S/0x13). XON/XOFF flow control is enabled on the ISOmodem
with AT\Q4.
DCD does not de-assert during a retrain (see Table 45: S9, Carrier presence timer and S10, Carrier loss timer).
CTS always deasserts during initial training, retrain, and at disconnect regardless of the \Qn setting. For \Q0 CTS,
flow control is disabled; CTS is inactive during data transfer. The modem remains in the data mode during normal
automatic retrains. The host can force a retrain by escaping to the command mode and sending ATO1 or ATO2.
The DCD and RI pins can be used as hardware monitors of the carrier detect and ring signals. Additionally, the INT
pin can be programmed to monitor the bits in register U70 listed in Table 20. The RI, PPD, OCD, CID, and RST bits
are sticky, and the AT:I command reads and clears these signals and deactivates the INT pin if INT is enabled.
Rev. 1.3
21
AN93
Table 20. Register U70 Signals INT Can Monitor
Signal
U70 Bit
Function
DCD
0
Data Carrier Detect—active high (inverse of DCD pin)
RI
1
Ring Indicator—active high (inverse of RI pin)
PPD
2
Parallel Phone Detect
OCD
3
Overcurrent Detect
CID
4
Caller ID Preamble Detect
1024 Character Elastic Tx Buffer
SRAM
CTS
CTS Deasserts
796 Characters
Tx Data
14-Character
Hardware
Buffer
Transmit
128 Characters
CTS Asserts
Figure 3. Transmit Data Buffers
1024 Character Elastic Rx Buffer
SRAM
796 Characters
Parallel RXF bit
Mode REM bit
Rx data
RTS
12-Character
Hardware
Buffer
Receive
128 Characters
Figure 4. Receive Data Buffers
22
Rev. 1.3
AN93
A block diagram of the UART in the serial interface mode is shown in Figure 5.
.
11 Bits
to Data Bus
MUX
RX FIFO
TX FIFO
TX Shift
Register
TXD
(10)
CONTROL
CTS
(11)
RTS
(8)
RX Shift
Register
INT
(16)
RXD
(9)
Figure 5. UART Serial Interface
2.2.4. Parallel and SPI Interface Operation
Refer to "2.1. Resetting the Device" on page 11 for interface selection. The parallel interface has an 8-bit data bus
and a single address bit. The SPI likewise operates with 8-bit data transfers, using a single address bit. When the
parallel or SPI interface mode is selected, the modem must be configured for a DTE interface or 8N1 only. The host
processor must calculate parity for the MSB. The modem sends bits as received by the host and does not calculate
parity. Refer to "Appendix C—Parallel/SPI Interface Software Implementation" on page 290 for detailed parallel or
SPI interface application information.
The parallel or SPI interface uses the FIFOs to buffer data in the same way as in UART mode, with the addition of
Hardware Interface Registers 0 (HIR0) and Hardware Interface Register 1 (HIR1). The Hardware Interface
Registers were formerly called Parallel Interface Registers (PIR0 and PIR1) in older products, because those
products would support only a parallel interface. Flow control must be implemented by monitoring REM and TXE in
HIR1. There is no protection against FIFO overflow. Data transmitted when the transmit FIFO is full are lost.
Figure 6 shows the interaction of the transmit and receive FIFOs with the Hardware (Parallel) Interface Registers in
the case of a parallel interface. The arrangement is similar when the SPI interface is selected. Table 21 on page 25
shows a bit map of HIR0 and HIR1.
UART oriented control lines, such as RTS and CTS, are not used in Parallel and SPI Interface mode. They are
replaced by bits in the HIR1 register.
SPI and parallel operation only supports 8-bit data words. The longer words that are implied by the \B5 (8P1) & \B6
8X1 commands are not allowed. These commands should not be used.
Rev. 1.3
23
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11 Bits
to Data Bus
MUX
TX FIFO
14 Characters
RX FIFO
12 Characters
Shared-Serial/Parallel
CONTROL
MUX
A0
(3)
D0
(16)
D1
(17)
D2
(18)
D3
(22)
D4
(23)
D5
(24)
D6
(4)
D7
(8)
Parallel Interface Unique
Figure 6. Parallel Interface
24
Rev. 1.3
RD
(9)
WR
(10)
CS
(11)
INT
(15)
Parallel mode pin number
Parallel I/F
Register 1
Parallel mode pin function
Parallel I/F
Register 0
AN93
Table 21. Hardware Interface Register Bit Map
A0
RD
WR
Action
Register
0
0
1
Read
HIR0
0
1
0
Write
1
0
1
Read
1
1
0
Write
D7
D6
D5
D4
D3
D2
D1
D0
Modem data or command from receive FIFO
Modem data or command to transmit FIFO
HIR1
RXF
TXE
REM
INTM
INT
ESC
RTS
CTS
RXF
TXE
*Note
INTM
*Note
ESC
RTS
n/a
*Note: REM and INT are read-only bits.
2.2.4.1. Hardware Interface Register 0
Hardware Interface Register 0 (HIR0) is the eight-bit wide read/write location where modem data and commands
are exchanged with the host. Writing a byte to the HIR0 adds that byte to the modem’s transmit FIFO (AT
command buffer in command mode or data transmission in data mode). If data are available (modem data in data
mode or command responses, such as OK, in command mode), reading from the HIR0 fetches data from the
modem’s receive FIFO. The maximum burst data rate is approximately 350 kbps (45 kBps).
2.2.4.2. Hardware Interface Register 1
Hardware Interface Register 1 (HIR1) contains various status and control flags for use by the host to perform data
flow control, to escape to command mode and to query various interrupt conditions. The HIR1 bit map is described
in Table 22. This register is reset to 0x63.
Table 22. Hardware Interface Register 1
Bit
Name
R/W
Reset
Function
7
RXF
R/W
0
Receive FIFO Almost Full
6
TXE
R/W
1
Transmit FIFO Almost Empty
5
REM
R
1
Receive FIFO Empty
4
INTM
R/W
0
Interrupt Mask
0 = INT pin triggered on rising edge of RXF or TXE only
1 = INT pin triggered on rising edge of RXF, TXE or INT (bit 3 below)
3
INT
R
0
Interrupt
0 = No interrupt
1 = Interrupt triggered
2
ESC
R/W
0
Escape
1
RTS
R/W
1
Request-to-Send (active low) — Deprecated — for flow control, use the
TXE and REM bits for polling- or interrupt-based communication.
This bit must be written to zero.
0
CTS
R
1
Clear-to-Send (active low) — Deprecated — for flow control, use the TXE
and REM bits for polling- or interrupt-based communication.
Bit 7 (RXF) is a read/write bit that gives the status of the 12-byte deep receive FIFO. If RXF = 0, the receive FIFO
contains less than 10 bytes. If RXF = 1, the receive FIFO contains more than 9 bytes and is full or almost full.
Writing RXF = 0 clears the interrupt.
Rev. 1.3
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AN93
Bit 6 (TXE) is a read/write bit that gives the status of the 14-byte deep transmit FIFO. If TXE = 0, the transmit FIFO
contains three or more bytes. If TXE = 1, the transmit FIFO contains two or fewer bytes. Writing TXE = 0 clears the
interrupt but does not change the state of TXE.
Bit 5 (REM) is a read-only bit that indicates when the receive FIFO is empty. If REM = 0, the receive FIFO contains
valid data. If REM = 1, the receive FIFO is empty. The timer interrupt set by U6F ensures that the receive FIFO
contents  9 bytes are serviced properly.
Bit 4 (INTM) is a read/write bit that controls whether or not INT (bit 3) triggers the INT pin.
Bit 3 (INT) is a read-only bit that reports Interrupt status. If INT = 0, no interrupt has occurred. If INT = 1, an
interrupt due to CID, OCD, PPD, RI, or DCD (U70 bits 4, 3, 2, 1, 0, respectively) has occurred. This bit is reset by :I.
Bit 2 (ESC) is a read/write bit that is functionally equivalent to the ESC pin in the serial mode. The operation of this
bit, like the ESC pin, is enabled by setting U70 [15] (HES) = 1.
The use of bits 1 and 0 (RTS and CTS) has been deprecated for both parallel and SPI interfaces. Instead, the use
of bits 6 and 5 (TXE and REM) is recommended for polling- and interrupt-based communication.
2.2.4.3. Parallel Interface Operation
When the device is powered up for parallel interface, the pins include eight data lines (D7–D0), a single address
(A0), a read strobe (RD), a write strobe (WR), an interrupt line (INT), and chip select (CS). Table 23 summarizes
the parallel-interface signals:
Table 23. Parallel Interface Signals
Signal
Function
Direction
CS
Chip Select (active low)
Input
A0
Register address
Input
RD
Read strobe (active low)
Input
WR
Write strobe (active low)
Input
D[7:0]
Data bus
Bidirectional
INT
Interrupt (active low)
Output
Refer to the device data sheet for timing characteristics. Address pin A0 allows the host processor to choose
between the two interface registers, HIR0 and HIR1. The timing diagrams below show typical parallel-interface
operation. Refer to the respective product data sheets for timing specifications.
26
Rev. 1.3
AN93
Figure 7. Parallel Interface Read Timing
Figure 8. Parallel Interface Write Timing
Rev. 1.3
27
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2.2.4.4. SPI Interface Operation
SPI interface operation is supported in the Si2493/57/34/15/04 Revision D or later and the Si2494/39 Revision A or
later. When the device is powered up for SPI interface, the modem becomes an SPI slave, and the pins are
configured to SS (chip select input, active low), MOSI (serial data input to modem), MISO (serial data output from
modem) and SCLK (serial data clock input). The HIR0 and HIR1 registers described above are also available in
SPI mode. Each SPI operation consists of a control-and-address byte and a data byte. The bit definitions of the
control-and-address byte are shown in Table 24. The timing diagrams that follow show SPI read and write
waveforms. Refer to the device data sheet for timing characteristics.
Table 24. SPI Control-and-Address Bit Definitions
Bit
Function
Meaning when High
Meaning when Low
7
Address
Access HIR1
Access HIR0
6
Read/Write
Read register
Write register
5:0
Reserved
Not allowed
Must be all zeroes
SCK NSS MISO Address/Control
Data
MOSI
Hi‐Z
Hi‐Z
SPI 2‐Byte Write Protocol
SCK NSS MISO Hi‐Z
Address/Control
MOSI
Data
Hi‐Z
SPI 2‐Byte Read Protocol
Figure 9. SPI Read and Write Timing Diagrams
2.2.4.5. Interface Communication Modes
Data flow control is implemented in the SPI and parallel interfaces differently from UART mode. When parallel or
SPI mode is selected, data communication may be driven by interrupts or by polling. Refer to "Appendix C—
Parallel/SPI Interface Software Implementation" on page 290 for implementation details for both methods. The
parallel and SPI interfaces have four sources of interrupts and only one interrupt pin. The four interrupts are:
1. RXF Interrupt: receive FIFO almost full
2. TXE Interrupt: transmit FIFO almost empty
3. Timer Interrupt: receive FIFO not empty
4. U70 Interrupt: various conditions, such as ringing, parallel phone pickup, etc. as defined in register U70
The source of the interrupt can be determined by reading HIR1.
28
Rev. 1.3
AN93
2.3. Isolation Capacitor Interface
The isolation capacitor is a proprietary high-speed interface connecting the modem chip and the DAA chip through
a high-voltage isolation barrier provided by two capacitors. It serves three purposes. First, it transfers control
signals and transmit data from the modem chip to the DAA chip. Second, it transfers receive and status data from
the DAA chip to the modem chip. Finally, it provides power from the modem chip to the DAA chip while the modem
is in the on-hook condition. The signaling on this interface is intended for communication between the modem and
the DAA chips and cannot be used for any other purpose. It is important to keep the length of the ISOcap™ path as
short and direct as possible. The layout guidelines for the pins and components associated with this interface are
described in "4.4. Layout Guidelines" on page 49 and must be carefully followed to ensure proper operation and
avoid unwanted emissions.
2.4. Low-Power Modes
2.4.1. Power-Down Mode
The Power-Down mode is a lower power state than sleep mode. It is entered immediately upon writing
U65 [13] (PDN) = 1. Once in the Power-Down mode, the modem requires a hardware reset via the RESET pin to
become active again.
2.4.2. Wake-on-Ring Mode
The ISOmodem can be set to enter a low-power wake-on-ring mode when not connected. Wake-on-ring mode is
entered using the command AT&Z. The ISOmodem returns to the active mode when one of the following happens:






There is a 1 to 0 transition on TXD in the UART mode
There is a 1 to 0 transition on CS in the parallel mode
There is a 1 to 0 transition on SSS in the SPI mode
An incoming ring is detected
A parallel telephone is picked up
Line polarity reversal
2.4.3. Sleep Mode
The ISOmodem can be set to enter a low-power sleep mode when not connected and after a period of inactivity
determined by the S24 register.
The ISOmodem enters the sleep mode S24 seconds after the last DTE activity, after the transmit FIFO is empty,
and after the last data are received from the remote modem. The ISOmodem returns to the active mode when one
of the following happens:

There is a 1 to 0 transition on TXD in the UART mode
 There is a 1 to 0 transition on CS in the parallel mode
 There is a 1 to 0 transition on SSS in the SPI mode
 An incoming ring is detected
 A parallel telephone is picked up
 Line polarity reversal
The delay range for S24 is 1 to 255 seconds. The default setting of S24 = 0 disables the sleep timer and keeps the
modem in the normal power mode regardless of activity level.
Rev. 1.3
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2.5. SSI/Voice Mode (24-Pin TSSOP and 38-Pin QFN Only)
Voice mode is supported in the Si2439 and the Si2494. Table 25 lists the pin connections for the ISOmodem SSI
interface. This interface enables Voice Mode operation. See "7. Handset, TAM, and Speakerphone Operation" on
page 173 for additional information.
Table 25. SSI Interface Pin Connection
Signal
Pin Number
(TSSOP-24)
Pin Number
(QFN-38)
CLKOUT
3
3
FSYNC
4
2
SDI
18
8
SDO
24
9
RESET
12
16
The Si3000 is used in conjunction with the ISOmodem to transmit and receive 16-bit voice samples to and from
telephone lines as shown in Figure 10.
HOST
AT commands
2- wire
Responses
Si24xx Modem
FSYNC
SDI
SDO
Si30xx
DAA
CLKOUT
TDMA Interface
FSYNC
SDO
SDI
MCLK
Handset
Si3000 Voice Codec
Figure 10. Voice Mode Block Diagram
30
Rev. 1.3
AN93
2.6. EEPROM Interface (24-Pin TSSOP and 38-Pin QFN Only)
The 24-pin TSSOP and 38-pin QFN packages feature an optional three-wire interface (EESD, EECS and EECLK)
that may be directly connected to SPI EEPROMs. An EEPROM may contain custom default settings, firmware
upgrades, and/or user-defined AT command macros for use in custom AT commands or country codes. Firmware
upgrades may also be automatically loaded into the ISOmodem using the BOOT format.
2.6.1. Supported EEPROM Types
The EEPROM must support SPI mode 3 with a 16-bit (8–64 kbit range) address. The EEPROM must be between
8192 and 65536 bits in size and support the commands given in Table 26. The EEPROM must also support 16-bit
addressing regardless of size, allow a clock frequency of at least 1 MHz, assert its output on falling edges of
EECLK and latch input data on rising edges of EECLK. All data are sent to and from the EEPROM with the LSB
first. Required EEPROM command format and signal timing are shown in Tables 26 to 28. A typical EEPROMaccess timing diagram is shown on Figure 11. Such EEPROMs are available from several different manufacturers,
for example:


Microchip: 25LC080..25LC640
Atmel: AT25080..AT25640
Table 26. EEPROM Commands
Instruction Name
Instruction Format
Description
READ
0000 0011
Read data from memory at address
WRITE
0000 0010
Write data to memory array beginning at address
WRDI
0000 0100
Clear write enable bit (disable write operation)
RDSR
0000 0101
Read status register
WRSR
0000 0001
Write status register
WREN
0000 0110
Set write enable bit (enable write operations)
Table 27. EEPROM Status Register (Any Other Bits are Unused)
7
6
5
4
3
2
1
0
—
—
—
—
—
—
WEL
WIP
WEL = write enable latch
WIP = write in progress
Table 28. EEPROM Timing
Parameter
Symbol
Min.
Typ.
Max.
Unit
EECLK period
ECLK
1.0
—
—
µs
EESD input setup time
EISU
100
—
—
ns
EESD input hold time
EIH
100
—
—
ns
EESD output setup time*
EOSU
500
—
—
ns
EESD output hold time*
EOH
500
—
—
ns
EECS asserted to EECLK positive edge
ECSS
500
—
—
ns
Rev. 1.3
31
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Table 28. EEPROM Timing
Parameter
Symbol
Min.
Typ.
Max.
Unit
EESD tristated before last falling EECLK edge during read
cycle. Last positive half of EECLK cycle is extended to provide
both 500 ns minimum EOH and 100 ns EESD before EECLK
falling edge.
EOZ
100
—
—
ns
EECS disable time between accesses
ECSW
500
—
—
ns
EECS asserted after final EECLK edge
ECSH
1
—
—
µs
*Note: EESD output at negative EECLK edge
EOZ
ECLK
EOH
MSB
EISU
EOSU
LSB
EIH
EDH
ECSH
ECSS
EEPROM Data Format
EESD
8-bit instruction
16-bit address
8-bit data
EECS
Figure 11. EEPROM Serial I/O Timing
32
Rev. 1.3
ECSW
AN93
2.6.2. Three-Wire SPI Interface to EEPROM
To enable the 3-wire SPI interface to EEPROM on the 24-pin TSSOP package, appropriate pins must be reset
strapped according to Table 6 on page 14, or Table 8 on page 15, depending on the interface selected. The
EEPROM option is not available on the 24-pin TSSOP package if the parallel host interface is selected.
Figure 12 shows the connection diagram for the 3-wire SPI interface to EEPROM. A four-wire EEPROM (with
separate serial input and output data wires) may also be used with the input and output pins connected to EESD, if
its SO output is tristated on the last falling edge of EECLK during a read cycle.
SPI EEPROM
SI/SO
CS
SCLK
EESD
EECS
SCLK
TELEPHONE LINE
HOST
Si3018/10
MODEM
Figure 12. Three-Wire EEPROM Connection Diagram
2.6.3. Detailed EEPROM Examples
Upon powerup, if the option is selected, the ISOmodem attempts to detect an EEPROM. The modem looks for a
carriage return in the first 10 memory locations. If none is found, the modem assumes the EEPROM is not
programmed and stops reading it. If a programmed EEPROM is detected, customer defaults that are programmed
into the EEPROM between the optional heading "BOOT" and the "<CR><CR>" delimiter are executed immediately,
and AT command macros are loaded into the ISOmodem RAM. The memory that may be allocated to the
<commands> portion of the EEPROM is limited to 1000 bytes. Three <CR> must be the last three entries in the
EEPROM.
EEPROM Data are stored and read in hexadecimal ASCII format in eight address blocks beginning at a specified
hexadecimal address. For example, the AT:M0000,y0,y1,y2,y3,y4,y5,y6,y7 command writes the hexadecimal
values y0…y7 at addresses from 0 to 7, respectively. The AT:E0000 command reads the hexadecimal values
y0…y7 from addresses 0 to 7, respectively.
The following sections give specific examples of EEPROM usage for command macros, firmware upgrades, boot
commands, etc.
2.6.4. Boot Commands (Custom Defaults)
Commands to be executed upon boot-up are stored between the heading BOOT and the first <CR><CR> delimiter.
The boot command has the following format:
BOOT<CR>
<commands><CR>
<commands><CR>
<CR>
Rev. 1.3
33
AN93
The commands end with a <CR>, which, in combination with the final<CR>, provides the <CR><CR> delimiter.
Boot commands must be the first entry in the EEPROM and are used to set the modem up with custom defaults,
such as settings for specific countries, auto answer, or other special settings upon power up or after a hardware or
software reset.
This saves the host processor from reloading special configuration strings at power up or after a reset, and allows
the modem to be customized by programming the EEPROM or by substituting preprogrammed EEPROMs. If the
BOOT command is the final entry in the EEPROM, it must end with an additional <CR> to provide the
<CR><CR><CR> delimiter indicating the end of the EEPROM.
2.6.5. AT Command Macros (Customized AT Commands)
Macros allow the creation of single custom AT commands that execute combinations of default AT commands
including special register configurations. AT command macros have the following format:
<command name><CR>
<commands><CR>
<commands><CR>
<CR>
Each AT Command Macro ends with a <CR><CR>. The final entry in the EEPROM ends with an additional <CR>
to provide the <CR><CR><CR> delimiter indicating the end of the EEPROM. AT command macros can have a
name consisting of any string of characters but must be the only command on a line.
2.6.6. Firmware Upgrades
Firmware upgrades (“patches”) are typically executed upon boot-up and stored between the heading, BOOT, and
the first <CR><CR> delimiter. A firmware upgrade has the format: BOOT<firmware upgrade><CR>. The firmware
upgrade ends with a <CR>, which, in combination with the final<CR>, provides the <CR><CR> delimiter, which
marks the end of the EEPROM contents. A firmware upgrade can also be stored as an AT command macro in a
system where using the firmware upgrade is optional. The following are examples of boot commands, AT
command macros, and automatically-loaded firmware upgrades.
2.6.6.1. Boot Command Example
On power-up or reset, it is desired to set the UART rate to 115.2 kbps and limit the ISOmodem to V.34 and lower
operation.
The AT commands required to do this manually are:
AT\T12<CR>
AT&H2<CR>
To implement this as a boot command, the commands are:
BOOT<CR>
AT\T12<CR>
AT&H2<CR>
<CR>
This must be written to the EEPROM as ASCII hexadecimal in eight address blocks. The actual AT commands to
store this boot command in the EEPROM starting at address 0 are:
AT:M0000,42,4F,4F,54,0D,41,54,5C
AT:M0008,54,31,32,0D,41,54,26,48
AT:M0010,32,0D,0D,00,00,00
The value 0x41 corresponds to the display character A, 0x54 to T, 0x42 to B, 0x4F to O etc., and the value 0x0D,
for carriage return corresponds to the decimal value, 13, stored in S-register 3 (S3). Table 30 shows the
relationship between the decimal values, hexadecimal values, and display characters.
34
Rev. 1.3
AN93
2.6.6.2. AT Command Macro Example
This example creates the AT command macro ATN<CR> to configure the ISOmodem for operation in Norway.
The AT commands required to do this manually are:
AT:U2C,00B0,0080<CR>
AT:U67,000C,0010,0004<CR>
AT:U4D,001<CR>
To implement this as an AT command macro, the EEPROM contents should be:
N<CR>
AT:U2C,00B0,0080<CR>
AT:U67,000C,0010,0004<CR>
AT:U4D,001<CR>
<CR><CR>
This must be written to the EEPROM as ASCII hexadecimal in eight address blocks. The actual AT commands to
store this boot command in the EEPROM starting at address 0 are:
AT:M0000,4E,0D,41,54,3A,55,32,43
AT:M0008,2C,30,30,42,30,0D,0D,30
AT:M0010,38,30,0D,41,54,3A,55,36
AT:M0018,37,2C,30,30,30,43,2C,30
AT:M0020,30,31,30,2C,30,30,30,34
AT:M0028,0D,41,54,3A,55,34,44,2C
AT:M0030,30,30,31,0D,0D,0D
With this macro installed in the EEPROM, the command ATN<CR> configures the modem for operation in Norway.
2.6.6.3. Autoloading Firmware Upgrade Example
This example stores a firmware upgrade in EEPROM that is automatically loaded into the modem after power-up or
hardware/software reset if the EEPROM option is selected.
The AT commands required to load the firmware upgrade manually are:
AT*Y254:W0050,0000<CR>
AT:PF800.08D5
To implement this as a boot command macro, the commands are:
BOOT<CR>
AT*Y254:W0050,0000<CR>
AT:PF800.08D5
This must be written to the EEPROM as ASCII hexadecimal in eight address blocks. The actual AT commands to
store this boot command in the EEPROM starting at address 0 are:
AT:M0000,42,4F,4F,54,0D,41,54,2A
AT:M0008,59,32,35,34,3A,57,30,30
AT:M0010,35,30,2C,30,30,30,30,0D
AT:M0018,41,54,3A,50,46,34,30,30
AT:M0020,2C,30,38,44,35,0D,0D,0D
This firmware upgrade (patch) is only an example meant to illustrate the procedure for loading a patch into the
EEPROM. Loading this code into a ISOmodem causes undesirable behavior.
Rev. 1.3
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2.6.6.4. Combination Example
This example shows boot commands and custom AT commands stored in the same EEPROM.
Table 29. Combination Example
Command
Function
Start of EEPROM contents
BOOT<CR>
<commands><CR>
<commands><CR>
End of BOOT string
<CR>
<Custom AT Command Name 1><CR> Start of Custom AT Command 1
<commands><CR>
<commands><CR>
End of Custom AT Command 1
<CR>
<Custom AT Command Name 2><CR> Start of Custom AT Command 2
<commands><CR>
<commands><CR>
End of Custom AT Command 2
<CR>
<Custom AT Command Name 3><CR> Start of Custom AT Command 3
<commands><CR>
<commands><CR>
36
<CR>
End of Custom AT Command 3
<CR>
End of EEPROM Contents
Rev. 1.3
AN93
Table 30. ASCII Chart
dec
hex
Display
dec
hex
Display
dec
hex
Display
dec
hex
Display
0
00
<NUL>
32
20
<space>
64
40
@
96
60
`
1
01
<SOH>
33
21
!
65
41
A
97
61
a
2
02
<STX>
34
22
“
66
42
B
98
62
b
3
03
<ETX>
35
23
#
67
43
C
99
63
c
4
04
<EOT>
36
24
$
68
44
D
100
64
d
5
05
<ENQ>
37
25
%
69
45
E
101
65
e
6
06
<ACK>
38
26
&
70
46
F
102
66
f
7
07
<BEL>
39
27
'
71
47
G
103
67
g
8
08
<BS>
40
28
(
72
48
H
104
68
h
9
09
<HT>
41
29
)
73
49
I
105
69
i
10
0A
<LF>
42
2A
*
74
4A
J
106
6A
j
11
0B
<VT>
43
2B
+
75
4B
K
107
6B
k
12
0C
<FF>
44
2C
,
76
4C
L
108
6C
l
13
0D
<CR>
45
2D
-
77
4D
M
109
6D
m
14
0E
<SO>
46
2E
.
78
4E
N
110
6E
n
15
0F
<SI>
47
2F
/
79
4F
O
111
6F
o
16
10
<DLE>
48
30
0
80
50
P
112
70
p
17
11
<DC1>
49
31
1
81
51
Q
113
71
q
18
12
<DC2>
50
32
2
82
52
R
114
72
r
19
13
<DC3>
51
33
3
83
53
S
115
73
s
20
14
<DC4>
52
34
4
84
54
T
116
74
t
21
15
<NAK>
53
35
5
85
55
U
117
75
u
22
16
<SYN>
54
36
6
86
56
V
118
76
v
23
17
<ETB>
55
37
7
87
57
W
119
77
w
24
18
<CAN>
56
38
8
88
58
X
120
78
x
25
19
<EM>
57
39
9
89
59
Y
121
79
y
26
1A
<SUB>
58
3A
:
90
5A
Z
122
7A
z
27
1B
<ESC>
59
3B
;
91
5B
[
123
7B
{
28
1C
<FS>
60
3C
<
92
5C
\
124
7C
|
29
1D
<GS>
61
3D
=
93
5D
]
125
7D
}
30
1E
<RS>
62
3E
>
94
5E
^
126
7E
~
31
1F
<US>
63
3F
?
95
5F
_
127
7F
Rev. 1.3
37
AN93
3. DAA (Line-Side) Device
The Si3018/10 DAA or line-side device, contains an ADC, a DAC, control circuitry, and an isolation capacitor
interface. The Si3018/10 and surrounding circuitry provide all functionality for telephone line interface requirement
compliance, including a full-wave rectifier bridge, hookswitch, dc termination, ac termination, ring detection, loop
voltage and current monitoring, and call-progress monitoring. The Si3018/10 external circuitry is largely
responsible for EMI, EMC, safety, and surge performance.
3.1. Hookswitch and DC Termination
The DAA has programmable settings for the dc impedance, current limiting, minimum operational loop current, and
Tip-to-Ring voltage. The dc impedance of the DAA is normally represented by a 50  slope as shown in Figure 13,
but can be changed to an 800  slope by setting the DCR bit. This higher dc termination presents a higher
resistance to the line as the loop current increases.
FCC DCT Mode
Voltage Across DAA (V)
12
11
10
9
8
7
6
.01 .02 .03 .04 .05 .06 .07 .08 .09 .1 .11
Loop Current (A)
Figure 13. FCC Mode I/V Characteristics
DCV[1:0] = 11, MINI[1:0] = 00
For applications requiring current limiting per the legacy TBR21 standard, the ILIM bit may be set to select this
mode. In this mode, the dc I/V curve is changed to a 2000  slope above 40 mA, as shown in Figure 14. This
allows the DAA to operate with a 50 V, 230  feed, which results in the highest current possible in the old TBR21
standard.
TBR21 DCT Mode
Voltage Across DAA (V)
45
40
35
30
25
20
15
10
5
.015 .02 .025 .03 .035 .04 .045 .05 .055 .06
Loop Current (A)
Figure 14. TBR21 (Legacy) Mode I/V Characteristics
DCV[1:0] = 11, MINI[1:0] = 00
The MINI[1:0] bits select the minimum operational loop current for the DAA, and the DCV[1:0] bits adjust the DCT
pin voltage, which affects the Tip-to-Ring voltage of the DAA. These bits allow important trade-offs to be made
between signal headroom and minimum operational loop current. Increasing the Tip-Ring voltage increases signal
headroom, whereas decreasing the voltage allows compliance to PTT standards in low-voltage countries, such as
Japan or Malaysia. Increasing the minimum operational loop current above 10 mA also increases signal headroom
and prevents degradation of the signal level in low-voltage countries.
38
Rev. 1.3
AN93
3.2. AC Termination
The ISOmodem has four ac termination impedances when used with the Si3018 line-side device, selected by the
ACT bits in Register U63. The four available settings for the Si3018 are listed in Table 31. If an ACT[3:0] setting
other than the four listed in Table 31 is selected, the ac termination is forced to 600  (ACT[3:0] = 0000).
Table 31. AC Termination Settings for the Si3018 Line-Side Device
ACT[3:0]
AC Termination
0000
600 
0011
220  + (820  || 120 nF) and 220  + (820  || 115 nF)
0100
370  + (620  || 310 nF)
1111
Global complex impedance
3.3. Ringer Impedance and Threshold
The ring detector in many DAAs is ac coupled to the line with a large 1 µF, 250 V decoupling capacitor. The ring
detector on the ISOmodem is resistively coupled to the line. This produces a high ringer impedance to the line of
approximately 20 M. This meets the majority of country PTT specifications, including FCC and ETSI ES 203 021.
Several countries, including Poland, South Africa, and Slovenia, require a maximum ringer impedance that can be
met with an internally synthesized impedance by setting the RZ bit (Register 67, bit 1).
Some countries specify different ringer thresholds. The RT bit (Register U67, bit 0) selects between two different
ringer thresholds: 15 V ±10% and 21.5 V ±10%. These two settings satisfy ringer threshold requirements
worldwide. The thresholds are set so that a ring signal is guaranteed to be detected above the maximum and not
detected below the minimum.
3.4. Pulse Dialing and Spark Quenching
Pulse dialing is accomplished by going off- and on-hook at a certain cadence to generate make and break pulses.
The nominal rate is ten pulses per second. Some countries have strict specifications for pulse fidelity that include
make and break times, make resistance, and rise and fall times. In a traditional, solid-state dc holding circuit, there
are many problems in meeting these requirements. The ISOmodem dc holding circuit actively controls the on-hook
and off-hook transients to maintain pulse dialing fidelity.
Spark-quenching requirements in countries such as Italy, the Netherlands, South Africa and Australia deal with the
on-hook transition during pulse dialing. These tests provide an inductive dc feed resulting in a large voltage spike.
This spike is caused by the line inductance and sudden decrease in current through the loop when going on-hook.
The traditional solution to the problem is to put a parallel resistive capacitor (RC) shunt across the hookswitch
relay. However, the capacitor required is bulky (~1 µF, 250 V) and relatively costly. In the ISOmodem, the loop
current can be controlled to achieve three distinct on-hook speeds to pass spark-quenching tests without additional
BOM components. Through settings of two bits in two registers, OHS (Register U67, bit 6) and OHS2 (Register
U62, bit 8), a delay between the time the OH bit is cleared and the time the DAA actually goes on-hook, can be
created, which induces a slow ramp-down of the loop current.
3.5. Line Voltage and Loop Current Sensing
There are two methods for line voltage and loop current sensing. The first method is the legacy mode using
U79 (LVCS) [4:0]. The legacy mode is intended for backward compatibility in applications originally designed for
the previous generation ISOmodem. This mode is used in the intrusion detection algorithm implemented on the
device.
The second method of measuring line voltage and loop current takes advantage of the improved resolution
available on the Si3018 and Si3010 DAA chips. U63 (LCS) [15:8] represents the value of off-hook loop current as a
non-polar binary number with 1.1 mA/bit resolution. Accuracy is not guaranteed if the loop current is less than the
minimum required for normal DAA operation. U6C (LVS) [15:8] represents the value of on-hook and off-hook loop
voltage as a signed, two’s complement number with a resolution of 1 V/bit.
Rev. 1.3
39
AN93
Bit 15 represents the polarity of the Tip-Ring voltage, and a reversal of this bit represents a Tip-Ring polarity
reversal. LVS = 0x0000 if the Tip-Ring voltage is less than 3.0 V and, in the on-hook state, can be taken as “no line
connected.”
The ISOmodem reports the on-hook line voltage with the LVS bits in two’s complement. LVS has a full scale of 87 V
with an LSB of 1 V. The first code step (going from 0 to 1) is offset so that a 0 indicates a line voltage of less than
3 V. The accuracy of the LVS bits is ±10%. The user can read these bits directly through the LVS register. A typical
transfer function is shown in Figure 15.
When the ISOmodem is off-hook, the LCS bits measure loop current in 1.1 mA/bit resolution. These bits enable the
user to detect another phone going off-hook by monitoring the dc loop current. Line-current sensing is detailed in
Figure 16 and Table 32.
128
112
96
LVS Bits
80
64
48
32
16
0
0
16
32
48
64
80
96
Tip/Ring Voltage (Volts )
Figure 15. Typical Loop Voltage LVS Transfer Function
40
Rev. 1.3
112
128
AN93
256
ILIM = 1
224
ILIM = 0
192
LCS Bits
160
128
96
64
32
0
0
16
32
48
64
80
Loop Curre nt (m A)
96
112
128
144
Figure 16. Typical Loop Current LCS Transfer Function
Table 32. Loop Current Transfer Function
LVCS[4:0]
Condition
00000
Insufficient line current for normal operation.
00001
Minimum line current for normal operation.
11111
Loop current overload. Overload is defined as 128 mA or more, except
in TBR21, where overload is defined as 56 mA or more.
Rev. 1.3
41
AN93
3.6. Legacy-Mode Line Voltage and Loop Current Measurement
The 5-bit LVCS register, U79 (LVCS) [4:0], reports line voltage measurements when on-hook and loop current
measurements when off-hook.
Using the LVCS bits, the user can determine the following:

When on-hook, detect if a line is connected.
 When on-hook, detect if a parallel phone is off-hook.
 When off-hook, detect if a parallel phone goes on or off-hook.
 Detect if enough loop current is available to operate.
3.7. Billing Tone Detection
Billing tones or metering pulses generated by the central office can cause connection difficulties in modems. The
billing tone is typically a 12 kHz or 16 kHz signal and is sometimes used in Germany, Switzerland, and South
Africa. Depending on line conditions, the billing tone may be large enough to cause major modem errors. The
ISOmodem chipset can provide feedback when a billing tone occurs and when it ends.
Billing tone detection is enabled by setting the BTE bit (U68, bit 2). Billing tones less than 1.1 VPK on the line are
filtered out by the low-pass digital filter on the ISOmodem. The ROV bit (U68, bit 1) is set when a line signal is
greater than 1.1 VPK, indicating a receive overload condition. The BTD bit is set when a line signal (billing tone) is
large enough to excessively reduce the line-derived power supply of the line-side device (Si3018/10). When the
BTE bit is set, the dc termination is changed to an 800  dc impedance. This ensures minimum line voltage levels
even in the presence of billing tones.
The OVL bit should be polled following billing-tone detection. When the OVL bit returns to 0, indicating that the
billing tone has passed, the BTE bit should be written to 0 to return the dc termination to its original state. It takes
approximately 1 second to return to normal dc operating conditions. The BTD and ROV bits are sticky and must be
written to 0 to be reset. After the BTE, ROV, and BTD bits are cleared, the BTE bit can be set to reenable billingtone detection.
Certain line events, such as an off-hook event on a parallel phone or a polarity reversal, may trigger the ROV bit or
the BTD bit, after which the billing-tone detector must be reset. Look for multiple events before qualifying whether
billing tones are actually present.
Although the DAA remains off-hook during a billing-tone event, the received data from the line is corrupted (or a
modem disconnect or retrain may occur) in the presence of large billing tones. To receive data in the presence of a
billing tone, an external LC filter must be added. A modem manufacturer can provide this filter to users in the form
of a dongle that connects on the phone line before the DAA. This keeps the manufacturer from having to include a
costly LC filter internal to the modem when it may only be necessary to support a few countries or customers.
Alternatively, when a billing tone is detected, the host software may notify the user that a billing tone has occurred.
This notification can be used to prompt the user to contact the telephone company to have the billing tones
disabled or purchase an external LC filter.
42
Rev. 1.3
AN93
4. Hardware Design Reference
This section describes hardware design requirements for optimum Si24xx ISOmodem chipset implementation.
There are three important considerations for any hardware design. First, the reference design and components
listed in the associated bill of materials should be followed exactly. These designs reflect field experience with
millions of deployed units throughout the world and are optimized for cost and performance. Any deviation from the
reference design schematic and components will likely have an adverse affect on performance. Second, circuit
board layouts must follow "4.4. Layout Guidelines" rigorously. Deviations from these layout techniques will likely
affect modem performance and regulatory compliance. Finally, all reference designs use a standard component
numbering scheme. This simplifies documentation references and communication with the Silicon Laboratories
technical support team. It is strongly recommended that these same component reference designators be used in
all ISOmodem designs.
4.1. Component Functions
In spite of the significant internal complexity of the chip, the external support circuitry is very simple. The following
section describes the modem’s functions in detail.
4.1.1. Power Supply and Bias Circuitry
Power supply bypassing is important for the proper operation of the ISOmodem, suppression of unwanted
radiation, and prevention of interfering signals and noise from being coupled into the modem via the power supply.
C50 and C52 provide filtering of the 3.3 V system power and must be located as close to the ISOmodem chip as
possible to minimize lead lengths. The best practice is to use surface-mount components connected between a
power plane and a ground plane. This technique minimizes the inductive effects of component leads and PCB
traces and provides bypassing over the widest possible frequency range, and minimizes loop areas that can
radiate radio frequency energy.
Two bias voltages used inside the modem chip require external bypassing and/or clamping. VDA (pin 7) is
bypassed by C51. VDB (pin 19) is bypassed by C53. R12 and R13 are optional resistors that can, in some cases,
reduce radiated emissions due to signals associated with the isolation capacitors. These components must be
located as close to the ISOmodem chip as possible to minimize lead lengths.
The Si3018/10 is powered by a small current passed across the ISOcap in the on-hook mode and by the loop
current in the off-hook mode. Since there is no system ground reference for the line-side chip due to isolation
requirements, a virtual ground, IGND, is used as a reference point for the Si3018/10. Several bias voltages and
signal reference points used inside the DAA chip require external bypassing, filtering, and/or clamping. VREG2
(pin 10) is bypassed by C6. VREG (pin 7) is bypassed by C5. These components must be located as close to the
Si3018/10 chip as possible to minimize lead lengths.
4.1.2. Hookswitch and DC Termination
The hookswitch and dc termination circuitry are shown in Figure 18 on page 46. Q1, Q2, Q3, Q4, R5. R6, R7, R8,
R15, R16, R17, R19, and R24 perform the hookswitch function. The on-hook/off-hook condition of the modem is
controlled by Si3018/10 pins 13 (QB) and 1 (QE).
4.1.3. Clocks
The crystal oscillator circuit has three operating frequencies/modes that are selected by using the correct clock
source and by installing the correct pulldown resistors on the modem in order to signal the ISOmodem which mode
to operate. Selecting among these modes of operation is described in "2.1. Resetting the Device" on page 11.
One mode requires a 4.9152 MHz fundamental mode parallel-resonant crystal. Typical crystals require a 20 pF
load capacitance. This load is calculated as the series combination of the capacitance from each crystal terminal to
ground, including parasitic capacitance due to package pins and PCB traces. The parasitic capacitance is
estimated as 7 pF per terminal. This, in combination with the 33 pF capacitor, provides 40 pF per terminal, which,
in series, yields the proper 20 pF load for the crystal.
Instead of using a 4.9152 MHz crystal, a signal at 4.9152 MHz can be applied to the XTALI pin. In such a case, the
crystal loading caps should not be used.
Rev. 1.3
43
AN93
The second mode is a 32.768 kHz fundamental mode parallel-resonant crystal. Typical crystals require a 12.5 pF
load capacitance. This load is calculated as the series combination of the capacitance from each crystal terminal to
ground, including parasitic capacitance due to package pins and PCB traces. The parasitic capacitance is
estimated as 7 pF per terminal. This, in combination with the 18 pF capacitors, provides 25 pF per terminal, which,
in series, yields the proper 12.5 pF load for the crystal.
Instead of a using a 32.768 kHz crystal, a signal at 32.768 kHz can be applied to the XTALI pin. In such a case, the
crystal loading caps should not be used.
The third mode is to use a 27 MHz clock signal. A crystal cannot be used for this mode, and the signal must be
applied to the XTALI pin.
Frequency stability and accuracy are critically important to the performance of the modem. ITU-T specifications
require less than 200 ppm difference between the carrier frequencies of two modems. This value, split between the
two modems, requires the oscillator frequency of each modem to be accurate and stable over all operating
conditions within ±100 ppm. This tolerance includes the initial accuracy of the crystal, the frequency drift over the
temperature range that the crystal is expected to experience, and the five-year aging of the crystal. Other factors
affecting the oscillator frequency include the tolerance and temperature drift of the load capacitor values. For
optimal V.92 performance, it is recommended to increase the oscillator stability to ±25 ppm.
For all the above three modes of operation, the CLKIN/XTALI pin (Pin 1) can accept a 3.3 V external clock signal
meeting the accuracy and stability requirements described above.
The CLKOUT/A0 pin outputs a signal derived from the 4.9152 MHz clock. If the frequency of the output is
controlled via register U6E (CK1) using the Si2404 or Si2415, this signal is programmable from 2.64 MHz to
40.96 MHz. If using the Si2434 or Si2457, this signal is programmable from 3.17 MHz to 49.152 MHz. There are
two special cases for the value of R1: R1 = 00000, CLKOUT is disabled, and R1 = 11111 (default),
CLKOUT = 2.048 MHz.
On older parts, the CLKOUT pulse starts immediately after RESET goes high, but, on the most recent versions
(those including SPI and 32 kHz operation), there is a small delay after RESET goes high. The delay is of
approximately 200 µs when using 4.91592 MHz or 27 MHz and approximately 8 ms when using a 32 kHz clock.
4.1.4. Ringer Network
R7 and R8 comprise the ringer network. These components determine the modem’s on-hook impedance at Tip
and Ring. These components are selected to present a high impedance to the line, and care must be taken to
ensure the circuit board area around these components is clean and free of contaminants, such as solder flux and
solder flakes. Leakage on RNG1 (Si3018/10 pin 8) and RNG2 (Si3018/10 pin 9) can impair modem performance.
R7 and R8 are also used by the modem to monitor the line voltage.
4.1.5. Optional Billing-Tone Filter
To operate without degradation during billing tones in Germany, Switzerland, and South Africa, an external LC
notch filter is required. (The Si3018/10 will remain off-hook during a billing tone event, but modem data may be lost,
or a modem disconnect or retrain may occur, in the presence of large billing-tone signals.) The notch filter design
requires two notches: one at 12 kHz and one at 16 kHz. Because these components are expensive and few
countries require billing-tone support, this filter is typically placed in an external dongle or added as a population
option. Figure 17 shows an example billing tone filter. L3 must carry the entire loop current. The series resistance
of the inductors is important to achieve a narrow and deep notch. This design has more than 25 dB of attenuation
at 12 kHz and 16 kHz. The billing tone filter degrades the ac termination and return loss slightly, but the global
complex ac termination passes worldwide return-loss specifications with and without the billing tone filter by at
least 3 dB.
44
Rev. 1.3
AN93
C1
C2
L3
TIP
FROM
LINE
L4
To
DAA
C3
RING
Figure 17. Billing-Tone Filter
Table 33. Optional Billing Tone Filters Component Values
Symbol
Value
C1,C2
0.027 µF, 50 V, ±10%
C3
0.01 µF, 250 V, ±10%
L3
3.3 mH, >120 mA, <10 , ±10%
Coilcraft RFB0810-332 or equivalent
L4
10 mH, >40 mA, <10 , ±10%
Coilcraft RFB0810-103 or equivalent
Rev. 1.3
45
RESET_
RTS_/D7
RXD/RD_
TXD/WR_
CTS_/CS_/ALE_
CLKOUT/A0/EECS
INT_/D0
RI_/D1
EESD/D2
EECLK/D5/RXCLK
DCD_/D4
ESC/D3
AOUT/INT_
alt_RI_/D6/TXCLK
12
8
9
10
11
3
16
17
18
24
23
22
15
4
5
21
RESET
RTS/D7
RXD/RD
TXD/WR
CTS/CS/ALE
CLKOUT/A0/EECS
13
14
2
1
C51
C53
Y1
R13
R12
C41
C40
R9
C5
Bias
Rev. 1.3
C6
10
7
4
6
5
VREG2
VREG
IB
C2B
C1B
U2
8
9
1
12
13
16
14
2
3
Si3018
RNG1
RNG2
QE
QE2
QB
DCT2
DCT3
DCT
RX
C4
R1
Q5
R10
C7
Ring Detect/CID
R2
R11
DC Term
ACT
Q4
R4
R7
R8
R5
Q1
Z1
R3
Q2
Q3
C10
Hookswitch
Hookswitch/DCT
R6
No Ground Plane In DAA Section
Figure 18. Si3018/10 Component Functions
Bypass
ISOcap
C2
C1
External crystal option
Emissions option
Si2493/57/34/15/04
C2A
C1A
EECLK/D5/RXCLK
DCD/D4
CLKIN/XTALI
ESC/D3
AOUT/INT
alt_RI/D6/TXCLK
XTALO
INT/D0
RI/D1
EESD/D2
U3
1
2
VD3.3
VD 3.3
GND
GND
VDA
VDB
6
20
7
19
C52
IGND
15
C50
SC
46
+
11
VDD
+
D1
C3
FB2
RING
-
C9
C8
R15
EMI/EMC
Capacitors
FB1
TIP
RV1
Conducted Disturbance
R16
Emissions option
AN93
RESET_
RTS_/D7
RXD/RD_
TXD/WR_
CTS_/CS_/ALE_
CLKOUT/A0/EECS
INT_/D0
RI_/D1
EESD/D2
EECLK/D5/RXCLK
DCD_/D4
ESC/D3
AOUT/INT_
alt_RI_/D6/TXCLK
12
8
9
10
11
3
16
17
18
24
23
22
15
4
5
21
RESET
RTS/D7
RXD/RD
TXD/WR
CTS/CS/ALE
CLKOUT/A0/EECS
13
14
2
1
C51
Rev. 1.3
Y1
R13
R12
C41
C40
R9
C5
C2
C1
C6
10
7
4
6
5
VREG2
VREG
IB
C2B
C1B
U2
8
9
1
12
13
16
14
2
3
Si3018/10
RNG1
RNG2
QE
QE2
QB
DCT2
DCT3
DCT
RX
C4
R1
Q5
R2
R11
R10
C7
Q4
R4
R7
R8
R5
Q1
Z1
R3
Q2
Q3
C10
R6
No Ground Plane In DAA Section
+
D1
C3
-
Figure 19. Si3018/10 Schematic
Note: See Section "10.4.2. Safety" for information regarding the use of a fuse or PTC resistor.
Si2493/57/34/15/04
C2A
C1A
EECLK/D5/RXCLK
DCD/D4
CLKIN/XTALI
ESC/D3
AOUT/INT
alt_RI/D6/TXCLK
XTALO
INT/D0
RI/D1
EESD/D2
U3
1
2
VD3.3
VD 3.3
GND
GND
VDA
VDB
6
20
7
19
C52
IGND
C50
SC
15
+
11
VDD
FB1
FB2
C9
C8
R15
R16
TIP
RV1
RING
AN93
4.2. Schematic
47
AN93
4.3. Bill of Materials
Component
Value
Supplier(s)
C1, C2
33 pF, Y2, X7R, ±20%
Panasonic, Murata, Vishay,
Holy Stone
C3
10 nF, 250 V, X7R, ±20%
Venkel, SMEC
1.0 µF, 50 V, Elec/Tant, ±20%
Panasonic
C4
1
C5, C6, C50, C52
0.1 µF, 16 V, X7R, ±20%
Venkel, SMEC
C7
2.7 nF, 50 V, X7R, ±20%
Venkel, SMEC
C8, C9
680 pF, Y2, X7R, ±10%
Panasonic, Murata, Vishay,
Holy Stone
C10
0.01 µF, 16 V, X7R, ±20%
Venkel, SMEC
C40
C41
32.768 kHz, 18 pF, 16 V, NPO, ±5%
4.9152 MHz, 27 MHz, 33 pF, 16 V, NPO, ±5%
Venkel, SMEC
C51, C531
0.22 µF, 16 V, X7R, ±20%
Venkel, SMEC
D1, D22
Dual Diode, 225 mA, 300 V, MMBT3004S
Diodes Inc.
FB1, FB2
Ferrite Bead, BLM18AG601SN1
Murata
Q1, Q3
NPN, 300 V, MMBTA42
Diodes Inc., Fairchild
Q2
PNP, 300 V, MMBTA92
Diodes Inc., Fairchild
Q4, Q5
NPN, 80 V, 330 mW, MMBTA06
Diodes Inc., Fairchild
RV1
Sidactor, 275 V, 100 A
Teccor, Protek, ST Micro
R1
1.07 k, 1/2 W, 1%
Venkel, SMEC, Panasonic
R2
150 , 1/16 W, 5%
Venkel, SMEC, Panasonic
R3
3.65 k, 1/2 W, 1%
Venkel, SMEC, Panasonic
R4
2.49 k, 1/2 W, 1%
Venkel, SMEC, Panasonic
R5, R6
100 k, 1/16 W, 5%
Venkel, SMEC, Panasonic
R7, R8
20 M, 1/16 W, 5%
Venkel, SMEC, Panasonic
R9
1 M, 1/16 W, 1%
Venkel, SMEC, Panasonic
R10
536 , 1/4 W, 1%
Venkel, SMEC, Panasonic
R11
73.2 , 1/2 W, 1%
Venkel, SMEC, Panasonic
56 , 1/16 W, 1%
Venkel, SMEC, Panasonic
R15, R16
0 , 1/16 W
Venkel, SMEC, Panasonic
U1
Si24xx ISOmodem
Silicon Labs
U2
Si3018
Silicon Labs
R12, R13
3
32.768 kHz, 12 pF, 100 ppm, 50 k max ESR
Y14
4.9152 MHz, 20 pF, 100 ppm, 150  ESR
27 MHz (from external clock)
ECS Inc., Siward, Abracon
Z1
Zener Diode, 43 V, 1/2 W, BZT84C43
On Semi
Notes:
1. C52 and C53 should not be populated with the Si2493 16-pin package option.
2. Several diode bridge configurations are acceptable. For example, a single DF04S or four 1N4004 diodes may be used.
3. Murata BLM18AG601SN1 may be substituted for R15–R16 (0 ) to decrease emissions.
4. To ensure compliance with ITU specifications, frequency tolerance must be less than 100 ppm including initial
accuracy, 5-year aging, 0 to 70 °C, and capacitive loading. For optimal V.92 PCM upstream performance, the
recommended crystal accuracy is ±25 ppm.
48
Rev. 1.3
AN93
4.4. Layout Guidelines
The key to a good layout is proper placement of the components. It is best to copy the placement shown in
Figure 20. Alternatively, follow the following steps, referring to the schematics and Figure 21. It is strongly
recommended to complete the checklist in Table 34 on page 51 while reviewing the final layout.
1. All traces, open pad sites, and vias connected to the following components are considered to be in the DAA
section and must be physically separated from non-DAA circuits by 5 mm to achieve the best possible surge
performance: R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R15, R16, U2, Z1, D1, FB1, FB2, RJ11, Q1, Q2,
Q3, Q4, Q5, C3, C4, C5, C6, C7, C8, C9, C10, RV1, C1 pin 2 only, C2 pin 2 only, C8 pin 2 only, and C9 pin 2
only.
2. The isolation capacitors, C1, C2, C8 and C9, are the only components permitted to straddle between the DAA
section and non-DAA section components and traces. This means that for each of these capacitors, one of the
terminals is on the DAA side, and the other is not. Maximize the spacing between the terminals (between pin 1
and pin 2) of each of these capacitors.
3. Place and group the following components: U1, U2, R12*, R13*, C1, C2.
*Note: Do not use ferrite beads in place of R12 and R13.
a.U1 and U2 are placed so that the right side of U1 faces the left side of U2.
b.C1 and C2 are placed directly between U1 and U2.
c.Keep R12 and R13 close to U1.
d.Place U1, U2, C1, and C2 so that the minimum creepage distance for the target application is met.
e.Place C1 and C2 so that traces connected to U2 pin 5 (C1B) and U2 pin 6 (C2B) are physically separated
from traces connected to:
i.C8, R15, FB1
ii.C9, R16, FB2
iii.U2 pin 8, R7
iv.U2 pin 9, R9
4. Place and group the following components around U2: C4, R9, C7, R2, C5, C6, R7, R8. These components
should form the critical “inner circle” of components around U2.
a.Place C4 close to U2 pin 3. This is best achieved by placing C4 northwest of U2.
b.Place R9 close to U2 pin 4. This is best achieved by placing R9 horizontally, directly to the north of U2.
c.Place C7 close to U2 pin 15. This is best achieved by placing C7 next to R9.
d.Place R2 next to U2 pin 16. This is best achieved by placing R2 northeast of U2.
e.Place C6 close to U2 pin 10. This is best achieved by placing C6 southeast of U2.
f.Place R7 and R8 close to U2. This is best achieved by placing these components to the south of U2.
g.Place C5 close to U2 pin 7. This is best achieved by placing C5 southwest of U2.
5. Place Q5 next to R2 so that the base of Q5 can be connected to R2 directly.
6. Place Q4 so that the base of Q4 can be routed to pin 13 of U2 easily and the emitter of Q4 can be routed to U2
pin 12 easily. Route these two traces next to each other so that the loop area formed by these two traces is
minimized.
7. Place and group the following components around the RJ11 jack: FB1, FB2, RV1, R15, R16, C8, and C9.
a.Use 20-mil-wide traces on this grouping to minimize impedance.
b.Place C8 and C9 close to the RJ11 jack, recognizing that a GND trace will be routed between C8 and C9
back to the Si24xx GND pin through a 20-mil-wide trace. The GND trace from C8 and C9 must be isolated
from the rest of the Si3018/10 traces.
c.The trace from C8 to GND and the trace from C9 to GND must be short and of equal lengths.
Rev. 1.3
49
AN93
8. After the previous step, there should be some space between the grouping around U2 and the grouping of
components around the RJ11 jack. Place the rest of the components in this area, given the following guidelines:
a.Space U2, Q4, Q5, R1, R3, R4, R10 and R11 away from each other for best thermal performance.
b.The tightest layout can be achieved by grouping R6, C10, Q2, R3, R5, and Q1.
c.Place C3 next to D1.
d.Make the size of the Q1, Q3, Q4, and Q5 collector pads each sufficiently large for the transistor to safely
dissipate 0.5 W under worst case conditions. See the transistor data sheet for thermal resistance and
maximum operating temperature information. Implement collector pads on both the component and solder
side, and use vias between them to improve heat transfer for best performance. When ambient conditions
are a moderate 50 deg or less, use 0.05 square inches of copper at the collectors of Q1, Q3, Q4, Q5. Both
sides of the PCB can be used to double the available area.
9. U2, IGND, is the return path for many of the discrete components and requires special mention:
a.Traces associated with IGND should be 20 mils wide.
b.U2's IGND should not be a large ground plane and should only occupy the space under U2. Beyond this
area, use traces and avoid getting close to the components on the other side of the diode bridge.
c.C5, C6, C7 IGND return path should be direct.
10.The traces from R7 to FB1 and from R8 to FB2 should be well matched. This can be achieved by routing these
traces next to each other as much as possible. Ensure that these traces are not routed close to the traces
connected to C1 or C2.
11. Minimize all traces associated with Y1, C40, and C41.
12.Decoupling capacitors (0.22 µF and 0.1 µF capacitors connected to VDA, VDB, VDD) must be placed next to
those pins. Traces of these decoupling capacitors back to the Si24xx GND pin should be direct and short.
Figure 20. Reference Placement
50
Rev. 1.3
AN93
11
C27
C26
Y1
1
2
11
11
1
8D
U1 Si24HS
1
2
C50
5
6
7
12
3A
XTALI
XTALO
C52
VDD3.3
VDD3.3 GND
GND
VDDB
VDDA
C51
21
20
19
4B
C53
12
2
R12*
12
C1A
C1B
4C
12
C1
4A
3B
+
C4
14
13
3C
3E
C2
*Note: Do NOT use ferrite
beads in place of R12 and
R13.
2
4D
8D
R2
QE
DCT
RX
IB
C1B
C2B
VREG
RNG1
3E
C5
DCT2
IGND
DCT3
QB
QE2
SC
VREG2
RNG2
9B
R7
4G
Q5
9C
R9
3A
1
2
3
4
5
6
7
8
R13*
5
C7
U2
4F
Traces, pad sites and vias
enclosed in box are in the DAA
section, and must be separated
from all other circuits by 5 mm.
16
15
14
13
12
11
10
9
3E
Si3018
C6
4E
R8
4F
9C
9C
9A
Q4
6
C3
3E
8C
RING
D1
10
-
3E
FB2
R16
+
7A
RV1
10
TIP
FB1
R15
C9
7B 7C
7B
C8
7C 7B
2
2
Note: Encircled references are described in the numbered paragraphs in Appendix A.
This is not a complete schematic. Only critical component placement and nets are drawn.
Figure 21. Illustrated Layout Guidelines
4.4.1. ISOmodem Layout Check List
Table 34 is a checklist that the designer can use during the layout process to ensure that all the recommendations
in this application note have been implemented. Additionally, Figure 21 provides an annotated diagram of all
relevant layout guidelines for the SI3054 CNR/AMR/ACR applications. See "10.4.2. Safety" on page 254 for
information about design for safety compliance.
Table 34. Layout Checklist
P
#
Layout Items
1
U1 and U2 are placed so that pins 9–16 of U1 are facing pins 1–8 of U2. C1 and C2
are placed directly between U1 and U2.
2
Place U1, U2, C1, and C2 so that the recommended minimum creepage spacing for
the target application is implemented. R12 and R13 should be close to U1.
3
C1 and C2 should be placed directly between U1 and U2. Short, direct traces should
be used to connect C1 and C2 to U1 and U2. These traces should not be longer than
two inches and should be minimized in length. Place C2 such that its accompanying
trace to the C2B pin (pin 6) on the Si3018 is not close to the trace from R7 to the
RNG1 pin on the Si3018 (pin 8).
4
Place R7 and R8 as close as possible to the RNG1 and RNG2 pins (pins 8 and 9),
ensuring a minimum trace length from the RNG1 or RNG2 pin to the R7 or R8 resistor.
In order to space the R7 component further from the trace from C2 to the C2B pin, it is
acceptable to orient it 90 degrees relative to the RNG1 pin (pin 8).
Rev. 1.3
Required
51
AN93
Table 34. Layout Checklist (Continued)
P
52
#
Layout Items
5
The area of the loop from C50 to U1 pin 4 and from C51 to pin 13 back to pin 12
(DGND) should be minimized. The return traces to U2 pin 12 (DGND) should be on
the component side.
6
The loop formed by XTALI, Y1, and XTALO should be minimized and routed on one
layer. The loop formed by Y1, C40, and C41 should be minimized and routed on one
layer.
7
The digital ground plane is made as small as possible, and the ground plane has
rounded corners.
8
Series resistors on clock signals are placed near source.
9
Use a minimum of 15-mil-wide traces in DAA section, use a minimum of 20-mil-wide
traces for IGND.
10
C3 should be placed across the diode bridge, and the area of the loop formed from
Si3018 pin 11 through C3 to the diode bridge and back to Si3018 pin 15 should be
minimized.
11
FB1, FB2, and RV1 should be placed as close as possible to the RJ11.
12
C8 and C9 should be placed so that there is a minimal distance between the nodes
where they connect to digital ground.
13
Use at least a 20-mil-wide trace from RJ11 to FB1, FB2, RV1, C8, and C9.
14
The routing from Tip and Ring of the RJ11 to the ferrite beads should be wellmatched.
15
The traces from the RJ11 through R7 and R8 to U2 Pin 8 and Pin 9 should be well
matched. These traces may be up to 10 cm long.
16
The distance from Tip and Ring through EMC capacitors C8 and C9 to digital ground
must be short.
17
There should be no digital ground plane in the DAA Section.
18
Minimize the area of the loop from U2 pin 7 and pin 10 to C5 and C6 and from those
components to U2 pin 15 (IGND).
19
R2 should be placed next to the base of Q5, and the trace from R2 to U2 pin16 should
be less than 20 mm.
20
Place C4 close to U2 and connect C4 to U2 using a short, direct trace.
21
The area of the loop formed from U2 pin 13 to the base of Q4 and from U2 pin 12 to
the emitter of Q4 should be minimized.
22
The trace from C7 to U2 pin 15 should be short and direct.
23
The trace from C3 to the D1/D2 node should be short and direct.
24
Provide a minimum of 5 mm creepage (or use the capacitor terminal plating spacing
as a guideline for small form factor applications) from any TNV component, pad or
trace, to any SELV component, pad or trace.
Rev. 1.3
Required
AN93
Table 34. Layout Checklist (Continued)
P
#
Layout Items
25
Minimize the area of the loop formed from U2 pin 4 to R9 to U2 pin 15.
26
Cathode marking for Z1.
27
Pin 1 marking for U1 and U2.
28
Space and mounting holes to accommodate for fire enclosure if necessary.
29
IGND does not extend under C3, D1, FB1, FB2, R15, R16, C8, C9, or RV1.
30
Size Q1, Q3, Q4, and Q5 collector pads to safely dissipate 0.5 W (see text).
31
Submit layout to Silicon Laboratories for review.
Required
4.4.2. Module Design and Application Considerations
Modem modules are more susceptible to radiated fields and ESD discharges than modems routed directly on the
motherboard because the module ground plane is discontinuous and elevated from the motherboard’s ground
plane. This separation also creates the possibility of loops that couple interfering signals to the modem. Moreover,
a poor motherboard layout can degrade the ESD and EMI performance of a well-designed module.
4.4.2.1. Module Design
Particular attention should be paid to power-supply bypassing and reset-line filtering when designing a modem
module. Trace routing is normally very short on modules since they are generally designed to be as small as
possible. Care should be taken to use ground and power planes in the low-voltage circuitry whenever possible and
to minimize the number of vias in the ground and power traces. Ground and power should each be connected to
the motherboard through only one pin so as not to create loops. Bypassing and filtering components should be
placed as close to the modem chip as possible with the shortest possible traces to a solid ground. It is
recommended that a pi filter be placed in series with the module VCC pin with a filter such as the one shown in
Figure 22 on the reset line. This filter also provides a proper power-on reset to the modem. Careful module design
is critical since the module designer often has little control over the motherboard design and the environment in
which the module will be used.
4.4.2.2. Motherboard Design
Motherboard design is critical to proper modem module performance and immunity to EMI and ESD events. First
and foremost, good design and layout practices must be followed. Use ground and power planes whenever
possible. Keep all traces short and direct. Use ground fill on the top and bottom layers. Use adequate power supply
bypassing, and use special precautions with the power and reset lines to the modem module. Bypass VCC right at
the modem module connector. Be sure the modem module is connected to VCC through a single pin. Likewise, be
sure ground is connected to the modem module through one pin connected to the motherboard ground plane. The
modem reset line is sensitive and must be kept very short and routed well away from any circuitry or components
that could be subjected to an ESD event. Finally, mount the modem module as close to the motherboard as
possible. Avoid high-profile sockets that increase the separation between the modem module and the
motherboard.
Rev. 1.3
53
AN93
Murata BLM 18A
G601 SN1
Motherboard
Connector
To Modem Chip VCC
(Si24xx Pins 5, 21)
VCC
1.0 F
0.1 F
0.1 F
1.0 F
10 k
To RESET
(Si24xx Pin 12)
2.2 F
GND
GND
RESET
Figure 22. Modem Module VCC and RESET Filter
4.5. Analog Output
The call progress tone provided by AOUT and discussed in this section comes from a PWM output pin on the
ISOmodem. AOUT is a 50% duty cycle, 32 kHz square wave, pulse-width modulated (PWM) by voice band audio,
such as call progress tones.
The PWM signal should be processed by a high-pass filter (R2, R3, R4, C2,C3 and C4), and, with the aid of a
bridge mode amplifier, provides low-cost 100 mW to 250 mW power with a 3 to 5 V supply. See the circuit in
Figure 23. A slightly more expensive amplifier (LM4862) is available and, while still pin-compatible, provides twice
as much power.
Figure 23. PWM Audio Processing and Amplifying Circuit
4.5.1. Interaction between the AOUT Circuit and the Required Modem Reset Time
When modifying the circuit shown in Figure 23, it is important to examine the reset timing and know that when
external reset is applied to the modem, the AOUT pin still has time to rise to VCC due to the pullup installed on it.
One has to assume that the modem has been operating prior to reset and has put AOUT into a PWM state that is
100% low.
This is important because the AOUT pin, which is shared with INT in some packages, is read by the strapping
option logic in the modem at the end of the reset time to set the operational mode as shown in "2.1.3. Reset-Strap
Options for 16-Pin SOIC Package" and "2.1.4. Reset-Strap Options for 24-Pin TSSOP Package" on page 13 and
"2.1.5. Reset Strapping Options for QFN Parts" on page 15.
The value of the capacitors and resistors in the above circuit thus has an effect on the minimum required
ISOmodem reset time.
54
Rev. 1.3
AN93
4.5.2. Audio Quality
The mulipole filter illustrated in this diagram is designed to shape the response for a pleasant sound and remove
interference, but note that, when PWM is demodulated in this way, it carries all the audio spectrum noise that is
present in the power supply of the modem minus 6 dB. This requires VCC to be as clean as one wants the call
progress audio to be. An alternative is for the AOUT signal to be buffered to a clean supply domain using a logic
gate or transistor buffer.
The 3-pole low-pass filter, with a 3 dB point at approximately 2 kHz, filters the 32 kHz square wave from AOUT and
allows only audio signals below 2 kHz to pass. See Figure 24 below. The amplifier provides differential speaker
drive, eliminating the need for a large coupling capacitor. Some additional design work and optimization must be
done to select the optimum gain and frequency response of this circuit, depending on speaker efficiency, final
product enclosure, and performance requirements. A two- or even one-pole filter may be adequate in some
applications.
Keep this audio circuitry well away from digital signals and use generous ground fill in the PCB layout.
Figure 24. Audio Filter Response
Rev. 1.3
55
AN93
5. Modem Reference Guide
This section provides information about the architecture of the modem, its functional blocks, its registers, and their
interactions. The AT command set is presented, and options are explained. The accessible memory locations (S
registers and U registers) are described. Instructions for writing to and reading from them are discussed along with
any limitations or special considerations. A large number of configuration and programming examples are offered
as illustrations of actual testable applications. These examples can be used alone or in combination to create the
desired modem operation. The use of S registers and U registers to control the operation, features, and
configuration of the modem is documented.
The Si24xx ISOmodem chipset family is controller-based. No modem driver is required to run on the system
processor. This makes the Si24xx ISOmodem family ideal for embedded systems because a wide variety of
processors and operating systems can interface with the ISOmodem through a simple UART driver.
The modems in this family operate at maximum connect rates of 48 kbps upstream/V.92 (Si2494/93), 56 kbps
downstream/V.90 (Si2457), 33.6 kbps/V.34 (Si2439/34), 14.4 kbps/V.32b (Si2415), and 2400 bps/ V.22b (Si2404)
with support for all standard ITU-T fallback modes. These chipsets can be programmed to comply with FCC, JATE,
ETSI ES 203 021 and other country-specific PTT requirements. They also support V.42 and MNP2–4 error
correction and V.42b and MNP5 compression. “Fast connect” and “transparent HDLC” modes are also supported.
The basic ISOmodem functional blocks are shown in Figure 1 on page 1. The ISOmodem includes a controller,
data pump (DSP), ROM, RAM, an oscillator, phase-locked loop (PLL), timer, UART interface, a parallel interface
option, an SPI interface option, and a DAA interface. An optional voice mode is supported through an SSI interface
and an external Si3000 voice codec. The modem software is permanently stored in the on-chip ROM. Only modem
setup information (other than defaults) and other software updates need to be stored on the host or optional
external EEPROM and downloaded to the on-chip RAM during initialization. There is no nonvolatile on-chip
memory other than program ROM.
The following memory notation conventions are followed in this document:

Single-variable U registers are identified in this document as the register type (i.e., U) followed by the register’s
hexadecimal address and finally the register identifier in parenthesis, e.g. U4A (RGFD). Once the full register
reference is made, continuing discussion refers to the register name to simplify the text. The address and value
of a single variable U register are always read from or written to the ISOmodem in hexadecimal.
 Bit-mapped U registers are identified in this document at the top level as the register type (i.e., U) followed by
the register’s hexadecimal address and finally the register identifier in parenthesis, e.g. U67 (ITC1). Once the
full register reference is made, continuing discussion of the register at the top level refers to the register name
to simplify the text. The address and value of a bit-mapped U register is always read from or written to the
ISOmodem in hexadecimal.
 Bits within bit-mapped registers are identified in this document as the register type (i.e., U) followed by the
register’s hexadecimal address, the bit or bit range within the register in brackets, and finally the bit or bit range
identifier in parenthesis. Example: U67 [6] (OHS) or U67 [3:2] (] (DCT). Once the full register reference is made,
continuing discussion of the bits or bit range refers to the bit or bit range name to simplify the text. The bit or bit
range inside the bracket represents the actual bit or bit range within the register. The value of a bit or bit range
is presented in binary for clarity. However, the address and value of a bit-mapped U register is always read from
or written to the ISOmodem in hexadecimal.
 ISOmodem S registers are identified with a decimal address (e.g., S38), and the number stored in an S register
is also a decimal value.
5.1. Controller
The controller provides several vital functions, including AT command parsing, DAA control, connect sequence
control, DCE (data communication equipment) protocol control, intrusion detection, parallel phone off-hook
detection, escape control, Caller ID control and formatting, ring detection, DTMF (dual tone multi-frequency)
control, call progress monitoring, error correction, and data compression. The controller also writes to the control
registers that configure the modem. Virtually all interaction between the host and the modem is done via the
controller. The controller uses AT (ATtention) commands, S registers, and U registers to configure and control the
modem.
56
Rev. 1.3
AN93
5.2. DSP
The DSP (data pump) is primarily responsible for modulation, demodulation, equalization, and echo cancellation.
Because the ISOmodem is controller-based, all interaction with the DSP is via the controller through AT
commands, S registers, and/or U registers.
5.3. Memory
The user-accessible memory in the ISOmodem includes the S registers, accessed via the ATSn command, and the
U registers, accessed via the AT:Rhh and AT:Uhh commands. These memory locations allow the modem to be
configured for a wide variety of functions and applications and for global operation.
5.4. AT Command Set
AT commands begin with the letters AT, end with a carriage return, and are case-insensitive. However, case cannot
be mixed in a single command. The only exception to this format is the A/ command. This command is neither
preceded by AT nor followed by a carriage return but re-executes the previous command immediately when the “/”
character is typed. Generally, AT commands can be divided into two groups: control commands and configuration
commands. Control commands, such as ATD, cause the modem to perform an action (in this case, dialing). The
value of this type of command is changed at a particular time to perform a particular action. For example, the
command ATDT1234<CR> causes the modem to go off-hook and dial the number 1234 via DTMF. No change is
made to the modem settings during the execution of an action command. Configuration commands change
modem characteristics until they are modified or reversed by a subsequent configuration command or the modem
is reset. Modem configuration status can be determined with the use of ATY$, ATSn?, or AT:Rhh commands where
Y is a group of AT command arguments, n is an S-register number (decimal), and hh is the hexadecimal address of
a U register.
The AT commands for reading configuration status are listed in Table 35. Each command is followed by a carriage
return.
Table 35. Configuration Status
Command
Action
ATY$ settings
Displays status of a group of
settings.
AT$
Basic AT command settings.
AT&$
AT& command settings.
AT%$
AT% command settings.
AT\$
AT\ command settings.
ATSn?
Displays contents of S-register n
ATS$
Displays contents of all S registers
AT:Rhh
Displays contents of U-register hh
AT:R
AT+VCID?
Displays the current contents of all U registers.
Displays Caller ID setting.
The examples in Table 36 assume the modem is reset to its default condition. Each command is followed by a
carriage return.
Rev. 1.3
57
AN93
Table 36. Command Examples
Command
Result
Comment
AT$
E = 001
M = 000
Configuration status of basic
AT commands.
Q = 000
V = 001
X = 004
Y = 000
AT&$
&D = 001
&G = 017
Configuration of &AT
commands.
&H = 000
(Si2457)
&P = 000
ATS2?
043
S-register 2 value—Escape
code character (+).
AT:R2C
00A0
Value stored in register U2C.
The modem has a 48-character buffer, which makes it possible to enter multiple AT commands on a single line.
The multiple commands can be separated with spaces or linefeed characters to improve readability. AT, space and
linefeed characters are not loaded into the buffer and are not included in the 48-character count. The command
line must end with carriage return for the modem to begin executing it. The modem ignores command lines longer
than 48 characters and reports ERROR. Table 37 shows examples of multiple AT commands on a single line.
Table 37. Multiple AT Commands on a Single Line
Command
Result
ATS0=4M1X1<CR>
The modem auto-answers on the
fourth ring. The speaker is on during
dial and handshake only. Blind dialing is enabled.
AT S0=4 M1 X1 <CR>
Same as above (spaces do not matter).
ATS0=4<CR>
Same as above.
ATM1<CR>
ATX1<CR>
When concatenating commands on the same line, the following must also be taken in to account:





58
A semicolon is used to append to :U or :R commands. For example, AT:U42,0022;:R43;S6=4.
The command +IPR cannot be on the same line as a :U or :R command.
The commands *Y, :W, :P, +MS and +MR cannot be appended to. They must be the last command in a string.
The command AT+GCI=9 must be on a line of its own.
Consecutive U registers can be written in a single command as AT:Uhh,xxxx,yyyy,zzzz where hh is the first Uregister address in the three register consecutive series. This command writes a value of xxxx to Uhh, yyyy to
Uhh+1, and zzzz to Uhh+2. Additional consecutive values may be written up to the 48 character limit.
Rev. 1.3
AN93
Table 38. Consecutive U-Register Writes on a Single Line
Command
Result
AT:U00,0078,67EF,C4FA
0x0078 written to U00
0x67EF written to U01
0xC4FA written to U02
Caution: Some U-register addresses are reserved for internal use and hidden from the user. Consequently, there
are gaps in the addresses of available U registers. Writing to reserved registers can cause unpredictable results.
Care must therefore be taken not to write to reserved or undefined register locations. This is especially likely when
writing to consecutive U-register addresses: all addresses covered by a conscutive write operation must be defined
and allowed to the user.
The AT command execution time is as long as 300 ms. The host must wait for a response after each command
(e.g., OK) before issuing additional commands. The reset recovery time (the time between a hardware reset or the
carriage return of an ATZ command and the time the next AT command can be executed) must also be respected,
as described in "2.1.1. Reset Sequence" on page 11.
Characters must not be sent between the ATDT command and the protocol message. During this time, the modem
is in a transition between command and data modes. Any characters sent during this time will cause the
connection attempt to fail.
Blind dialing (dialing without waiting for dial tone) is enabled by ATX0, ATX1, and ATX3. Whether or not blind
dialing is enabled, use of the W dial modifier causes the modem to look for a dial tone before dialing the number
string after the W. For example, an AT command string, ATX1 DT 9, W123456<CR>, causes the modem to dial 9
immediately without detecting a dial tone but does not dial 123456 until a dial tone is detected. AT commands and
result codes are listed in Tables 39–43. The default settings are shown in bold.
Table 39. Basic AT Command Set
Command
Action
$
Display Basic AT command mode settings (see text for details).
Answer incoming call.
Re-execute last command (executes immediately, not preceded by
AT or followed by <CR>)
A
A/
Rev. 1.3
59
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
Dial
The dial command, which may be followed by one or more dial
command modifiers, dials a phone number:
Modifier
! or &
, or <
;
Dn
@
G
L
P
T
W
En
Local DTE echo.
E0
Disable.
E1
Enable.
Hn
Hook-switch.
H0
Go on-hook (hang up modem).
H1
Go off-hook.
In
Identification and checksum.
I0
Display Si24xx revision code.
A = Revision A.
B = Revision B, etc.
I1
Display Si24xx firmware revision code (numeric).
No Patch
60
AT Command
Chip Revision
ATI0
A
ATI1
A
ATI0
B
ATI1
B
ATI0
C
ATI1
C
ATI0
D
Rev. 1.3
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
ATI1
D
Revision B Patch (rb_pX_YYYY)
AT Command
Chip Revision
ATI0
B
ATI1
B
ATI0
C
ATI1
C
Revision C Patch (rc_pX_YYYY)
AT Command
Chip Revision
ATI0
B (not allowed)
ATI1
B (not allowed)
ATI0
C
ATI1
C
Command
Action
I3
Display line-side revision code.
18 (10)C = Si3018/10 Revision C.
I6
Display the ISOmodem model number.
2404 = Si2404
2415 = Si2415
2434 = Si2434
2457 = Si2457
2493 = Si2493
I7
Diagnostic Results 1.
Format
RX <rx_rate>,TX <tx_rate>
PROTOCOL: <protocol>
LOCAL NAK <rre>
REMOTE NAK <rte>
RETRN/RR <rn>
DISC REASON <dr>
I8
Diagnostic Results 2.
Format
RX LEVEL <rx_level>
TX LEVEL <tx_level>
EFFECTIVE S/N <esn>
RESIDUAL ECHO <re>
Rev. 1.3
61
AN93
Table 39. Basic AT Command Set (Continued)
Command
62
Action
Ln
Speaker Volume
L1
Low
L2
Medium
L3
High
L4
Very High
Mn
Speaker operation (via AOUT).
M0
Speaker is always off.
M1
Speaker is on while dialing and handshaking; off in data mode.
M2
Speaker is always on.
M3
Speaker is off while dialing; on during handshaking and retraining.
On
Return to data mode from command mode.
O0
Return to data mode.
O1
Return to data mode and perform a full retrain (at any speed
except 300 bps).
O2
Return to data mode and perform rate renegotiation.
Qn
Response mode.
Q0
Enable result codes (See Table 43.)
Q1
Disable result codes (enable quiet mode)
R
Initiate V.23 Reversal (U53 bit 15 must be set.)
Sn
S-register operations (see Table 45)
S$
List contents of all S registers.
Sn?
Display contents of S-register n.
Sn=x
Set S-register n to value x (n and x are decimal values).
Vn
Result code type (See Table 43)
V0
Numeric result codes.
Rev. 1.3
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
V1
Verbal result codes.
Xn
Call Progress Monitor (CPM)—This command controls which CPM
signals are monitored and reported to the host from the ISOmodem (See Table 43).
X0
Basic results; disable CPM—Blind dial (does not wait for dial tone).
CONNECT message does not include speed.
X1
Extended results; disable CPM—Blind dial. CONNECT message
includes speed.
X2
Extended results and detect dial tone only. X1 with dial tone detection.
X3
Extended results and detect busy only. X1 with busy tone detection.
X4
Extended results, full CPM. X1 with dial and busy tone detection.
X5
Extended results—Full CPM enabled including ringback detection.
X4 with ring back detection.
Yn
Long space disconnect—Modem hangs up after 1.5 seconds or
more of continuous space while on-line.
*Y0
Disable data memory access by disallowing :W and :Q Commands.
*Y1
Enable continuous DTMF tone (ATxY1D9 sends continuous “9”
tone).
*Y2
Enable continuous answer tone. To enable continuous answer
tone and answer, use ATxY2A.
*Y254
Enables Data Memory Access, i.e. allows :W and :Q commands.
Z
Hard reset—This command is functionally-equivalent to pulsing
the RESET pin low.
:E
Read from serial EEPROM. The format is AT:Ehhhh, where hhhh
is the EEPROM address in hexadecimal.
:I
Interrupt read—This command causes the ISOmodem to report
the lower eight bits of the interrupt register U70 (IO0). The CID,
OCD, PPD, and RI bits of this register are cleared, and the INT pin
(HIR1 INT flag in parallel or SPI mode) is deactivated on this read.
:LPhh
:M
Read Quick Connect data.
hh is a hexadecimal value. Data are read as follows:
:LP0
d1...d8
:LP8
d9...d16
:LP10
d17...d24
:LP18
d25...d32
Write to serial EEPROM. The format is AT:Mhhhh,xxxx, where
hhhh is the EEPROM address in hexadecimal and xxxx is the
EEPROM data in hexadecimal.
Rev. 1.3
63
AN93
Table 39. Basic AT Command Set (Continued)
64
Command
Action
:P
Program RAM write: this command is used to upload firmware
supplied by Silicon Labs to the ISOmodem. The format for this
command is AT:Phhhh,xxxx,yyyy,.... where hhhh is the first
address in hexadecimal, and xxxx,yyyy,.... is data in hexadecimal.
Only one :P command is allowed per AT command line. No other
command can be concatenated in the :P command line. This command is only for use with special files provided by Silicon Laboratories. Do not attempt to use this command for any other purpose.
Use &T6 to display checksum for patch verification.
:Q
:Qaaaa reads hexadecimal address aaaa. Returns hexadecimal
data value dddd. Only one command per line.
:R
U-register read—This command reads U-register values in hexadecimal.
The format is AT:Rhh, where
hh = A particular U-register address in hexadecimal.
The AT:R command displays all U-register values.
Only one :R command is allowed per AT command line.
:U
U-register write—This command writes to the 16-bit U registers.
The format is AT:Uhh,xxxx,yyyy,zzzz,..., where
hh = user-access address in hexadecimal.
xxxx = data in hexadecimal to be written to location hh.
yyyy = data in hexadecimal to be written to location (hh + 1).
zzzz = data in hexadecimal to be written to location (hh + 2).
etc.
Only one :U command is allowed per AT command line.
:W
:Waaaa,dddd writes hexadecimal data value dddd to hexadecimal
data address aaaa. Only one command per line.
Rev. 1.3
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
Special Access Mode—This command enables special modes and
data memory access.
Description
[sequence]
254:Waaaa,dddd
Write hexadecimal data value dddd to
hexadecimal data address
aaaa. Only one 254:W command per line.
254:Qaaaa
Read hexadecimal address aaaa. Returns
hexadecimal data value
dddd. Only one 254:Q command per line.
2
Enable continuous answer tone for the
ATA command. Use ATZ to clear this
*Y[sequence]
mode. For example, the single-line, multiple command is AT*Y2A.
1
Enable continuous DTMF tone for first digit
used in the ATD command. Use ATZ to
clear this mode. For example, the singleline, multiple command for a continuous
DTMF “1” digit would be AT*Y1D1.
0
Exit from 254:W or 254:Q access mode.
Must reside on a separate line and must
be the final sequence be sent after the
final 254:W or 254:Q command.
+DR=X
Data compression reporting.
Mode
X
0
Disabled
1
Enabled
If enabled, the intermediate result code is transmitted at the point
after error control negotiation. The format of this result code is as
follows:
Result code
Mode
+DR:NONE
Data compression is not in use
+DR:V42B
Rec. V.42bis is in use in both directions
+DR:V42B RD Rec. V.42bis is in use in receive direction only
+DR:V42B TD Rec. V.42bis is in use in transmit directions only
+DR:V44
Rec. V.44 is in use in both directions
+DR:V44 RD
Rec. V.44 is in use in receive direction only
+DR:V44 TD
Rec. V.44 is in use in transmit directions only
Rev. 1.3
65
AN93
Table 39. Basic AT Command Set (Continued)
Command
+DS=
A,B,C,D
Action
Controls V.42bis data compression function.
A
Direction
0
No compression (V.42bis P0 = 0)
1
Transmit only
2
Receive only
3
Both Directions (V.42bis P0 = 11)
B
Compression negotiation
0
Do not disconnect if Rec. V.42 is not negotiated.
1
Disconnect is Rec. V.42 is not negotiated.
C
Max_dict 512 to 65535
D
Max_string 6 to 250
Controls V.44 data compression function*
A
Direction
0
No compression (V.42bis P0 = 0)
1
Transmit only
2
Receive only
3
Both Directions (V.42bis P0 = 11)
B
Compression negotiation
0
Do not disconnect if Rec. V.42 is not negotiated
1
Disconnect is Rec. V.42 is not negotiated
+DS44 =
C
Capability
A,B,C,D,E,F,G,
0
Stream method
H,I
1
Packet method
2
Multi-packet method
D
Max_codewords_tx 256 to 65536
E
Max_codewords_rx 256 to 65536
F
Max_string_tx 32 to 255
G
Max_string_rx 32 to 255
H
Max_history_tx  512
I
Max_history_rx  512
*Note: Si2493 only
Enable synchronous access mode
A – specifies the mode of operation when initiating a modem
connection
D = Disable synchronous access mode
6 = Enable synchronous access mode when connection is
completed and data state is entered.
+ES = A, B, C
B – This parameter should not be used.
C – Specifies the mode of operation when answer a modem
connection
D = Disable synchronous access mode
8 = Enable synchronous access mode when connection is
completed and data state is entered.
66
Rev. 1.3
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
Synchronous access mode control options
A – Specifies action taken if an underrun condition occurs
during transparent sub-mode
0 = Modem transmits 8-bit SYN sequences (see
+ESA[G]) on idle.
B – Specifies action taken if an underrun condition occurs
after a flag during framed sub-mode
0 = Modem transmits 8-bit HDLC flags on idle.
C – Specifies action taken if an underrun or overrun condition
occurs after a non-flag during framed sub-mode
0 = Modem transmits abort on underrun in middle of
+ESA =
frame.
A,B,C,D,E,F,G
1 = Modem transmits flag on underrun in middle of frame
and notifies host of underrun or overrun.
D – Specifies V.34 half duplex operation. This parameter should
not be used.
E – Specifies CRC polynomial used while in framed sub-mode
0 = CRC generation checking disable
1 = 16-bit CRC generation and checking is performed by the
modem
F – Specifies NRZI encoding and decoding
0 = NRZI encoding and decoding disabled
G – Defines 8-bit SYN
255 = Fixed at 255 (marks)
Class 1 Mode Enable.
X
Mode
0
Off
+FCLASS = X
1
Enables support for V.29 Fast Connect mode.
8
Enables voice mode.
256
SMS mode
+FRM = X
Class 1 Receive Carrier.
X
Mode
2
Detect V.21 (980 Hz) tone for longer than 100 ms, then
send answer tone
(2100/2225 Hz) for 200 ms.
95
V.29 short synchronous.
96
V.29 full synchronous.
200
Returns to data mode prepared to receive an SMS message.
Rev. 1.3
67
AN93
Table 39. Basic AT Command Set (Continued)
68
Command
Action
+FTM = X
Class 1 Transmit Carrier.
X
Mode
2
Transmit V.21 (980 Hz) tone and detect (2100/2225 Hz).
Stop transmit 980 Hz when (2100/2225 Hz is detected.
53
Same as &T4, but transmit V.29 7200 bps. Data pattern
set by S40 register. AT + FCLASS = 0 must be sent to
restore the ISOmodem to normal operation after test.
54
Same as &T4, but transmit V.29 9600 bps. Data pattern
set by S40 register. AT + FCLASS = 0 must be sent to
restore the ISOmodem to normal operation after test.
95
V.29 short synchronous.
96
V.29 full synchronous.
201
Returns to data mode prepared to transmit an SMS protocol 1 message.
202
Returns to data mode prepared to transmit an SMS protocol 2 message.
Rev. 1.3
AN93
Table 39. Basic AT Command Set (Continued)
Command
+GCI = X
Action
Country settings: Automatically configure all registers for a particular country.
X
Country
9
Australia
A
Austria
F
Belgium
16
Brazil
1B
Bulgaria
20
Canada
26
China
27
Columbia
2E
Czech Republic
31
Denmark
35
Ecuador
3C
Finland
3D
France
42
Germany
46
Greece
50
Hong Kong
51
Hungary
53
India
57
Ireland
58
Israel
59
Italy
0
Japan
61
South Korea
69
Luxembourg
6C
Malaysia
73
Mexico
7B
Netherlands
7E
New Zealand
82
Norway
87
Paraguay
89
Philippines
8A
Poland
8B
Portugal
B8
Russia
9C
Singapore
9F
South Africa
A0
Spain
A5
Sweden
A6
Switzerland
FE
Taiwan
B4
United Kingdom
B5
United States (default)
Note: U registers are configured to Silicon Laboratories’ recommended
values. Changes may be made by writing individual registers after
sending the AT+GCI command. The +GCI command resets U
registers through U86 and S6 (in Japan) to default values before
setting country-specific values. Refer to the chart and setup tables
beginning with "6.2.2.1. Country Initialization Table" on page 134.
Rev. 1.3
69
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
+GCI?
List current country code setting (response is: + GCI:<setting>)
+GCI = ?
List all possible country code settings.
+IFC Options
+IFC = A
+IFC = A,B
Specifies the flow control to be implemented.
A
Specifies the flow control method used by the host to control
data from the modem
0 None
1 Local XON/OFF flow control. Does not pass XON/XOFF
character to the remote
modem.
2 Hardware flow control (RTS)
B
Specifies the flow control method used by the modem to control data from the host
0 None
1 Local XON/OFF flow control.
2 Hardware flow control (CTS).
Fixed DTE Rate.
<rate>
Description
0
Automatically detect the baud rate.
[BPS]
The decimal value of the rate in bits per second.
+IPR = <rate>
Note that the <rate> parameter represents the DTE rate in bps and
may be set to any of the following values: 300, 600, 1200, 2400,
4800, 7200, 9600, 12000, 14400, 19200, 38400, 57600, 115200,
230400, 245760, and 307200.
+ITF Options
+ITF = A
+ITF = A,B
+ITF = A,B,C
+MR=X
70
Transmit flow control threshold.
A
Threshold above which the modem will generate a flow off
signal
<0 to 511> bytes
B
Threshold below which the modem will generate a flow on
signal
<0 to 511> bytes
C
Polling interval for <EM><BNUM> indicator
0 to 300 in 10 msec units.
Modulation reporting control.
X
Mode
0
Disabled
1
Enabled
If enabled, the intermediate result code is transmitted at the point
during connect negotiation. The format of this result code is as follows:
+MCR: <carrier> e.g. +MCR: V32B
+MRR: <rate> e.g. +MRR: 14400
Rev. 1.3
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
+MS Options
+MS = A
+MS = A,B
+MS = A,B,C
+MS = A,B,C,
D
+MS = A,B,C,
D,E
+MS = A,B,C,
D,E,F
Modulation Selection.
A
Preferred modem carrier
V21
ITU-T V.21
V22
ITU-T V.22
V22B ITU-T V.22bis (default for Si2404)
V32
ITU-T V.32
V32B ITU-T V.32bis (default for Si2415)
V34
ITU-T V.34 (default for Si2434)
V90
ITU-T V.90 (default for Si2457)
V92
ITU-T V.92 (default for Si2493)
B
Automatic modulation negotiation
0
Disabled
1
Enabled (default)
C
Min Tx rate. Specifies minimum transmission rate.
0
Not configurable; always set to 0.
D
Max Tx rate. Specifies highest transmission rate. If not
specified, it is determined by the carrier and automode
settings.
V21 300
V32 9600
V90 33600
V22 1200
V32B 14400 V92 48000
V22B 2400
V34 33600
E
Min Rx rate. Specifies minimum receive rate.
0
Not configurable; always set to 0.
F
Max Rx rate. Specifies maximum receive rate. If not
specified (set to 0), it is determined by the carrier and
automode settings.
V21 300
V32 9600
V90 54666
V22 1200
V32B 14400 V92 54666
V22B 2400
V34 33600
+PCW = X
Controls the action to be taken upon detection of call waiting.
X
Mode
0
Toggle RI and collect type II Caller ID if enabled by +VCID.
1
Hang up.
2
Ignore call waiting.
+PIG=X
Controls the use of PCM upstream in a V.92 DCE.
X
Mode
0
Enable PCM upstream.
1
Disable PCM upstream.
+PMH=X
Controls the modem-on-hold procedures.
X
Mode
0
Enables V.92 MOH.
1
Disables V.92 MOH.
+PMHF=X
V.92 MOH hook flash. This command causes the DCE to go onhook and then return off-hook. If this command is initiated and the
modem is not On Hold, Error is returned.
Rev. 1.3
71
AN93
Table 39. Basic AT Command Set (Continued)
Command
72
Action
+PMHR=X
Initiate MOH. Requests the DCE to initiate or to confirm a MOH
procedure. Valid only if MOH is enabled.
Mode
X
0
V.92 MOH request denied or not available.
1
MOH with 10 s timeout granted.
2
MOH with 20 s timeout granted.
3
MOH with 30 s timeout granted.
4
MOH with 40 s timeout granted.
5
MOH with 1 min. timeout granted.
6
MOH with 2 min. timeout granted.
7
MOH with 3 min. timeout granted.
8
MOH with 4 min. timeout granted.
9
MOH with 6 min. timeout granted.
10 MOH with 8 min. timeout granted.
11 MOH with 12 min. timeout granted.
12 MOH with 16 min. timeout granted.
13 MOH with indefinite timeout granted.
14 MOH request denied. Future request will also be denied.
+PMHT=X
Controls access to MOH request and sets the timeout value.
X
Mode
0
Deny V.92 MOH request.
1
Grant MOH with 10 s timeout.
2
Grant MOH with 20 s timeout.
3
Grant MOH with 30 s timeout.
4
Grant MOH with 40 s timeout.
5
Grant MOH with 1 min. timeout.
6
Grant MOH with 2 min. timeout.
7
Grant MOH with 3 min. timeout.
8
Grant MOH with 4 min. timeout.
9
Grant MOH with 6 min. timeout.
10 Grant MOH with 8 min. timeout.
11 Grant MOH with 12 min. timeout.
12 Grant MOH with 16 min. timeout.
13 Grant MOH with indefinite timeout.
+PQC=X
V.92 Phase 1 and Phase 2 Control.
X
Mode
0
Enable Short Phase 1 and Short Phase 2.
1
Enable Short Phase 1.
2
Enable Short Phase 2.
3
Disable Short Phase 1 and Short Phase 2.
Rev. 1.3
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
+PSS=X
Selection of full or short startup procedures.
Mode
X
0
The DCEs decide to use short startup procedures.
1
Forces the use of short startup procedures on next and subsequent connections.
2
Forces the use of full startup procedures on next and subsequent connections.
+VCDT = n
Caller ID Type.
n Mode
0 = After ring only
1 = Always on
2 = UK with wetting pulse
3 = Japan
6 = DTMF
+VCID = n
Caller ID Enable.
n Mode
0 = Off
1 = Formatted Caller ID enabled.
2 = Raw data Caller ID enabled.
+VCIDR?
Type II Caller ID information—”+VCIDR:” will be followed by raw
Caller ID information including checksum. NO DATA will be displayed if no Type II data are available.
+VDR = n
Distinctive Ring.
Mode
n
0,x
Disable distinctive ring
1,0
Enable distinctive ring. The ISOmodem will report
DROF and DRON result codes only. DROF and
DRON are reported in 100 ms units.
1,x
Enable distinctive ring. The ISOmodem will report
DROF and DRON result codes as well as well as
a RING result code x/10 seconds after the falling
edge of a ring pulse. DROF and DRON are
reported in 100 ms units.
+VGR
Receive Gain Selection.
The <gain> parameter has a range of 112-134 with 128 being the
nominal value. This represents a range of -48 dB to 18 dB. The
default is 128 (0 dB). This command is used to control the receive
gain at the DTE from either the Si3000 Codec or the DAA. The
purpose is to adjust the DTE receive gain for the TAM voice stream
during idle state.
Rev. 1.3
73
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
+VGT
Transmit Gain Selection.
The <gain> parameter has a range of 112-134 with 128 being the
nominal value. This represents a range of -48 to 18 dB. The default
is 128 (0 dB). This command is used to control the transmit gain at
the DTE to either the Si3000 Codec or the DAA. The purpose is to
adjust the DTE transmit gain for the TAM voice stream during idle
state.
+VIP
Load Voice Factory Defaults.
+VIT
DTE/DCE Inactivity Timer.
The <timer> parameter has a range of 0–255 with units of seconds.
The default is 0 (disable).
+VLS = n
Analog Source / Destination Select.
n
Description
0
ISOmodem on-hook. AOUT disabled. Tone detectors disabled. Si3000 sample pass-through to
DAA is inactive.
1
ISOmodem off-hook. AOUT disabled. Tone detectors
disabled.
4
ISOmodem on-hook. AOUT connected to ISOmodem tone generators. Tone detectors disabled.
5
ISOmodem off-hook. AOUT connected to PSTN.
Tone detectors enabled.
15
ISOmodem goes off-hook, begins V.253 tone event
reporting and Si3000 to DAA sample pass-through
becomes active. Dial tone can be heard on handset.
20
ISOmodem on-hook. AOUT disabled. Tone detectors
enabled.
21
ISOmodem on-hook. AOUT connected to ISOmodem tone generators. Tone detectors enabled.
+VNH = <hook Automatic Hangup Control.
>
<hook>
Hook control description
0
The ISOmodem retains automatic hangups as
is normal in the other modes (such as hanging
up the phone when the ISOmodem does not
detect a data carrier with a given time interval).
1
2
74
The ISOmodem shall disable automatic hangups
in the other non-voice modes.
The ISOmodem shall disable all hang-ups in other
non-voice modes. The ISOmodem shall only perform a “logical” hangup (return the OK result
code).
Rev. 1.3
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
+VRA = n
Ringing Tone Goes Away Timer.
The ISOmodem only uses this command in call origination transactions. This command sets the amount of time in 0.1 second units
the ISOmodem shall wait between Ringing Tone before it can
assume that the remote modem has gone off-hook. Default time
is five seconds.
+VRID = n
Repeat Caller ID.
n
Description
0
Display Caller ID information of the last incoming
call in formatted form.
1
Display Caller ID information of the last incoming
call in unformatted form.
+VRN = n
Ringing Tone Never Appeared Timer.
This command sets the amount of time in seconds the ISOmodem
will wait looking for Ringing Tone. If the ISOmodem does not
detect Ringing Tone in this time period, the ISOmodem shall
assume that the remote station has gone off-hook and return an
OK result code. Default time is 0 seconds.
+VRX
Receive Voice Stream.
Enable DTE receive of voice stream. The DCE will return a CONNECT response followed by the voice stream as defined by the
+VSM command. The DTE can issue a <DLE><!> or
<DLE><ESC> sequence to terminate the receive stream. The
DCE will return a <DLE><ETX> followed by an OK response for
<DLE><!> and <DLE><ESC> followed by an OK response for
<DLE><ESC>. The DCE can be configured to terminate the
stream using the DTE/DCE Inactivity Timer, which is configured
using the +VIT command. The DTE will need to process any
<DLE> shielded events present in the data stream. Any
<DLE><DLE> sequences can be preserved to allow less overhead
during playback of the stream with the +VTX command.
+VSD =
<sds>, <sdi>
Silence Detection.
<sds>
Noise level sensitivity
127
Less aggressive [more sensitive, lower noise levels considered to be silence].
128
Nominal level of sensitivity.
129
More aggressive [less sensitive, higher noise levels considered to be silence].
<sdi> sets the length of a time interval in 0.1 second units, which
must contain no or little activity, before the ISOmodem will report
(QUIET) (<DLE><q>). Default is five seconds.
Rev. 1.3
75
AN93
Table 39. Basic AT Command Set (Continued)
Command
Action
+VSM = n
Voice Compression Method.
0 Signed PCM
1 Unsigned PCM
4 G.711 µ-Law
5 G.711 A-Law
129 ADPCM 2-bit (2 kB/s storage)
131 ADPCM 4-bit (4 kB/s storage)
+VSP
Voice Speakerphone State
<mode> Description
0 Speakerphone AEC, AES and LEC disabled.
Handset FIR filter coefficients are selected.
1 Speakerphone AEC, AES and LEC enabled.
Speakerphone FIR filter coefficients are selected.
The +VLS=13 command must be used in combination with this
setting.
+VTD = n
DTMF / Tone Duration Timer.
This command sets the default DTMF / tone generation duration in
10 ms units for the +VTS command. Default time is 1 second
(n = 100).
+VTS = [<freq DTMF and Tone Generation.
1>, <freq2>,
This command can be used to produce DTMF tones, single-fre<dur>]
quency tones, and double-frequency tones. Note that the bracket
characters are required for correct operation.
<freq1>
Frequency one, which has a range of 0, 2003200 Hz.
<freq2>
Frequency two, which has a range of 0, 2003200 Hz.
<dur>
Duration of the tone(s) in 10 ms units.
+VTX
76
Transmit Voice Samples.
Used for sending digitized voice samples from host memory
through the UART interface. The +VSM command determines the
format of the samples. Multiple routing options are available.
Rev. 1.3
AN93
5.5. Extended AT Commands
The extended AT commands, described in Tables 40–42, are supported by the ISOmodem.
Table 40. Extended AT& Command Set
Command
&$
Action
Display AT& current settings (see text for details).
&Dn
Escape pin function (similar to DTR)
&D0
Escape pin is not used.
&D1
Escape pin escapes to command mode from data mode. The escape pin must be enabled by
setting bit HES (Enable Hardware Escape Pin, U70 bit 15).
&D2
Escape pin assertion during a modem connection causes the modem to go on-hook and return to
command mode. The escape pin must be enabled by setting bit HES (Enable Hardware Escape
Pin, U70 bit 15).
&D3
Escape pin assertion causes ATZ command (reset and return OK result code). The escape pin must
be enabled by setting bit HES (Enable Hardware Escape Pin, U70 bit 15).
&Gn
Line connection rate limit—This command sets an upper limit on the line speed that the ISOmodem
can connect. The &Hn commands may limit the line speed as well (&Gn not used for &H0 or &H1).
Not all modulations support rates given by &G. Improper settings are ignored.
&G3
1200 bps max.
&G4
2400 bps max.
&G5
4.8 kbps max.
&G6
7.2 kbps max.
&G7
9.6 kbps max.
&G8
12 kbps max.
&G9
14.4 kbps max (default for Si2415)
&G10
16.8 kbps max.
&G11
19.2 kbps max.
&G12
21.6 kbps max.
&G13
24 kbps max.
&G14
26.4 kbps max.
&G15
28.8 kbps max.
&G16
31.2 kbps max.
&G17
33.6 kbps max (default for Si2457 transmit and Si2434)
&Hn
Switched network handshake mode—&Hn commands must be on a separate command line from
ATD, ATA, or ATO commands.
&H0
V.90 with automatic fallback (56 kbps to 300 bps) (default for Si2457)
Notes:
1. The initial number attempted to test for an outside line is controlled by S51 (default = 1).
2. AT&$ reflects the last AT&P command issued but does not reflect any subsequent changes made by writing U registers
with AT:U.
Rev. 1.3
77
AN93
Table 40. Extended AT& Command Set (Continued)
&H1
V.90 only (56 kbps to 28 kbps)
&H2
V.34 with automatic fallback (33.6 kbps to 300 bps) (default for Si2434)
&H3
V.34 only (33.6 kbps to 2400 bps)
&H4
ITU-T V.32bis with automatic fallback (14.4 kbps to 300 bps) (default for Si2415)
&H5
ITU-T V.32bis only (14.4 kbps to 4800 bps)
&H6
ITU-T V.22bis only (2400 bps or 1200 bps) (default for Si2404)
&H7
ITU-T V.22 only (1200 bps)
&H8
Bell 212 only (1200 bps)
&H9
Bell 103 only (300 bps)
&H10
ITU-T V.21 only (300 bps)
&H11
V.23 (1200/75 bps)
&H12
V.92 with automatic fallback (default for Si2493)
&Pn
Japan pulse dialing*
&P0
Configure ISOmodem for 10 pulse-per-second pulse dialing
&P1
Configure ISOmodem for 20 pulse-per-second pulse dialing (Japan)
&Tn
Test mode.
&T2
Initiate ITU-T V.54 (ANALOOP) test. Modem mode set by &H. Test loop is through the DSP and
DAA interface section of the ISOmodem only. ISOmodem echoes data from TX pin (Hardware Interface Register 0 in parallel or SPI mode) back to RX pin (Hardware Interface Register 0 in parallel or
SPI mode). This test mode is typically used during board-level debug.
&T3
Initiate ITU-T V.54 (ANALOOP) test. Modem mode set by &H. Test loop is through the DSP (ISOmodem), DAA interface section (ISOmodem), ISOcap interface (Si3018/10), and analog hybrid circuit
(Si3018/10). ISOmodem echoes data from TX pin (Hardware Interface Register 0 in parallel or SPI
mode) back to RX pin (Register 0 in parallel or SPI mode). Phone line termination required as in
Figure 25. In order to test only the ISOcap link operation, the hybrid and AFE codec can be removed
from the test loop by setting U62 [1] (DL) = 1.
&T4
Initiate transmit as originating modem with automatic data generation. Modulation, data rate, and
symbol rate are set by &H, &G, and S41. Data pattern is set by the S40 register. Continues until the
ATH command is sent after an escape into command mode. Data are also demodulated as in
ANALOOP. The test can be ended by escaping and issuing the ATH command.
&T5
Initiate transmit as answering modem with automatic data generation. Modulation, data rate, and
symbol rate are set by &H, &G, and S41. Data pattern is set by the S40 register. Continues until the
ATH command is sent after an escape into command mode. Data are also demodulated as in
ANALOOP. The test can be ended by escaping and issuing the ATH command.
&T6
Compute checksum for firmware-upgradeable section of program memory. If no firmware upgrade
is installed, &T6 returns C:4474.
&Xn
Automatic determination of telephone line type.
&X0
Abort &x1 or &x2 command.
Notes:
1. The initial number attempted to test for an outside line is controlled by S51 (default = 1).
2. AT&$ reflects the last AT&P command issued but does not reflect any subsequent changes made by writing U registers
with AT:U.
78
Rev. 1.3
AN93
Table 40. Extended AT& Command Set (Continued)
&X1
Automatic determination of telephone line type.
Result code: WXYZn
W:
0 = line supports DTMF dialing.
1 = line is pulse dial only.
X:
0 = line supports 20 pps dialing.
1 = line supports 10 pps dialing only.
Y:
0 = extension network present (PBX).
1 = outside line (PSTN) connected directly.
Z:
0 = continuous dial tone.
1 = make-break dial tone.
n:
0–9 (number required for outside line if Y = 0).1
&X2
Same as &X1, but Y result (PBX) is not tested.
Y2A2
Produce a constant answer tone (ITU-T) and return to command mode. The answer tone continues
until the ATH command is received or the S7 timer expires.
&Z
Enter low-power wake-on-ring mode.
Notes:
1. The initial number attempted to test for an outside line is controlled by S51 (default = 1).
2. AT&$ reflects the last AT&P command issued but does not reflect any subsequent changes made by writing U registers
with AT:U.
TIP
+
600 
IL
Si3018 V TR
10 µF
RING
–
Figure 25. Phone Line Termination Circuit
Rev. 1.3
79
AN93
Table 41. Extended AT% Command Set
Command
Action
%$
Display AT% command settings (see text for details).
%B
Report blacklist. See also S42 register.
%Cn
Data compression.
%C0
Disable V.42bis and MNP5 data compression.
%C1
Enable V.42bis in transmit and receive paths.
If MNP is selected (\N2), %C1 enables MNP5 in transmit and receive paths.
%C2
Enable V.42bis in transmit path only.
%C3
Enable V.42bis in receive path only.
%On
Answer mode.
%O1
ISOmodem answers a call in answer mode.
%O2
ISOmodem answers a call in originate mode.
%Vn
Automatic Line Status Detection.
After the %V1 and %V2 commands are issued, the ISOmodem automatically checks the telephone
connection for whether a line is present. If a line is present, the ISOmodem automatically checks if
the line is already in use. Finally, the ISOmodem checks line status both before going off-hook and
again before dialing. %V1 uses the fixed method, and %V2 uses the adaptive method. %V0
(default) disables this feature.
%V0
Disable automatic line-in-use detection.
Automatic Line Status Detection - Fixed Method.
Description: Before going off-hook with the ATD, ATO, or ATA commands, the ISOmodem compares
the line voltage (via LVCS) to registers NOLN (U83) and LIUS (U84):
%V1
Loop Voltage
0  LVCS  NOLN
NOLN  LVCS  LIUS
LIUS  LCVS
Action
Report NO LINE and remain on-hook.
Report LINE IN USE and remain on-hook.
Go off-hook and establish a modem connection.
Once the call has begun, the off-hook intrusion algorithm (described in "6.6.2. Off-Hook Condition"
on page 162) operates normally. In addition, the ISOmodem reports NO LINE if the line is completely disconnected. If the HOI bit (U77, bit 11) is set, LINE IN USE is reported upon intrusion.
80
Rev. 1.3
AN93
Table 41. Extended AT% Command Set (Continued)
%V2
Automatic Line Status Detection - Adaptive Method.
Description: Before going off-hook with the ATD, ATO, or ATA commands, the ISOmodem compares
the line voltage (via LVCS) to the NLIU (U85) register:
Loop Voltage
Action
0  LVCS  (0.0625 x NLIU)
Report NO LINE and remain on-hook.
(0.0625 x NLIU) < LVCS  (0.85 x NLIU) Report LINE IN USE and remain on-hook.
(0.85 x NLIU) < LCVS
Go off-hook and establish a modem connection.
The NLIU register is updated every 1 ms with the minimum non-zero value of LVCS in the last
30 ms. This allows the ISOmodem to eliminate errors due to 50/60 Hz interference and also adapt
to relatively slow changes in the on-hook dc reference value on the telephone line. This algorithm
does not allow any non-zero values for NLIU below 0x0007. The host may also initialize NLIU prior
to issuing the %V2 command. Once the call has begun, the off-hook intrusion algorithm (described
in "6.6.2. Off-Hook Condition" on page 162) operates normally. In addition, the ISOmodem reports
NO LINE if the telephone line is completely disconnected. If the HOI (U77, bit 11) bit is set, LINE IN
USE is reported upon intrusion.
Table 42. Extended AT\ Command Set
Command
\$
Action
Display AT\ command settings (see text for details).
\Bn
Character length is automatically set in autobaud mode.
\B0
Reserved
\B1
7N1—Seven data bits, no parity, one stop bit, one start bit, nine bits total (\N0 only)
\B2
7P1—Seven data bits, parity optioned by \P, one stop bit, one start bit, ten bits total
\B3
8N1—Eight data bits, no parity, one stop bit, one start bit, 10 bits total (default)
\B5
8P1—Eight data bits, parity optioned by \P, one stop bit, one start bit, 11 bits total (\N0 only) This
mode is not allowed with a parallel or SPI interface.
\B6
8X1—Eight data bits, one escape bit, one stop bit, one start bit, 11 bits total (enables ninth-bit
escape mode) This mode is not allowed with a parallel or SPI interface.
\Nn
Asynchronous protocol.
\N0
Wire mode (no error correction, no compression).
Notes:
1. When in autobaud mode, \B0, \B1, and \P1 is not detected automatically. The combination of \B2 and \P3 is detected.
This is compatible with seven data bits, no parity, two stop bits. Seven data bits, no parity, one stop bit may be forced by
sending AT\T17\B1.
2. After changing the baud rate, the result code OK is sent at the old DTE rate. Subsequent commands must be sent at
the new rate. If the ISOmodem is configured in autobaud mode, AT commands \T0 through \T15 lock the new baud rate
and disable autobaud. To eliminate any possibility of a race condition between the receipt of the result code and the
changing of the UART speed, CTS is de-asserted while the result code is being sent until after the rate has been
successfully changed. The host should send the \T command and wait for the OK response. After OK has been
received, the host may send data at the new rate as soon as CTS is asserted. The \T command should be the last
command sent in a multi-command line and may not be used on the same command line as :U or :R commands. If it is
not, the OK from the \T command is sent at the old DTE rate, and other result codes are sent at the new DTE rate.
3. The autobaud feature does not detect this rate.
4. Default is \T16 if autobaud is selected by reset-strap option; otherwise default is \T9 (19.2 kbps).
Rev. 1.3
81
AN93
Table 42. Extended AT\ Command Set (Continued)
Command
Action
\N2
MNP reliable mode. The ISOmodem attempts to connect with the MNP protocol. If unsuccessful, the
call is dropped. Compression is controlled by %Cn.
\N3
V.42 auto-reliable—The ISOmodem attempts to connect with the V.42 protocol. If unsuccessful, the MNP protocol is attempted. If unsuccessful, wire mode is attempted. Compression is
controlled by %Cn.
\N4
V.42 (LAPM) reliable mode (or drop call)—Same as \N3 except that the ISOmodem drops the call
instead of connecting in MNP or wire mode. Compression is controlled by %Cn.
\N5
V.42 and MNP reliable mode - The ISOmodem attempts to connect with V.42. If unsuccessful, MNP
is attempted. If MNP is unsuccessful, the call is dropped. Wiremode is not attempted. Compression
is controlled by %Cn.
\Pn
Parity type is automatically set in autobaud mode.
\P0
Even
\P1
Space1
\P2
Odd
\P3
Mark.
\Qn
Modem-to-DTE flow control.
\Q0
Disable all flow control—This may only be used if the DTE speed and the line (DCE) speed are guaranteed to match throughout the call.
\Q2
Use CTS only.
\Q3
Use RTS/CTS.
\Q4
Enable XON/XOFF flow control for modem-to-DTE interface. Does not enable modem-to-modem
flow control.
\Tn
DTE rate2
\T0
300 bps
\T1
600 bps
\T2
1200 bps
Notes:
1. When in autobaud mode, \B0, \B1, and \P1 is not detected automatically. The combination of \B2 and \P3 is detected.
This is compatible with seven data bits, no parity, two stop bits. Seven data bits, no parity, one stop bit may be forced by
sending AT\T17\B1.
2. After changing the baud rate, the result code OK is sent at the old DTE rate. Subsequent commands must be sent at
the new rate. If the ISOmodem is configured in autobaud mode, AT commands \T0 through \T15 lock the new baud rate
and disable autobaud. To eliminate any possibility of a race condition between the receipt of the result code and the
changing of the UART speed, CTS is de-asserted while the result code is being sent until after the rate has been
successfully changed. The host should send the \T command and wait for the OK response. After OK has been
received, the host may send data at the new rate as soon as CTS is asserted. The \T command should be the last
command sent in a multi-command line and may not be used on the same command line as :U or :R commands. If it is
not, the OK from the \T command is sent at the old DTE rate, and other result codes are sent at the new DTE rate.
3. The autobaud feature does not detect this rate.
4. Default is \T16 if autobaud is selected by reset-strap option; otherwise default is \T9 (19.2 kbps).
82
Rev. 1.3
AN93
Table 42. Extended AT\ Command Set (Continued)
Command
Action
\T3
2400 bps
\T4
4800 bps
\T5
7200 bps
\T6
9600 bps
\T7
12.0 kbps3
\T8
14.4 kbps.
\T9
19.2 kbps4
\T10
38.4 kbps
\T11
57.6 kbps
\T12
115.2 kbps
\T13
230.4 kbps
\T14
245.760 kbps3
\T15
307.200 kbps
\T16
Autobaud On4
\T17
Autobaud Off. Lock at current baud rate.
In UART mode:
1. Causes a low pulse (25 ms) on RI and DCD
\U
2. Makes INT the inverse of ESC
3. Makes RTS the inverse of CTS
In parallel or SPI mode, causes a low pulse (25 ms) on INT.
This command terminates with RESET and does not generate an OK message.
\Vn
Connect message type.
\V0
Report connect and protocol message.
\V2
Report connect message only (exclude protocol message).
\V4
Report connect and protocol message with both upstream and downstream connect rates.
Notes:
1. When in autobaud mode, \B0, \B1, and \P1 is not detected automatically. The combination of \B2 and \P3 is detected.
This is compatible with seven data bits, no parity, two stop bits. Seven data bits, no parity, one stop bit may be forced by
sending AT\T17\B1.
2. After changing the baud rate, the result code OK is sent at the old DTE rate. Subsequent commands must be sent at
the new rate. If the ISOmodem is configured in autobaud mode, AT commands \T0 through \T15 lock the new baud rate
and disable autobaud. To eliminate any possibility of a race condition between the receipt of the result code and the
changing of the UART speed, CTS is de-asserted while the result code is being sent until after the rate has been
successfully changed. The host should send the \T command and wait for the OK response. After OK has been
received, the host may send data at the new rate as soon as CTS is asserted. The \T command should be the last
command sent in a multi-command line and may not be used on the same command line as :U or :R commands. If it is
not, the OK from the \T command is sent at the old DTE rate, and other result codes are sent at the new DTE rate.
3. The autobaud feature does not detect this rate.
4. Default is \T16 if autobaud is selected by reset-strap option; otherwise default is \T9 (19.2 kbps).
Rev. 1.3
83
AN93
The connect messages shown in Table 43 are sent when link negotiation is complete.
Table 43. Result Codes
Meaning
Numeric1
Verbal Response
X0
X1
X2
X3
X4
X5
0
Command was successful
OK
X
X
X
X
X
X
1
Link established at 300 bps
or higher
CONNECT
X
X
X
X
X
X
2
Incoming ring detected
RING
X
X
X
X
X
X
3
Link dropped
NO CARRIER
X
X
X
X
X
X
4
Command failed
ERROR
X
X
X
X
X
X
5
Link established at 1200
CONNECT 1200
X
X
X
X
X
6
Dial tone not present
NO DIALTONE
X
X
7
Line busy
BUSY
X
X
X
X
X
X
X
2
8
Remote not answering
NO ANSWER
9
Ringback detected
RINGING
10
Link established at 2400
CONNECT 2400
X
X
X
X
X
11
Link established at 4800
CONNECT 48003
X
X
X
X
X
12
Link established at 9600
3
CONNECT 9600
X
X
X
X
X
14
Link established at 19200
CONNECT 192004
X
X
X
X
X
X
X
X
X
X
X
X
X
X
3
15
Link established at 7200
CONNECT 7200
16
Link established at 12000
CONNECT 120003
X
X
X
X
X
17
Link established at 14400
3
CONNECT 14400
X
X
X
X
X
18
Link established at 16800
CONNECT 168004
X
X
X
X
X
19
Link established at 21600
4
CONNECT 21600
X
X
X
X
X
20
Link established at 24000
CONNECT 240004
X
X
X
X
X
21
Link established at 26400
4
CONNECT 26400
X
X
X
X
X
22
Link established at 28800
CONNECT 288004
X
X
X
X
X
23
Link established at 31200
4
CONNECT 31200
X
X
X
X
X
24
Link established at 33600
CONNECT 336004
X
X
X
X
X
30
Caller ID mark detected
CIDM
X
X
X
X
X
X
31
Hookswitch flash detected
FLASH
X
X
X
X
X
X
Notes:
1. Numeric mode: Result code <CR>.
2. Response for [email protected] is silence is not found.
3. This message is supported only on the Si2493, Si2457, Si2434, and Si2415.
4. This message is supported only on the Si2493, Si2457, and Si2434.
5. X is not preceded by <CR><LF>.
6. This message is supported only on the Si2493 and Si2457.
7. V.44 with data compression disabled (+DS = 0) emits this result code.
8. If data compression is disabled (+DS = Q), the modem returns the message PROTOCOL:V42.
84
Rev. 1.3
AN93
Table 43. Result Codes (Continued)
Numeric1
Meaning
Verbal Response
X0
X1
X2
X3
X4
X5
32
UK CID State Tone Alert
Signal detected
STAS
X
X
X
X
X
X
33
Overcurrent condition
X5
X
X
X
X
X
X
Blacklist is full
BLACKLIST FULL (enabled
via S42 register)
X
X
X
X
X
X
Attempted number is blacklisted.
BLACKLISTED (enabled via
S42 register)
X
X
X
X
X
X
No phone line present
NO LINE (enabled via %Vn
commands)
X
X
X
X
X
X
Telephone line is in use
LINE IN USE (enabled via
%Vn commands)
X
X
X
X
X
X
Polarity reversal detected
POLARITY REVERSAL
(enabled via G modifier)
X
X
X
X
X
X
45
Polarity reversal NOT
detected
NO POLARITY REVERSAL
(enabled via G modifier)
X
X
X
X
X
X
52
Link established at 56000
CONNECT 560006
X
X
X
X
X
60
Link established at 32000
CONNECT
320006
X
X
X
X
X
61
Link established at 48000
CONNECT 480006
X
X
X
X
X
63
Link established at 28000
CONNECT
280006
X
X
X
X
X
64
Link established at 29333
CONNECT 293336
X
X
X
X
X
65
Link established at 30666
CONNECT
306666
X
X
X
X
X
66
Link established at 33333
CONNECT 333336
X
X
X
X
X
67
Link established at 34666
CONNECT
346666
X
X
X
X
X
68
Link established at 36000
CONNECT 360006
X
X
X
X
X
69
Link established at 37333
CONNECT
373336
X
X
X
X
X
70
No protocol
PROTOCOL: NONE
Set with \V0 command.
75
Link established at 75
CONNECT 75
X
77
V.42 protocol
PROTOCOL: V427
Set with \V0 command.
40
41
42
43
44
79
V.42bis protocol
PROTOCOL:
V42bis3
X
X
X
X
Set with \V0 command.
Notes:
1. Numeric mode: Result code <CR>.
2. Response for [email protected] is silence is not found.
3. This message is supported only on the Si2493, Si2457, Si2434, and Si2415.
4. This message is supported only on the Si2493, Si2457, and Si2434.
5. X is not preceded by <CR><LF>.
6. This message is supported only on the Si2493 and Si2457.
7. V.44 with data compression disabled (+DS = 0) emits this result code.
8. If data compression is disabled (+DS = Q), the modem returns the message PROTOCOL:V42.
Rev. 1.3
85
AN93
Table 43. Result Codes (Continued)
Numeric1
80
81
82
83
84
Meaning
Verbal Response
X0
X1
X2
X4
MNP2 protocol
PROTOCOL:
ALTERNATE, +CLASS 2
Set with \V command.
MNP3 protocol
PROTOCOL:
ALTERNATE, +CLASS 3
Set with \V command.
MNP4 protocol
PROTOCOL:
ALTERNATE, +CLASS 4
Set with \V command.
MNP5 protocol
PROTOCOL:
ALTERNATE, +CLASS 53
Set with \V command.
V.44 protocol
PROTOCOL: V.448
6
X5
Set with +DR command
90
Link established at 38666
CONNECT 38666
X
X
X
X
X
91
Link established at 40000
CONNECT 400006
X
X
X
X
X
92
Link established at 41333
6
CONNECT 41333
X
X
X
X
X
93
Link established at 42666
CONNECT 426666
X
X
X
X
X
94
Link established at 44000
CONNECT
440006
X
X
X
X
X
95
Link established at 45333
CONNECT 453336
X
X
X
X
X
96
Link established at 46666
CONNECT
466666
X
X
X
X
X
97
Link established at 49333
CONNECT 493336
X
X
X
X
X
98
Link established at 50666
CONNECT
506666
X
X
X
X
X
99
Link established at 52000
CONNECT 520006
X
X
X
X
X
100
Link established at 53333
CONNECT
533336
X
X
X
X
X
101
Link established at 54666
CONNECT 546666
X
X
X
X
X
102
DTMF dial attempted on a
pulse dial only line
UN-OBTAINABLE NUMBER
X
X
X
X
X
X
Notes:
1. Numeric mode: Result code <CR>.
2. Response for [email protected] is silence is not found.
3. This message is supported only on the Si2493, Si2457, Si2434, and Si2415.
4. This message is supported only on the Si2493, Si2457, and Si2434.
5. X is not preceded by <CR><LF>.
6. This message is supported only on the Si2493 and Si2457.
7. V.44 with data compression disabled (+DS = 0) emits this result code.
8. If data compression is disabled (+DS = Q), the modem returns the message PROTOCOL:V42.
86
X3
Rev. 1.3
AN93
Table 44. Disconnect Codes
Disconnect Code
8002
8
8008
9
8009
Reason
Handshake stalled.
No dial tone detected.
No line available.
No loop current detected.
Parallel phone pickup disconnect.
A
No ringback.
B
Busy signal detected.
D
V.42 requested disconnect.
E
MNP requested disconnect.
10
Drop-dead timer disconnect.
8014
Loop-current loss.
8017
Remote modem requested disconnect.
8018, 8019
Soft-reset command received.
1a
V.42 Protocol error.
1b
MNP Protocol error.
801c
Loss-of-carrier disconnect.
801e
Long-space disconnect.
801f
Character-abort disconnect.
802a
Rate request failed.
802b
Answer modem energy not detected.
802c
V.8 negotiation failed.
2d
TX data timeout.
Rev. 1.3
87
AN93
5.6. S Registers
S registers are typically used to set modem configuration parameters during initialization and are not usually
changed during normal modem operation. S-register values other than defaults must be written via the ATSn=x
command after every reset event. S registers are specified as a decimal value (S1 for example), and the contents
of the register are also decimal numbers. Table 45 lists the S registers available on the ISOmodem, their functions,
default values, ranges of values, and units.
Many S registers are industry standards, such as S0 (number of rings for auto answer), S1 (ring count), and S2
(escape character) among others. However, there are usually variations in the function (and availability) of S
registers from one chipset to another or from one chipset manufacturer to another. These variations are due to a
combination of feature availability and choices made during the chip design. It is prudent to verify the compatibility
of S-register functions, defaults, ranges, and values when adapting the ISOmodem to an existing design that uses
another chipset. This simple step can save time and help speed product development. If a particular S register is
not available on the ISOmodem, the register may not be necessary, or the function of the S register may be
available with the use of U registers (discussed later) or through an AT command.
Table 45. S-Register Descriptions
Definition
S Register
(Decimal)
Function
Default
(Decimal)
Range
Units
0
Automatic answer—This value represents the number
of rings the ISOmodem must detect before answering
a call. 0 disables auto answer.
0
0–255
rings
1
Ring counter—Counts rings received on current call.
0
0–255
rings
2
ESC code character
43 (+)
0–255
(ASCII)
3
Carriage return character
13 (CR)
0–255
(ASCII)
4
Linefeed character
10 (LF)
0–255
(ASCII)
5
Backspace character
08 (BS)
0–255
(ASCII)
6
Dial tone wait timer—This timer sets the number of
seconds the ISOmodem waits before blind dialing and
is only active if blind dialing is enabled (X0, X1, X3).
02
0–255
seconds
7
Carrier wait timer—This timer starts when dialing is
completed. It sets the number of seconds the modem
waits without carrier before hanging up and the number of seconds the modem waits for ringback when
originating a call before hanging up. The register also
sets the number of seconds the answer tone continues
while using the AT*Y2A command.
80
0–255
seconds
8
Dial pause timer for “,” and “<” dial command modifiers
02
0–255
seconds
9
Carrier presence timer—Time the remote modem carrier must be detected before activating or reactivating
DCD (carrier loss debounce time).
06
1–255
0.1 second
88
Rev. 1.3
AN93
Table 45. S-Register Descriptions (Continued)
Definition
S Register
(Decimal)
Function
Default
(Decimal)
Range
Units
10
Carrier loss timer—The time a remote modem carrier
must be lost before the ISOmodem disconnects. Setting this timer to 255 disables the timer, and the
modem does not time out and disconnect. If S10 is
less than S9, even a momentary loss of carrier causes
a disconnect. Use for V.22bis and lower data rates.
14
1–255
0.1 second
12
Escape code guard timer—Minimum guard time
before and after +++ to recognize a valid escape
sequence.
50
10–255
0.02 second
14
Wait for dial tone delay timer. This timer starts when
the W command is executed in the dial string.
12
0–255
seconds
24
Sleep inactivity time—This is the time the modem
operates in normal power mode with no activity on the
UART, parallel port, SPI port, or telephone line before
entering the low-power sleep mode and waking on
ring. The modem remains in the normal power mode,
regardless of activity, if the timer is set to 0.
0
0–255
seconds
30
Disconnect activity timer—Sets the length of time that
the modem stays online before disconnecting with no
activity on the UART, parallel port, SPI port, or telephone line (ring, hookswitch flash, or Caller ID). This
feature is disabled if set to 0.
0
0–255
minutes
38
Hang up delay time—Maximum delay between receipt
of the ATH0 command and hang up. If time out occurs
before all data can be sent, the NO CARRIER (3)
result code is sent. An OK response is sent if all data
are transmitted prior to time out. This register applies
to V.42 mode only. S38=255 disables time out, and the
modem only disconnects if data are successfully sent
or carrier lost.
20
0–255
seconds
40
Data Pattern - Data pattern generated during &T4 and
&T5 transmit tests.
0 – All spaces (0s)
1 – All marks (1s)
2 – Random data
0
0–2
–
Rev. 1.3
89
AN93
Table 45. S-Register Descriptions (Continued)
Definition
S Register
(Decimal)
Function
Default
(Decimal)
Range
Units
41
V.34 symbol rate - Symbol rate for V.34 when using
the &T4 and &T5 commands.
0 – 2400
symbols/second
1 – 2743
symbols/second
2 – 2800
symbols/second
3 – 3000
symbols/second
4 – 3200
symbols/second
5 – 3429
symbols/second
A valid combination of symbol rate (S41) and data rate
(&G) must be selected.
Symbol Rate
Allowable Data Rates
2400
2400 – 21600
2743
4800 – 26400
2800
4800 – 26400
3000
4800 – 28800
3200
4800 – 31200
3429
4800 – 33600
0
0–5
–
42
Blacklisting—The ISOmodem does not dial the same
number more than two times in S44 seconds. An
attempt to dial a third time within S44 seconds results
in a BLACKLISTED result code. If the blacklist memory is full, any dial to a new number will result in a
BLACKLIST FULL result code. Numbers are added to
the blacklist only if the modem connection fails. The
%B command lists the numbers on the blacklists.
0 – disabled
1 – enabled
0 (disabled)
0–1
–
43
Dial attempts to blacklist.
When blacklisting is enabled with S42, this value controls the number of dial attempts that result in a number being blacklisted.
4
0–4
–
44
Blacklist Timer
Period during which blacklisting is active
180
0–255
seconds
50
Minimum on-hook time—Modem remains on-hook for
S50 seconds. Any attempt to go off-hook is delayed
until this timer expires.
3
0–255
seconds
51
Number to start checking for an outside PBX line.
1
0–9
–
90
Rev. 1.3
AN93
5.7. U Registers
U registers (user-access registers) are 16-bit registers written by the AT:Uhh command and read by the AT:R (read
all U registers) command or AT:Rhh (read U-register hh) command. See the AT command list in Table 39 on
page 59. All values associated with the U registers, the address, and the value written to or read from the register
are hexadecimal.
Some U registers are reserved and not available to the user. Therefore, there are gaps in the available U-register
address sequence. Additionally, some bits within available U registers are reserved. Any attempt to write to a nonlisted U register or to write a reserved bit can cause unpredictable modem operation.
There are two types of U registers. The first represents a single 16-bit term, such as a filter coefficient, threshold,
delay, or other quantity. These registers can be read from or written to as a single 16-bit value. The second type of
U register is bit mapped. Bit-mapped registers are also written and/or read in hexadecimal, but each bit or
combination of bits in the register represents an independent value. These individual bits are used to enable or
disable features and indicate states. Bits in these registers can be read/write, read only, reserved, or they may be
required to always be set to a certain value. Pay particular attention when writing to bit-mapped registers to ensure
no reserved bits are overwritten. When changing bits in a U register with reserved bits, use a read-modify-write
procedure: read the register value with AT:R; modify only the desired bits, then write the new value with AT:U. This
will ensure the reserved bits are not altered. All U registers revert to their default settings after a reset.
The U registers can be broken into three groups: call progress (U0–U33, U49–U4C), dialing (U37–U48), line
interface, and extended functions (U4D–UA9). Table 46 lists the available U registers, a brief description, and their
default values. Table 47 summarizes the signals and values available in the bit-mapped registers. Country-specific
register values are presented in "6.2. Country-Dependent Setup" on page 133. All default settings are chosen to
meet FCC requirements.
Table 46. U-Register Descriptions
Register
Address
(Hex)
Name
Description
U00
0x0000
DT1A0
U01
0x0001
DT1B1
0x0000
U02
0x0002
DT1B2
0x0000
U03
0x0003
DT1A2
0x0000
U04
0x0004
DT1A1
0x0000
U05
0x0005
DT2A0
U06
0x0006
DT2B1
0x6EF1
U07
0x0007
DT2B2
0xC4F4
U08
0x0008
DT2A2
0xC000
U09
0x0009
DT2A1
0x0000
U0A
0x000A
DT3A0
U0B
0x000B
DT3B1
0x78B0
U0C
0x000C
DT3B2
0xC305
U0D
0x000D
DT3A2
0x4000
U0E
0x000E
DT3A1
0xB50A
Dial-tone detection filters stage 1 biquad coefficients.
Dial-tone detection filters stage 2 biquad coefficients.
Dial-tone detection filters stage 3 biquad coefficients.
Rev. 1.3
Default
Value
0x0800
0x00A0
0x00A0
91
AN93
Table 46. U-Register Descriptions (Continued)
Register
Address
(Hex)
Name
U0F
0x000F
DT4A0
U10
0x0010
DT4B1
0x70D2
U11
0x0011
DT4B2
0xC830
U12
0x0012
DT4A2
0x4000
U13
0x0013
DT4A1
0x80E2
U14
0x0014
DTK
U15
0x0015
U16
92
Description
Dial-tone detection filter stage 4 biquad coefficients.
Default
Value
0x0400
Dial-tone detection filter output scaler.
0x0009
DTON
Dial-tone detection ON threshold.
0x00A0
0x0016
DTOF
Dial-tone detection OFF threshold.
0x0070
U17
0x0017
BT1A0
Busy-tone detection filters stage 1 biquad coefficients.
0x0800
U18
0x0018
BT1B1
0x0000
U19
0x0019
BT1B2
0x0000
U1A
0x001A
BT1A2
0x0000
U1B
0x001B
BT1A1
0x0000
U1C
0x001C
BT2A0
U1D
0x001D
BT2B1
0x6EF1
U1E
0x001E
BT2B2
0xC4F4
U1F
0x001F
BT2A2
0xC000
U20
0x0020
BT2A1
0x0000
U21
0x0021
BT3A0
U22
0x0022
BT3B1
0x78B0
U23
0x0023
BT3B2
0xC305
U24
0x0024
BT3A2
0x4000
U25
0x0025
BT3A1
0xB50A
U26
0x0026
BT4A0
U27
0x0027
BT4B1
0x70D2
U28
0x0028
BT4B2
0xC830
U29
0x0029
BT4A2
0x4000
U2A
0x002A
BT4A1
0x80E2
U2B
0x002B
BTK
U2C
0x002C
U2D
0x002D
Busy-tone detection filter stage 2 biquad coefficients.
Busy-tone detection filter stage 3 biquad coefficients.
Busy-tone detection filter stage 4 biquad coefficients.
0x00A0
0x00A0
0x0400
Busy-tone detection filter output scaler.
0x0009
BTON
Busy-tone detection ON threshold.
0x00A0
BTOF
Busy-tone detection OFF threshold.
0x0070
Rev. 1.3
AN93
Table 46. U-Register Descriptions (Continued)
Register
Address
(Hex)
Name
Description
U2E
0x002E
BMTT
Busy cadence minimum total time in seconds multiplied by 7200.
0x0870
U2F
0x002F
BDLT
Busy cadence delta in seconds multiplied by 7200.
0x25F8
U30
0x0030
BMOT
Busy cadence minimum on time in seconds multiplied by 7200.
0x0438
U31
0x0031
RMTT
Ringback cadence minimum total time in seconds multiplied by
7200.
0x4650
U32
0x0032
RDLT
Ringback cadence delta in seconds multiplied by 7200.
0xEF10
U33
0x0033
RMOT
Ringback cadence minimum on time in seconds multiplied by
7200.
0x1200
U34
0x0034
DTWD
Window to look for dial tone in seconds multiplied by 1000.
0x1B58
U35
0x0035
DMOT
Minimum dial tone on time in seconds multiplied by 7200.
0x2D00
U37
0x0037
PD0
Number of pulses to dial 0.
0x000A
U38
0x0038
PD1
Number of pulses to dial 1.
0x0001
U39
0x0039
PD2
Number of pulses to dial 2.
0x0002
U3A
0x003A
PD3
Number of pulses to dial 3.
0x0003
U3B
0x003B
PD4
Number of pulses to dial 4.
0x0004
U3C
0x003C
PD5
Number of pulses to dial 5.
0x0005
U3D
0x003D
PD6
Number of pulses to dial 6.
0x0006
U3E
0x003E
PD7
Number of pulses to dial 7.
0x0007
U3F
0x003F
PD8
Number of pulses to dial 8.
0x0008
U40
0x0040
PD9
Number of pulses to dial 9.
0x0009
U42
0x0042
PDBT
Pulse dial break time (ms units).
0x003D
U43
0x0043
PDMT
Pulse dial make time (ms units).
0x0027
U45
0x0045
PDIT
Pulse dial interdigit time (ms units).
0x0320
U46
0x0046
DTPL
DTMF power level.
0x09B0
U47
0x0047
DTNT
DTMF on time (ms units).
0x0064
U48
0x0048
DTFT
DTMF off time (ms units).
0x0064
U49
0x0049
RGFH
Ring frequency high (2400/maximum valid ring frequency in Hz).
0x0022
U4A
0x004A
RGFD
Ring frequency delta = (2400/minimum valid ring frequency in Hz)
– (2400/maximum valid ring frequency in Hz)
0x007A
U4B
0x004B
RGMN
Ring cadence minimum ON time in seconds multiplied by 2400.
0x0258
U4C
0x004C
RGNX
Ring cadence maximum total time in seconds multiplied by 2400.
0x6720
U4D
0x004D
MOD1
This is a bit-mapped register.
0x0000
Rev. 1.3
Default
Value
93
AN93
Table 46. U-Register Descriptions (Continued)
Register
Address
(Hex)
Name
U4E
0x004E
PRDD
U4F
0x004F
FHT
U50
0x0050
U51
94
Description
Default
Value
Pre-dial delay-time—(ms units).
0x0000
Flash hook time—(ms units).
0x01F4
LCDN
Loop current debounce on time (ms units).
0x015E
0x0051
LCDF
Loop current debounce off time (ms units).
0x00C8
U52
0x0052
XMTL
Transmit level adjust (1 dB units)
0x0000
U53
0x0053
MOD2
This is a bit-mapped register.
0x0000
U62
0x0062
DAAC1
This is a bit-mapped register.
0x0804
U63
0x0063
DAAC3
This is a bit-mapped register.
0x0003
U65
0x0065
DAAC4
This is a bit-mapped register.
0x00E0
U66
0x0066
DAAC5
This is a bit-mapped register.
0xXX40
U67
0x0067
ITC1
This is a bit-mapped register.
0x0008
U68
0x0068
ITC2
This is a bit-mapped register.
0x0000
U6A
0x006A
ITC4
This is a bit-mapped register (read only).
U6C
0x006C
LVS
This is a bit-mapped register.
0xXX00
U6E
0x006E
CK1
This is a bit-mapped register.
0x1FA0
U6F
0x006F
PTME
This is a bit-mapped register.
0x0001
U70
0x0070
IO0
This is a bit-mapped register.
0x2700
U71
0x0071
IO1
This is a bit-mapped register.
0x0000
U76
0x0076
GEN1
This is a bit-mapped register.
0x3240
U77
0x0077
GEN2
This is a bit-mapped register.
0x401E
U78
0x0078
GEN3
This is a bit-mapped register.
0x0000
U79
0x0079
GEN4
This is a bit-mapped register.
0x00XX
U7A
0x007A
GENA
This is a bit-mapped register.
0x0000
U7C
0x007C
GENC
This is a bit-mapped register.
0x0000
U7D
0x007D
GEND
This is a bit-mapped register.
0x4001
U80
0x0080
This is a bit-mapped register.
0x0168
U83
0x0083
NOLN
No-Line threshold. If %V1 is set, NOLN sets the threshold for
determination of line present vs. line not present. 3 V/bit
0x0001
U84
0x0084
LIUS
Line-in-use threshold. If %V1 is set, LIUS sets the threshold for
determination of line in use vs. line not in use. 3 V/bit
0x0007
U85
0x0085
NLIU
Line-in-use/No-line threshold. If %V2 is set, NLIU sets the threshold reference for the adaptive algorithm (see %V2). 3 V/bit
0x0000
Rev. 1.3
N/A
AN93
Table 46. U-Register Descriptions (Continued)
Register
Address
(Hex)
Name
Description
U86
0x0086
V9AGG
V.90 rate reduction in 1333 bps units. The V.90 connect rate is
reduced by this amount during negotiation.
0x0000
U87
0x0087
SAMCO
This is a bit-mapped register
0x0000
U9F1
0x009F
SASF
SAS frequency detection.
0x0000
UA02
0x00A0
SC0
SAS cadence 0. Sets the duration of the first SAS tone (ms).
0x001E
UA12
0x00A1
SC1
SAS cadence 1. Sets the duration of the first SAS silence (ms).
0x0000
UA22
0x00A2
SC2
SAS cadence 2. Sets the duration of the second SAS tone (ms).
0x0000
UA32
0x00A3
SC3
SAS cadence 3. Sets the duration of the second SAS silence (ms).
0x0000
2
UA4
0x00A4
SC4
SAS cadence 4. Sets the duration of the third SAS tone (ms).
0x0000
UA52
0x00A5
SC5
SAS cadence 5. Sets the duration of the third SAS silence (ms).
0x0000
UA62
0x00A6
SC6
SAS cadence 6. Sets the duration of the fourth SAS tone (ms).
0x0000
UA72
0x00A7
SC7
SAS cadence 7. Sets the duration of the fourth SAS silence (ms).
0x0000
2
UA8
0x00A8
SC8
SAS cadence 8. Sets the duration of the fifth SAS tone (ms).
0x0000
UA92
0x00A9
SC9
SAS cadence 9. Sets the duration of the fifth SAS silence (ms).
0x0000
UAA2
0x00AA
UIDA
0x01DA
V29MODE This is a bit-mapped register.
Delay (ms) to the response to an answer tone
Default
Value
0x0000
0x0000
Notes:
1. See Table 100 for details.
2. See Table 101 for details.
Rev. 1.3
95
AN93
5.7.1. U-Register Summary
Table 47. Bit-Mapped U-Register Summary
Register
Name
U4D
MOD1
U53
MOD2
U54
CALT
U62
DAAC1
U63
DAAC3
U65
DAAC4
U66
DAAC5
U67
ITC1
U68
ITC2
U6A
ITC4
U6C
LVS
U6E
CK1
U6F
PTME
U70
IO0
U71
IO1
U76
GEN1
U77
GEN2
U78
GEN3
U79
GEN4
U7A
GENA
U7C
GENC
U7D
GEND
U80
XMITDEL
U87
SAM
UAA
V29MODE
96
Bit
15
Bit
14
Bit
13
TOCT
Bit
12
Bit
11
Bit
10
NHFP
NHFD
CLPD
Bit 9
Bit 8
Bit 7
FTP
SPDM
Bit 6
Bit 5
Bit 4
Bit 3
GT18
GT55
CTE
Bit 2
Bit 1
FOH
DL
Bit 0
REV
OHCT
OHS2
LCS
PWM
G
ACT
PDN
PDL
FDT
MINI
ILIM
DCR
OHS
DCV
BTE
SQ1
SQ0
RZ
RT
ROV
BTD
RI
DCD
OVL
LVS
R1
HRS
PTMR
HES
TES
CIDM
OCDM
PPDM
RIM
DCDM
CID
OCD
PPD
COMP
OHSR
IST
FACL
HOI
PRT
DCL
AOC
ACL
OHT
IB
IS
LVCS
ARMLO
DOP
ADD
HDLC
RIGPO
NLM
TCAL
RIGPOEN
CALD
ATZD
V22F
CDF
V22FCDEL
MINT
SERM
FSMS
XMTT
RUDE
Rev. 1.3
FAST
V29ENA
FDP
AN93
5.7.2. U00–U16 (Dial Tone Detect Filter Registers)
U00–U13 set the biquad filter coefficients for stages 1–4 of the dial-tone detection filter. U14, U15, and U16 set the
dial-tone detection output scaler, on threshold and off threshold, respectively.
The thresholds are empirically found scalars and have no units. These coefficients are programmed as 16-bit,
two’s complement values. All A0 values are in 3.12 format where 1.0 = 0x1000. All other coefficients are in 1.14
format where 1.0 = 0xC000. Default settings meet FCC requirements. Additionally, register U34 sets the time
window in which a dial tone can be detected. Register U35 sets the minimum time within the U34 window that the
dial tone must be present for a valid detection. See "5.7.5. U34–U35 (Dial Tone Timing Register)" for more
information.
Table 48. U0–U16 (Dial Tone Registers)
Register
Name
Description
U00
DT1A0
0x0800
U01
DT1B1
0x0000
U02
DT1B2
U03
DT1A2
0x0000
U04
DT1A1
0x0000
U05
DT2A0
0x00A0
U06
DT2B1
0x6EF1
U07
DT2B2
U08
DT2A2
0xC000
U09
DT2A1
0x0000
U0A
DT3A0
0x00A0
U0B
DT3B1
0x78B0
U0C
DT3B2
U0D
DT3A2
0x4000
U0E
DT3A1
0xB50A
U0F
DT4A0
0x0400
U10
DT4B1
0x70D2
U11
DT4B2
U12
DT4A2
0x4000
U13
DT4A1
0x80E2
U14
DTK
U15
U16
Dial-tone detection filters stage 1 biquad coefficients.
Dial-tone detection filters stage 2 biquad coefficients.
Dial-tone detection filters stage 3 biquad coefficients.
Dial-tone detection filters stage 4 biquad coefficients.
Default
0x0000
0xC4F4
0xC305
0xC830
Dial-tone detection filter output scaler.
0x0009
DTON
Dial-tone detection ON threshold.
0x00A0
DTOF
Dial-tone detection OFF threshold.
0x0070
Rev. 1.3
97
AN93
5.7.3. U17–U30 (Busy Tone Detect Filter Registers)
U17–U2A set the biquad filter coefficients for stages 1–4 of the busy-tone detection filter, and U2B, U2C, and U2D
set the busy-tone detection output scalar on threshold and off threshold, respectively (see Table 49). The
thresholds are empirically found scalars and have no units. These coefficients are programmed as 16-bit, two’s
complement values. All A0 values are in 3.12 format where 1.0 = 0x1000. All other coefficients are in 1.14 format
where 1.0 = 0xC000. Default values meet FCC requirements.
U2E, U2F, and U30 set the busy cadence minimum total time (BMTT), busy cadence delta time (BDLT), and busy
cadence minimum on time (BMOT), respectively. Settings for busy cadences are specified as a range for ON time
(minimum ON and maximum ON) and a range for OFF time (minimum OFF and maximum OFF). The three values
represented by BMTT, BDLT, and BMOT fully specify these ranges. BMTT (minimum total time) is equal to the
minimum ON time plus the minimum OFF time. BDLT (allowable delta) is equal to the maximum total time
(maximum ON time plus the maximum OFF time) minus the minimum total time (BMTT). BMOT is the minimum
ON time. The values stored in the registers are the hexadecimal representation of the times in seconds multiplied
by 7200. Default values meet FCC requirements (see Figure 26, “Cadence Timing,” on page 100).
Table 49. U17–U30 (Busy Tone Detect Registers)
Register
Name
U17
BT1A0
0x0800
U18
BT1B1
0x0000
U19
BT1B2
U1A
BT1A2
0x0000
U1B
BT1A1
0x0000
U1C
BT2A0
0x00A0
U1D
BT2B1
0x6EF1
U1E
BT2B2
U1F
BT2A2
0xC000
U20
BT2A1
0x0000
U21
BT3A0
0x00A0
U22
BT3B1
0x78B0
U23
BT3B2
U24
BT3A2
0x4000
U25
BT3A1
0xB50A
U26
BT4A0
0x0400
U27
BT4B1
0x70D2
U28
BT4B2
U29
BT4A2
0x4000
U2A
BT4A1
0x80E2
U2B
BTK
U2C
98
Description
Busy-tone detection filter stage 1 biquad coefficients.
Busy-tone detection filter stage 2 biquad coefficients.
Busy-tone detection filter stage 3 biquad coefficients.
Busy-tone detection filter stage 4 biquad coefficients.
Default
0x0000
0xC4F4
0xC305
0xC830
Busy-tone detection filter output scaler.
0x0009
BTON
Busy-tone detection ON threshold.
0x00A0
U2D
BTOF
Busy-tone detection OFF threshold.
0x0070
U2E
BMTT
Busy cadence minimum total time in seconds multiplied by 7200.
0x0870
U2F
BDLT
Busy cadence delta time in seconds multiplied by 7200.
0x25F8
U30
BMOT
Busy cadence minimum on time in seconds multiplied by 7200.
0x0438
Rev. 1.3
AN93
Table 50. BPF Biquad Values
BPF Biquad
Values
Stage 1
Stage 2
Stage 3
Stage 4
Output Scalar
310/510 (Default Busy and Dial Tone)
A0
0x0800
0x00A0
0x00A0
0x0400
—
B1
0x0000
0x6EF1
0x78B0
0x70D2
—
B2
0x0000
0xC4F4
0xC305
0xC830
—
A2
0x0000
0xC000
0x4000
0x4000
—
A1
0x0000
0x0000
0xB50A
0x80E2
—
K
—
—
—
—
0x0009
300/480
A0
0x0800
0x01A0
0x01A0
0x03A0
—
B1
0x0000
0x6E79
0x7905
0x7061
—
B2
0x0000
0xC548
0xC311
0xC8EF
—
A2
0x0000
0xC000
0x4000
0x4000
—
A1
0x0000
0x0000
0xA7BE
0x8128
—
K
—
—
—
—
0x0009
320/630
A0
0x0078
0x0210
0x0330
0x0330
—
B1
0x67EF
0x79E0
0x68C0
0x7235
—
B2
0xC4FA
0xC252
0xCB6C
0xC821
—
A2
0x4000
0x4000
0x4000
0x4000
—
A1
0x0214
0x8052
0xB1DC
0x815C
—
K
—
—
—
—
0x0008
325/550
A0
0x0100
0x0600
0x0600
0x0600
—
B1
0x71CC
0x78EF
0x69B9
0x68F7
—
B2
0xC777
0xC245
0xC9E4
0xC451
—
A2
0x4000
0x4000
0x4000
0x4000
—
A1
0x81C2
0x806E
0xAFE9
0xFCA6
—
K
—
—
—
—
0x0009
100/550
A0
0x0800
0x01C0
0x01C0
0x01C0
—
B1
0x7DAF
0x5629
0x7E3F
0x6151
—
B2
0xC1D5
0xCF51
0xC18A
0xDC9B
—
A2
0x4000
0xC000
0x4000
0x4000
—
A1
0x8000
0x0000
0xB96A
0x8019
—
Rev. 1.3
99
AN93
Table 50. BPF Biquad Values (Continued)
BPF Biquad
Values
Stage 1
Stage 2
Stage 3
Stage 4
Output Scalar
K
—
—
—
—
0x0005
400/440
A0
0x0020
0x0200
0x0400
0x0040
—
B1
0x7448
0x7802
0x73D5
0x75A7
—
B2
0xC0F6
0xC0CB
0xC2A4
0xC26B
—
A2
0x4000
0x4000
0x4000
0x4000
—
A1
0x96AB
0x8359
0x8D93
0x85C1
—
K
—
—
—
—
0x0008
Example: The United States specifies a busy tone “on” time from 450 to 550 ms and “off” time from 450 to 550 ms.
Thus the minimum “on” and “off” times are 0.45 s each , and the maximum “on” and “off” times are 0.55 s each.

The busy cadence minimum on time is 0.45 s, thus BMOT = 0.45 x 7200 = 0x0CA8.
 The busy cadence minimum total time is 0.45 s + 0.45 s = 0.9 s, thus BMTT = 0.9 x 7200 = 6480 = 0x1950.
 The maximum total time is 0.55 s + 0.55 s = 1.1 s, thus BDLT = (1.1 – 0.9) x 7200 = 1440 = 0x05A0.
The hexadecimal values are stored in the appropriate registers using the AT:Uhh command. Detection parameters
can be wider than the minimum specifications. This is often done in the modem defaults and other suggested
settings so that one set of parameters can cover a broad number of different country requirements.
Maximum Cadence
TOTAL Time
Minimum ON Time
(BMOT)
(RMOT)
Minimum Cadence Cadence Delta
TOTAL Time
Time (BDLT)
(BMTT)
(RDLT)
(RMTT)
Figure 26. Cadence Timing
100
Rev. 1.3
AN93
5.7.4. U31–U33 (Ringback Cadence Registers)
U31, U32, and U33 set the ringback cadence minimum total time (RMTT), ringback cadence delta time (RDLT),
and ringback cadence minimum on time (RMOT) (see Table 51). Country-specific settings for ringback cadences
are specified as a range for “on” time (minimum “on” and maximum “on”) and a range for “off” time (minimum “off”
and maximum “off”). The three values represented by RMTT, RDLT, and RMOT fully specify these ranges. RMTT,
minimum total time, is equal to the minimum “on” time plus the minimum “off” time. RDLT (allowable delta) is equal
to the maximum total time (maximum “on” time plus the maximum “off” time) minus the minimum total time (RMTT).
RMOT is the minimum “on” time. The values stored in the registers are the hexadecimal representation of the times
in seconds multiplied by 7200. Default values meet FCC requirements.
Table 51. Ringback Cadence Registers
Register
Name
Description
Default
U31
RMTT
Ringback cadence minimum total time in seconds multiplied by 7200.
0x4650
U32
RDLT
Ringback cadence delta in seconds multiplied by 7200.
0xEF10
U33
RMOT
Ringback cadence minimum on time in seconds multiplied by 7200.
0x1200
5.7.5. U34–U35 (Dial Tone Timing Register)
U34 determines the period of time the modem attempts to detect a dial tone. U35 sets the time within this window
that the dial tone must be present in order to return a valid dial tone detection. The value stored in U35 is the
hexadecimal representation of the time in seconds multiplied by 7200.
The value in U34 is the hexadecimal representation of the time in seconds multiplied by 1000. The time window
represented in U34 must be larger than the dial tone present time represented in register U35 (see Table 52).
Table 52. Dial Tone Timing Register
Register
Name
Description
Default
U34
DTWD
Window to look for dial tone in seconds multiplied by 1000
0x1B58
U35
DMOT
Minimum dial tone on time in seconds multiplied by 7200
0x2D00
5.7.6. U37–U45 (Pulse Dial Registers)
Registers U37–U40 set the number of pulses to dial digits 0 through 9, respectively (see Table 53). The values are
entered in hexadecimal format with digit 0 having a default setting of 0x000A (10 decimal) pulses, digit 1 having a
default setting of one pulse, digit 2 having a default setting of two pulses, etc. This pulse arrangement is used
throughout most of the world. There are, however, two exceptions—New Zealand and Sweden. New Zealand
requires 10 pulses for 0, nine pulses for 1, eight pulses for 2, etc. Sweden, on the other hand, requires one pulse
for 0, two pulses for 1, etc. Complete information is provided in "6.2. Country-Dependent Setup" on page 133.
U42, U43, and U45 set the pulse dial break time (PDBT), make time (PDMT), and interdigit delay time (PDIT),
respectively. The values are entered in hexadecimal format and represent milliseconds. The default values meet
FCC requirements. The default dialing speed is 10 pps. See "6.2. Country-Dependent Setup" on page 133 for
Japanese 20 pps dialing configuration.
Rev. 1.3
101
AN93
Table 53. Pulse Dial Registers
Register
Name
Description
Default
U37
PD0
Number of pulses to dial 0.
0x000A
U38
PD1
Number of pulses to dial 1.
0x0001
U39
PD2
Number of pulses to dial 2.
0x0002
U3A
PD3
Number of pulses to dial 3.
0x0003
U3B
PD4
Number of pulses to dial 4.
0x0004
U3C
PD5
Number of pulses to dial 5.
0x0005
U3D
PD6
Number of pulses to dial 6.
0x0006
U3E
PD7
Number of pulses to dial 7.
0x0007
U3F
PD8
Number of pulses to dial 8.
0x0008
U40
PD9
Number of pulses to dial 9.
0x0009
U42
PDBT
Pulse dial break time (ms units).
0x003D
U43
PDMT
Pulse dial make time (ms units).
0x0027
U45
PDIT
Pulse dial interdigit time (ms units).
0x0320
5.7.7. U46–U48 (DTMF Dial Registers)
U46–U48 set the DTMF power level, DTMF “on” time, and DTMF “off” time, respectively (see Table 54). The DTMF
power levels are set in register U46 as a 16-bit value with the format 0x0HL0, where H is a hexadecimal number
(0–F) for the dBm level of the high-frequency DTMF tone, and L is a hexadecimal number (0–F) for the dBm level
of the low-frequency DTMF tone. The power level is specified in –1 dB units. The DTMF output level is 0 dBm for
each tone if U46 = 0x0000 and –15 dBm if U46 = 0x0FF0. The default power level is –9 dBm for the high tone and
–11 dBm for the low tone.
U47 and U48 set the DTMF “on” time (DTNT) and “off” time (DTFT) respectively as hexadecimal values in
milliseconds. The default value for both U47 and U48 is 100 ms, and the range of values is 0–1000 ms.
Table 54. DTMF Dial Registers
Register
Name
U46
DTPL
DTMF power level
0x09B0
U47
DTNT
DTMF “on” time (ms units).
0x0064
U48
DTFT
DTMF “off” time (ms units).
0x0064
102
Description
Rev. 1.3
Default
AN93
5.7.8. U49–U4C (Ring Detect Registers)
U49, U4A, U4B, and U4C set a representation of the maximum ring frequency, the difference between the highest
and lowest valid ring frequency, minimum ring “on” time, and maximum ring cadence time (time on plus time off),
respectively. U49 is set as the hexadecimal equivalent of 2400 divided by the highest valid ring frequency in Hz.
U4A is set as the hexadecimal equivalent of 2400 divided by the minimum valid ring frequency in Hz minus 2400
divided by the maximum valid ring frequency in Hz.
U4B and U4C are set as the hexadecimal equivalents of the times in seconds multiplied by 2400. The default high
ring frequency, RGFH (U49), is 70.6 Hz. The default ring cadence minimum on time, RGMN, is 250 ms. The default
ring cadence maximum total time is 11 seconds.
Table 55. Ring Detect Registers
Register
Name
Description
Default
U49
RGFH
Ring frequency high (2400/maximum valid ring frequency in Hz).
0x0022
U4A
RGFD
Ring frequency delta (2400/minimum valid ring frequency in Hz) –
(2400/maximum valid ring frequency in Hz).
0x007A
U4B
RGMN
Ring cadence minimum “on” time in seconds multiplied by 2400.
0x0258
U4C
RGNX
Ring cadence maximum total time in seconds multiplied by 2400.
0x6720
5.7.9. U4D (Modem Control Register 1—MOD1)
U4D is a bit-mapped register that controls various telephony functions, including the enabling of calling and guard
tones and loop current verification prior to dialing. All bits in this register are read/write, except for bits, 15, 13, 9, 6,
2, and 0, which are reserved. These bits must not be written with a logic 1, and reading them returns a value of 0
(see Table 56).
Bit 14 (TOCT) = 0 (default) turns off the calling tone after answer tone detection and allows the calling-tone
cadence to complete before proceeding with the connect sequence (per V.25). TOCT = 1 turns off the calling tone
200 ms after answer-tone detection begins.
Bit 12 (NHFP) = 0 (default) disables hook-flash during pulse dialing (ignores & and ! dial modifiers). NHFP = 1
enables hook-flash during pulse dialing.
Bit 11 (NHFD) = 0 (default) disables hook-flash during dial string (tone or pulse). NHFD = 1 enables hook-flash
during (tone or pulse) dial string.
Bit 10 (CLPD) = 0 (default) Modem ignores loop current prior to dialing. If CLPD = 1, modem measures loop
current prior to dialing. This bit is used in conjunction with the loop-current debouncing registers, U50 and U51
(LCDN and LCDF), and U4D bit 1 (LLC). U50 provides a delay between the modem going off-hook and the loop
current measurement. The delay allows the loop current to stabilize prior to the measurement. Some countries
require the presence of loop current prior to dialing.
Bit 8 (FTP) = 0 (default) allows mixing tone and pulse dialing in a single AT command. FTP = 1 forces the first
dialing mode encountered (tone or pulse) for the entire AT command.
Bit 7 (SPDM) = 0 (default) causes the modem to pulse dial if an ATDP command is given. If this bit is set to 1 the
pulse dial modifier, P, is ignored, and the dial command is carried out as a tone dial (ATDT).
Bit 5 (GT18) = 0 (default) disables the 1800 Hz guard tone. GT18 = 1 enables the 1800 Hz guard tone.
Bit 4 (GT55) = 0 (default) disables the 550 Hz guard tone. GT55 = 1 enables the 550 Hz guard tone.
Bit 3 (CTE) = 0 (default) disables and CTE = 1 enables the calling tone referred to in bit 14 (TOCT). The calling
tone is a 1300 Hz tone in originate mode with a 0.5–0.7 sec on/1.5–2.0 sec off cadence as described in V.25.
Rev. 1.3
103
AN93
Table 56. Register U4D Bit Map
104
Bit
Name
Function
15
Reserved
14
TOCT
13
Reserved
12
NHFP
No Hook-Flash Pulse.
0 = Disable.
1 = Enable.
11
NHFD
No Hook-Flash Dial.
0 = Disable.
1 = Enable.
10
CLPD
Check Loop Current Before Dialing.
0 = Ignore.
1 = Check.
9
Reserved
8
FTP
7
SPDM
6
Reserved
5
GT18
1800 Hz Guard Tone Enable (UK Guard Tone)
0 = Disable.
1 = Enable.
4
GT55
550 Hz Guard Tone Enable.
0 = Disable.
1 = Enable.
3
CTE
Calling Tone Enable.
0 = Disable.
1 = Enable.
2
Reserved
Read returns zero.
1
Reserved
Read returns zero.
0
Reserved
Read returns zero.
Read returns zero.
Turn Off Calling Tone.
0 = Disable.
1 = Enable.
Read returns zero.
Read returns zero.
Force Tone or Pulse.
0 = Disable.
1 = Enable.
Skip Pulse Dial Modifier.
0 = No.
1 = Yes.
Read returns zero.
Rev. 1.3
AN93
5.7.10. U4E (Pre-Dial Delay Time Register)
U4E sets the delay time between the ATD command carriage return and when the modem goes off-hook and starts
dialing (either tone or pulse—see Table 57). This delay establishes the minimum time the modem must be on-hook
prior to going off-hook and dialing. France, Sweden, Switzerland, and Japan have minimum on-hook time
requirements. The value stored in U4E is the desired delay in milliseconds minus 100 ms. The 100 ms offset is due
to a delay inherent in the dialing algorithm. "6.2. Country-Dependent Setup" on page 133 contains information
about country-specific values for this register.
5.7.11. U4F (Flash Hook Time Register)
U4F sets the time the modem goes on-hook as a result of a “!” or “&” dial modifier (flash hook). The value is stored
in the register in milliseconds (see Table 58).
5.7.12. U50–U51 (Loop Current Debouncing Registers)
U50 (LCDN) sets the loop-current debouncing “on” time, and U51 (LCDF) sets the loop current debouncing “off”
time (see Table 59). Loop-current debounce is used in cases where the presence or absence of loop current must
be determined prior to taking some action. For example, it may be necessary to verify the presence of loop current
prior to dialing. The loop current debounce on-time, LCDN, is used to program a delay in measuring loop current
after the modem goes off-hook to ensure the loop current is stable prior to the measurement. LCDN is used in
conjunction with U4D [10] (CLPD) and U4D [0] (LCN). Loop current debounce off-time, LCDF, is used in
conjunction with LCN to delay the modem going on-hook if loop current is interrupted during a connection. The
values are stored in the registers in milliseconds. The default value for LCDN is 350 ms. The default value for
LCDF is 200 ms. The range of values for both registers is 0–65535 ms.
5.7.13. U52 (Transmit Level Register)
U52 (XMTL) adjusts the modem transmit level referred to a 600  line (see Table 60). The default value of 0x0000
results in a –9.85 dBm transmit level. U52 can be used to decrease this level in –1 dBm steps approximately to the
minimum modem receive threshold of –48 dBm with a register value of 0x0026.
Table 57. Pre-Dial Delay Timer Register
Register
Name
U4E
PRDD
Description
Pre-dial delay-time after ATD command that modem waits to dial (ms
units). The ISOmodem stays on-hook during this time.
Default
0x0000
Table 58. Flash Hook Time Register
Register
Name
U4F
FHT
Description
Flash hook time (ms units).
Default
0x01F4
Table 59. Loop Current Debounce Registers
Register
Name
Description
Default
U50
LCDN
Loop-current debouncing “on” time (ms units).
0x015E
U51
LCDF
Loop-current debouncing “off” time (ms units).
0x00C8
Table 60. Transmit Level Register
Register
Name
U52
XMTL
Description
Transmit level adjust (–1 dB units).
Rev. 1.3
Default
0x0000
105
AN93
5.7.14. U53 (Modem Control Register 2)
U53 (MOD2) is a bit-mapped register with all bits, except bit 15, reserved (see Table 61). The AT&H11 command
sets the V.23 1200/75 bps mode. Bit 15 (REV) is used to enable V.23 reversing. This bit is set to 0 (disable
reversing) by default. Setting this bit to 1 enables reversing transmit and receive speeds. Reversing is initiated by
the modem in the “origination mode” (low speed TX and high speed RX). U53 resets to 0x0000 with a power-on or
manual reset.
5.7.15. U54 (Calibration Timing Register)
U54 (CALT) sets the time between off-hook and DAA calibration if timed calibration is enabled with the TCAL bit
(U7D, bit 12). The OHCT bits (15:8) control this timing in 32 ms units.
5.7.16. U62–U66 (DAA Control Registers)
U62 (DAAC1) is a bit-mapped register with only bits 1, 2, and 8 available. All other bits in this register are reserved
and must be set according to Table 63. U62 resets to 0x0804 with a power-on or manual reset.
Bit 1 (DL) = 1 or 0 causes digital loopback to occur beyond the isolation capacitor interface out to and including the
analog hybrid circuit. Setting bit 1 high enables digital loopback across the isolation barrier only. This setting is
used in conjunction with the AT&H and AT&T3 commands. DL must be set low for normal operation.
Bit 2 (FOH) controls when automatic Si3018/10 calibration takes place.
Table 61. U53 Bit Map
Bit
15
Name
REV
14:0
Reserved
Function
V.23 Reversing.
0 = Disable.
1 = Enable.
Read returns zero.
Table 62. U54 Bit Map
Bit
15:8
Name
OHCT
7:0
Reserved
Function
Off-hook to calibration timing in 32 ms units. If enabled with TCAL (U7D bit 12), this value
controls the time between off-hook and DAA calibration.
Must be set to zero.
Table 63. U62 Bit Map
Bit
15:12
11
10:9
8
Name
Reserved
Reserved
Reserved
OHS2
Function
Must be set to zero.
Must be set to one.
Must be set to zero.
On-Hook Speed 2
This bit, in combination with the OHS bit and the SQ[1:0] bits on-hook speeds specified
are measured from the time the OH bit is cleared until loop current equals zero.
OHS
OHS2
SQ[1:0] Mean On-Hook Speed
0
0
00
Less than 0.5 ms
0
1
00
3 ms ±10% (meets ETSI standard)
1
X
11
26 ms ±10% (meets Australia spark quenching spec)
Note: The +GCI command does not modify OHS2, SQ[1:0].
7
Full 1
6:5
Reserved
106
0 = Disable
1 = Enable. +3.2 dBm maximum into 600  (Si3018 only)
Must be set to zero.
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Table 63. U62 Bit Map (Continued)
4
3
2
Reserved
Reserved
FOH
1
DL
0
Reserved
Must be set to zero.
Must be set to zero.
0 = Automatic calibration timer set to 426 ms.
1 = Automatic calibration timer set to 106 ms.
0 = Digital loopback beyond ISOcap interface.
1 = Digital loopback across ISOcap interface only.
Must be set to zero.
U63 (DAAC2) is a bit-mapped register with bits 3:0 reserved and should be modified through a read-modify-write
operation.
Bits 15:8 (LCS) function as an 8-bit unsigned measure of off-hook loop current with a resolution of 1.1 mA/bit.
Bits 7:4 (ACT) set the ac termination the Si3010/Si3018 presents to Tip and Ring. The ac impedance setting is
dictated by the certification requirements for the country in which the modem is used.
Table 64. U63 Bit Map
Bit
Name
Function
15:8
LCS
Off-hook loop current (1.1 mA/bit).
7:4
ACT
AC Termination Select
ACT AC Termination
0000
Real 600 
0011
220  + (820  || 120 nF) and 220  + (820  || 115 nF)
0100
370  + (620  || 310 nF)
1111
Global complex impedance
3:0
Reserved
Read returns 0011.
U65 (DAAC4) is a bit-mapped register with bits 3:0, 12:5, and 15 reserved. Bits 1:0 and 6:5 must not be changed.
Bit 14 (PWMG) = 0 (default) provides 0 dB gain to AOUT. PWMG = 1 provides a 6 dB gain to AOUT.
Bit 13 (PDN) = 0 enables the device for normal operation. PDN = 1 completely powers down both the Si3018/10
and the Si24xx chips. The bit takes effect at the carriage return of the AT command setting this bit high. Once this
bit is set, the modem must be reset via the RESET pin to become active. When reset, the modem reverts to the
default settings.
Bit 4 (PDL) = 0 (default) enables the device for normal operation. PDL = 1 powers the Si3018/10 down. This is a
test mode typically used for board-level debugging, not normal modem operation.
U65 resets to 0x00E0 with a power-on or manual reset.
Table 65. U65 Bit Map
Bit
Name
15
Reserved
14
PWMG
13
PDN
Function
Read returns zero.
PWM gain.
0 = No gain.
1 = 6 dB gain applied to AOUT.
Power Down.
0 = Normal.
1 = Power Down.
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Table 65. U65 Bit Map (Continued)
12:7
Reserved
Read returns zero.
6:5
Reserved
Do not change (use read-modify-write).
4
PDL
3:2
Reserved
Read returns zero.
1:0
Reserved
Do not change (use read-modify-write).
Line-Side Chip Power Down.
0 = Normal operation.
1 = Places the Si3018/10 in Power-Down mode.
U66 (DAAC5) is a bit-mapped register with all bits except bit 6 reserved (see Table 66).
Bit 6 (FDT) is a read-only bit that reports whether or not an isolation capacitor frame lock is established. FDT is
typically used for board-level debugging and is not used during normal modem operation.
U66 resets to 0xXX40 with a power-on or manual reset assuming framelock is established. The upper byte is
variable.
5.7.17. U67–U6A (International Configuration Registers)
International Configuration Registers include U67 through U6A. These are bit-mapped registers that control
international configuration settings, such as dc and ac termination, ringer impedance and detection, current limit,
and billing tone protection.
U67 is a bit-mapped register with bits 5:4, 8, 11:10, and 15:14 reserved (see Table 67). U67 resets to 0x0008 with
a power-on or manual reset.
Bit 7 (DCR) is used to set the dc line termination of the modem. DCR = 0 is the normal mode of operation with dc
impedance selected by U67 [3:2] (DCV).
When DCR = 1, the device presents a dc line impedance of 800 ,which can be used to enhance operation with a
parallel phone, for improved low line voltage performance, and for overload. This bit must be set to 0 when the
modem is on-hook. See "6.2.1. DC Termination" on page 133 for details.
Bit 6 (OHS) is used to control the speed with which the modem drops the line. The default setting, OHS = 0,
causes the modem to go from the off-hook state (drawing loop current) to the on-hook state (not drawing loop
current) quickly. This operation is acceptable in many countries. However, some countries, such as Italy, South
Africa, and Australia, have spark quenching requirements. Spark quenching can be accomplished by placing a
resistor and a capacitor across the hookswitch or by controlling the off-hook to on-hook transition speed to prevent
excessive voltage buildup. Slowly reducing the loop current to zero fulfills the spark quenching requirement without
the extra components. Setting OHS = 1 causes the hookswitch to turn off the loop current with a ramp instead of a
step.
Bits 3:2 (DCV) select the dc termination for the modem. DCV = 00 is the lowest voltage mode supported on the
ISOmodem. DCV = 01 is the next lowest voltage mode. See "6.2.1. DC Termination" on page 133 for details.
Bit 1 (RZ) = 0 (default) allows ringer impedance to be determined by external components. This impedance is
typically 800–900 k. RZ = 1 enables on-chip synthesis of a lower ringer impedance for countries, such as Poland,
South Africa, and South Korea.
Bit 0 (RT), Ring Threshold, is used to satisfy various country ring detect requirements. RT = 0 (default) sets the ring
threshold for 11–22 VRMS. RT = 1 sets the ring threshold for 17–33 VRMS. Signals below the lower level of the
range are not detected. Signals above the upper level of the range are always detected.
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Table 66. U66 Bit Map
Bit
Name
15:7
Reserved
6
FDT
5:0
Reserved
Function
Read returns zero.
Frame Detect.
0 = ISOcap frame lock not established
1 = ISOcap frame lock established
Read returns zero.
Table 67. U67 Bit Map*
Bit
Name
Function
15:14 Reserved Read returns zero.
13:12 MINI[1:0] Minimum Operational Loop Current.
Adjusts the minimum loop current at which the DAA can operate. Increasing the minimum operational loop current can improve signal headroom at lower Tip-Ring voltages.
MINI[1:0] Min Loop Current
00
10 mA
01
12 mA
10
14 mA
11
16 mA
11:10 Reserved Read returns zero
9
ILIM
Current Limiting Enable.
0 = Current limiting mode disabled.
1 = Current limiting mode enabled. This mode limits loop current to a maximum of 60 mA per
the legacy TBR21 standard.
8
Reserved Read returns zero.
7
DCR
DC Impedance Selection.
0 = 50  dc termination slope is selected. This mode should be used for all standard
applications.
1 = 800  dc termination is selected.
6
OHS
On-Hook Speed.
See OHS2.
5:4 Reserved Read returns zero.
3:2 DCV[1:0] Tip-Ring Voltage Adjust.
These bits adjust the voltage on the DCT pin of the line-side device, which affects the Tip-Ring
voltage on the line. Low-voltage countries should use a lower Tip-Ring voltage. Raising the TipRing voltage can improve signal headroom.
DCV[1:0] DCT Pin Voltage
00
3.1 V
01
3.2 V
10
3.35 V
11
3.5 V
1
RZ
Ringer Impedance.
0 = Maximum (high) ringer impedance.
1 = Synthesize ringer impedance. C15, R14, Z2, and Z3 must not be installed when setting this
bit.
Rev. 1.3
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Table 67. U67 Bit Map* (Continued)
Bit
0
Name
RT
Function
Ringer Threshold Select.
Used to satisfy country requirements on ring detection. Signals below the lower level do not
generate a ring detection; signals above the upper level are guaranteed to generate a ring
detection.
0 = 11 to 22 Vrms.
1 = 17 to 33 Vrms.
U68 is a bit-mapped register with bits 15:3 reserved. Reading these bits returns zero. Bits 4 and 2:0 are all read/
write (see Table 68).
Bit 2 (BTE) = 0 (default) is disabled by default. When BTE = 1, the DAA automatically responds to a collapse of the
line-derived power supply during a billing tone event. When off-hook, if BTE = 1 and BTD goes high, the dc
termination is increased to 800  to reduce loop current. If BTE and U70 [9] (RIM) are set to 1, an interrupt from
U70 [1] (RI) also occurs when BTD goes to 1 (high).
Bit 1 (ROV) is normally 0 and is set to 1 to report an excessive receive input level. ROV is cleared by writing it to 0.
Bit 0 (BTD) = 0 normally but is set to 1 if a billing tone is detected. BTD is cleared by writing a 0 to BTD.
U68 resets to 0x0000 with a power-on or manual reset.
U6A is a bit-mapped register with bits 15:3 and 1:0 reserved. Reading these bits returns zero. Bit 2 is read-only
(See Table 69).
Bit 2 (OVL) is a read-only bit that detects a receive overload. This bit is similar to U68 [1] (ROV) except OVL clears
itself after the overload condition is removed.
Table 68. U68 Bit Map*
Bit
Name
15:8
Reserved
Read returns zero.
7:3
Reserved
Do not modify.
2
BTE
Billing Tone Protect Enable.
0 = Disabled.
1 = Enabled.
1
ROV
Receive Overload.
0 = Normal receive input level.
1 = Excessive receive input level.
0
BTD
Billing Tone Detected.
0 = No billing tone.
1 = Billing tone detected (cleared by writing 0).
110
Function
Rev. 1.3
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Table 69. U6A Bit Map*
Bit
Name
Function
15
Reserved
14
SQ1
13
Reserved
12
SQ0
11:3
Reserved
2
OVL
1
Reserved
Read only; value indeterminate.
0
Reserved
Read returns zero.
Read returns zero.
Spark quenching. See OHS2.
Read returns zero.
Spark quenching. See OHS2.
Read returns zero.
Overload Detected.
This bit has the same function as ROV, but clears itself after the overload has been removed.
This bit is only masked by the off-hook counter and is not affected by the BTE bit.
5.7.18. U6C (Line-Voltage Status Register)
U6C contains the line voltage status register, LVS, and resets to 0xXX00. Bits 7:0 are reserved, and a read returns
zero.
5.7.19. U6E–U7D (Modem Control and Interface Registers)
Modem Control and Interface registers include registers U6E, U70–U71, and U76–U79. These are bit-mapped
registers that control functions including TX/RX gain, clocking, I/O, SSI codecs, intrusion detection, and LVCS (line
voltage current sense).
U6E controls the clockout divider. Bits 15:13 and 7:0 are reserved. U6E resets to 0x1FA0 with a power-on or
manual reset (see Table 71).
Bits[12:8] (R1) control the R1 clockout divider. A 196.608 MHz clock signal passes through a divide-by (R1+1)
circuit to derive the CLKOUT signal. If R1 = 00000, CLKOUT is disabled. R1 is set at a default value of 11111,
which results in CLKOUT = 2.048 MHz. The CLKOUT adjustment range (15 < R1 < 30) is 12.288 MHz to
6.342194 MHz.
U6F contains the parallel/SPI port receive FIFO interrupt timer and resets to 0x00FF.
Bits [15:8] are reserved and should not be written to any value other than 0.
Bits[7:0] set the period of an internal timer that is reset whenever the parallel or SPI port receive FIFO (Hardware
Interface Register 0) is read. If the internal timer expires with data in the receive FIFO, an interrupt is generated
regardless of the state of RXF (Hardware Interface Register 1 bit 7). This ensures that the host always removes all
receive data from the parallel or SPI port receive FIFO even if RXF is not set.
Table 70. U6C Bit Map
Bit
Name
Function
15:8
LVS[7:0]
Line Voltage Status.
Eight-bit signed, two’s complement number representing the on-hook or off-hook tip-ring voltage. Each bit represents 1 V. Polarity of the voltage is represented by the MSB (sign bit). A
value of zero indicates a measured voltage of less than 3 V.
7:3
Reserved
Read returns zero.
2:0
RXG[2:0]
Global Receive Gain in dB (Default = 000b).
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Table 71. U6E Bit Map
Bit
Name
15:13
Reserved
Function
Do not modify.
12:8
R1
CLKOUT Divider (Default = 11111b)
7:5
Reserved
Read returns 101b. Do not modify.
4
HRS
3:0
Reserved
Hardware Reset
0 = Normal operation.
1 = Device will perform hardware reset. All registers will return to default settings.
Read returns 0. Do not modify.
Table 72. U6F Bit Map
Bit
15:8
7:0
Name
Function
Reserved Do not modify
PTMR Parallel/SPI Port Receive FIFO Interrupt Timer (in milliseconds)
U70 controls escape and several indicator and detector masks and provides several read-only status bits (see
Table 73). Bits 5, 6, 7, and 14 are reserved.
Bits 4:0 are read only, and bits 15 and 13:8 are read/write. U70 resets to 0x2700 with a power-on or manual reset.
Bit 15 (HES) = 0 (default) disables the hardware escape pin.
Setting HES = 1 enables ESC. When ESC is enabled, escape from the data mode to the command mode occurs at
the rising edge of the ESC pin. Multiple escape options can be enabled simultaneously.
For example, U70 [13] (TES) = 1 by default, which enables the +++ escape. If HES is also set (HES = 1), either
escape method works. Additionally, the 9th bit escape can also be enabled with the AT\B6 command or through
autobaud.
Bit 13 (TES) = 1 (default) enables the standard +++ escape sequence. To successfully escape from data mode to
command mode using +++, there must be no UART, parallel or SPI activity (depending on the interface mode) for a
guard period determined by register S12, both before and after the +++. S12 can be set for a period ranging from
200 ms to 5.1 seconds.
Bit 12 (CIDM) = 0 (default) prevents a change in U70 [4] (CID), Caller ID, from triggering an interrupt. If CIDM = 1,
an interrupt is triggered with a low-to-high transition on CID.
Bit 11 (OCDM) = 0 (default), an interrupt is not triggered with a change in OCD. If OCDM = 1, a low-to-high
transition on U70 [3] (OCD), overcurrent detect, triggers an interrupt. This bit must be set for Australia and Brazil.
Bit 10 (PPDM) = 1 (default) causes a low-to-high transition in U70 [2] (PPD), parallel phone detect, to trigger an
interrupt. If PPDM = 0, an interrupt is not triggered with a change in PPD.
Bit 9 (RIM) = 1 (default) causes a low-to-high transition in U70 [1] (RI), ring indicator, to trigger an interrupt. If
RIM = 0, an interrupt is not triggered with a change in RI.
Bit 8 (DCDM) = 1 (default) causes a high-to-low transition in U70 [0] (DCD), data carrier detect, to trigger an
interrupt. If DCDM = 0, an interrupt is not triggered with a change in DCD.
Bits 4:0 are the event indicators described below. All are “sticky” (i.e., remain high after the event) and are cleared
upon an interrupt read command (AT:I).
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Table 73. U70 Bit Map
Bit
Name
Function
15
HES
14
Reserved
13
TES
12
CIDM
Caller ID Mask.
0 = Change in CID does not affect INT.
1 = CID low-to-high transition triggers INT.
11
OCDM
Overcurrent Detect Mask.
0 = Change in OCD does not affect INT.
(“X” result code is not generated in command mode.)
1 = OCD low-to-high transition triggers INT.
(“X” result code is generated in command mode.)
10
PPDM
Parallel Phone Detect Mask.
0 = Change in PPD does not affect INT.
1 = PPD low-to-high transition triggers INT.
9
RIM
8
DCDM
7:5
Reserved
4
CID
Caller ID (sticky).
1 = Caller ID preamble detected; data to follow. Clears on :I read.
3
OCD
Overcurrent Detect (sticky).
1 = Overcurrent condition has occurred. Clears on :I read.
2
PPD
Parallel Phone Detect (sticky).
1 = Parallel phone detected since last off-hook event. Clears on :I read.
1
RI
0
DCD
Enable Hardware Escape Pin.
0 = Disable.
1 = Enable.
Read returns zero.
Enable Escape (+++).
0 = Disable.
1 = Enable.
Ring Indicator Mask.
0 = Change in RI does not affect INT.
1 = RI low-to-high transition triggers INT.
Data Carrier Detect Mask.
0 = Change in DCD (U70, bit 0) does not affect INT.
1 = DCD high-to-low transition triggers INT.
Read returns zero.
Ring Indicator (sticky).
1 = Ring event has occurred (ISOmodem on-hook). Clears on :I read.
Data Carrier Detect (status).
1 = carrier detected (inverse of DCD pin).
Rev. 1.3
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U71 IO1
Bit
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
Name
COMP
PRT
Type
R/W
R/W
Reset settings = 0x0000
Bit
Name
15:5
Reserved
4
COMP
3:1
Reserved
0
PRT
Function
Read returns zero.
0 – Disables compression (PCM mode).
1 – Enables linear compression.
0 – Disables PCM mode.
1 – Enables PCM mode.
U76 provides control for parallel phone detect (PPD) intrusion parameters including the off-hook sample rate
(OHSR), absolute current level with modem off-hook (ACL), ACL update from LVCS (FACL), and the difference in
current between ACL and LVCS that triggers an off-hook intrusion detection (DCL). All bits in U76 are read/write
(see Table 74).
OHSR[15:9] sets the off-hook loop current sampling interval for intrusion algorithms in 40 ms units. The default
value is 25 (1 s). The minimum recommended value is 5 (200 ms). The interval can be adjusted to much lower
values; however, the likelihood of false intrusion detections increases sharply with intervals of less than 520 ms.
Bit 8 (FACL). If FACL = 0 (default), the ACL register is automatically updated to the LVCS value at the sampling
interval determined by OHSR. This feature is used to ensure the ACL value is continuously updated. Updating ACL
allows host software to determine the loop current (value returned in ACL) provided the modem is off-hook longer
than the time defined by U77 (IST). Loop current on a particular line can vary over time due to a variety of factors
including temperature and weather conditions. Updating ACL reduces the probability of false intrusion detection by
ensuring the ACL reference reflects the most recent off-hook conditions. If FACL = 1, a value can be written into
ACL by the host. This value is not updated and remains in the ACL register until overwritten by the host or until
FACL is returned to 0 and updates from LVCS overwrite the stored value. Writing an initial value to ACL eliminates
the possibility of the modem going off-hook for the first time simultaneously with an intrusion and storing the
intrusion loop current in ACL.
Bits 7:5 (DCL) set the differential level between ACL and LVCS that triggers an off-hook PPD interrupt. DCL is
adjustable in 3 mA units. The default value is 2 (6 mA).
Bits 4:0 (ACL): ACL provides a means of detecting a parallel phone intrusion during the time between the modem
going off-hook and the U77 [15:12] (IST) time value. If ACL = 0, the ISOmodem has no reference and must use the
loop current sample from the first off-hook event as a reference for parallel phone intrusion detection. Typically, the
host sets ACL to an approximate value and FACL = 0 before the first off-hook event after powerup or reset. This
allows the updated ACL value to be used for subsequent calls and eliminates a potential detection problem if an
intrusion occurs simultaneously when the modem goes off-hook for the first time after a powerup or reset. If
ACL = 0, it is ignored by the off-hook intrusion algorithm. A PPD interrupt is generated if U79 [4:0] (LVCS) is DCL
less than ACL for two consecutive samples. The ISOmodem writes ACL with the contents of LVCS after an
intrusion with the last LVCS value before the intrusion. The default value for ACL is 0.
U76 resets to 0x3240 with a power-on or manual reset (see Table 74).
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Table 74. U76 Bit Map
Bit
Name
Function
15:9
OHSR
Off-Hook Sample Rate for Intrusion Detection (40 ms units).
(1 second default)
8
FACL
Force ACL.
0 = While off-hook, ACL is automatically updated with LVCS value.
1 = While off-hook, ACL saves previously written value.
7:5
DCL
Differential Current Level (3 mA units, 6 mA default)
4:0
ACL
Absolute Current Level (3 mA units, 0 mA default)
U77 is a bit-mapped register that controls parameters relating to intrusion detection and overcurrent detection. U77
resets to 0x401E with a power-on or manual reset (see Table 75).
Bits 15:12 (IST) set the delay between the time the modem goes off-hook and the intrusion detection algorithm
begins. This register has 250 ms increments, and the default value is 4 (1 sec).
Bit 11 (HOI) determines whether the host or modem responds to an intrusion. HOI = 0 (default) prevents the
modem from hanging-up in response to an intrusion without host intervention. In this case, the host monitors
U70 [2] (PPD) and takes the appropriate action when PPD is asserted indicating an intrusion. If HOI = 1, the
modem hangs up immediately and will not go off-hook and dial when an intrusion is detected without host
intervention. If %VN commands are set, HOI also causes the LINE IN USE result code upon PPD interrupt.
Bit 9 (AOC) = 0 (default) disables AutoOvercurrent. If enabled and an overcurrent condition is detected, the dc
termination switches to 800 , thus, reducing the current. If AOC = 0, the overcurrent condition is only reported by
U70 [3] (OCD).
Bits 8:0 (OHT) set the delay between the time the modem goes off-hook and LVCS is read for an overcurrent
condition. The default value for this register is 30 ms (see Table 75).
U78 is a bit-mapped register that controls intrusion detection blocking and intrusion suspend. U78 resets to 0x0000
with a power-on or manual reset (see Table 76).
Bits 15:14 (IB) controls intrusion blocking after dialing has begun. Table 76 defines the bit values and intrusion
blocking.
Bits 7:0 (IS) set the delay between the start of dialing and the start of the intrusion algorithm when IB = 10 (see
Table 76).
Table 75. U77 Bit Map
Bit
Name
Function
15:12
IST
Intrusion Settling Time (250 ms units) 1 second default.
11
HOI
Hang-Up On Intrusion.
0 = ISOmodem does not automatically hang up after an off-hook PPD interrupt.
1 = ISOmodem automatically hangs up after an off-hook PPD interrupt.
10
Reserved
Read returns zero.
9
AOC
AutoOvercurrent.
0 = Disable.
1 = Enable.
8:0
OHT[8:0]
Off-Hook Time (1 ms units) 30 ms default.
Rev. 1.3
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Table 76. U78 Bit Map
Bit
Name
15:14
IB
13:8
Reserved
7:0
IS
Function
Intrusion Blocking.
00 = No intrusion blocking.
01 = Intrusion disabled from start of dial to end of dial.
10 = Intrusion disabled from start of dial to IS register time-out.
11 = Intrusion disabled from start of dial to CONNECT XXX, NO DIALTONE, or
NO CARRIER
Read returns zero.
Intrusion Suspend (500 ms units) default = 0 ms.
U79 is a bit-mapped register. Bits 15:6 are reserved.
Bits 5:0 represent the line voltage, loop current, or on-hook line monitor (see Table 77). While the modem is onhook, the value in the LVCS register measures loop voltage (see Table 78). This value can be used to determine if
a line is connected or if a parallel phone or other device goes off-hook or on-hook. The accuracy of the LVCS bits is
±20%. When the modem goes off-hook, the value in the LVCS register measures loop current. LVCS can indicate
when a parallel phone or other device goes on-hook or off-hook and detect whether enough loop current is
available for the modem to operate or if an overload condition exists.
The line voltage monitor full scale may be modified by changing R5 as follows:
VMAX = VMIN + 4.2 x (10 MΩ + R5 + 1.78 kΩ) / (R5 + 1.78 kΩ) / 5
See Table 78. LVCS is backward-compatible with older ISOmodem revisions. The value is absolute and does not
reflect loop polarity. See U6C (LVS) [15:8] for 1 V/bit resolution and signed, two’s complement format and
U63 (LCS) [15:8] for 1.1 mA/bit loop current measurement. The values for loop voltage and loop current in U79 are
calculated by the modem from the values in U6C and U63 respectively.
Table 77. Monitor Mode Values
On-Hook Voltage Monitor Mode
Off-Hook Current Monitor Mode
00000 = No line connected.
00001 = Minimum line voltage (VMIN = 2.5 V ±0.5 V).
11111 = Maximum line voltage (87 V ±20%)
00000 = No loop current.
00001 = Minimum loop current.
11110 = Maximum loop current.
11111 = Overload (more than 60 mA in legacy TBR21
mode or more than 155 mA in other modes)
Table 78. U79 Bit Map
Bit
Name
15:6
Reserved
5:0
LVCS
Function
Read returns zero.
Line Voltage Current Sense.
On-Hook = Voltage Monitor (2.75 V/bit).
Off-Hook = Loop Current Monitor (3 mA/bit).
U7A is a bit-mapped register. U7A resets to 0x0000. Bits 12, 10:8, and 5:3 are reserved.
Bit 7 (DOP) is used in a method to determine whether a phone line supports DTMF or only pulse dialing. See "6.10.
Pulse/Tone Dial Decision" on page 169 for details.
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Bit 6 (ADD) attempts DTMF dial, then falls back to pulse dialing if unsuccessful. The first digit is dialed as DTMF. If
a dial tone is still present after two seconds, this suggests that the DTMF digit was not taken into account by the
central office. In that case, the ISOmodem redials the first digit and remaining digits as pulses. If a dial tone is not
present after two seconds, the ISOmodem assumes that the first DTMF digit was recognized and dials the
remaining digits as DTMF. However, in a typical PBX environment, where dialing a DTMF digit (typically 8 or 9) is
required to obtain an outside line, this method does not give any indication that the outside line can accept TDMF
dialing.
Bit 1 (HDLC) controls whether the normal asynchronous mode (default) is used or the transparent HDLC mode is
enabled. See "5.14. Legacy Synchronous DCE Mode/V.80 Synchronous Access Mode" on page 125 for more
details on these modes.
Bit 0 controls whether the normal ITU/Bellcore modem handshake (default) or a special fast-connect handshake is
used. Fast connect is typically used in specialized applications, such as point-of-sale terminals, where it is
important to connect and transfer a small amount of data rapidly (see Table 79).
Table 79. U7A Bit Map
Bit
Name
Function
15
V29FC
Enable V29 Fast Connect; used in conjunction with AT +FCLASS=1.
1 = Enable
0 = Disable
14
CNSMS
Chinese EPOS SMS enable
1 = Enable
0 = Disable
13
V29EM
Use EM shielding to change direction of half duplex V.29FC.
0 = EM shielding
1) <EM><rrn>=<0x19><0xBC> to receive a V29FC packet.
2) <EM><rtn>=<0x19><0xBD> to send a V29FC packet.
1 = RTS pin toggle.
12
Reserved
11
ARMLO
10:8
Reserved
7
DOP
0 = Normal ATDTW operation.
1 = Use ATDTW for pulse/tone dial detection (see "6.10. Pulse/Tone Dial Decision" on page
169 for details).
6
ADD
Adaptive Dialing.
1 = Enable
0 = Disable
5
Reserved
Read returns zero.
4
NEWFC
3:2
Reserved
Read returns zero.
0 = Normal operation.
1 = Accomodate remote modem with large clock offset, such as 340 ppm. May degrade
training for normal modems; enable only when necessary.
Read returns zero.
New V.22 handshake enable. This bit is mutually exclusive with bit 0. This bit makes hardcoded U80 timing unnecessary. Without this bit, the appropriate value in U80 is required.
Read returns zero.
*Note: When HDLC or FAST is set, the \N0 (Wire mode) setting must be used.
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Table 79. U7A Bit Map (Continued)
Bit
Name
Function
1
HDLC
Synchronous Mode.
0 = Normal asynchronous mode.
1 = Transparent HDLC mode.*
0
FAST
Fast Connect. This bit is mutually exclusive with bit 4; only one bit can be enabled at a
given time.
0 = Normal modem handshake timing per ITU/Bellcore standards.
1 = Fast-connect modem handshake timing.*
*Note: When HDLC or FAST is set, the \N0 (Wire mode) setting must be used.
U7C is a bit-mapped register with bits 15:5 and bits 3:1 reserved. U7C resets to 0x0000 with a power-on or manual
reset.
Bit 4 (RIGPO) is output on RI pin when U7C [0] (RIGPOEN) = 1. This allows the RI pin to be configured as a
general-purpose output pin under host processor control. The RI pin must not pulled down. Doing so forces the
modem to enter an undocumented emulation mode.
Bit 0 (RIGPOEN)=0 (default) allows the RI pin to indicate a valid ring signal. When Bit 0 = 1, RI outputs the value of
RIGPO (See Table 80).
U7D is a bit-mapped register with bits 15,13:9, and bits 8:2 reserved. U7D resets to 0x4001 with a power-on or
manual reset.
Bit 14 (NLM) = 0 (default) causes the modem to automatically detect loop current absence or loss. When bit
14 = 1, this feature is disabled.
Bit 12 (TCAL) = 0 (default) when set to 1 forces the DAA to calibrate at a programmable time after going off-hook.
The time between going off-hook and the start of calibration is programmed with U54 [15:8] in 32 ms units.
Bit 11 (OHCT) = 0 (default) when set to 1 forces the DAA to calibrate at the start of dialing. The first dial character
should be a delay (“,”) to prevent interference with the first digit.
Bit 1 (ATZD) = 0 (default) allows the ATZ command to be active. When Bit 1 = 1, the ATZ command is disabled.
Bit 0 (FDP) = 0 (default). FSK data processing stops when the carrier is lost. Unprocessed data are lost. Setting
Bit 0 = 1 causes FSK data processing to continue for up to two bytes of data in the pipeline after carrier is lost.
Table 80. U7C Bit Map
Bit
Name
15:5
Reserved
4
RIGPO
3:1
Reserved
0
118
Function
Read returns zero.
RI pin
Follow this bit when U7C [0] (RIGPIOEN) = 1.
Read returns zero.
RIGPOEN 0 = RI pin indicates valid ring signal.
1 = RI pin follows U7C [4] (RIGPO).
Rev. 1.3
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Table 81. U7D Bit Map
Bit
Name
Function
15
Reserved
14
NLM
13
Reserved
12
TCAL
0 = Timed calibration disabled.
1 = Timed calibration. The time between off-hook and calibration is set in U54 (OHCT).
11
CALD
0 = No calibration during dial.
1 = Calibrate during dial. It is recommended that the dial string start with “,” to prevent first
digit loss.
10:2
Reserved
Read returns zero.
1
ATZD
0 = ATZ enabled.
1 = ATZ disabled.
0
FDP
0 = FSK data processing stops when carrier is lost.
1 = FSK data processing continues for two bytes after carrier is lost.
Read returns zero.
Host software recommended to always set this to bit.
0 = Enables “No Loop Current” Detect.
1 = Disables “No Loop Current” Detect.
Read returns zero.
5.7.20. U80 (Transmit Delay for V.22 Fast Connect)
U80 controls delay parameters when the modem is in V.22 Fast Connect mode (+MS=V22, AT:U7A,3) and the
server does not respond with a short answer tone prior to scrambled data or HDLC flags. U80 configures the
modem to operate without these tones. Bit 15 turns this function on. After the end of dialing, the modem waits for a
time set by U80 [14:0], then begins transmitting scrambled data (or HDLC Flags). The delay units are 1/600 s. For
example, to command the modem to begin transmitting three seconds after the end of dialing:
3 x 600 = 1800 = 0x0708. Issue command AT:U80,8708.
This register is only used when U7A[4] = 0.
U80 XMITDEL Transmit Delay for V.22 Fast Connect
Bit
15
Name
Function
V22FCDF 0 = Normal operation (default)
1 = Transmit scrambled data (or HDLC flags) after delay set in bits 14 - 0
14:0
V22FCDEL When V22FCDF = 1, V22FCDEL is the delay between end of dialing and sending
scrambled data (or HDLC flags) in 1/600 s units. Default is 0x0168 (600 ms).
When V22FCDEL = 0, V22FCDEL is the delay between ANS tone detected to start of
training.
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5.7.21. U87 (Synchronous Access Mode Configuration Register)
U87 SAM Synchronous Access Mode Configuration Options
120
Bit
Name
Function
15:11
Reserved
10
MINT
Minimal Transparency
Host software must always set this bit.
0 = Generate two-byte <EM> transparency sequences. This option will use codes
<EM><T5> through <RM><T20> (if possible) for received data containing two back-toback bytes requiring transparency (Rev C and later).
1 = Generate one-byte <EM>transparency sequences. This option will only use codes
<EM><T1> through <EM><T4> for received data (Rev B and later).
9
SERM
Special Error Reporting Mode
0 = Ignore unrecognized in-band commands.
1 = Generate <EM><0x45> (“E” for error) in response to any unrecognized in-band
commands.
8
FSMS
Framed Sub-Mode Startup
0 = Upon successful connection, enter Transparent Sub-Mode. An <EM><FLAG>
is required to enter Framed Sub-Mode.
1 = Upon successful connection, immediately enter Framed Sub-Mode. The first
received <EM><err> (from a successful hunt) is transformed into an <EM><flag>.
7:0
XMTT
Transmitter Threshold
This value represents the number of bytes before a transmission is started. The following values are special:
0
The same as ten. Upon receipt of ten bytes, data are transferred. The DTE must
supply a closing flag within the required time or an underrun will occur.
255 The same as infinity, e.g. never start a packet until the closing flag is received.
Read returns zero.
Rev. 1.3
AN93
5.7.22. UAA (V.29 Mode Register)
UAA V.29 MODE
Bit
Name
Function
15:3
Reserved
2
RUDE
1
V29ENA
0 = Disables V.29.
1 = Enables V.29.
0
Reserved
Read returns zero.
Read returns zero.
0 = Disables rude disconnect.
1 = Enables rude disconnect.
5.7.23. UIDA Response and Answer Tone Delay Register
This register, which is reset to 0, allows the user to add a delay in increments of milliseconds to the time the
modem waits before responding to an answer tone. This is useful in dealing with non-standard answering modems.
5.8. Firmware Upgrades
The Si24xx ISOmodem family contains an on-chip program ROM that includes the firmware required for the
features listed in the data sheet. Additionally, the ISOmodem contains on-chip program RAM to accommodate
minor changes to ROM firmware. This allows Silicon Labs to provide future firmware updates to optimize the
characteristics of new modem designs and those already deployed in the field.
Firmware upgrades (patches) provided by Silicon Labs are files loaded into the ISOmodem program RAM after a
reset using the AT:P command (see Table 39 on page 59). Once loaded, the upgrade status can be read using the
ATI1 command to verify the firmware revision number. The entire firmware upgrade in RAM is always cleared on
reset. To reload the file after reset or power down, the host processor rewrites the file using the AT:P command
during post-reset initialization.
Patch files may be more than 6000 characters in some cases. They come in a .txt file containing multiple lines that
are sent serially to the ISOmodem. Several patch-loading techniques can be used in different environments. See
the description and Table 82. Whichever technique is used, it is suggested to do AT&T6 to verify the CRC of the
loaded patch.
5.8.1. Method 1 (Fastest)
Send the entire file in quiet mode using a program that waits for a set amount of time after every line. This can
result in load times as short as 0.7 seconds for a 6235-byte patch at 115 kbaud (UART interface mode). The file
transfer should be preceded by ATZ or reset and followed by ATE0 and ATQ1. After the transfer, perform ATE1 and
ATQ0 as needed. The delay between lines must be increased when using the parallel or SPI interface.
1. Low pulse on RESET signal for at least 5.0 ms.
2. Wait the reset-recovery time.
3. Send ATE0.
4. Wait for OK.
5. Send ATQ1 to the modem.
6. Wait 20 ms.
7. Send AT:PIC (first line of the patch).
8. Wait 20 ms.
...
(n-5) Send AT:PIC0 (last Line of Patch).
(n-4) Wait 20 ms.
(n-3) Send ATQ0 to the modem.
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(n-2) Wait for OK.
(n-1) Send AT&T6 to the modem.
(n) Wait for OK.
5.8.2. Method 2
Send the entire file using a program that waits for OK after every line. This will require 3.98 seconds for a 6235 byte
patch at 115 kbaud or longer if the OS has latency.
5.8.3. Method 3
For development purposes, send the entire patch file using a program that allows a timed preprogrammed pause
between lines, e.g. HyperTerminal or ProComm. This will give times of around 16 seconds for a 6235 byte patch (at
115 kbaud). Due to the granularity of a typical desktop operating system, be sure to set the time delay between
lines to 100 ms.
Table 82. Load Technique and Speed Table*
Start Condition
Delay
Between
Lines
Load time, 6235-Byte
Patch, 115 kbaud UART
Approach Used With
Reset, then
ATE0 and ATQ1
0.5 ms
0.694
Embedded systems
1 ms
0.771
Embedded systems
2 ms
0.925
Embedded systems
5 ms
1.385
Embedded systems
10 ms
2.152
Embedded systems
Reset
Wait for OK
3.998
Windows or embedded system where
time precision is worse than 10 ms
Reset
100 ms
15.962
Windows without writing a patch loader
*Note: The delay times do not include the time to empty the UART's possibly long TX buffer. The time quoted is between the
end of transmission of the last character of a line and the start of transmission of the first character of the next line.
A CRC can be run on the upgrade file loaded into on-chip Program RAM with the AT&T6 command to verify that
the upgrade was correctly written to the on-chip memory. The CRC value obtained from executing the AT&T6
command should match the CRC value provided with the upgrade code.
5.9. Escape Methods
There are four ways to escape from data mode and return to command mode once a connection is established.
Three of these, +++, “9th Bit”, and the “Escape Pin”, allow the connection to be maintained while one or both
modems are in the command mode. The fourth method is to terminate the connection. The three escape methods
that maintain the connection are combined by a logical OR. For example, if +++ and the “Escape Pin” are both
enabled, either returns the modem to the command mode from the data mode. In parallel or SPI mode, the escape
pin is not available. Instead the system can set the ESC flag in Hardware Interface Register 1 (HIR1).
While in data mode, an escape to command mode occurs if an escape command is sampled as negated for at
least 60 ms, then sampled asserted for at least 60 ms. The modem is then prepared to accept AT commands,
regardless of whether OK has been sent to the host. If the modem is already in command mode, the modem does
not send OK. The host should always wait for OK before entering the next command after an escape.
When making a new connection, the host must not try to escape between the connect message and the protocol
message. An escape attempt in this interval may fail because the modem is not in data mode until after the
protocol message. In practice, it is difficult to determine the exact boundary between command mode and data
mode. The recommendation is to time the escape command 100 ms low and 100 ms high, and expect that the
modem has transitioned to command mode.
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The system should then flush the receive buffer 100 ms after the escape command has been removed, send AT,
and wait for OK. This ensures that the modem is in command mode because OK is caused by the AT command
and not by the escape command.
5.9.1. +++ Escape
The +++ escape is enabled by default and is controlled by U70 [13] (TES). There are equal guard time periods
before (leading) and after (trailing) the +++ set by the register S12, during which there must be no interface (UART,
SPI or parallel) activity. If this inactivity criterion is met, the ISOmodem escapes to the command mode at the end
of the S12 time period following the +++. Any activity in the host interface during either the leading or trailing time
period causes the ISOmodem to ignore the escape request and remain in data mode. Timing for this escape
sequence is illustrated in Figure 27.
+++
Leading Guard
Tim e
Trailing Guard
Tim e
Guard Tim e = S12 (20 m sec units)
Default Guard Tim e S12 = 50 (1.0 sec)
Guard Tim e Range = 10–255 (0.2–5.1 sec)
Figure 27. +++ Escape Timing
5.9.2. “9th Bit” Escape
The “9th Bit” escape mode feature is enabled by sending the AT\B6 command through autobaud, which detects a
9th bit space as “9th bit” escape mode. If this escape method is selected, a 1 detected on the ninth bit in a data
word returns the modem to the command mode. The 9th bit is ignored when the modem is in the command mode.
Timing for this escape sequence is illustrated in Figure 28.
UART Tim ing for Modem Transm it Path (9N1 Mode with 9th Bit Escape)
9-Bit Data
Mode
TX
Start
D0
D1
D2
D3
D4
D5
D6
t RTS
D7
ESC
Stop
t CTH
CTS
Figure 28. “9th Bit” Escape Timing
5.9.3. “Escape Pin” Escape
The “escape pin is controlled by U70 [15] (HES). This bit is 0 by default, which disables the escape pin, ESC. If
HES is set to a 1, a high level on the ESC pin causes the modem to transition to the on-line command mode. The
ESC pin status is polled by the processor, and there is a latency before OK is received and the modem is in
command mode. The escape pin must be kept active until OK is received. In parallel or SPI interface mode, the
function of the escape pin is replaced by bit 2 in Hardware Interface Register 1, described in "2.2.4.2. Hardware
Interface Register 1" on page 25. Setting that bit high causes the modem to escape to the command mode.
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5.10. Data Compression
The modem can achieve DTE (host-to-ISOmodem) speeds greater than the maximum DCE (modem-to-modem)
speed through the use of a data-compression protocol. The compression protocols available are the ITU-T V.44,
V.42bis, and MNP5 protocols. Data compression attempts to increase throughput by compressing the information
to be sent before actually sending it. The modem is thus able to transmit more data in a given period of time.
Table 83 details the ISOmodem error correction and data compression modes of operation.
Table 83. Enabling Error Correction/Data Compression
To Enable
Use AT Commands
V.44*
V.42bis
V.42 (LAPM)
MNP5
MNP2–4
Wire
+DS44 (argument)
\N3 and %C1 (default)
V.42 and
V.42bis only
\N4 and %C1
V.42 only
\N4 and %C0
MNP2-4 only
\N2 and %C0
MNP2-5 only
\N2 and %C1
No data compression and
no error correction
\N0 and %C0
*Note: V.44 is available only on Si2493.
5.11. Error Correction
The ISOmodem can employ error correction (reliable) protocols to ensure error-free delivery of data sent between
two modems. The error control methods are based on grouping data into frames with checksums determined by
the contents of each frame. The receiving modem checks the frames and sends acknowledgments to the
transmitting modem. When it detects a faulty frame, the receiving modem requests a retransmission. Frame length
varies according to the amount of data transmitted and the number of retransmissions requested from the opposite
end.
The ISOmodem supports V.42 and MNP2–4 error correction protocols. V.42 (LAPM) is most commonly used and is
enabled in the \N3 and \N4 modes. In the default mode (\N3), the ISOmodem attempts to connect with V.42 error
correction and V.42bis data compression (Si2457/34/15), and falls back to either V.42 only, MNP 2–5, or no error
correction (wire mode) if necessary. In \N4 mode, the ISOmodem hangs up if a V.42 connection cannot be
established. If the ISOmodem hangs up in V.42 mode after all data are successfully sent, the result code is OK. If
the modem hangs up before all data are successfully sent, the result code is NO CARRIER. If the modem connects
without a protocol, NO CARRIER is always sent.
The V.42 specification allows an alternate error correction protocol, MNP2-4. MNP2-4 is enabled in \N2 mode. In
\N2 mode, the ISOmodem hangs up if an MNP2, 3, or 4 connection cannot be established.
5.12. Wire Mode
Wire mode (\N0) is used to communicate with standard, non-error-correcting modems. When optioned with \N3,
the ISOmodem falls back to Wire mode if it fails in an attempt to negotiate a V.42 or MNP2-4 link with the remote
modem. Error correction and data compression are not active in wire mode.
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5.13. EPOS (Electronic Point of Sale) Applications
EPOS applications are discussed in "Appendix A—EPOS Applications" on page 257.
5.13.1. EPOS Fast Connect
The ISOmodem supports several fast connect modes of operation to reduce the time of a connect sequence in
originate mode.
5.13.2. EPOS V.29 Fast Connect
In addition to the low modulation speed fast-connect modes, the modem (only Si2493/57/34/15) also supports a
fast-connect mode based on the 9600 bps V.29 fax modulation standard. V.29 Fast Connect is available as a
patch. Please contact Silicon Laboratories for additional details.
5.14. Legacy Synchronous DCE Mode/V.80 Synchronous Access Mode
The ISOmodem supports two different DTE interfaces to implement an Asynchronous DTE to Synchronous DCE
conversion. Table 84 provides high-level options to choose between the Legacy Synchronous DCE Mode and the
newer V.80 synchronous access mode.
Table 84. Synchronous Mode Overview
Mode
U Register
AT+ES
Settings
Neither
U7A [2] = 0
+ES = D,,D
Legacy Synchronous
DCE Mode
U7A [2] = 1
+ES = D,,D
Synchronous Access
Mode
+ES = 6,,8
The synchronous access mode has more features than the Legacy Synchronous DCE Mode. For new designs,
use of the newer synchronous access mode interface is recommended. Otherwise, existing software written with
the Legacy Synchronous DCE Mode interface can still be used as long as the AT+ES command settings are not
changed from the default value.
5.15. V.80 Mode
As shown in Table 85, the synchronous access mode is chosen by using the AT+ES=6,,8 command setting.
When using the synchronous access mode, it is expected that the AT\N0 command will be used to disable all other
error correction protocols that may interfere with V.80 synchronous access mode operation.
The V.80 Mode has two distinct submodes. Switching between these two submodes can be accomplished within
the confines of the same connection through the use of In-Band commands. The submodes are:

Transparent Submode
Framed Submode
The Transparent Submode creates a direct bit-by-bit translation from the DTE to and from the DCE. Any
application that requires a method of reconstructing a serial bit-stream at the DCE can use the Transparent Submode.

The Framed Sub-mode represents data at the DCE in HDLC/SDLC frames. This submode is typically used in
point-of-sale terminals. A common feature used in conjunction with the Framed Submode is the use of the 16-bit
CRC. When used with the CRC option, the Framed Submode can be used in the same applications currently using
the Legacy Synchronous DCE Mode.
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Prior to sending the ATDT to establish a synchronous access mode connection, the following commands and
registers require initialization: +MS, +ES, +ESA, +ITF, +IFC, U87, and U7A.
As an example, the closest equivalent to the Legacy Synchronous DCE Mode is the following initialization setting.
With either Synchronous Access Submode, once a connection has been established, payload data are multiplexed
with command/indicator information by use of <EM> shielding. With <EM> shielding, either of the two bytes
<0x19> or <0x99> (used to represent <EM>) precedes a special command or special indicator.
Synchronous access mode <EM> shielding is designed to support XON/XOFF handshaking. As such, the bytes
0x13 and 0x11 (XON/XOFF) are considered to be special characters in the same way the 0x19 and 0x99 bytes,
used for <EM>, are special.
Since the payload data are multiplexed with <EM> shielded command/indicator and possibly XON/XOFF
characters, Transparency <EM> codes are defined for the purpose of allowing the host software to send 0x13,
0x11, 0x19 and 0x99 bytes to/from the DCE. For example, if one <0x99> character needs to be sent as payload,
the host software sends <EM><0x76> instead. For a complete list <EM> commands and statuses, see Table 86.
Table 85. Synchronous Access Mode Settings
126
AT\N0
Required to disable MNP,V.42
and other protocols
AT+ES = 6,,8
Enable synchronous access
mode on originate or answer
AT+ESA = 0,0,0,,1,0
Send Abort on underrun/overrun in Framed Submode.
Enable CRC generation and
checking.
AT+IFC = 2,2
CTS/RTS Flow Control
AT+ITF = 0383,0128
Controls CTS Flow Control
Threshold. CTS off at 383
bytes, CTS On at 128 bytes.
AT:U87,050A
Direct to Framed Sub-mode
upon connection. DCE starts
to transmit upon receipt of 10
bytes from the DTE.
Rev. 1.3
AN93
Table 86. EM In-Band Commands and Statuses
Command–
Indicator pair
Hex
Code
Supported
in
Transparent
Submode
Supported
in Framed
Submode
Transmit Direction
Receive Direction
<EM><t1>
0x5C Transmit one 0x19 byte
Received one 0x19 byte
Yes1
Yes1
<EM><t2>
0x76 Transmit one 0x99 byte
Received one 0x99 byte
Yes1
Yes1
<EM><t3>
0xA0 Transmit one 0x11 byte
Received one 0x11 byte
Yes1
Yes1
<EM><t4>
0xA1 Transmit one 0x13 byte
Received one 0x13 byte
Yes1
Yes1
<EM><t5>
0x5D Transmit two 0x19 bytes
Received two 0x19 bytes
Yes
Yes
<EM><t6>
0x77 Transmit two 0x99 bytes
Received two 0x99 bytes
Yes
Yes
<EM><t7>
0xA2 Transmit two 0x11 bytes
Received two 0x11 bytes
Yes
Yes
<EM><t8>
0xA3 Transmit two 0x13 bytes
Received two 0x13 bytes
Yes
Yes
<EM><t9>
0xA4 Transmit 0x19, 0x99
Received 0x19, 0x99
Yes
Yes
<EM><t10>
0xA5 Transmit 0x19, 0x11
Received 0x19, 0x11
Yes
Yes
<EM><t11>
0xA6 Transmit 0x19, 0x13
Received 0x19, 0x13
Yes
Yes
<EM><t12>
0xA7 Transmit 0x99, 0x19
Received 0x99, 0x19
Yes
Yes
<EM><t13>
0xA8 Transmit 0x99, 0x11
Received 0x99, 0x11
Yes
Yes
<EM><t14>
0xA9 Transmit 0x99, 0x13
Received 0x99, 0x13
Yes
Yes
<EM><t15>
0xAA Transmit 0x11,0x19
Received 0x11,0x19
Yes
Yes
<EM><t16>
0xAB Transmit 0x11,0x99
Received 0x11,0x99
Yes
Yes
<EM><t17>
0xAC Transmit 0x11,0x13
Received 0x11,0x13
Yes
Yes
<EM><t18>
0xAD Transmit 0x13,0x19
Received 0x13,0x19
Yes
Yes
<EM><t19>
0xAE Transmit 0x13,0x99
Received 0x13,0x99
Yes
Yes
<EM><t20>
0xAF Transmit 0x13,0x11
Received 0x13,0x11
Yes
Yes
<EM><mark>
0xB0 Begin Transparent Mode
Abort Detected in Framed
Submode
Yes
Yes, Receive
Only
<EM><flag>
Transmit a flag; enter
Framed Submode if currently in Transparent Sub0xB1 mode. If +ESA[E] = 1,
append FCS to end of
frame before sending
closing HDLC flag.
Detected a non-flag to flag
transition. Preceding data was
a valid
frame. If +ESA[E]=1, sent FCS
matches that of the calculated
CRC.
Yes
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Table 86. EM In-Band Commands and Statuses (Continued)
Command–
Indicator pair
Hex
Code
Transmit Direction
Receive Direction
Supported
in
Transparent
Submode
Yes
Supported
in Framed
Submode
<EM><err>
0xB2 Transmit an Abort
Detected a non-flag to flag
transition.
Preceding data are not a valid
frame.
<EM><under>
0xB4 not applicable
Detected Transmit Data
Underrun
Yes
Yes
<EM><tover>
0xB5 not applicable
Detected Transmit Data Overrun
Yes
Yes
<EM><rover>
0xB6 not applicable
Detected Receive Data Overrun
Yes
Yes
<EM><resume
>
Resume after a data
underrun or overrun
0xB7
(applicable if
+ESA[C] = 1)
Not applicable
0xB8 not applicable
<octnum0><octnum1> specifies
number of octets in the transmit data
buffer if +ITF[C] is non-zero2.
<EM><unum>
0xB9 not applicable
<octnum0><octnum1> specifies
number of discarded octets following
a data overrun/underrun, after
the
<EM><resume> command.
This is
applicable if +ESA[C] = 12.
<EM><eot>
0xBA
<EM><ecs>
Escape to On-Line com0xBB mand
mode
<EM><rrn>
0xBC
<EM><bnum>
128
Yes
Yes
Yes
Yes
Confirmation of Escape to OnLine
command mode.
Yes
Yes
Indicate rate renegotiation
Yes
Yes
Loss of carrier detected, return
Terminate carrier, return to
to
command mode.
command mode
Request rate renegotiation
Yes
Rev. 1.3
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Table 86. EM In-Band Commands and Statuses (Continued)
Command–
Indicator pair
Hex
Code
Transmit Direction
Receive Direction
Supported
in
Transparent
Submode
Supported
in Framed
Submode
Yes
Yes
Retrain/Rate Reneg completed, following octets
<tx><rx> indicate tx and rx
rates.
0x20–1200 bps
0x21–2400 bps
0x22–4800 bps
0x23–7200 bps
0x24–9600 bps
0x25–12 kbps
<EM><rate>
0xBE not supported
0x26–14.4 kbps
0x27–16.8 kbps
0x28–19.2 kbps
0x29–21.6 kbps
0x2A–24 kbps
0x2B–26.4 kbps
0x2C–28.8 kbps
0x2D–31.2 kbps
0x2E–33.6 kbps
Notes:
1. U87 [10] = 1 Can be used to limit the transparency characters in the receive direction, to these four cases only.
2. The actual value represented in <octnum0><octnum1> = (octnum0 / 2) + (octunum1 x 64)
3. <EM><0x45> indicates that an unrecognized <EM> command was sent to the modem.
In addition, a common Point-of-Sale V.22 Fast Connect Handshake Protocol (with transparent HDLC) requires
these additional settings:
Table 87. Fast Connect Settings
AT+MS = V22
AT:U7A,3
V22 Protocol
Set Fast Connect, Transmit
HDLC Flags instead of Marks
during handshake negotiation.
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Given the example initialization settings shown in Table 87, after an ATDT command has been sent to establish a
connection, the modem responds with the following:
ATDT12345
CONNECT 1200
PROTOCOL: NONE
<0x19> <0xBE> <0x20> <0x20> <0x19> <0xB1>
The first <EM><rate> indicator shows that the modem connected with a transmit rate of 1200 bps and a receive
rate of 1200 bps. The <EM><flag> that occurs immediately after the <EM><rate> indicates that a non-flag to flag
transition has occurred and that the receiver has now been synchronized. An <EM><flag> indicator is applicable
only to the first occurrence of a non-flag to flag transition. Future occurrences of non-flag to flag transitions are
indicated with an <EM><err> instead. Also, this feature is unique to the U87 [8]=1 option. Also, with U87 [8]=1, the
Framed Submode is entered immediately upon connection. Otherwise, if U87 [8]=0, the Transparent Submode is
entered instead, and the host is expected to send an <EM> <flag> to switch to the Framed Submode.
After a connection has been established, the modem is ready to transmit and receive frames. For example, if it is
desired to send a frame whose contents are:
<0x10><0x11><0x12><0x13><0x14><0x15>
The host software sends the following:
<0x10><0x19><0xA0><0x12><0x19><0xA1>
<0x14><0x15><0x19><0xB1>
Note the bytes <0x11> and <0x13> are <EM> shielded because these bytes could have been used for XON /
XOFF handshaking. In this example, CTS/RTS hardware handshaking is used, so it is also possible for the host to
have sent this series of bytes instead:
<0x10><0x11><0x12><0x13><0x14><0x15>
<0x19><0xB1>
However, if the host does not <EM> shield the 0x11 and 0x13 characters, XON / XOFF software handshaking can
no longer be used.
In either of the above transmit frames, the <EM><flag> is used to indicate that a logical frame has completed. The
modem does not begin transmitting the frame at the DCE until the <EM><flag> is received or the number of bytes
sent to the modem exceeds the number of bytes programmed into U87 [7:0].
In the above example, the following transmission:
<0x10><0x19><0xA0><0x12><0x19><0xA1>
<0x14><0x15><0x19><0xB1>
meets both criteria of having 10 bytes received at the DTE and receipt of an <EM><flag> command. In this
example, the transmission at the DCE begins approximately after the receipt of the <0xB1> byte.
Once an HDLC frame begins transmitting at the DCE, the host must ensure transmit overrun and underrun do not
occur. It is expected that the +ITF command be used to adjust the transmit flow control thresholds so that it is tuned
to the system's ability to process the interrupt.
If a transmit underrun occurs, the <EM><tunder> indicator always appears in the receive path, regardless of how
+ESA[C] is programmed.
If +ESA[C] = 0, the modem transmits an abort character at the DCE at the point of the transmit underrun. Additional
transmit frames can then be transmitted normally.
If +ESA[C] = 1, the modem transmits an HDLC flag at the point of the transmit underrun, and the DCE continues to
send only HDLC flags until the host sends an <EM><resume> command. The <EM><resume> is then followed by
the <EM><unum> command so that the host software can correct this problem.
A transmit overrun can occur if the host does not properly implement transmit flow control. When a transmit
overflow occurs, the <EM><tover> indicator always appears in the receive path. A transmit overflow is considered
to be a catastrophic failure and results in non-deterministic behavior at the DCE. It is recommended that the
session be terminated immediately.
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It is expected that the <EM><tover> and <EM><tunder> indicators be encountered during system debug, and
designing the system software properly to avoid having these indicators occur should be the design goal.
In the receive direction, assuming that the remote modem is another Si2493/57/34/15, this is the expected
sequence at the remote receiver DTE, representing the frame sequence of:
<0x10><0x11><0x12><0x13><0x14><0x15>
<0x10><0x19><0xA0><0x12><0x19><0xA1>
<0x14><0x15><0x19><0xB1>
In the receive direction, the <EM><flag> indicates that the CRC check is successful, and the preceding frame was
received correctly. If there had been an error in the preceding frame, the <EM><err> would have been sent instead
of the <EM><flag>. The host is expected to discard the entire frame based on whether or not the frame is
terminated with an <EM><flag> or <EM><err>. The host should also expect to occasionally see the <EM><mark>
indicator if the sending modem experienced a transmitter underrun or overrun problem.
In general, the RTS flow control is not used. However, if it is used, and if RTS is negated for too long, the receive
buffers will eventually overflow. This is called a receiver overrun, and the modem sends an <EM><rover> indicator.
A receiver overrun is considered to be a catastrophic failure, and the host is expected to terminate the session.
Host software must be designed so that an <EM><rover> indicator never occurs.
It is expected that the <EM><rover> indicator be encountered during system debug, and designing the system
software properly to avoid having these indicators occur should be the design goal.
Please note that there is an option available in the U87 [10]. The reason for this option is to determine what the
modem sends to the DTE when the modem receives back-to-back occurrences of the special characters, 0x19,
0x99, 0x11, and 0x13, at the DCE.
As an example, if the following string is received at the DCE:
<0x19><0x19><0x11><0x11>
If U87 [10] = 0, this is what the host software will receive at the DTE:
<0x19><0x5D><0x19><0xA2>
If U87 [10] = 1, this is what the host software will receive at the DTE:
<0x19><0x5C><0x19><0x5C><0x19><0xA0><0x19><0xA0>
The choice of how to program U87 [10] is based on whether or not it is desired to simplify the host receive parsing
algorithm or to guarantee that the receive throughput is not overly affected by the <EM> <shielding>. In the worst
case, if there is a large frame consisting only of special characters, the required throughput at the DTE will have to
be at least 2x that of the DCE rate to account for the <EM> shielding overhead.
There are two methods of ending a call. One is to use the <EM><eot> command followed by an ATH. Sending the
<EM><eot> command will cause the modem to go to command mode and stop the transmitter; however, the
modem does not go back on hook until ATH. The other method is to use the <EM><esc> command to escape to
command mode, and then issue the ATH command. The main difference is that the <EM><esc> does not shut off
the transmitter. The <EM><esc> can also be followed by an ATO to resume the connection.
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6. Programming Examples
The following programming examples are intended to facilitate the evaluation of various modem features and serve
as example command strings that can be used singly or in combination to create the desired modem operation.
6.1. Quick Reference
Table 88 summarizes the modem function/feature and the associated hardware pins, AT commands, S registers,
and U registers. When a command string is created to enable a particular feature, Table 88 should be reviewed to
make sure all necessary commands and registers have been considered.
Table 88. Modem Feature vs. Hardware, AT Command and Register Setting
Function/Feature
AT Commands
Autobaud
\T16, \T17
Blacklisting
%B
Type I Caller ID
+VCID, +VCDT
Type II Caller ID
+PCW
+VCID
+VCIDR
S Registers
42, 43, 44
U70 [12,4]
Country-dependent settings
U0–U4C, U4D [10,1,0], U50–U52,
U62 [8], U67 [6, 3:2, 1, 0],
U68 [2, 1, 0], U69 [6, 5, 4]
DTE interface
En, \Bn, \Pn, \Qn,
\Tn, \U
DTMF dialing
D
EEPROM
:E, :M
6, 8, 14
Escape (parallel/SPI)
Escape (UART)
U46–U48, U4E
U70 [15], Parallel Register 1 [2]
\B6
12
Intrusion detection
U70 [13,15]
U6A [1], U69 [2], U70 [10, 2],
U76 [15:9, 8, 7:5, 4:0], U77 [15:12, 11],
U78 [15:14, 7:0], U79 [4:0], UAE
Line rate
&Gn, &Hn
Modem-on-hold
+PCW
+PMHF
+PMHR
+PMHT
+PMH
+ATO
Overcurrent detection
132
U Registers
U67 [7], U70 [11, 3],
U77 [10, 9, 8:0], U79 [4:0]
Power control
&Z
24
U65 [13]
Pulse dialing
D
6, 8, 14
U37–U45, U4E
Rev. 1.3
AN93
Table 88. Modem Feature vs. Hardware, AT Command and Register Setting (Continued)
Function/Feature
AT Commands
Quick connect
+PQC
+PSS
Reset
Z
S Registers
U Registers
U6E [4], U70 [7,5]
SAS detect
U9F–UA9
Self Test
&Tn, &Hn
40, 41
SMS
+FCLASS
+FRM
+FTM
V.29
+FCLASS
+FTM
+FRM
V.42/V.42b
+DR, %Cn, \Nn,
+DS
V.44*
+DS44, +DR
V.92
+MS
+PIG
*Note: Si2493 only.
6.2. Country-Dependent Setup
Configuring the ISOmodem for operation in different countries is done easily with AT commands. In all but rare
instances, no hardware change is required (the exceptions being an optional maximum ringer impedance, a billingtone filter, etc.). For this reason, the ISOmodem is truly a global modem solution. Modem initialization commands
for various countries are presented in "6.2.2.1. Country Initialization Table". All U-register values are in
hexadecimal. The settings for different countries can be broken into three groups: call progress, dialing, and lineinterface control. Call-progress settings include filter coefficients, cadence data, and threshold values. Dialing
includes DTMF levels, thresholds, timing and pulse-dialing parameters. Line-interface settings include ac line
impedance, off-hook voltage and current characteristics, ringer sensitivity, and transmit levels. CID (Caller ID)
settings are discussed in a separate section. Tables 89–93 describe the registers and bits used for global
configuration and the functions performed by each. Many countries use some or all of the default FCC settings.
6.2.1. DC Termination
The ISOmodem offers a great deal of flexibility in setting dc termination. Several bits can be used to adapt to
particular country requirements and unusual line conditions. The dc termination control bits are shown in Table 89.
Table 89. DC Termination Control Bits
Reg
Bit
U67
7
DCR DC Impedance Select
Val
Function
U67
3:2
DCV DC Termination Select
U7D
10
LLV
Special low-voltage mode
A detailed description of each bit is given in the relevant U-register description section of this manual. The following
discussion centers on the use of these bits alone or in combination to meet particular country requirements.
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6.2.2. Country Configuration
The modem default settings are for the US-like countries. Many countries use at least some of the default register
settings. Default values do not have to be written when configuring the modem to operate in a particular country,
assuming the modem was reset just prior to the configuration process. To avoid confusion and possible errors,
the modem should be reset prior to reconfiguration between countries.
Some countries have unusual requirements. For example, registers U37–U40 set the number of pulses to dial
digits 0 through 9, respectively. By default, digit 1 has a setting of 1 pulse; digit 2 has a setting of 2 pulses, and so
on. Digit 0 has a setting of 0xA (10 decimal) pulses. This pulse arrangement is used nearly universally throughout
the world. However, New Zealand requires ten pulses for 0, nine pulses for 1, eight pulses for 2, and so on.
Sweden, on the other hand, requires one pulse for 0, two pulses for 1, and so on.
Japan requires both the usual 10 pps pulse dialing and 20 pps pulse dialing. To configure the modem for 20 pps,
set U42 (PDBT) = 0x0022, U43 (PDMT) = 0x0010, and U45 (PDIT) = 0x0258. The %P command may also be
used.
The Netherlands has a unique dial-tone filter. Other countries, such as Japan, have special low-voltage loop
requirements. South Korea, Poland, and South Africa have special ringer impedance requirements. Set all countryspecific parameters listed in Table 90.
In order to use the +GCI command for a given country and modify one or more U registers, it is necessary to
execute the +GCI command first, then modify the desired register or registers. The +GCI command resets all U
registers through U86 and S7 to factory defaults before applying the country-specific settings. A compliance
laboratory can verify whether the countries that accept the legacy TBR21 specification still accept their previous
settings. It is advantageous in terms of heat dissipation to disable the TBR21 current limit. In order to disable loopcurrent limiting, bit ILIM (U67 [9]) should be set to zero after the +GCI command.
Table 90 contains recommended updates to the +GCI register settings. The U-register writes must be loaded after
the +GCI command. Some TBR21 and ES 203 021 countries require blacklisting. This can be enabled with
S42 = 1. Some also require a minimum period of time between calls that can be set with S50 = 6.
6.2.2.1. Country Initialization Table
Table 90. Country Initialization Table
Country
Initialization
Algeria*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
Argentina*
AT+GCI=51
AT:U46,680
AT:U52,1
ATS007=50
Armenia*
AT+GCI=73
ATS007=80
Australia
AT+GCI=9
AT:U42,55,F
AT:U4F,79
AT:U52,2
ATS006=3
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
Austria
AT+GCI=A
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Bahamas
Defaults
Bahrain*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
Belarus*
AT+GCI=73
Belgium
AT+GCI=F
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Bermuda
Defaults
Brazil
AT+GCI=16
AT:U67,8
Brunei*
AT+GCI=9C
Bulgaria
AT+GCI=1B
AT:U35,10E0
AT:U46,9B0
AT:U62,904
AT:U67,8
Canada
AT+GCI=20
Caribbean
Defaults
Chile*
AT+GCI=73
AT:U49,28,83
ATS007=180
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
China
AT+GCI=26
AT:U67,8
Colombia
AT+GCI=27
Costa Rica
Defaults
Croatia*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
Cyprus*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
AT:U67,8
Czech Republic
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
AT:U67,8
Denmark
AT+GCI=31
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Dominican Republic
Defaults
Dubai
Defaults
Egypt*
AT+GCI=6C
AT:U35,10E0
AT:U62,904,33
AT:U67,208
ATS006=3
El Salvador
Defaults
Ecuador
AT+GCI=35
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
Estonia*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
AT:U67,8
Finland
AT+GCI=3C
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
France
AT+GCI=3D
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
French Polynesia*
AT+GCI=1B
AT:U62,904
Georgia*
AT+GCI=73
Germany
AT+GCI=42
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Ghana*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
Greece
AT+GCI=46
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Guadeloupe*
AT+GCI=1B
AT:U62,904
AT:U67,8
Guam
Defaults
Hong Kong
AT+GCI = 50
Hungary
AT+GCI=51
AT:U35,10E0
AT:U62,904,33
Iceland*
AT+GCI=2E
AT:U62,904
India
AT+GCI=53
AT:U63,3
AT:U67,8
Indonesia
Defaults
Ireland
AT+GCI=57
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Israel
AT+GCI=58
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,1
AT:U62,904
AT:U67,1004
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
Italy
AT+GCI=59
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Japan
AT+GCI=0
Jordan*
AT+GCI=16
AT:U49,22,7A
Kazakhstan*
AT+GCI=73
Korea (South)
AT+GCI=61
AT:U67,A
Kuwait
Defaults
Kyrgyzstan*
AT+GCI = 73
Latvia*
AT+GCI=1B
AT:U35,10E0
AT:U46,9B0
AT:U62,904
AT:U67,8
Lebanon*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
Lesotho*
AT+GCI=9F
AT:U63,33
AT:U67,A
ATS006=3
Liechtenstein*
AT+GCI=2E
AT:U62,904
Lithuania*
AT+GCI=73
AT:U45,344
AT:U62,904,33
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
Luxembourg
AT+GCI=69
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Macao
Defaults
Malaysia
AT+GCI=6C
AT:U46,A80
Malta*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
AT:U67,8
Martinique*
AT+GCI=1B
AT:U62,904
AT:U67,8
ATS007=50
Mexico
AT+GCI=73
Moldova*
AT+GCI=73
Morocco*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
Netherlands
AT+GCI=7B
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
New Zealand
AT+GCI=7E
AT:U38,9,8,7,6
AT:U3D,4,3,2,1
AT:U46,8A0
AT:U52,2
AT:U67,8
Nigeria*
AT+GCI=1B
AT:U62,904
Norway
AT+GCI=82
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
ATS006=3
Oman*
AT+GCI=89
Pakistan*
AT+GCI=89
AT:U46,8A0
Paraguay
AT+GCI=87
Peru
Defaults
Philippines
AT+GCI=89
Poland
AT+GCI=8A
AT:U14,7
AT:U52,2
AT:U62,904
AT:U67,8
AT:U77,4410
ATS006=3
Portugal
AT+GCI=8B
AT:U35,10E0
AT:U42,41,21
AT:U46,9B0
AT:U4F,64
AT:U52,1
AT:U62,904
AT:U67,8
Puerto Rico
Defaults
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
Qatar*
AT+GCI=16
AT:U49,22,7A
Reunion*
AT+GCI=1B
AT:U62,904
AT:U67,8
Romania*
AT+GCI=73
AT:U62,904,33
Russia
AT+GCI=B8
AT:U67,4
Saudi Arabia
Defaults
Singapore
AT+GCI=9C
Slovakia*
AT+GCI=73
AT:U35,10E0
AT:U47,5A,5A
AT:U62,904,33
Slovenia*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
AT:U67,8
South Africa
AT+GCI=9F
AT:U63,33
AT:U67,A
ATS006=3
Spain
AT+GCI=A0
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Sri Lanka*
AT+GCI=9C
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
Sweden
AT+GCI=A5
AT:U14,7
AT:U35,10E0
AT:U37,1,2,3,4,5,6,7,8,9,A
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Switzerland
AT+GCI=A6
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
ATS006=3
Syria*
AT+GCI=16
AT:U49,22,7A
Taiwan
AT+GCI=FE
AT:U67,8
Thailand*
AT+GCI=6C
AT:U46,240
AT:U67,4
Tunisia*
AT+GCI=51
AT:U46,680
AT:U52,1
ATS007=50
Turkey*
AT+GCI=1B
AT:U35,10E0
AT:U46,9B0
AT:U62,904
UAE*
AT+GCI=6C
AT:U67,8
ATS006=3
USA
AT+GCI=B5
Ukraine*
AT+GCI=73
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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Table 90. Country Initialization Table (Continued)
Country
Initialization
United Kingdom
AT+GCI=B4
AT:U14,7
AT:U35,10E0
AT:U46,9B0
AT:U4F,64
AT:U52,2
AT:U62,904
AT:U67,8
ATS006=3
Uruguay
Defaults
Uzbekistan
Defaults
Venezuela
Defaults
Yemen
Defaults
Zambia*
AT+GCI=2E
AT:U35,10E0
AT:U46,9B0
AT:U62,904
*Note: These countries do not have a built-in +GCI support but are
using the settings of other countries as a shortcut.
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6.2.2.2. Country-Setting Register Tables
Table 91. International Call Progress Registers
Register
Value
Function
Dial Tone Control
U0–U14
Dial Tone Detect Filter
Coefficients
U15
DTON
Dial Tone On Threshold
U16
DTOF
Dial Tone Off Threshold
U34
DTWD
Dial Tone Detect Window
U35
DMOT
Dial Tone Minimum On Time
Busy Tone Control
U17–U2B
Busy Tone Detect Filter Coefficients
U2C
BTON
Busy Tone On Threshold
U2D
BTOF
Busy Tone Off Threshold
U2E
BMTT
Busy Tone Minimum Total Time
U2F
BDLT
Busy Tone Delta Time
U30
BMOT
Busy Tone Minimum On Time
Ringback Cadence Control
U31
RMTT
Ringback Tone Minimum Total
Time
U32
RDLT
Ringback Tone Delta Time
U33
RMOT
Ringback Tone Minimum On
Time
Ring Detect Control
U49
RGFH
Ring Frequency High
U4A
RGFD
Ring Frequency Delta
U4B
RGMN
Ring Cadence Minimum On
Time
U4C
RGNX
Ring Cadence Maximum Total
Time
Rev. 1.3
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AN93
Table 92. Dial Registers
Register
Value
Function
Pulse Dial Control
U37–U40
Pulse per Digit Definition
U42
PDBT
Pulse Dial Break Time
U43
PDMT
Pulse Dial Make Time
U45
PDIT
Pulse Dial Interdigit Time
DTMF Control
U46
DTPL
DTMF Power Level (and
Twist)
U47
DTNT
DTMF On Time
U48
DTFT
DTMF Off Time
Table 93. Line Interface/Control Registers
Register
U4D
Bit
10
Value
CLPD
1
LLC
0
U50
LCN
LCDN
U51
LCDF
U52
U67:
13:12
MINI
9 ILIM
U68
7
6
3:2
1
0
2
1
0
XMTL
DCR
OHS
DCV
RZ
RT
BTE
ROV
BTD
Function
Check Loop Current Before
Dialing
Low Loop Current Detect
(set for legacy TBR21)
Loop Current Needed
Loop Current Debounce
On Time
Loop Current Debounce
Off Time
Transmit Level
DC Impedance Select
On-Hook Speed
DC Termination Select
Ringer Impedance
Ringer Threshold Select
Billing Tone Protect Enable
Receive Overload
Billing Tone Detected
6.2.2.3. Special Requirements for India
To output a 0 dBm sine wave, use the following commands:
AT:PF800, C4DD, 7B5C, 595F
AT*Y254:W50, 0, 5B86,1
AT:U46,0
AT*Y1X1DT1
This command string turns off the high-frequency DTMF tone, leaving only the low-frequency DTMF tone when an
ATDT is sent. The tone is output continuously until any key is pressed. To restart the tone output, type AT*Y1DT1.
To change the tone power level, type ATU46,00X0 (where X is a hexadecimal value 0–F representing output power
in –1 dBm steps from 0 to –15 dBm).
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6.2.2.4. Special Requirements for Serbia and Montenegro
The following are special network requirements for Serbia and Montenegro. These specifications are based on the
best information available and are believed to be correct.









DC Feed: 48 or 60 V
Feeding Bridge: 2 x 400  or 2 x 500 
Network Impedance: 600 resistive
On-Hook (Idle State) Noise: < –60 dBm
On-Hook ac (Ringer) impedance: >2.5 k
DTMF Transmit: –11 to –9 dBm and –8 to –6 dBm
Data Transmit Level: 0 dBm to –15 dBm in 1 dB steps (average –13 dBmo)
Out-of-band energy: not specified
Pulse Dial: 1.6/1 ±15 % (pulse/pause)
Rep
Rate: 10 pps
Pause: 250 ms <x> 800 ms, ±10 %
Interdial

Ring signal: 25 Hz 80–90 VRMS

Dial Tone: 425 Hz ±15 %
Level:
–8 dBm > x > –12 dBm
200 ms ±10% ON
300 ms ±10% OFF
700 ms ±10% ON
800 ms ±10% OFF
Cadence:

Busy Tone: 425 Hz ±15 %
Level:
–8 dBm > x > –12 dBm
500 ms ±10 % ON
500 ms ±10 % OFF
Cadence:
6.2.3. Blacklisting
Blacklisting prevents dialing the same phone number more than three times in three minutes. Any attempt to dial a
fourth time within three minutes results in a BLACKLISTED result code. If the blacklisting memory is full, any dial to
a new number results in a BLACKLIST FULL result code. The number of allowable calls may be adjusted in S43. If
S43 = 3, the third call in S44 seconds is blacklisted. The blacklisting time may be adjusted with register S44
(second units). A number is added to the blacklist only if the connection fails. The S42 register controls blacklisting.
Any number that is currently blacklisted is reported with the %B command.
S42
Blacklisting
0 (default)
Disabled
1
Enabled
AT Command
Function
%B
Report blacklisted number (if
any) followed by OK
Example: AT%B\r
5121234567
OK
Rev. 1.3
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AN93
6.3. Caller ID
The ISOmodem supports all major Caller ID (CID) types. CID is disabled by default (+VCID = 0). Setting +VCID = 1
via the AT+VCID = 1 command enables decoded (formatted) CID, while setting +VCID = 2 causes raw Caller ID
data to be output. The specific CID mode is selected by +VCDT, which is set to the US Telcordia standard by
default. The AT+VCDT = n command is used to define the CID mode according to the decimal values of n defined
in Table 94. U70 [4] (CID) is a sticky bit that is set when a CID preamble is received and cleared with an AT:I
(“Interrupt read”) command.
Table 94. Caller ID Modes
n
+VCDT Settings
0
After ring only (default)
1
Force CID monitor (always on)
2
UK with wetting pulse
3
Japan
The following sections describe each CID mode.
6.3.1. Force Caller ID Monitor (Always On)
In this mode, the ISOmodem, when on-hook, continuously monitors the line for the CID mark sequence and FSK
data. This mode can be used in all systems, especially those requiring detection of CID data before the ring burst.
It is also useful for detecting voicemail indicator signals and for supporting Type II Caller ID. In most systems,
“Always On” is the preferred method, since it separates CID detection from ring detection.
6.3.2. Caller ID After Ring Only
The ISOmodem detects the first ring burst, echoes RING to the host, and prepares to detect the CID preamble. On
preamble detection, the modem echoes the CIDM response to the host (indicating the preamble was received and
FSK modulated CID data will follow), and INT is triggered if enabled.
Next the CID algorithm looks for the start bit, assembles the characters, and sends them to the host as they are
received. When the CID burst is finished, there is no more carrier and NO CARRIER is echoed to the host. The
ISOmodem continues to detect subsequent ring bursts, echoes RING to the host, increments the ring counter, S1,
and automatically answers after the number of rings specified in S0.
6.3.3. UK Caller ID with Wetting Pulse
The ISOmodem first detects a line-polarity reversal, echoes FLASH to the host, and triggers the INT pin. The
ISOmodem then searches for the Idle State Tone Alert signal and, when detected, echoes STAS to the host. After
the Idle State Tone Alert Signal is completed, the ISOmodem goes off-hook then on-hook to apply the 15 ms
wetting pulse to the local loop. Next, the ISOmodem prepares to detect the CID preamble. After 50 continuous
mark bits (1s) are detected, the CIDM response is echoed to the host indicating that the mark sequence was
received and that FSK-modulated CID data will follow, and INT is again triggered. Then, the CID algorithm looks for
the start bit, assembles the characters, and sends them to the host as they are received. When the CID burst is
finished, the carrier is lost, and NO CARRIER is echoed to the host. The ISOmodem detects ring bursts, echoes
RING to the host, increments the ring counter, S1, and automatically answers after the number of rings specified in
S0. If the wetting pulse is not required, +VCDT = 0 or 1 can be used in the UK.
6.3.4. Japan Caller ID
The ISOmodem detects a line-polarity reversal and a brief ring burst, then goes off-hook and triggers the INT pin.
CID data are sent using the V.23 specification. After detecting 40 mark bits (1s), the ISOmodem searches for a
start-bit. CIDM is echoed to the host when a start bit is received. The ISOmodem then begins to assemble
characters and sends them to the host. When the CID signal ends, the ISOmodem hangs up and echoes NO
CARRIER to the host. The modem then waits for the normal ring signal. Table 95 shows the AT command strings
that configure the ISOmodem for Japan Caller ID.
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Table 95. Japan Caller ID
Command
Function
AT+VCID = 1 Enables Caller ID.
AT+VCDT = 3 Selects Japan CID mode.
6.3.5. DTMF Caller ID
DTMF Caller ID is supported in the Si2493/57/34/15/04 Revision D or above and Si2494/39 Revision A or above.
DTMF Caller ID detection is needed to provide complete CID support for Brazil, China and other countries. The
ISOmodem detects the preamble and start code (0x41, or ASCII 'A'), then echoes CIDM to the host. The
ISOmodem assembles the rest of the characters in the message and sends them to the host. It detects the stop
code (0x44, or ASCII 'D') and proceeds with the rest of the call processing.
For ISOmodems that support voice mode, detection of DTMF CID is done automatically in +FCLASS = 8 mode
after being enabled by a “+VLS = 14” command. The user can also enable FSK CID with the AT+VCID and
AT+VCDT commands. This gives simultaneous support of DTMF and FSK modes.This is useful in countries like
Brazil, China and Taiwan, where the use of DTMF or FSK varies from region to region.
6.4. SMS Support
Short Message Service (SMS) allows text messages to be sent and received from one telephone to another via an
SMS service center. The ISOmodem provides a flexible interface that can handle multiple SMS standards. This
flexibility is possible because most of the differences between standards is handled by the host in the data stream
itself. The ISOmodem performs the necessary data modulation and provides two options for message packet
structure (Protocol 1 and Protocol 2, as defined in ETSI ES 201 912). The rest of the data link layer and transfer
layer are defined by the host system. The ISOmodem uses a V.23 half-duplex modulation to transmit and receive
the data over the PSTN. Protocol 2 differs from Protocol 1 in that a packet is preceded by a 300-bit long channelseizure preamble. ETSI ES 201 912 describes the other differences between Protocols 1 and 2, but the host
processor handles these when structuring the data within the packet.
Table 96. Protocol 1
80 bits of mark (constant ones)
Message
Table 97. Protocol 2
Channel seizure (300-bit
stream of alternating ones
and zeroes)
80-bit stream
of ones
Message
Four commands control the behavior of the SMS feature, as described in Table 98 below:
Table 98. SMS Commands
Command
SMS Feature Behavior
AT+FCLASS = 256
Prepares the modem for
handling SMS calls.
ATDT;
Goes off-hook and returns to
command mode. If a phone
number is provided, it is dialed
prior to returning to command
mode.
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AN93
Table 98. SMS Commands
AT+FRM = 200
Returns to data mode prepared
to receive an SMS message.
AT+FTM = 201
Returns to data mode prepared
to transmit an SMS Protocol 1
message.
AT+FTM = 202
Returns to data mode prepared
to transmit an SMS Protocol 2
message.
To enable the SMS features on the ISOmodem, the host must send AT+FCLASS = 256 to the modem prior to
handling an SMS call. The host can then dial or answer an SMS call using ATDTxxxx; (where xxxx is the number to
be dialed), or ATDT; respectively. Note the semicolon at the end of the command, which places the modem into
command mode immediately after dialing and returns OK. The host can then prepare the modem for transmitting or
receiving SMS data.
To receive Protocol 1 or Protocol 2 data, the host must send AT+FRM = 200. This causes the modem to return to
data mode silently, listening for data from the remote SMS server. If the modem detects a valid Protocol 1 or
Protocol 2 packet, it responds with a CONNECT 1 or CONNECT 2 message respectively, followed by the SMS
message (without channel seizure and mark). When the carrier stops, the modem returns to command mode and
responds with OK.
To transmit Protocol 1 or Protocol 2 data, the host must send AT+FTM = 201 or AT+FTM = 202. This causes the
modem to return to data mode and wait silently until data are received from the host processor for transmission.
Once data are received from the host, the modem transmits the proper number of channel seizure and mark bits
followed by the data it received from the host. After the modem has begun transmitting, it will send marks when it
does not have data to send and will continue to do so until the host escapes to command mode.
The content of the data message is entirely up to the host including any checksum or CRC. ETSI ES 201 912
describes two standard data and transfer layers that are commonly used. SMS typically relies on caller
identification information to determine if the call should be answered using an SMS device or not. Refer to "6.3.
Caller ID" for more information on how to configure the modem for Caller ID detection.
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6.5. Type II Caller ID/SAS Detection
When a call is in progress, the Subscriber Alerting Signal (SAS) tone is sent by the central office to indicate a
second incoming call. The central office may also issue a CPE Alert Signal (CAS) after the SAS to indicate that call
waiting Caller ID (CWCID) information is available. If properly configured, the modem will acknowledge the CAS
tone, receive the CWCID data, and perform a retrain.
The ISOmodem is configured through the +PCW command to toggle the RI pin (+PCW=0), hang up (+PCW=1), or
do nothing (+PCW=2) upon receipt of the SAS tone. The default is to ignore the SAS tone. The modem, enabled
through the +VCID command, will collect Caller ID information if +PCW is set to toggle the RI pin. The AT:I
command can be used to verify receipt of the SAS and CWCID data. Bit 9 will be set for SAS receipt due to the RI
toggle. Bit 4 will be set if CWCID data are received.
The CWCID data are collected using the +VCIDR? command. The data message is displayed in hexadecimal
format using ASCII text. The modem will return NO DATA if no Caller ID is available. The +VCIDR response is
listed below for the following example CWCID message:
Date & Time:
09/11 16:21
ICLID Number: 512-555-1234
Calling Name: JOHN_DOE
+VCIDR:
80 20 01 08 30 39 31 31 31 36 32 31 02 0A 35 31
32 35 35 35 31 32 33 34 07 08 4A 4F 48 4E 5F 44
4F 45 40
OK
Table 99 defines the Multiple Data Message Format (MDMF) parameters in the example response.
Table 99. MDMF Parameters
Character Description
Hexadecimal Value
Message Type (MDMF)
80
Message Length
20
Parameter Type (Date/Time)
01
Parameter Length
08
ASCII Value
Month
30 39
09
Day
31 31
11
Hour
31 36
16
Minutes
32 31
21
Parameter Type (Number)
02
Parameter Length
0A
Number
35 31 32 35 35 35 31 32 33 34
Parameter Type (Name)
07
Parameter Length
08
Name
4A 4F 48 4E 5F 44 4F 45
Checksum
5125551234
JOHN_DOE
40
The SAS tone varies between countries and requires configuration of user registers U9F to UA9. The SAS_FREQ
(U9F) register sets the expected SAS tone frequency as shown in Table 100. The default SAS frequency is 440 Hz.
The expected cadence is set in cadence registers SAS_CADENCE0 (UA0) through SAS_CADENCE9 (UA9).
Rev. 1.3
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AN93
The even-numbered registers, (UA0, UA2, etc.), control the amount of time the tone is expected to be present, and
the odd-numbered registers select the amount of time the tone must not be present. The values are expressed in
10 millisecond units. For example, a cadence of on 500 ms, off 300 ms then on for 500 ms may be selected by
writing 0x0032 to UA0, 0x001E to UA1 and 0x0032 to UA2. The unused registers should be written to 0. The
default cadence setting is UA0 equal to 001Eh, and the remaining nine registers are set to zero.
Table 101 defines the SAS cadence for each supported country. The on-time is listed in bold. These data were
obtained from ITU-T Recommendation E.180 Supplement 2 (04/98).
Table 100. SAS Tone Frequency
SAS_FREQ (U9F) SAS Frequency
0x0000
440 Hz (Default)
0x0001
400 Hz
0x0002
420 Hz
0x0003
425 Hz
0x0004
480 Hz
0x0005
450 Hz
0x0006
900 Hz
0x0007
950 Hz
0x0008
523 Hz
0x0009
1400 Hz
Table 101. SAS Cadence for Supported Countries*
Country
Angola
Tone
Frequency (Hz)
Cadence (seconds)
U Registers
Waiting Tone
400
1.0 – 5.0
U9F = 0x0001
UA0 = 0x0064
UA1 = 0x01F4
0.5 – 10.0 – 0.5
U9F = 0x0000
UA0 = 0x0032
UA1 = 0x03E8
UA2 = 0x0032
0.6 – 10.0
U9F = 0x0004
UA0 = 0x003C
UA1 = 0x03E8
0.4 – 0.2 – 0.4 – 4.0
U9F = 0x0003
UA0 = 0x0028
UA1 = 0x0014
UA2 = 0x0028
UA3 = 0x0190
Anguilla
Waiting Tone
Antigua and
Barbuda
Call Waiting
Tone
Argentine Republic
152
Waiting Tone
440
480
425
Rev. 1.3
AN93
Table 101. SAS Cadence for Supported Countries* (Continued)
Country
Aruba
Tone
Call Waiting
Tone
Frequency (Hz)
425
Cadence (seconds)
U Registers
0.2 – 0.2 – 0.2 – 4.4
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0014
UA2 = 0x0014
UA3 = 0x01B8
Australia
Call Waiting
Tone
425
0.2 – 0.2 – 0.2 – 4.4
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0014
UA2 = 0x0014
UA3 = 0x01B8
Austria
Waiting Tone
420
0.04 – 1.95
U9F = 0x0002
UA0 = 0x0004
UA1 = 0x00C3
Bermuda
Waiting Tone
440
(Two bursts, ten seconds
apart)
Bhutan
Waiting Tone
400
0.5 – 0.25
U9F = 0x0001
UA0 = 0x0032
UA1 = 0x0019
Botswana
Waiting Tone
425
0.2 – 1.0
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0064
Brazil
Waiting Tone
425
0.05 – 1.0
U9F = 0x0003
UA0 = 0x0005
UA1 = 0x0064
U9F = 0x0000
British Virgin
Islands
Waiting Tone
440
0.5 – 10.0 – 0.5
U9F = 0x0000
UA0 = 0x0032
UA1 = 0x03E8
UA2 = 0x0032
Brunei
Darussalam
Call Waiting
Tone
400×24
0.5 – 0.25
U9F = 0x0001
UA0 = 0x0032
UA1 = 0x0019
Channel Islands:
Jersey
Waiting Tone
400
0.1 – 2.5 – 0.1
U9F = 0x0000
UA0 = 0x000A
UA1 = 0x00FA
UA2 = 0x000A
Chile
Waiting Tone
900+1300
0.5 – 0.5
U9F = 0x0006
UA0 = 0x0032
UA1 = 0x0032
Rev. 1.3
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Table 101. SAS Cadence for Supported Countries* (Continued)
Country
Tone
Frequency (Hz)
Cadence (seconds)
U Registers
China
Waiting Tone
450
0.4 – 4.0
U9F = 0x0005
UA0 = 0x0028
UA1 = 0x0190
Croatia
Call Waiting
Tone
425
0.3 – 8.0
U9F = 0x0003
UA0 = 0x001E
UA1 = 0x0320
Cyprus
Call Waiting
Tone
425
0.1 – 0.1 – 0.1 – 5.3
U9F = 0x0003
UA0 = 0x000A
UA1 = 0x000A
UA2 = 0x000A
UA3 = 0x0212
Czech Republic
Call Waiting
Tone
425
0.33 – 9.0
U9F = 0x0003
UA0 = 0x0021
UA1 = 0x0384
Dominica
(Commonwealth of)
Call Waiting
Tone
10.5 – 10.0 – 0.5
U9F = 0x0000
UA0 = 0x0032
UA1 = 0x03E8
UA2 = 0x0032
Ecuador
Call Waiting
Tone
425
0.2 – 0.6
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x003C
Estonia
Call Waiting
Tone
950/1400/1800
3×(0.33 – 0.3)
Ethiopia
Call Waiting
Tone
425
0.2 – 0.6
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x003C
0.15 – 8.0
U9F = 0x0003
UA0 = 0x000F
UA1 = 0x0320
0.2 – 0.2 – 0.2 – 5.0
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0014
UA2 = 0x0014
UA3 = 0x01F4
0.8 – 0.2 – 0.3 – 3.2
U9F = 0x0001
UA0 = 0x0050
UA1 = 0x0014
UA2 = 0x001E
UA3 = 0x0140
Finland
Germany
Ghana
154
Waiting Tone
Waiting Tone
Waiting Tone
440
425
425
400
Rev. 1.3
U9F = 0x0007
AN93
Table 101. SAS Cadence for Supported Countries* (Continued)
Country
Gibraltar
Tone
Frequency (Hz)
Cadence (seconds)
U Registers
Waiting Tone
400
0.1 – 3.0
U9F = 0x0001
UA0 = 0x000A
UA1 = 0x012C
Greece
Call Waiting
Tone
425
0.3 – 10.0 – 0.3 – 10.0
U9F = 0x0003
UA0 = 0x001E
UA1 = 0x03E8
UA2 = 0x001E
UA3 = 0x03E8
Guyana
Waiting Tone
480
0.5 – 18.0
U9F = 0x0004
UA0 = 0x0032
UA1 = 0x0708
0.5 – 0.5 – 0.2 – 4.0
U9F = 0x0000
UA0 = 0x0032
UA1 = 0x0032
UA2 = 0x0014
UA3 = 0x0190
Honduras
Call Waiting
Tone
440
Hong Kong
Call Waiting
Tone
440
3×(0.5 – 0.5) – 8.0)
U9F = 0x0000
UA0 = 0x0032
UA1 = 0x0032
UA2 = 0x0032
UA3 = 0x0032
UA4 = 0x0032
UA5 = 0x0352
Hungary
Waiting Tone
425
0.04 – 1.96
U9F = 0x0003
UA0 = 0x0004
UA1 = 0x00C4
4x (0.2 – 0.2 – 0.2 – 3.6 –
0.2 – 0.2 – 0.2)
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0014
UA2 = 0x0014
UA3 = 0x0168
UA4 = 0x0014
UA5 = 0x0014
UA6 = 0x0014
0.2 – 0.2 – 0.2 – 10.0
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0014
UA2 = 0x0014
UA3 = 0x03E8
Iceland
Iran
Waiting Tone
Waiting Tone
425
425
Rev. 1.3
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AN93
Table 101. SAS Cadence for Supported Countries* (Continued)
Country
Israel
Japan
Tone
Call Waiting
Tone
Call Waiting
Tone I
Call Waiting
Tone Ii
Call Waiting
Tone Iii
Call Waiting
Tone Iv
Frequency (Hz)
Cadence (seconds)
U Registers
1x(0.15 – 10.0 – 0.15)
U9F = 0x0001
UA0 = 0x000F
UA1 = 0x03E8
UA2 = 0x000F
0.5 – 0.0~4.0 – 0.05 – 0.45
– 0.05 – 3.45 – 0.05 – 0.45
– 0.05 – 3.45
U9F = 0x0001
UA0 = 0x0032
UA1 = 0x0000 to 0x0190
UA2 = 0x0005
UA3 = 0x002D
UA4 = 0x0005
UA5 = 0x0159
UA6 = 0x0005
UA7 = 0x002D
UA8 = 0x0005
UA9 = 0x0159
0.1 – 0.1 – 0.1 – 3.0
U9F = 0x0001
UA0 = 0x000A
UA1 = 0x000A
UA2 = 0x000A
UA3 = 0x012C
0.064 – 0.436 – 0.064 –
3.436
U9F = 0x0001
UA0 = 0x0007
UA1 = 0x002C
UA2 = 0x0007
UA3 = 0x0158
0.25 – 0.25 – 0.25 – 3.25
U9F = 0x0001
UA0 = 0x0019
UA1 = 0x0019
UA2 = 0x0019
UA3 = 0x0145
U9F = 0x0001 or 0x0002
UA0 = 0x0032
UA1 = 0x001E
UA2 = 0x0014
UA3 = 0x001E
UA4 = 0x0014
UA5 = 0x012C
400
400x16/400
400×16/400
400×16/400
400×16/400
Jordan
Waiting Tone
420×40//
400+440
0.5 – 2×(0.3 – 0.2) – 3.0
Kenya
Call Waiting
Tone
425
CONTINUOUS
156
Rev. 1.3
U9F = 0x0003
AN93
Table 101. SAS Cadence for Supported Countries* (Continued)
Country
Kiribati
Tone
Waiting Tone
Frequency (Hz)
425
Cadence (seconds)
U Registers
0.1 – 0.2 – 0.1 – 4.7
U9F = 0x0003
UA0 = 0x000A
UA1 = 0x0014
UA2 = 0x000A
UA3 = 0x01D6
Korea (Republic Of)
Waiting Tone
350+440
0.25 – 0.25 – 0.25 – 3.25
U9F = 0x000
UA0 = 0x0019
UA1 = 0x0019
UA2 = 0x0019
UA3 = 0x0145
Lao P.D.R.
Waiting Tone
425
0.4 – 0.4
U9F = 0x0003
UA0 = 0x0028
UA1 = 0x0028
Lithuania
Waiting Tone
950/1400/1800
3×(0.333 – 1.0)
U9F = 0x0007
Macau
Call Waiting
Tone
425
0.2 – 0.6
U9F = 0x0001
UA0 = 0x0014
UA1 = 0x003C
Madagascar
Call Waiting
Tone
440
0.1 – 1.9
U9F = 0x0000
UA0 = 0x000A
UA1 = 0x00BE
Malaysia
Waiting Tone
425
1.0 – 10.0 – 0.5 – 0.25 – 0.5
– 10.0 – 0.5 – 0.25
U9F = 0x0003
UA0 = 0x0064
UA1 = 0x03E8
UA2 = 0x0032
UA3 = 0x0019
UA4 = 0x0032
UA5 = 0x03E8
UA6 = 0x0032
UA7 = 0x0019
Maldives
Call Waiting
Tone
400
1.0 – 10.0
U9F = 0x0001
UA0 = 0x0064
UA1 = 0x03E8
Montserrat
Waiting Tone
440
0.5 – 10.0 – 0.5
U9F = 0x0000
UA0 = 0x0032
UA1 = 0x03E8
UA2 = 0x0032
Netherlands
Waiting Tone
425
0.5 – 9.5
U9F = 0x0003
UA0 = 0x0032
UA1 = 0x03B6
New Zealand
Waiting Tone I
400+450
0.5
U9F = 0x0001
UA0 = 0x0032
Rev. 1.3
157
AN93
Table 101. SAS Cadence for Supported Countries* (Continued)
Country
Tone
Waiting Tone Ii
Nigeria
Oman
Papua New Guinea
Paraguay
Poland
Portugal
158
Frequency (Hz)
400
Cadence (seconds)
U Registers
0.25 – 0.25 – 0.25 – 3.25
U9F = 0x0001
UA0 = 0x0019
UA1 = 0x0019
UA2 = 0x0019
UA3 = 0x0145
Waiting Tone
Iii
523/659
3×(0.2 – 3.0) – 0.2
U9F = 0x0008
UA0 = 0x0014
UA1 = 0x012C
UA2 = 0x0014
UA3 = 0x012C
UA4 = 0x0014
UA5 = 0x012C
UA6 = 0x0014
Call Waiting
Tone
400
2.0 – 0.2
U9F = 0x0001
UA0 = 0x00C8
UA1 = 0x0014
0.3 – 1.0
U9F = 0x0003
UA0 = 0x001E
UA1 = 0x0064
0.04 – 10.0 – 0.04 – 20.0 –
0.04 – 20.0
U9F = 0x0003
UA0 = 0x0004
UA1 = 0x03E8
UA2 = 0x0004
UA3 = 0x07D0
UA4 = 0x0004
UA5 = 0x07D0
0.65 – 0.325 – 0.125 – 1.3
– 2.6
U9F = 0x0007
UA0 = 0x0041
UA1 = 0x0021
UA2 = 0x00D
UA3 = 0x0082
UA4 = 0x0104
0.15 – 0.15 – 0.15 – 4.0
U9F = 0x0003
UA0 = 0x000F
UA1 = 0x000F
UA2 = 0x000F
UA3 = 0x0190
0.2 – 0.2 – 0.2 – 5.0
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0014
UA2 = 0x0014
UA3 = 0x01F4
Waiting Tone
Waiting Tone
Waiting Tone
Waiting Tone
Call Waiting
Tone
425
425
950/950/1400
425
425
Rev. 1.3
AN93
Table 101. SAS Cadence for Supported Countries* (Continued)
Country
Russia
St.-Kitts-and-Nevis
St. Lucia
Tone
Frequency (Hz)
Cadence (seconds)
U Registers
Waiting Tone
950/1400/1800
3×0.333 – 1.0
U9F = 0x0007
0.5 – 10.0 – 0.5
U9F = 0x0000
UA0 = 0x0032
UA1 = 0x03E8
UA2 = 0x0032
0.2 – 0.2 – 0.2 – 0.2
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0014
UA2 = 0x0014
UA3 = 0x0014
Waiting Tone
Call Waiting
Tone
440
425
Saudi Arabia
Call Waiting
Tone
425
0.15 – 0.2 – 0.15 – 10.0
U9F = 0x0003
UA0 = 0x000F
UA1 = 0x0014
UA2 = 0x000F
UA3 = 0x03E8
Sierra Leone
Waiting Tone
425
1.0
U9F = 0x0003
UA0 = 0x0064
Singapore
Call Waiting
Tone
425
0.3 – 0.2 – 0.3 – 3.2
U9F = 0x0003
UA0 = 0x001E
UA1 = 0x0014
UA2 = 0x001E
UA3 = 0x0140
Slovenia
Waiting Tone
425
0.3 – 10.0
U9F = 0x0003
UA0 = 0x001E
UA1 = 0x03E8
Solomon
Waiting Tone
400+450/400
0.5 – 0.5
U9F = 0x0001
UA0 = 0x0032
UA1 = 0x0032
South Africa
Call Waiting
Tone
400×33
0.4 – 4.0
U9F = 0x0001
UA0 = 0x0028
UA1 = 0x0190
Spain
Call Waiting
Tone
425
0.175 – 0.175 – 0.175 – 3.5
U9F = 0x0003
UA0 = 0x0012
UA1 = 0x0012
UA2 = 0x0012
UA3 = 0x015E
Sri Lanka
Call Waiting
Tone
425
0.5 – 2.5
U9F = 0x0003
UA0 = 0x0032
UA1 = 0x00FA
Rev. 1.3
159
AN93
Table 101. SAS Cadence for Supported Countries* (Continued)
Country
Tone
Frequency (Hz)
Cadence (seconds)
U Registers
Sweden
Call Waiting
Tone I
425
0.2 – 0.5 – 0.2
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0032
UA2 = 0x0014
Tajikistan
Call Waiting
Tone
950/1400/1800
0.8 – 3.2
U9F = 0x0007
UA0 = 0x0050
UA1 = 0x0140
0.3 – 10.0
U9F = 0x0000
UA0 = 0x001E
UA1 = 0x03E8
0.2 – 0.6 – 0.2 – 8.0
U9F = 0x0005
UA0 = 0x0014
UA1 = 0x003C
UA2 = 0x0014
UA3 = 0x0320
0.5 – 10.0 – 0.5
U9F = 0x0000
UA0 = 0x0032
UA1 = 0x03E8
UA2 = 0x0032
0.3
U9F = 0x0000
UA0 = 0x001E
UA1 = 0x03E8
UA2 = 0x001E
UA3 = 0x03E8
Trinidad and
Tobago
Waiting Tone
Call Waiting
Tone
Turkey
Turks and Caicos
Islands
United States
Waiting Tone
Call Waiting
Tone
440
450
440
440
Uruguay
Waiting Tone
425
0.2 – 0.2 – 0.2 – 4.4
U9F = 0x0003
UA0 = 0x0014
UA1 = 0x0014
UA2 = 0x0014
UA3 = 0x01B8
Vanuatu
Call Waiting
Tone
425
0.3 – 10.0
U9F = 0x0003
UA0 = 0x001E
UA1 = 0x03E8
Zimbabwe
Call Waiting
Tone
523/659
1.5 – 1.5
U9F = 0x0003
UA0 = 0x0096
UA1 = 0x0096
*Note:
1×f2
f1+f2
f1/f2
f1//f2
160
Explanation of Symbols:
f1 is modulated by f2.
the juxtaposition of two frequencies, f1 and f2, without modulation.
f1 is followed by f2.
in some exchanges, frequency f1 is used, and in others, frequency f2 is used.
Rev. 1.3
AN93
6.6. Intrusion/Parallel Phone Detection
The modem may share a telephone line with a variety of other devices, especially telephones. In most cases, the
modem has a lower priority for access to the phone line. Someone dialing 911 in an emergency, for example, has a
higher priority than a set-top box updating billing information. If someone is using a telephone, the modem should
not go off-hook. If someone picks up a phone while the modem is connected or dialing, the modem should drop the
connection and allow the phone call to proceed. The modem must monitor the phone line for intrusion in both the
on-hook and off-hook conditions.
6.6.1. On-Hook Condition
When the ISOmodem is on-hook, the U79 [4:0] (LVCS) value represents Tip-Ring voltage; the ISOmodem is in the
command mode, and the host can easily monitor LVCS with the AT:R79 command. A typical local loop has a Tip-toRing voltage greater than 40 V if all devices sharing the line (telephones, fax machines, modems, etc.) are onhook. The typical local loop has a large dc impedance that causes the Tip-Ring voltage to drop below 25 V when a
device goes off-hook. The host can monitor LVCS to determine whether the Tip-Ring voltage is approximately 40 V
or something less than 25 V to determine if a parallel device is off-hook. This type of monitoring may also be
performed with the %V1 command. Alternatively, the host could be programmed to periodically monitor LVCS and
store the maximum value as the “all devices on-hook” line voltage and establish the on-hook intrusion threshold as
a fraction (possibly 50%) of that value. This allows the system to adapt to different or changing local loop
conditions. An on-chip adaptive monitoring algorithm may be enabled with the %V2 command.
6.6.1.1. Line Not Present/In Use Indication (Method 1—Fixed)
If enabled with %V1, this feature checks the line status before going off-hook and again before dialing. Before
going off-hook with the ATD, ATO, or ATA command, the ISOmodem reads the line voltage and compares it to U83
(NOLN) [15:0] and U84 (LIUS) [15:0].
Loop Voltage
0 < LVCS < U83
Action
Report NO LINE and
remain on-hook
U83 < LVCS < U84 Report LINE IN USE and
remain on-hook
(U register)
U84 < LVCS
Go off-hook and establish
connection
A debouncing timer controlled by U-registers 50 and 51 prevents polarity reversals from being detected as a loss of
loop current. The intrusion detection algorithm continues to operate if U77 (HOI) [11] is set. In this case, a parallel
phone intrusion while off-hook gives a LINE IN USE result code to indicate the ISOmodem has gone on-hook due
to a parallel phone intrusion.
Note: This method may not be as desireable as method 2, particularly for low-voltage lines.
Pros:

Easy to understand and predict
Allows reference level control
Cons:


Chosen levels must work for all lines—not adaptive
Rev. 1.3
161
AN93
6.6.1.2. Line Not Present/In Use Indication (Method 2—Adaptive)
This method is enabled through %V2. This feature checks the line status before going off-hook and again before
dialing. While on-hook, the part monitors line voltage and updates U85 (5 (NLIU) [15:0] with this value.
Before going off-hook with the ATD, ATO, or ATA command, the ISOmodem reads the line voltage and compares it
with the stored reference.
Loop Voltage
0 < LVCS < 6.25 % x U85
Action
Report NO LINE and remain on-hook
6.25 % x U85 < LVCS < 85% x U85 Report LINE IN USE and remain on-hook
85% x U85 < LVCS
Go off-hook and establish connection
To prevent polarity reversals from being detected as a loss of loop current, a debounce timer controlled by Uregisters 50 and 51 is used. However, if the HOI bit is set, a parallel phone intrusion while off-hook will give a LINE
IN USE result code to indicate that the ISOmodem has gone on hook due to a parallel phone intrusion.
6.6.2. Off-Hook Condition
When the ISOmodem is off-hook, the U79 [4:0] (LVCS) value represents loop current. Additionally, the ISOmodem
is typically in the data mode, and it is difficult for the host to monitor the LVCS value. For this reason, a controllerbased off-hook intrusion algorithm is used.
There is a delay between the ISOmodem going off-hook and the start of the intrusion algorithm set by
U77 [15:12] (IST) (Intrusion Settling Time). This avoids false intrusion detections due to loop transients during the
on-hook to off-hook transition. The off-hook intrusion algorithm monitors the value of LVCS at a sample rate
determined by U76 [15:9] (OHSR). The algorithm compares each LVCS sample to the reference value in
U76 [4:0] (ACL). ACL = 0 at the first off-hook event after reset unless a value is written to it by the host. If ACL = 0,
the ISOmodem does not begin the intrusion algorithm until after two LVCS samples have been received. If the host
writes a non-zero value to ACL prior to the ISOmodem going off-hook, a parallel phone intrusion occurring during
the IST interval and maintained until the end of the IST interval triggers a PPD interrupt. The ISOmodem also
automatically updates ACL with the LVCS value while off-hook if an intrusion has not occurred. An ACL value can
be written by the host and forced to remain unchanged by setting U76 [8] (FACL) = 1. If LVCS is lower than ACL by
an amount greater than the value set in U76 [7:5] (DCL) (6 mA default) for two consecutive samples,
U70 [2] (PPD), Parallel Phone Detect is set. If U70 [10] (PPDM) (Parallel Phone Detect Mask) is set to 1 (default
condition), the INT pin in UART mode or the INT bit (Hardware Interface Register 1, bit 3) in parallel or SPI mode is
also triggered. The host can monitor PPD or issue an AT:I to verify the cause of an interrupt and clear PPD. The
host can take the appropriate action when the intrusion is confirmed.
The intrusion detection algorithm is as follows:
if LVCS(t) = LVCS (t – 40 ms x OHSR)
and ACL – LVCS(t) < DCL
then ACL = LVCS(t)
if (ACL – LVCS x (t – 40 ms x OHSR) > DCL
and ACL – LVCS x t > DCL
then PPD = 1
and the INT pin (or the INT bit in parallel or SPI mode) is asserted (PPDM = 1)
The ISOmodem can also be programmed to go on-hook automatically on a PPD interrupt by setting
U77 (HOI) [11] (Hang-Up On Intrusion) to 1.
The off-hook intrusion algorithm may be suspended for a period defined by U78 [15:14] (IB) after the start of
dialing. This guards against false PPD detects due to dial pulses or other transients caused by Central Office
switching.
Table 102 lists the U registers and bits used for Intrusion Detection.
162
Rev. 1.3
AN93
Table 102. Intrusion Detection
Register Bit(s)
Name
Function
U70
10
PPDM
Parallel Phone Detect
Mask
U70
2
PPD
Parallel Phone Detect
U76
15:9
OHSR
Off-Hook Sample Rate
U76
8
FACL
Force ACL
U76
7:5
DCL
Differential Current
Level
U76
4:0
ACL
Absolute Current Level
U77
15:12
IST
Intrusion Settling Time
U77
11
HOI
Hang-Up On Intrusion
U78
15:14
IB
Intrusion Blocking
U78
7:0
IS
Intrusion Suspend
U79
4:0
LVCS
Line Voltage/Current
Sense
U83
15:0
NOLN
No Line Threshold %V1
U84
15:0
LIUS
Line-in-use Threshold
%V1
U85
15:0
NLIU
Line-in-use/No Line
Threshold %V2
The ISOmodem has an internal analog-to-digital converter used to monitor the loop voltage when on-hook and
loop current when off-hook to check for parallel devices going off-hook. The host measures loop voltage or current
by reading U79 [4:0] (LVCS). To set the ISOmodem to monitor loop voltage in the on-hook state, the host issues
the following commands:
Command
AT:R79
Function
Host reads the loop voltage
from the LVCS Register U79
bits 4:0 while the modem is
on-hook.
To set the ISOmodem to monitor loop current, the host issues the following commands:
Command
ATH1
AT:R79
Function
To go off-hook
Host reads loop current from
the LVCS Register U79 bits
4:0 while the modem is offhook.
Rev. 1.3
163
AN93
6.7. Modem-On-Hold
The Si2494/93 supports modem-on-hold as defined by the ITU-T V.92 specification. This feature allows a
connected Si2494/93 to place a server modem on hold while a second call, typically a voice call, uses the phone
line. The maximum time the modems will remain on hold is controlled by the modem receiving the modem-on-hold
request. Once the second call has ended, the Si2494/93 will reinitiate the data connection if the time elapsed has
not exceeded the time negotiated by the two modems. The Si2494/93 can also be placed on hold itself by a remote
modem allowing a far-end user to make or receive a voice call. Modem-on-hold is only supported on the Si2494/93
for V.34 (14400–33600 bps) and higher speed modulations. The AT+PMH command is used to enable (+PMH = 0)
or disable (+PMH = 1) modem-on-hold.
6.7.1. Initiating Modem-On-Hold
Modem-on-hold is typically initiated when a connected client modem receives a subscriber alert signal (SAS) tone
as described in "6.5. Type II Caller ID/SAS Detection" on page 151. However, it may be initiated any time the
modem is on-line in command mode. The AT+PMHR command is used to initiate a modem-on-hold request. After
this command is issued, the modem will place a modem-on-hold request to the server, and the +PMHR: command
response will indicate the server’s response to the request. The possible responses are shown in Table 103.
If the server refuses to grant a modem-on-hold request, the modem will use the +PMHT setting to determine what
to do. If +PMHT = 0, the modem will remain connected to the server. If +PMHT is set to a non-zero value, the
modems will disconnect. The Si2494/93 will indicate these conditions with the result code, “MHnack;
Disconnecting…” or “MHnack; Reconnecting…”
Once modem-on-hold has been initiated, it may be necessary for the Si2494/93 to perform a hook-flash to indicate
to the central office the incoming call may be accepted. This is initiated with the AT+PMHF command. The Si2494/
93 will go on-hook for the time set in user register U4F and remain off-hook while on-hold. Usually, a second hookflash is necessary to reestablish a data connection with the remote modem.
The Si2494/93 will attempt to reestablish a data connection with the remote modem upon receipt of the ATO
command and will indicate the connection has been reestablished with the CONNECT message. If the modems fail
to renegotiate the connection, the Si2494/93 will send the NO CARRIER message.
Table 103. Possible Responses to PMHR Command from Remote Modem
<Value>
164
Description
0
Modem-on-hold request denied or not available.
The modem may initiate another modem-on-hold request at a later time.
1
MOH with 10 second timeout granted
2
MOH with 20 second timeout granted
3
MOH with 30 second timeout granted
4
MOH with 40 second timeout granted
5
MOH with 1 minute timeout granted
6
MOH with 2 minute timeout granted
7
MOH with 3 minute timeout granted
8
MOH with 4 minute timeout granted
9
MOH with 6 minute timeout granted
10
MOH with 8 minute timeout granted
11
MOH with 12 minute timeout granted
12
MOH with 16 minute timeout granted
13
MOH with indefinite timeout granted
14
MOH request denied. Future requests in the same session will also be denied.
Rev. 1.3
AN93
6.7.2. Receiving Modem-On-Hold Requests
If modem-on-hold is enabled via the +PMH=1 command, the Si2493 may be placed on hold by a remote modem.
The maximum time the modem will remain on hold is configured with the +PMHT setting. Possible values of
+PMHT are given in Table 107. Upon receipt of a modem-on-hold request, the Si2493 will indicate +PMHR:
followed by the code corresponding to the timeout granted. The DCD pin will be deasserted while the modem is on
hold, and the CONNECT result code will indicate a return to data mode. A modem disconnect due to a timeout or
failed negotiation will result in a NO CARRIER result code.
6.8. HDLC: Bit Errors on a Noisy Line
Bit errors can occur on an impaired line. The problem lies in determining and ignoring the spurious data resulting
from poor line conditions and recovering valid data. This example illustrates a typical data-corruption problem due
to a noisy line and the method used to analyze it. Here, the modem is an Si2404 configured with the following
initialization string after reset.
AT+ES=6,,8
AT+ESA=0,0,0,,1,0
AT+ITF=0383,0128
AT:U87,010A
AT+MS=V22
AT:U7A,3
The following data stream was received over a noisy line.
0D
19
19
BE
29
49
0A
B1
B0
C6
19
45
43
19
19
07
B0
52
4F
B2
B2
EA
19
0D
4E
30
29
D8
B2
0A
4E
93
C6
31
05
45
19
19
C2
CB
43
B1
B0
05
14
54
19
19
3C
9F
20
B2
B2
FA
7C
31
30
FF
C8
2D
32
93
98
86
19
30
19
89
C4
B0
30
B1
18
40
19
0D
19
19
E6
B2
0A
B2
B0
19
19
19
30
19
A0
B2
BE
93
B2
CA
19
20
19
92
EA
BA
20
B1
6E
A8
0D
19
19
EF
F9
0A
B1
B2
14
19
4E
19
19
65
B2
4F
B0
B2
19
8D
20
19
B6
B0
00
43
B2
9E
19
57
41
30
F7
B2
A5
52
93
46
DA
43
52
First, the data will be analyzed to point out the occurrence of bit errors and spurious data. Secondly, a simple
algorithm to filter the data will be proposed. Finally, the resulting valid data will be presented.
Table 104 lists an initial analysis of some recurring data patterns.
Rev. 1.3
165
AN93
Table 104. Bit Errors
Data
Meaning
19 B0
Is an indication the modem has detected a pattern with
more than 6 marks in a row. Once this occurs, the
receiver begins looking for HDLC flags. Until the occurrence of HDLC flags, 19 B2 and subsequent data are
discarded.
19 B2
This pattern has three meanings.

If the receiver is looking for HDLC flags, 19B2 means
that the receiver has found an HDLC flag.
 If 19B2 is received after a packet has started (prior
data exists), the receiver assumes the CRC check
does not match the FCS bytes sent by the remote
transmitter and declares the packet bad.
 An isolated 19 B2 pattern (no preceding data) is
normal. This can occur when the following example
data pattern is seen: 7E 7E XX 7E 7E (where XX can
be up to 2 bytes of non-FLAG bit patterns at the
DCE).
The data can be analyzed as follows with valid data
shown in bold.
0D 0A 43 4F 4E 4E 45 43 54 20 31 32 30 30
0D 0A
CONNECT 1200
19 BE 20 20
tx 1200 rx 1200
19 B1
Received first flag.
Beginning of Packet
19 B0
A spurious byte received with more than 6 mark bits in a
row. The modem is looking for HDLC flags.
19 B2
HDLC flag detected.
Beginning of Packet
30 93
19 B1
Good Packet.
Beginning of Packet
19 B2
If a 1-bit error is received in an HDLC flag, the modem
assumes a new single-byte packet. Since a 1-byte
packet is invalid, 19 B2 is generated by modem.
Beginning of Packet
30 93
19 B1
Good Packet
Beginning of Packet
166
Rev. 1.3
AN93
Table 104. Bit Errors (Continued)
Data
19 B2
Meaning
A 1-bit error is received in an HDLC flag. The modem
assumes a new single-byte packet. Since a 1-byte
packet is invalid, 19 B2 is generated by modem.
Beginning of Packet
30 93
19 B1
Good Packet
Beginning of Packet
19 B2
A 1-bit error is received in an HDLC flag. The modem
assumes a new single-byte packet. Since a 1-byte
packet is invalid, 19 B2 is generated by modem.
Beginning of Packet
30 93
19 B1
Good Packet
Beginning of Packet
19 B2
A 1-bit error received in an HDLC flag. The modem
assumes a new single-byte packet. Since a 1-byte
packet is invalid, 19 B2 is generated by modem.
Beginning of Packet
19 B2
A 1-bit error received in an HDLC flag. The modem
assumes a new single-byte packet. Since a 1-byte
packet is invalid, 19 B2 is generated by modem.
Beginning of Packet
B6 9E F7 46
Spurious data
19 B0
Followed by a data byte with more than 6 mark bits in a
row. The modem looks for HDLC flags.
19 B2
HDLC Flag detected
Beginning of Packet
29 C6
Spurious data
19 B0
Followed by a data byte with more than 6 mark bits in a
row. The modem looks for HDLC flags.
19 B2
HDLC Flag detected
Beginning of Packet
FF 98 89 18
19 B0
Spurious data
Data byte with more than 6 mark bits in a row. The
modem looks for HDLC flags.
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Table 104. Bit Errors (Continued)
Data
Meaning
HDLC Flag detected
19 B2
Beginning of Packet
Spurious data
92 6E EF 14 65
19 B0
Data byte with more than 6 mark bits in a row. The
modem looks for HDLC flags.
19 B2
HDLC Flag detected
Beginning of Packet
DA BE C6 07 EA D8 31 C2 05 3C FA C8 86 C4
40 E6
19 A0
CA EA A8 F9
19 B2
Spurious data
Transparency code, represents 0x11 data byte found in
receive data.
Spurious data
Calculated CRC not equal FCS. The modem assumes
this is a bad Frame.
Beginning of Packet
8D 00 57 A5 43 29
Spurious data
19 B0
Followed by a data byte with more than 6 mark bits in a
row. The modem looks for HDLC flags.
19 B2
HDLC Flag detected
Beginning of Packet
05 CB 14 9F 7C 2D
Spurious data
19 B0
Followed by a data byte with more than 6 mark bits in a
row. The modem looks for HDLC flags.
19 B2
HDLC Flag Detected
19 B2
If there is 1-bit error received in an HDLC flag, the
modem assumes a new single-byte packet. Since a 1byte packet is invalid, 19 B2 is generated by the modem.
19 BA
Loss of Carrier Detected
0D 0A 4E 4F 20 43 41 52 52 49 45 52 0D 0A NO CARRIER
168
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The following steps will allow the spurious data and bit errors to be eliminated while preserving the valid data.
1. Ignore 19 B0.
2. Use 19 B2 to discard all collected receive data.
The filtered version of the HDLC frames, based on this algorithm, is shown below with the valid data in bold.
0D
19
19
BE
29
49
0A
B1
B0
C6
19
45
43
19
19
07
B0
52
4F
B2
B2
EA
19
0D
4E
30
29
D8
B2
0A
4E
93
C6
31
05
45
19
19
C2
CB
43
B1
B0
05
14
54
19
19
3C
9F
20
B2
B2
FA
7C
31
30
FF
C8
2D
32
93
98
86
19
30
19
89
C4
B0
30
B1
18
40
19
0D
19
19
E6
B2
0A
B2
B0
19
19
19
30
19
A0
B2
BE
93
B2
CA
19
20
19
92
EA
BA
20
B1
6E
A8
0D
19
19
EF
F9
0A
B1
B2
14
19
4E
19
19
65
B2
4F
B0
B2
19
8D
20
19
B6
B0
00
43
B2
9E
19
57
41
30
F7
B2
A5
52
93
46
DA
43
52
6.9. Overcurrent Detection
The ISOmodem has a built-in overcurrent detection feature (disabled by default) that measures loop current a
programmable amount of time after going off-hook. This allows the modem to detect an improper line condition.
The overcurrent detect feature is enabled by setting U70 [11] (OCDM) = 1. During the time after the modem goes
off-hook, loop current is measured and set by U77 [8:0] (OHT). The default delay is 16 ms. After the delay, current
is sampled every 1 ms. An overcurrent is detected if two consecutive samples indicate an overcurrent condition. If
this feature is enabled and excessive current is detected, the ISOmodem sends the X result code and triggers an
interrupt by asserting the INT pin or by setting the INT bit in the parallel or SPI mode. After an interrupt is received,
the host issues the AT:I command to verify the OCD interrupt and clear the OCD bit. The delay between modem
off-hook and loop current measurement is set by the OHT bits. OHT is a 9-bit register with 1 ms units. The default
delay is 16 ms. When the modem is off-hook in an overload condition, LVCS = 11111 (full scale—overload error
condition), an X is sent to the DTE, and the OCD bit is set.
The Overcurrent Detection feature is controlled by changing U-register settings. The registers and bits that control
these features are shown in Table 105.
Table 105. Overcurrent Detection
Register
Bit
Value
Function
U67
7
DCR
DC Impedance Select
U70
11
OCDM
U70
3
OCD
Overcurrent Detect
U77
8:0
OHT
Off-Hook Time
U79
4:0
LVCS
Line Voltage Current Sense
Overcurrent Detect Mask
6.10. Pulse/Tone Dial Decision
There are three methods to detect whether a telephone line supports DTMF dialing or pulse dialing only. The first
method, which is the simplest, may require the modem to go off-hook more than once. The second method is
slightly more complicated but does not require the modem to go off-hook multiple times.
6.10.1. Method 1: Multiple Off-Hook Transitions
Use DTMF to dial the desired number with the ATDT command. If the line accepts tone dialing, the call is
completed, and connection to the remote modem proceeds as usual.
If the line only allows pulse dialing, the modem hangs up and reports UN-OBTAINABLE NUMBER. This indicates
that the modem detected a dial tone after the DTMF dial attempt. Dial the number again using the ATDP command
instead of ATDT to use pulse dialing.
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6.10.2. Method 2: Single Off-Hook Transition
Use this method if it is undesirable for the modem to go off-hook more than once or to DTMF dial a single digit. This
method is somewhat more complicated and is best illustrated with an example, dialing the number 1234 below.
Set bit 7 of U-register 7A (U7A [7] (DOP) = 1) and send ATDT1;<CR> (Dial the first digit using DTMF and wait for a
response). A response of OK indicates that DTMF digit 1 was sent, and the rest of the digits can be dialed. If a
response of NO DIALTONE is received, the command failed because there was no dial tone (no line available),
and the call cannot be completed.
If a response of OK is received after sending ATDT1;<CR>, continue by sending ATDTW;<CR> to perform the
second dial tone detection and wait for a response. A response of NO DIALTONE indicates that no dial tone was
detected for two seconds, and the line is DTMF capable. Complete the dialing by sending ATDT2345<CR> (DTMF
dial beginning with the second number since the first number was successfully sent initially).
If an OK (dial tone present) was received after the ATDTW;<CR>, the line requires pulse dialing. Pulse dial the
entire telephone number using ATDP12345<CR>.
6.10.3. Method 3: Adaptive Dialing
Adaptive dialing attempts to dial with DTMF, then falls back to pulse dialing. It is enabled with bit 6 of U7A. If bit 6 is
set, the first digit is dialed with DTMF, and the ISOmodem waits two seconds. If a dial tone is still present, the first
digit is resent with pulse dialing followed by the other digits in the dial string. If a dial tone is not present, the
remaining digits are dialed with DTMF. Adaptive dialing does not select 10 pps vs. 20 pps dialing. This must be
configured beforehand. In a PBX installation, this method typically results in pulse dialing, because the first digit
dialed, usually 8 or 9, is used to obtain an outside line and therefore results in a dial tone.
6.10.4. Automatic Phone-Line Configuration Detection
The modem may automatically determine the following characteristics of the telephone line:
DTMF or pulse dialing only

Determine if 20 pps is supported on a pulse dial only line.
Identify it as an outside line or extension network (PBX).
 If connected to a PBX, determine if the dial tone is constant or make/break.
 If connected to a PBX, determine the number to dial for an outside line.
The AT&X1 command automatically determines the above parameters through a series of off-hooks and dialed
digits.

Table 106. Automatic Phone Line Configuration
AT
Command
&X1
Result Code
WXYZn
W = 0 line supports DTMF dialing
1 line is pulse dial only
X = 0 line supports 20 pps dialing
1 line supports 10 pps dialing only
Y = 0 extension network (PBX)
1 connected to outside line
Z = 0 continuous dial tone
1 make-break dial tone
n = 0–9, number for outside line
6.10.5. Line Type Determination
The digit dialed to determine 10 pps vs. 20 pps is programmable through S51. The &X2 command works as
described above; however, only DTMF/20 pps/10 pps determination is made (no PBX). The &X1 and &X2
commands may be aborted by sending the command, AT&X0. The result code will be OK.
170
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6.11. Telephone Voting Mode
The telephone voting mode (TVM) of operation monitors the line to detect polarity reversals after dialing. It waits for
a busy tone to be detected and reports POLARITY REVERSAL or NO POLARITY REVERSAL followed by OK.
To enable TVM, use the G character in the dial string (eg. ATDTG1). The G character must be used for each TVM
call. The S7 timer operates during TVM and indicates NO CARRIER if a timeout occurs before the busy tone is
detected. Polarity reversal monitoring begins after the last digit is dialed and ends at the detection of the busy tone.
Any loss of line-side power (drop out) is considered a polarity reversal if loop current is restored within U51
milliseconds.
6.12. V.92 Quick Connect
The Si2493 supports ITU-T V.92 shortened Phase 1 and Phase 2 to decrease the time required to connect to a
server modem using the V.90 modulation. After the first call, the Si2493 will retain line parameters that allow it to
use shortened Phase 1 and 2 to reduce the total negotiation time. If line conditions change or the remote server
does not support the shortening of these phases, the modem will automatically connect with the normal Phase 1
and Phase 2 negotiation unless specifically commanded not to. Two AT commands control this feature: AT+PQC
and AT+PSS.
The AT+PQC command controls the enabling and disabling of shortened Phase 1 and Phase 2 individually
according to Table 108. It is recommended that both shortened phases be used to realize the maximum reduction
in connect time. The possible settings of the AT+PSS command are shown in Table 109. The AT+PSS command
may be used to force quick connect by setting AT+PSS = 1; however, this is not recommended because calling a
server that does not support this feature will result in a failed connection.
Table 107. Possible +PMHT Settings
<Value>
Description
0
Deny V.92 Modem-on-Hold Request
1
Grant MOH with 10 second timeout
2
Grant MOH with 20 second timeout
3
Grant MOH with 30 second timeout
4
Grant MOH with 40 second timeout
5
Grant MOH with 1 minute timeout
6
Grant MOH with 2 minute timeout
7
Grant MOH with 3 minute timeout
8
Grant MOH with 4 minute timeout
9
Grant MOH with 6 minute timeout
10
Grant MOH with 8 minute timeout
11
Grant MOH with 12 minute timeout
12
Grant MOH with 16 minute timeout
13
Grant MOH with indefinite timeout
Rev. 1.3
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Table 108. AT+PQC Parameters
<Value>
Description
0
Enable Short Phase 1 and Short Phase 2
1
Enable Short Phase 1
2
Enable Short Phase 2
3
Disable Short Phase 1 and Short Phase 2
Table 109. AT+PSS Parameters
<Value>
172
Description
0
The DCEs decide whether or not to use
the short startup procedures. The short
startup procedures shall only be used if
enabled by the +PQC command.
1
Forces the use of the short startup procedures on the next and subsequent connections if they are enabled by the +PQC
command.
2
Forces the use of the full startup procedures on the next and subsequent connections independent of the setting of the
+PQC command.
Rev. 1.3
AN93
7. Handset, TAM, and Speakerphone Operation
This section covers the voice functionality of the Si2494/39. The voice features of the Si2494/39 are divided into
three major categories: handset, telephone answering machine (TAM), and speakerphone. The Si2494/39
implements ITU-T V.253 commands for TAM and speakerphone operation. The TAM voice compression support
includes the following formats:

Signed linear 8-bit, 64 kbps
Unsigned linear 8-bit, 64 kbps
 G.711 µ-law 8-bit, 64 kbps
 G.711 A-law 8-bit, 64 kbps
 G.726 ADPCM 2-bit, 16 kbps
 G.726 ADPCM 4-bit, 32 kbps
All formats use a fixed 8 kHz sampling rate. For most applications, the user wants a high-quality message format
(64 kbps) for the Outgoing Message (OGM) and is less concerned about the quality of the Incoming Message
(ICM).

Speakerphone operation employs an acoustical echo canceller (AEC), acoustical echo suppressor (AES), doubletalk detector (DTD), and line-echo canceller (LEC). This solution provides the following performance:

Programmable echo tail filter length: up to 64 ms
 Convergence speed (white noise): less than 1.6 s
 Single-talk echo suppression: better than 48 dB
 Double-talk echo suppression: better than 30 dB
The software reference section presents the implemented V.253 AT Commands, V.253 <DLE> commands, V.253
<DLE> events, and U registers. The voice reference section covers the functional operation of handset, TAM, and
speakerphone modes and includes use cases with programming examples.
7.1. Software Reference
7.1.1. AT Command Set
In Voice Command State, AT commands are used to control the DCE. The DCE responds with verbose response
strings during Voice Command State. During the Voice Transmit, Voice Receive, and Voice Duplex States, the
<DLE> shielded commands are used. The <DLE> events can appear in all states.
7.1.2. AT+ Extended Commands
Table 110. Extended AT+ Command Set
Command
+FCLASS = <mode>
Action
Data/Voice Mode Selection
<mode>
Description
0
Data (default)
8
Voice mode
256
SMS mode
Note: An ATH command will automatically transition the DCE to +FCLASS=0.
+IPR = <rate>
Fixed DTE Rate
<rate>
Description
0
Automatically detect the baud rate.
[BPS]
The decimal value of the rate in bits per second.
The <rate> parameter represents the DTE rate in bps and may be set to any of the following values: 300, 600, 1200, 2400, 4800, 7200, 9600, 12000, 14400, 19200, 38400,
57600, 115200, 230400, 245760, and 307200.
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Table 110. Extended AT+ Command Set (Continued)
Command
+VCDT = <n>
Caller ID Type
<n>
0
1
2
3
4
5
6
7
Description
After ring only
Always on
UK
Japan
DTMF after polarity reversal
DTMF after polarity reversal (off-hook reception)
Always-on DTMF
DTMF after ring
+VCID = <pmode>
Caller ID Enable
<pmode>
Description
0
Off
1
On—formatted
2
On—raw data format
+VDR = <enable>,
<report>
Distinctive Ring Cadence Reporting
<enable>,<report>Mode
0, x
Disable distinctive ring
1, 0
Enable distinctive ring. The DCE will report DROF and DRON result
codes only. DROF and DRON are reported in 100 ms units.
1, 1
Enable distinctive ring. The DCE will report DROF and DRON result
codes as well as well as a Ring result code x/10 seconds after the falling edge of a
ring pulse. DROF and DRON are reported in 100 ms units.
+VGR = <gain>
Receive Gain Selection
The <gain> parameter has a range of 112-134 with 128 marking the nominal value.
The default is 128, which represents 0 dB. Step size is 3 dB. This represents a
range of -48 dB to 18 dB. This command is used to control the receive gain at the DTE
from either the Si3000 Codec or the DAA. The purpose is to adjust the DTE receive
gain for the TAM voice stream during idle state. See the <DLE><d> and <DLE><u>
commands discussed in Table 111 on page 178 for information on how to control the
receive gain during active voice stream processing.
+VGT = <gain>
Transmit Gain Selection
The <gain> parameter has a range of 112-134 with 128 marking the nominal value.
The default is 128, which represents 0 dB. Step size is 3 dB. This represents a
range of -48 dB to 18 dB. This command is used to control the transmit gain at the
DTE to either the Si3000 Codec or the DAA. The purpose is to adjust the DTE transmit
gain for the TAM voice stream during idle state. See the <DLE><d> and <DLE><u>
commands discussed in Table 111 on page 178 for information on how to control the
transmit gain during active voice stream processing.
+VIP
+VIT = <timer>
174
Action
Load Voice Factory Defaults.
DTE/DCE Inactivity Timer
The <timer> parameter has a range of 0-255 with units of seconds. The default is 0
(disable).
Rev. 1.3
AN93
Table 110. Extended AT+ Command Set (Continued)
Command
Action
+VLS = <label>
Analog Source / Destination Selection
<label>
Description
0
DCE is on-hook. AOUT disabled. Tone detectors disabled.
Si3000 sample pass-through to DAA is inactive.
1
DCE is off-hook. AOUT disabled. Tone detectors disabled.
4
DCE is on-hook. AOUT connected to tone generators.
Tone detectors disabled.
5
DCE is off-hook. AOUT connected to PSTN.
Tone detectors enabled.
13
DCE is off-hook. V.253 tone event reporting enabled. Si3000 sample
pass-through to DAA is active with options for speakerphone operation.
14
DCE is on-hook. V.253 tone event reporting enabled. Si3000 interface
is active for DTE voice stream pass-through.
15
DCE is off-hook. V.253 tone event reporting enabled. Si3000 sample
pass-through to DAA is active with options for handset operation.
20
DCE is on-hook. AOUT disabled. Tone detectors enabled.
21
DCE is on-hook. AOUT connected to tone generators. Tone detectors
enabled.
Table 117 on page 190 shows the voice-mode operation and the signal paths. See
10.2.4.2 of V.253 for an explanation of the AT +VLS=? command results. If an ATD
command is sent while the DCE is in VLS=0 and +FCLASS=8, the DCE will automatically transition to VLS=1. The ATH command will automatically force the DCE to
VLS=0. The main options of interest are the 0, 13, 14, and 5. The +VLS=0 setting
must be applied first before applying a new +VLS value to ensure the mode is exited
properly.
+VNH = <hook>
Automatic Hangup Control
<hook>
Description
0
The DCE retains automatic hangups as is normal in the other modes
(such as hanging up the phone when the ISOmodem does not detect a data carrier
with a given time interval).
1
The DCE shall disable automatic hangups in the other non-voice
modes.
2
The DCE shall disable all hang-ups in other non-voice modes. The
DCE shall only perform a “logical” hangup (return the OK result code).
+VRA = <interval>
Ringing Tone Goes Away Timer
The DCE only uses this command in call origination transactions. This command sets
the amount of time in 0.1 second units the DCE shall wait between Ringing Tone
before it can assume that the remote modem has gone off-hook. Default time is five
seconds.
+VRID = <rmode>
Repeat Caller ID
Description
<rmode>
0
Display Caller ID information of the last incoming call in formatted
form.
1
Display Caller ID information of the last incoming call in unformatted
form.
Rev. 1.3
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Table 110. Extended AT+ Command Set (Continued)
Command
Action
+VRN
Ringing Tone Never Appeared Timer
This command sets the amount of time in seconds the DCE will wait looking for Ringing Tone. If the DCE does not detect Ringing Tone in this time period, the DCE shall
assume that the remote station has gone off-hook and return an OK result code.
Default time is 0 seconds.
+VRX
Receive Voice Stream
Enable DTE receive of voice stream. The DCE will return a CONNECT response followed by the voice stream as defined by the +VSM command. The DTE can issue a
<DLE><!> or <DLE><ESC> sequence to terminate the receive stream. The DCE will
return a <DLE><ETX> followed by an OK response for <DLE><!> and <DLE><ESC>
followed by an OK response for <DLE><ESC>. The DCE can be configured to terminate the stream using the DTE/DCE Inactivity Timer, which is configured using the
+VIT command. The DTE will need to process any <DLE> shielded events present in
the data stream. Any <DLE><DLE> sequences can be preserved to allow less overhead during playback of the stream with the +VTX command.
+VSD = <sds>, <sdi>
Silence Detection
Silence Detection Sensitivity
<sds>
118
More sensitive: lower noise levels considered to be silence
128
Nominal level of sensitivity.
138
Less sensitive: higher noise levels considered to be silence
<sdi>
Silence Detection Interval
The time interval in 0.1 second units, which must contain no or little activity, before the
DCE will report (QUIET) (<DLE><q>). Default is five seconds.
+VSM = <cml>
Compression Selection Method
<cml>
Compression Mode
0
Signed linear PCM, 8-bit, 64 kbps
1
Unsigned linear PCM, 8-bit, 64 kbps
4
G.711U -law companding PCM, 8-bit, 64 kbps
5
G.711A A-law companding PCM, 8-bit, 64 kbps
129
G.726 ADPCM, 2-bit, 16 kbps
131
G.726 ADPCM, 4-bit, 32 kbps
All compression modes use a fixed sampling rate of 8 kHz. See 10.2.8.2 of V.253 for
an explanation of the +VSM=? command results.
+VSP = <mode>
Voice Speakerphone State
<mode>
Description
0
Speakerphone AEC, AES and LEC disabled. Handset FIR filter
coefficients are selected.
1
Speakerphone AEC, AES and LEC enabled. Speakerphone FIR filter
coefficients are selected. The +VLS=13 command must be used in combination with
this setting.
+VTD = <dur>
DTMF / Tone Duration Timer
This command sets the default DTMF / tone generation duration in 10 ms units for the
+VTS command. Default time is 1 second (<dur> = 100).
176
Rev. 1.3
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Table 110. Extended AT+ Command Set (Continued)
Command
Action
+VTS = [<freq1>,
<freq2>, <dur>],[...]...
DTMF and Tone Generation
This command can be used to produce single-frequency tones and double-frequency
tones (i.e. DTMF digit). All three parameters are required for correct operation.
<freq1>
Frequency one, which has a range of 0, 200-3200 Hz.
<freq2>
Frequency two, which has a range of 0, 200-3200 Hz.
<dur>
Duration of the tone(s) in 10 ms units.
For only a single tone, use <freq1> with zero value for <freq2>. Bracket syntax can be
used to group sets of tones to generate simple melodies, e.g.
+VTS=[500,0,10],[600,200,20],[700,250,30]
+VTX
Transmit Voice Stream
Enable DTE transmit of voice stream to DCE. The DCE will return a CONNECT
response. The DTE sends the voice stream as defined by the +VSM command. Any
0x10 character in the voice stream must be shielded with a <DLE>. The DTE issues a
<DLE><ETX> sequence to terminate the transmit stream. The DCE will respond with
<DLE><ETX> followed by OK. The DCE can be configured to terminate the stream
using the DTE/DCE Inactivity Timer, which is configured using the +VIT command.
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7.1.3. <DLE> Commands (DTE-to-DCE)
The characters listed in the Code column of Table 111 are referenced throughout this document with the <>
notation. Simple action commands consist of a <DLE> character plus a simple action-command character (two
bytes total).
Table 111. <DLE> Commands (DTE-to-DCE)
Format: <DLE>[Code]
Code
Hex
<DLE>
0x10
The DTE must shield any 0x10 characters in the voice data stream sent to the DCE to
avoid creation of a <DLE> simple-action command.
<SUB>
0x1A
More efficient representation of two 0x10 0x10 characters in the voice data stream.
<CAN>
0x18
Clear transmit buffer of voice data during +VTX session.
<NUL>
0x00
Do nothing. Refresh +VIT Inactivity Timer.
/
0x3C
Disable DTMF reporting.
~
0x2F
Enable DTMF reporting.
<ESC>
0x1B
End Voice Receive State started by the +VRX command.
!
0x21
Abort Voice Receive State started by the +VRX command.
u
0x75
Increase volume or gain during voice stream processing. For +VRX, increase the UBF
and UC0 receive gains by 3 dB. For +VTX, increase the UB8 and UB3 transmit gains by
3 dB. The voice driver should track this command and update the +VGR or +VGT setting.
Since this <DLE><u> command affects RS232 DAA and RS232 Si3000 gain registers,
the voice driver should maintain two sets of +VGT and +VGR. The voice driver will need
to know the +VLS state to determine if RS232 is connected to the Si3000 or the DAA.
This command is only processed during an active +VRX or +VTX operation.
d
0x64
Decrease volume or gain during voice stream processing. For +VRX, decrease the UB3
and UB8 receive gains by 3 dB. For +VTX, decrease the UB8 and UB3 transmit gains by
3 dB. The voice driver should track this command and update the +VGR or +VGT setting.
Since this <DLE><d> command affects RS232 DAA and RS232 Si3000 gain registers,
the voice driver should maintain two sets of +VGT and +VGR. The voice driver will need
to know the +VLS state to determine if RS232 is connected to the Si3000 or the DAA.
This command is only processed during an active +VRX or +VTX operation.
178
Simple Action Command Description
Rev. 1.3
AN93
7.1.4. <DLE> Events (DCE-to-DTE)
7.1.4.1. Simple Event Reporting
Table 112. <DLE> Simple Events (DCE-to-DTE)
Format: <DLE>[Code]
Code
Hex
Description
<DLE>
0x10
The DCE will shield a 0x10 character in the voice stream to create a 0x10 0x10
sequence sent to the DTE.
<SUB>
0x1A
DLE DLE in datastream
<ETX>
0x03
End of voice stream data state.
X
0x58
Packet Header "Complex Event Detection Report". Implemented for CID and Distinctive
Ring report only.
.
0x2E
Packet Terminator "Complex Event Detection Report". Implemented for CID and Distinctive Ring report only.
/
0x2F
DTMF tone detection started.
~
0x7F
DTMF tone detection ceased.
R
0x52
Ring incoming.
1
0x31
DTMF 1
2
0x32
DTMF 2
3
0x33
DTMF 3
4
0x34
DTMF 4
5
0x35
DTMF 5
6
0x36
DTMF 6
7
0x37
DTMF 7
8
0x38
DTMF 8
9
0x39
DTMF 9
0
0x30
DTMF 0
A
0x41
Extended keypad DTMF A
B
0x42
Extended keypad DTMF B
C
0x43
Extended keypad DTMF C
D
0x44
Extended keypad DTMF D
*
0x2A
Extended keypad DTMF E
#
0x23
Extended keypad DTMF F
Rev. 1.3
179
AN93
Table 112. <DLE> Simple Events (DCE-to-DTE) (Continued)
Format: <DLE>[Code]
180
Code
Hex
Description
o
0x6F
Receive buffer overrun
u
0x75
Transmit buffer underrun.
c
0x63
Fax Calling. DCE has detected T.30 1100 Hz tone.
e
0x65
Data Calling. DCE has detected V.25 1300 Hz tone.
h
0x68
Line voltage collapsed (phone line detached).
H
0x48
Line voltage restored (phone line reattached).
q
0x71
Presumed End of Message (QUIET).
l
0x6C
Loop current interruption.
b
0x62
Busy tone detected.
d
0x64
Dial tone detected.
r
0x72
Ringing tone detected.
p
0x70
Line voltage increased (parallel phone goes on-hook). DCE monitors loop current when
off-hook and line voltage when on-hook.
P
0x50
Line voltage decreased (parallel phone goes off-hook). DCE monitors loop current when
off-hook and line voltage when on-hook.
a
0x61
Fax or data answer. DCE has detected T.30 2100 Hz or V.21 1650 Hz answer tone.
f
0x66
Data answer. DCE has detected 2225 Hz, USB1 or AC answer sequence.
(
0x28
Negative (decreased) loop-current drift detected.
)
0x29
Positive (increased) loop-current drift detected.
Rev. 1.3
AN93
7.1.4.2. Complex Event Reporting
Table 113. <DLE> Complex Event Reports (DCE-to-DTE)
Format: <DLE><X>[Response]<DLE><.>
Response
Tag
Description
DRON
Distinctive Ring Cadence On-time tag. See +VDR for details.
DROF
Distinctive Ring Cadence Off-time tag. See +VDR for details.
DATE
CID DATE tag. Full format is DATE=HHMM. Type I and II supported.
TIME
CID TIME tag. Full format is TIME=MMDD. Type I and II supported.
NMBR
CID NMDR tag. Full format is NMBR=<Number> or P or O. Type I and II supported.
NAME
CID NAME tag. Full format is NAME=<Listing>. Type I and II supported.
MESG
CID MESG tag. Full format is MESG=<Data Tag><Length of Message><Data><Checksum>.
Type I and II supported.
TA, TB
Tone Detector A and B
Format is TA=<tonestate> or TB=<tonestate>
tonestate[31:16]
millisecond timestamp
tonestate[15:2]
reserved
tonestate[1]
Tone B detected
tonestate[0]
Tone A detected
7.1.5. U Registers
This section presents the set of U registers needed for the voice modes.
Table 114. Voice Mode U Registers
Register
Address
Name
Description
Default
U72
0x0072
CDCCTRL
Si3000 Audio Codec Control Interface.
—
UB1
0x00B1
TXGAIN
Si3000-to-DAA Transmit Gain.
0x1000
UB3
0x00B3
TXGAIN1
RS232-to-DAA Transmit Gain.
0x1000
UB4
0x00B4
TXGAIN2
VTS-to-DAA Transmit Gain.
0x1000
UB5
0x00B5
RXGAIN
DAA-to-Si3000 Receive Gain.
0x1000
UB6
0x00B6
STGAIN
Si3000-to-DAA Side Tone Gain.
0x0000
UB8
0x00B8
TXGAIN3
RS232-to-Si3000 Transmit Gain.
0x1000
UB9
0x00B9
TXGAIN4
VTS-to-Si3000 Transmit Gain.
0x0000
UBF
0x00BF
RXGAIN1
DAA-to-RS232 Receive Gain.
0x1000
UC0
0x00C0
RXGAIN2
Si3000-to-RS232 Receive Gain.
0x1000
Rev. 1.3
181
AN93
Table 114. Voice Mode U Registers (Continued)
182
Register
Address
Name
Description
U156
0x0156
HTXFIR1
0x4000
U157
0x0157
HTXFIR2
0x0000
U158
0x0158
HTXFIR3
0x0000
U159
0x0159
HTXFIR4
0x0000
U15A
0x015A
HTXFIR5
0x0000
U15B
0x015B
HTXFIR6
0x0000
U15C
0x015C
HTXFIR7
0x0000
U15D
0x015D
HTXFIR8
0x0000
U15E
0x015E
HTXFIR9
0x0000
U15F
0x015F
HTXFIR10
0x0000
U160
0x0160
HTXFIR11
U161
0x0161
HTXFIR12
0x0000
U162
0x0162
HTXFIR13
0x0000
U163
0x0163
HTXFIR14
0x0000
U164
0x0164
HTXFIR15
0x0000
U165
0x0165
HTXFIR16
0x0000
U166
0x0166
HTXFIR17
0x0000
U167
0x0167
HTXFIR18
0x0000
U168
0x0168
HTXFIR19
0x0000
U169
0x0169
HTXFIR20
0x0000
U16A
0x016A
HTXFIR21
0x0000
Handset TX FIR Filter Coefficients.
Rev. 1.3
Default
0x0000
AN93
Table 114. Voice Mode U Registers (Continued)
Register
Address
Name
Description
U16B
0x016B
HRXFIR1
0x4000
U16C
0x016C
HRXFIR2
0x0000
U16D
0x016D
HRXFIR3
0x0000
U16E
0x016E
HRXFIR4
0x0000
U16F
0x016F
HRXFIR5
0x0000
U170
0x0170
HRXFIR6
0x0000
U171
0x0171
HRXFIR7
0x0000
U172
0x0172
HRXFIR8
0x0000
U173
0x0173
HRXFIR9
0x0000
U174
0x0174
HRXFIR10
0x0000
U175
0x0175
HRXFIR11
U176
0x0176
HRXFIR12
0x0000
U177
0x0177
HRXFIR13
0x0000
U178
0x0178
HRXFIR14
0x0000
U179
0x0179
HRXFIR15
0x0000
U17A
0x017A
HRXFIR16
0x0000
U17B
0x017B
HRXFIR17
0x0000
U17C
0x017C
HRXFIR18
0x0000
U17D
0x017D
HRXFIR19
0x0000
U17E
0x017E
HRXFIR20
0x0000
U17F
0x017F
HRXFIR21
0x0000
U196
0x0196
OUTLIM
U197
0x0197
INLIM
U199
0x0199
VPCTRL
U19A
0x019A
U19B
0x019B
U19C
0x019C
AECREFG AEC Reference Gain.
0x1000
U19D
0x019D
AECMICG AEC Microphone Gain.
0x1000
U19E
0x019E
AECNRG
Handset RX FIR Filter Coefficients.
0x0000
Output Limiter Threshold.
0x5000
Input Limiter Threshold.
0x2000
This is a bit-mapped register.
AECHLEN AEC Filter Length.
AECDLY
Default
AEC Adjustable Delay.
This is a bit-mapped register.
Rev. 1.3
—
0x0200
0x001F
—
183
AN93
Table 114. Voice Mode U Registers (Continued)
184
Register
Address
Name
Description
U1A0
0x01A0
STXFIR1
0x0000
U1A1
0x01A1
STXFIR2
0x0000
U1A2
0x01A2
STXFIR3
0x0000
U1A3
0x01A3
STXFIR4
0x0000
U1A4
0x01A4
STXFIR5
0x0000
U1A5
0x01A5
STXFIR6
0x0000
U1A6
0x01A6
STXFIR7
0x0000
U1A7
0x01A7
STXFIR8
0x0000
U1A8
0x01A8
STXFIR9
0x0000
U1A9
0x01A9
STXFIR10
0x0000
U1AA
0x01AA
STXFIR11
U1AB
0x01AB
STXFIR12
0x0000
U1AC
0x01AC
STXFIR13
0x0000
U1AD
0x01AD
STXFIR14
0x0000
U1AE
0x01AE
STXFIR15
0x0000
U1AF
0x01AF
STXFIR16
0x0000
U1B0
0x01B0
STXFIR17
0x0000
U1B1
0x01B1
STXFIR18
0x0000
U1B2
0x01B2
STXFIR19
0x0000
U1B3
0x01B3
STXFIR20
0x0000
U1B4
0x01B4
STXFIR21
0x0000
Speakerphone TX FIR Filter Coefficients.
Rev. 1.3
Default
0x0000
AN93
Table 114. Voice Mode U Registers (Continued)
Register
Address
Name
U1B5
0x01B5
SRXFIR1
0x0000
U1B6
0x01B6
SRXFIR2
0x0000
U1B7
0x01B7
SRXFIR3
0x0000
U1B8
0x01B8
SRXFIR4
0x0000
U1B9
0x01B9
SRXFIR5
0x0000
U1BA
0x01BA
SRXFIR6
0x0000
U1BB
0x01BB
SRXFIR7
0x0000
U1BC
0x01BC
SRXFIR8
0x0000
U1BD
0x01BD
SRXFIR9
0x0000
U1BE
0x01BE
SRXFIR10
0x4000
U1BF
0x01BF
SRXFIR11 Speakerphone RX FIR Filter Coefficients.
0x0000
U1C0
0x01C0
SRXFIR12
0x0000
U1C1
0x01C1
SRXFIR13
0x0000
U1C2
0x01C2
SRXFIR14
0x0000
U1C3
0x01C3
SRXFIR15
0x0000
U1C4
0x01C4
SRXFIR16
0x0000
U1C5
0x01C5
SRXFIR17
0x0000
U1C6
0x01C6
SRXFIR18
0x0000
U1C7
0x01C7
SRXFIR19
0x0000
U1C8
0x01C8
SRXFIR20
0x0000
U1C9
0x01C9
SRXFIR21
0x0000
U1CD
0x01CD
LECHLEN LEC Filter Length.
0x0020
U1CE
0x01CE
LECDLY
Description
LEC Adjustable Delay.
Rev. 1.3
Default
0x002E
185
AN93
Table 115. U199 and U19E Register Bit Maps
Reg
Name
Bits
15-9
Bit8
Bit7
Bit6
U199 VPCTRL
SSP_LOCTALK SSP_PTT SSP_FLAG
U19E AECREF
SPKREF
Bits
4-5
Bit 3
Bit 2
Bit 1
Bit 0
MMUTE SPCAL SMUTE
MICREF
The SMUTE bit (U199 [1]) mutes the speaker output audio path. The bit should be cleared for normal
speakerphone operation. For recording during hands-free TAM, the bit should be set to mute the speaker output.
The MMUTE bit (U199 [3]) mutes the microphone input audio path. The bit should be cleared for the normal
speakerphone operation. For message review during hands-free TAM, the bit should be set to mute the
microphone.
Bit SPCAL (U199 [2]) in U199 must be set for speakerphone’s calibration and cleared for normal speakerphone
operation.
Bit fields SPKREF and MICREF in U19E contain the speakerphone’s speaker and microphone levels during
speakerphone calibration.
Table 116. U199 Bit Definitions
186
Bit
Name
Function
8
SSP_LOCTALK
7
SSP_PTT
6
SSP_FLAG
3
MMUTE
1 = Mute speaker of speakerphone or handset
0 = Unmute speaker
2
SPCAL
1 = AEC speaker / microphone calibration
0 = Normal mode
1
SMUTE
1 = Mute local talker
0 = Unmute local talker
1 = Local talker enabled
0 = Remote talker enabled
Toggled by <DLE><0x27>
1 = Manually switch between near/far talker (push-to-talk mode)
0 = Automatically switch based on signal levels
Toggled by <DLE><0x26>
1 = Enable SSP mode
0 = Disable SSP mode
Toggled by <DLE><0x25>
Rev. 1.3
AN93
7.2. Voice Reference—Overview
This document uses the term “handset mode” to describe the use of the microphone (MIC) and speaker (SPKRL/
SPKRR) connections on the Si3000. The term “hands-free or speakerphone mode” describes the use of the line
input (LINEI) and line out (LINEO) connections on the Si3000.
The term “handset” describes a handheld device containing a microphone and a speaker with a four-wire
connection for microphone signal pair (MIC/MBIAS and GND) and speaker signal pair (SPKRL and GND or
SPKRL and SPKRR). The Si3000 datasheet uses the term “handset” to describe a two-wire device that is
connected directly to the Public Switch Telephone Network (PSTN). This two-wire device is referenced as a
“telephone instrument” to avoid confusion.
The Si24xx-VMB EVB Rev. 2.0 mainboard with Si24xx2G-QFN Rev 1.0 daughtercard serves as the general
evaluation platform for the Si2494/39 parts. See the Si24xx-VMB Global Voice ISOmodem EVB User’s Guide for
details.
Figure 29 illustrates the handset and speakerphone voice path. The gain registers in Figure 29 use a 4.12 format,
with a range of 0x0001 (–72.247 dB) to 0xFFFF (24.082 dB). For the Si3000-to-DAA gain (UB1) and the DAA-toSi3000 gain (UB5), a value of zero is used to disable the path.
The Si2494/39 enters voice mode with +FCLASS=8. Figure 30 illustrates the gain and signal selection options for
the Si3000 codec. Table 117 provides a summary of how the +VLS command is used to control the various voice
mode operations. Table 118 shows the summary of +FCLASS and IDLE state transitions and the expected
responses.
Rev. 1.3
187
Figure 29. TAM, Handset, and Speakerphone Voice Paths
AN93
188
Rev. 1.3
Figure 30. Si3000 Codec Gain and Signal Selection Options
AN93
Rev. 1.3
189
AN93
Table 117. Voice Mode Operations (+FCLASS=8)
+VLS Mode
Primitive
DAA
Active
Detectors
0
None
On-Hook
Ring, CID1
Voice mode is disabled.
+VTX
+VRX
RS232>DAA
DAA>RS232
1
T
Off-Hook
FDV DTMF
2Tones*
TAM operation for call
answer with OGM playback
and record message using
DTE voice stream pass
through with no audio monitoring using Si3000.
4
S
On-Hook
Ring, CID1
Await call. Use +VTX for
melody playback via AOUT.
RS232>AOUT
5
ST
Off-Hook
FDV DTMF
2Tones*
Place call with audio call
progress on AOUT. +VTS
tone signal can be heard at
AOUT via DAA echo-back.
RS232>DAA
13
14
190
Description
M1S1T
H
On-Hook
TAM operation for OGM
record and OGM/message
playback via DTE voice
stream pass through.
DAARS232- >RS232
>Si3000 Si3000>RS232
Handset voice calls over
Si3000<-->DAA path.
TAM operation for call
answer with OGM playback
and record message using
DTE voice stream pass
through with audio monitoring using Si3000.
DAARS232>DAA >RS232
RS232- Si3000>Si3000 >RS232
Off-Hook
20
S
On-Hook
Ring, CID1
FDV DTMF
2Tones*
RS232>DAA
Speakerphone operation:
Use +VSP=1 to enable
AEC/LEC and speakerphone FIR filters without
side-tone gain. Only CID2
detector is active.
Ring, CID1
FDV DTMF
2Tones*
HT
RS232>DAA
DAA>RS232
Off-Hook
15
Si3000<
-->DAA
Handset operation: Use
+VSP=0 for handset operation with handset FIR filters
and side tone gain. All the
detectors are active. Same
as +VLS=15 without TAM
operation.
Await call.
Rev. 1.3
+VTS
RS232>AOUT
CID2
FDV DTMF
2Tones*
CID2
FDV DTMF
2Tones*
+VSP
RS232>DAA
RS232>Si3000
RS232>DAA
RS232>Si3000
AN93
Table 117. Voice Mode Operations (+FCLASS=8) (Continued)
+VLS Mode
Primitive
DAA
Active
Detectors
Description
21
S
On-Hook
Ring, CID1
FDV DTMF
2Tones*
Await call with tone generator connections to AOUT for
control beeps, ring tone, etc.
+VTX
+VRX
+VSP
+VTS
RS232>AOUT
* 2Tones =
Detector for
2 programmed
tones.
Table 118. +FCLASS and IDLE State Transitions Expected Response
Input
Command or
Event
Current Modem Settings
+FCLASS=0,1
+VNH = 0
+VNH = 1
+FCLASS=8
+VNH = 2
DTR off (&D3)
Key Abort
DCE Initiated
disconnects
+FCLASS = 8
+FCLASS = 0,1
+VNH = 2
+FCLASS = 0
+VLS = 0
ON-HK,
+VNH = 0,
+FCLASS = 0
+VLS = 0
ON-HK
ON-HK
ON-HK
ON-HK
+VNH = 0
+VNH = 0
+VNH = 0
+VNH = 0
+FCLASS = 0 +FCLASS = 0 +FCLASS = 0 +FCLASS = 0
+VLS = 0
ON-HK,
+VNH = 0,
+FCLASS = 0
+VLS = 0
ON-HK,
+VNH = 0,
+FCLASS = 0
+VLS = 0
ON-HK
ON-HK
ON-HK
ON-HK
+VNH = 0
+VNH = 0
+VNH = 0
+VNH = 0
+FCLASS = 0 +FCLASS = 0 +FCLASS = 0 +FCLASS = 0
+VLS = 0
ON-HK
+VNH = 0
+FCLASS = 0
+VLS = 0
ON-HK
+VNH = 0
+FCLASS = 0
+VLS = 0
ON-HK
OFF-HK
OFF-HK
ON-HK
+VLS = 0
ON-HK
+VLS = 0
ON-HK
+VLS = 0
ON-HK
OFF-HK
OFF-HK
ON-HK
OFF-HK
OFF-HK
ON-HK,
+VNH = 0
OFF-HK,
+VNH = 0
DTR off (&D2)
ATZ or
+VNH = 1
ON-HK,
+VNH = 0,
+FCLASS = 0
+VLS = 0
ON-HK
ATH or
AT&F
+VNH = 0
+FCLASS = 8 +FCLASS = 8
Go to IDLE
Go to IDLE
Keep HK
Keep HK
+VNH = 0*
+FCLASS = 8
Go to IDLE
Keep HK
+VNH = 0*
Go to IDLE
Keep HK
Go to IDLE
Keep HK
Go to IDLE
Keep HK
ON-HK,
+FCLASS = 0,1 +FCLASS = 0,1
Go to IDLE
Go to IDLE
Keep HK
Keep HK
+VNH = 0*
+FCLASS = 0,1
Go to IDLE
Keep HK
+VNH = 0*
Notes:
1. “HK”: Hook
2. “Keep HK”: Maintain ON or OFF hook status.
3. *If no +VNH=x command executed since last +FCLASS change.
Rev. 1.3
191
AN93
7.3. Si3000 Configuration
7.3.1. Microphone and Speaker Ports
The TAM and Speakerphone applications use two sets of microphones and speakers: one for the handset and one
for hands-free operation. For the Si24xxVMB REV 2.0, the handset circuit uses the MIC input and SPKR_L output.
The Si24xxVMB REV 2.0 allows configuration of the MIC, SPKR_L, and matching ground signals on any handset
pinout. There is no industry standard for handset pinout. For the Si24xx-VMB REV 2.0, the speakerphone/handsfree TAM circuit uses the LINEI input and the LINEO output. The LINEO is sent to an external amplifier.
7.3.2. Register Settings
Figure 30 illustrates the register bit fields and corresponding values used to control the gain/attenuation, filtering,
output drivers, and signal selection. From the software driver perspective, the Si3000 has three configuration
groups that are applied for the given system states: handset, speakerphone, and hands-free TAM. For applications
requiring handset recording of the OGM, the software may use a fourth configuration for handset TAM. These
configuration groups define the digital gains, analog gains, and control bit settings for registers 1, 5, 6, 7, and 9 of
the Si3000. Speakerphone algorithm includes input and reference gains that require a lower gain in the Si3000. For
Hands-Free TAM, the speakerphone voice path is disabled, so a higher analog gain can be used.
7.3.3. System Voice Modes
A system voice mode consists of the Si24xx ISOmodem and Si3000 settings combined with the PSTN status to
achieve a desired function. These modes describe the status of the hook switch, the modem voice path, Si3000
configuration (input, output, and gains), and the allowed operations. Figure 31 illustrates the transition events
among these modes.
7.3.3.1. TAM Hands-Free
This is the general idle mode for recording an OGM/local message (+VRX) and reviewing an ICM/local message
(+VTX). All detectors are functional and incoming rings are indicated on the speaker via a tone or a melody. The
modem is on-hook routing audio between the Si3000 and the DTE interface. The modem voice path is configured
for half-duplex audio with speakerphone algorithm disabled. The Si3000 audio transmit and receive path is muted/
unmuted to allow half-duplex control for proper TAM operations. Side tone is disabled. Handset TX/RX coefficients
are applied. The Si3000 is using the LINEI and LINEO signals with hands-free TAM gain settings.
7.3.3.2. TAM Handset
This is variation to the TAM Hands-Free mode above, with the exception that the handset is used to review a
locally-recorded message or ICM privately. The Si3000 is using the MIC and SPKRR and/or SPKRL signals with
handset gain settings. A raised handset usually triggers off-hook transition, so the controller would have to support
a special mode to not switch off-hook into Handset mode.
7.3.3.3. Speakerphone
This mode is used to conduct a hands-free voice call. The modem is off-hook and routing audio between Si3000
and DAA. The modem voice path is configured for full-duplex audio with speakerphone algorithm enabled. Side
tone is disabled. Speakerphone TX/RX filter coefficients are applied. The Si3000 is using the LINEI and LINEO
signals with speakerphone gain settings.
7.3.3.4. Handset
This mode is used to conduct a private voice call. The modem is off-hook and routing audio between the Si3000
and DAA. The modem voice path is configured for full-duplex audio with speakerphone algorithm disabled. Side
tone is enabled. Handset TX/RX filter coefficients are applied. The Si3000 is using the MIC and SPKRR and/or
SPKRL signals with handset gain settings. This mode is supported by all parts.
192
Rev. 1.3
AN93
7.3.3.5. TAM PSTN
This mode is used to answer an incoming call with OGM playback and ICM recording. The caller may perform local
TAM operations (i.e. record OGM, review ICM) via remote DTMF control. The modem is off-hook routing audio
between the DAA and the DTE interface; however, audio is also available at the Si3000 (via UB5 path) so call
screening is possible via the speaker (LINEO) while the microphone is muted. The modem voice path is configured
for half-duplex audio with the speakerphone algorithm disabled. Side tone is disabled. Handset TX/RX coefficients
are applied. The Si3000 is using the LINEI and LINEO signals with speakerphone gain settings. This mode is
supported by the Si2418/29/36/38 parts.
t+
es
q u is ed
e
R Ra
t
er
U s n ds e nts
e
a
v
H
E
TAM
Handset
L Ha
Ab ow nd
or ere set
tE d
ve or
nt
Initialize
et nt
d s ve
an E
H ed
s
ai
R a H a nd
ise
s
d E et
ve
nt
SP Butt
on
Off Eve
nt
(Hands
et On-H
ook)
k
H oo
O n- ent
E v o us )
er
n
( um
R
TAM
PSTN
TAM
Hands-Free
et nt
ds ve
an E
H red
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e
w
A ns
n
tto
Bu nt
SP Eve
On
SP B
ut
On E ton
vent
Handset
n
tto
B u ent
P
S
Ev
On
t t
se
n d ve n
a
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Speakerphone
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Figure 31. System Voice Modes
Rev. 1.3
193
AN93
7.4. Initialization
The following sequence is used after power up or hardware reset to prepare the modem for voice operations. This
procedure occurs in the Initialize state presented in Figure 31. After initialization, the system will be in the TAM
Hands-Free mode, which is discussed in "7.3.3.1. TAM Hands-Free".
Table 119. Initialization Sequence
Host to Modem Commands
Modem to
Host Result
Codes
Local Modem Actions
ATZ
OK
Reset. The Si3000 is not reset by this
command.
ATE0+FCLASS = 0
OK
Disable local AT command echo and
enter data mode, which is necessary for
patch loading.
AT+IPR = 115200
OK
Disable autobaud and set rate to
115,200 bps.
[ Apply Patch Commands ]
OK
Apply the modem patch commands.
AT:U199|A
OK
Mute the microphone and speaker
paths to the codec.
ATE0+FCLASS = 8
OK
Disable local AT command echo and
enter voice mode. Limited V.253 event
reporting enabled with default setting of
+VLS=0.
AT+VLS = 0
OK
Disable voice mode. Used as a transition point between non-zero +VLS voice
modes.
AT+VLS = 14
OK
Setup on-hook TAM voice mode. See
AT*Y254:W59|1
OK
Enable the SSI interface to the Si3000.
AT*Y0
OK
Exit the AT*Y command mode.
AT+VCDT = 1
OK
Enable always-on Type I Caller ID.
AT+VCID = 1
OK
Enable formatted Caller ID.
AT+VSD = 129
OK
Set silence detection sensitivity level.
AT+PCW = 0
OK
Enable Type II Caller ID reporting.
AT:U0B1,0500
OK
Set Si3000-to-DAA transmit gain.
AT:U0B5,0200
OK
Set DAA-to-Si3000 receive gain.
AT:U0B6,0100
OK
Set Sidetone gain.
AT:U0B9,0300
OK
Set VTS-to-Si3000 transmit gain.
AT:U0B4,0600
OK
Set VTS-to-DAA transmit gain.
194
Rev. 1.3
Table 117 on page 190 for details.
AN93
Table 119. Initialization Sequence (Continued)
AT:U196,5000
OK
Set output limiter threshold gain.
AT:U197,2000
OK
Set input limiter threshold gain.
AT:U19C,2400
OK
Set AEC reference gain.
AT:U19D,1800
OK
Set AEC microphone gain.
AT:U19A,01E0
OK
Set AEC filter length.
AT:U19B,001F
OK
Set AEC adjustable delay.
AT:U04F,01F4
OK
Set flash hookswitch period.
AT:U156,FF10,FFA2,FFD7,FF35,FEF3,FE68,FB7E
OK
AT:U15D,F90C,FDDF,091D,4F51,091D,FDDF,F90C
OK
AT:U164,FB7E,FE68,FEF3,FF35,FFD7,FFA2,FF10
OK
AT:U16B,0041,00B1,00AA,0001,FF92,0042,0183
OK
AT:U172,0165,FEC0,FB05,3940,FB05,FEC0,0165
OK
AT:U179,0183,0042,FF92,0001,00AA,00B1,0041
OK
AT:U1A0,0000,0000,0000,0000,0000,0000,0000
OK
AT:U1A7,0000,0000,0000,0000,0000,0000,0000
OK
AT:U1AE,0000,0000,0000,0000,0000,0000,4000
OK
AT:U1B5,0173,0273,045A,043B,0121,FD54,FE41
OK
AT:U1BC,0197,0543,FD03,30D6,FD03,0543,0197
OK
AT:U1C3,FE41,FD54,0121,043B,045A,0273,0173
OK
AT:U72,0108
AT:U72,05D7
AT:U72,065E
Rev. 1.3
Set Handset Transmit FIR coefficients.
Set Handset Receive FIR coefficients.
Set Speakerphone Transmit FIR coefficients.
Set Speakerphone Receive FIR coefficients.
OK
Configure Si3000 Register 1:
Disable speaker driver
Enable line output driver
Disable telephone instrument driver
Disable MBIAS output
OK
Configure Si3000 Register 5:
20 dB Line In gain
Enable Line In
20 dB MIC input gain
Mute MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Enable Line Out
Disable telephone instrument output
195
AN93
Table 119. Initialization Sequence (Continued)
AT:U72,075E
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT:U0B1,0
OK
Disable Si3000-to-DAA transmit gain
path. This ensures codec tones are not
sent to the FDV and DTMF.
AT:U0B5,0
OK
Disable DAA-to-Si3000 receive gain
path. This ensures line events such as
CID and ring tone are not heard via the
codec.
AT:U199&FFF7
OK
Enable speaker for local ring tone/alert
tones.
7.5. Handset
7.5.1. Overview
This mode uses the voice pass-through connection to route SSI data between the Si3000 and the DAA. The
modem remains in AT command mode and provides V.253 event notifications. The host controller is responsible
for detecting the status of the handset position. The following sections provides detailed examples of originating
and answering a voice call with the handset.
7.5.2. Handset Configuration
Table 120 contains the initial configuration that is used by all dialing use cases. The sequence is also sent for the
answer case. The user will have been notified of the incoming call through a local +VTS ring tone and a raised
handset event would prompt the Handset Configuration sequence to answer the call. The UB1, UB5, UB6, and
Si3000 register configuration vary with the customer’s production hardware. The UB5 register serves as the
general volume control in this mode.
196
Rev. 1.3
AN93
Table 120. Handset Configuration
Modem to Host
Result Codes/
Data
Local Modem Actions
AT:U199|A
OK
Mute the microphone and speaker paths to
the codec.
AT+VLS=0
OK
Disable voice mode. Used as a transition
point between non-zero +VLS voice modes.
AT+VLS=13
OK
AT:U0B1,0500
OK
Restore Si3000-to-DAA transmit gain path.
AT:U0B5,0200
OK
Restore DAA-to-Si3000 receive gain path.
OK
Configure Si3000 Register 1:
Enable speaker driver
Disable line output driver
Disable telephone instrument driver
Enable MBIAS output
OK
Configure Si3000 Register 5:
10 dB Line In gain
Mute Line In
20 dB MIC input gain
Enable MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Disable Line Out
Disable telephone instrument output
AT:U72,075E
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT+VSP=0
OK
Select handset voice path. See Figure 29 on
page 188 for details.
AT:U199&FFF5
OK
Enable the microphone and speaker paths
to the codec.
Host to Modem Commands / Data
AT:U72,0110
AT:U72,05B3
AT:U72,065C
Rev. 1.3
Setup off-hook voice mode. See Table 117
on page 190 for details.
197
AN93
7.5.3. Call – Automatic Tone Dial
Table 121 lists the commands that occur after the configuration defined in Table 120.
Table 121. Handset Automatic Tone Dial
Host to Modem
Commands / Data
Modem to Host Result
Codes/Data
ATDT102
Local Modem Actions
Perform automatic tone dial of 102. Modem will return OK.
Depending on the number of rings the host may receive
<DLE><r> events for ring-back notifications. If the line is
busy, a <DLE><b> event will be sent to the host. After
connection, the host will receive <DLE><q> events during
quiet periods of no voice.
OK
7.5.4. Call – Manual Off-Hook Tone Dial
Table 122 lists the commands that occur after the configuration defined in Table 120.
Table 122. Handset Manual Off-Hook Dial
Host to Modem Commands
/ Data
Modem to Host Result
Codes/Data
AT+VTS=[697,1209,20]
OK
AT+VTS=[941,1336,20]
OK
AT+VTS=[697,1336,20]
OK
Local Modem Actions
The user is free to dial manually using the +VTS commands to create the DTMF digits.
Generate DTMF 1 digit for 200 ms.
Generate DTMF 0 digit for 200 ms.
Generate DTMF 2 digit for 200 ms.
Depending on the number of rings the host may receive
<DLE><r> events for ring-back notifications. If the line
is busy, a <DLE><b> event will be sent to the host.
After connection, the host will receive <DLE><q>
events during quiet periods of no voice.
7.5.5. Call – Automatic Pulse Dial
Table 123 lists the commands that occur after the configuration defined in Table 120.
Table 123. Handset Automatic Pulse Dial
Host to Modem
Commands / Data
ATDP102
Modem to Host Result
Codes/Data
OK
Local Modem Actions
Perform automatic pulse dial of 102. Modem will return
OK. Depending on the number of rings the host may
receive <DLE><r> events for ring-back notifications. If
the line is busy, a <DLE><b> event will be sent to the
host. After connection, the host will receive <DLE><q>
events during quiet periods of no voice.
7.5.6. Answer
A ring event will prompt the user to lift the handset. This will generate a Handset Raised Event and the Handset
Configuration procedure defined in Table 120 should be used to answer the call. For ring detection and local ring
tone/melody generation, see "7.6.2. TAM Hands-Free—Idle" .
198
Rev. 1.3
AN93
7.5.7. Terminate
Upon detection of the Handset Lowered Event, the host should issue the commands in Table 124 to transition to
the TAM Hands-Free mode.
Table 124. Handset to TAM Hands-Free Transition
Host to Modem
Commands / Data
Modem to Host Result
Codes/Data
AT:U199|A
OK
Mute the microphone and speaker paths to the codec.
AT+VSP=0
OK
Select handset voice path. See Figure 29 on page 188 for details.
+VSP must be zero when exiting from +VLS=13.
AT+VLS=0
OK
Disable voice mode. Used as a transition point between
non-zero +VLS voice modes.
AT+VLS=14
OK
Setup on-hook voice mode. See Table 117 on page 190 for
details. This will return the modem to on-hook state.
AT:U0B1,0
OK
Disable Si3000-to-DAA transmit gain path. This ensures
codec tones are not sent to the FDV and DTMF.
AT:U0B5,0
OK
Disable DAA-to-Si3000 receive gain path. This ensures line
events such as CID and ring are not heard via the codec.
OK
Configure Si3000 Register 1:
Disable speaker driver
Enable line output driver
Disable telephone instrument driver
Disable MBIAS output
OK
Configure Si3000 Register 5:
20 dB Line In gain
Enable Line In
20 dB MIC input gain
Mute MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Enable Line Out
Disable telephone instrument output
AT:U72,075E
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT:U199&FFF7
OK
Enable speaker for local ring tone/alert tones.
AT:U72,0108
AT:U72,05D7
AT:U72,065E
Local Modem Actions
Rev. 1.3
199
AN93
7.5.8. Speakerphone Transition
In the Handset mode, the SP Button On Event will trigger the transition from Handset to Speakerphone mode. See
"7.7. Speakerphone" on page 212 for details on Speakerphone mode. The voice driver should track the handset
hook switch state, such that if the user exits Speakerphone mode, the system will switch back to Handset
configuration without losing the active call.
Table 125. Handset to Speakerphone Transition
Host to Modem
Commands / Data
Modem to Host Result
Codes/Data
AT:U199|A
OK
Mute the microphone and speaker paths to the codec.
OK
Configure Si3000 Register 1:
Disable speaker driver
Enable line output driver
Disable telephone instrument driver
Disable MBIAS output
OK
Configure Si3000 Register 5:
20 dB Line In gain
Enable Line In
20 dB MIC input gain
Mute MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Enable Line Out
Disable telephone instrument output
AT:U72,075E
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT+VSP=1
OK
Enable speakerphone voice path. See Figure 29 on
page 188 for details.
AT:U199&FFF5
OK
Enable the microphone and speaker paths to the codec.
AT:U72,0108
AT:U72,05D7
AT:U72,065E
200
Local Modem Actions
Rev. 1.3
AN93
7.6. Telephone Answering Machine
7.6.1. Overview
The Si2494/39 supports telephone answering machine (TAM) operations. These parts use the V.253 command set
to control operation. This section covers the three major TAM-related system voice modes. Some modes offer
multiple operations.
The TAM Hands-Free mode is the general voice idle mode. It is used for OGM recording/review and local ICM
recording/review via hands-free operation. The TAM Handset mode is similar to TAM Hands-Free except that the
audio is handled over the handset. The TAM PSTN mode is for playback of the OGM and recording the ICM. The
TAM PSTN mode also permits remote OGM and ICM record/review via DTMF tone control. The +VTX command is
used to play voice menu options/prompts. All the use cases in this section start with the modem in TAM
Hands-Free mode, which is configured in the initialization sequence in Table 119 on page 194.
7.6.2. TAM Hands-Free—Idle
The modem will use the events listed in Table 112 on page 179 to communicate status. The <DLE><R> event
indicates ring detection. The +VTS command can be used to play one or more single/dual tone sequences. If
enabled, Type I CID is decoded after the first ring and sent via a complex <DLE> event report. See Table 126 for
details.
Table 126. Local Ring Notification with Type I CID Event
Host to Modem Commands / Data
Modem to Host Result
Codes/Data
<DLE><R>
AT+VTS=[700,500,80]
OK
Local Modem Actions
Ring Detection
Play local ring tone.
<DLE><X>
CIDM
DATE=0101
Receive Type I CID DLE complex report.
TIME=0110
NMBR=102
NAME=JONES JENNIFER
<DLE><.>
<DLE><R>
AT+VTS=[700,500,80]
OK
<DLE><R>
AT+VTS=[700,500,80]
OK
Ring Detection.
Play local ring tone.
Ring Detection. The voice driver will use a
rings-to-answer count. This example uses
three rings before answer.
Play local ring tone.
Based upon the TAM answer function settings, a ring counter will validate the number of rings before answer. If the
TAM Answer function is disabled or the number of rings before answer has not been reached, the user has the
opportunity to answer the call via handset or speakerphone.
Rev. 1.3
201
AN93
7.6.2.1. Record OGM
The Si3000-to-RS232 gain register UC0 in the ISOmodem can be used to adjust the voice stream gain. Use the
+VGR command to adjust the UC0 value in command mode. It is best to maintain two versions of +VGR: one for
Si3000-to-RS232 and another for DAA-to-RS232.
Table 127. TAM Hands-Free Record OGM
Host to Modem Commands / Modem to Host Result
Data
Codes/Data
OK
Set the Si3000-to-RS232 receive gain (UC0) for TAM
Hands-Free.
AT:U0B1,0500
OK
Restore Si3000-to-DAA transmit gain path to allow
voice samples to reach FDV block for silence detection.
This allows the driver to automatically end OGM
recording.
AT+VSD=129
OK
Set sensitivity level for OGM recording silence detection.
AT+VSM=4
OK
Select G.711U -law PCM, 8-bit, 64 kbps format. The
voice driver will need to track the OGM format with the
OGM PCM file.
AT+VTS=[1000,0,100]
OK
Play user record tone prompt.
AT:U199|8
OK
Mute speaker to avoid echo (speakerphone algorithm
off).
AT:U199&FFFD
OK
Enable microphone for OGM recording.
AT+VRX
CONNECT
Trigger receive operation. The first byte after the newline character following the CONNECT message will be
the first data stream byte.
[Voice Stream]
Receive OGM voice stream. During voice stream capture, the user can adjust the UC0 value via the
<DLE><u> and <DLE><d> commands. The host voice
driver will need track the number of adjustments and
update the +VGR value for future use.
<DLE><!>
<DLE><ETX>
OK
Terminate the receive operation. The modem will
respond with <DLE><ETX> to mark the end of the data
stream. The OK denotes the return to command mode.
AT:U0B1,0
OK
Disable Si3000-to-DAA transmit gain path. This
ensures codec tones are not sent to the FDV and
DTMF.
AT:U199|2
OK
Mute the microphone.
AT:U199&FFF7
OK
Enable speaker for local ring tone/alert tones.
AT+VGR=128
202
Local Modem Actions
Rev. 1.3
AN93
7.6.2.2. Review OGM
The RS232-to-Si3000 gain register UB8 in the ISOmodem can be used to adjust the voice stream gain. Use the
+VGT command to adjust the UB8 value in command mode. It is best to maintain two versions of +VGT: one for
RS232-to-Si3000 and another for RS232-to-DAA.
Table 128. TAM Hands-Free Review OGM
Host to Modem Commands Modem to Host Result
/ Data
Codes/Data
Local Modem Actions
AT+VGT=128
OK
Set the RS232-to-Si3000 transmit gain (UB8) for TAM
Hands-Free.
AT+VSM=4
OK
Select G.711U -law PCM, 8-bit, 64 kbps format. The
voice driver will need to track the OGM format with the
OGM PCM file.
AT+VTX
CONNECT
Trigger transmit operation.
<DLE><u>
TX Underrun. Appears at the start of +VTX before transmit data are seen.
Transmit OGM voice stream. During voice stream capture, the user can adjust the UB8 value via the
<DLE><u> and <DLE><d> commands. The host voice
driver will need track the number of adjustments and
update the +VGT value for future use.
[Voice Stream]
<DLE><ETX>
OK
Terminate the transmit operation. The modem will
respond with OK to denote the return to command
mode.
7.6.2.3. Record Local ICM
The Record Local ICM is identical to the Record OGM procedure provided in Table 127 on page 202. The main
difference is that one of the ADPCM formats is generally used and the PCM file is stored with the other ICM files
recorded from the PSTN.
7.6.2.4. Review ICM
The Review ICM is identical to the Review OGM procedure provided in Table 128 on page 203. The main
difference is that one of the ADPCM formats is generally used to conserve message space.
7.6.2.5. Speakerphone Transition
The SP Button On Event will trigger this transition. See Table 136 on page 219 for configuration sequence.
7.6.2.6. Handset Transition
The Handset Raised Event will trigger this transition. See Table 120 on page 197 for configuration sequence.
7.6.3. TAM Handset
Using the handset to record the OGM will result in better message quality. The handset can also be used to screen
messages in private. The host will need to correctly process the Handset Raised Event to keep the modem onhook during record/review operations.
7.6.3.1. Record OGM
The host will prompt the user to lift the handset to begin OGM recording. The procedure restores the TAM HandsFree settings before completion.
Rev. 1.3
203
AN93
Table 129. TAM Handset Record OGM
Host to Modem Commands / Data
Modem to
Host Result
Codes/Data
Local Modem Actions
AT:U199|A
OK
Mute the microphone and speaker paths to
the codec.
OK
Configure Si3000 Register 1:
Enable speaker driver
Disable line output driver
Disable telephone instrument driver
Enable MBIAS output
OK
Configure Si3000 Register 5:
10 dB Line In gain
Mute Line In
20 dB MIC input gain
Enable MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Disable Line Out
Disable telephone instrument output
AT:U72,075E
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT+VGR=128
OK
Set the Si3000-to-RS232 receive gain
(UC0) for TAM Hands-Free.
AT:U0B1,0500
OK
Restore Si3000-to-DAA transmit gain path
to allow voice samples to reach FDV block
for silence detection. This allows the driver
to automatically end OGM recording.
AT+VSD = 129
OK
Set sensitivity level for OGM recording
silence detection.
AT+VSM = 4
OK
Select G.711U -law PCM, 8-bit, 64 kbps
format. The voice driver will need to track
the OGM format with the OGM PCM file.
AT+VTS = [1000,0,100]
OK
Play user record tone prompt.
AT:U199|8
OK
Mute speaker.
AT:U199&FFFD
OK
Enable microphone for OGM recording.
AT:U72,0110
AT:U72,05B3
AT:U72,065C
204
Rev. 1.3
AN93
Table 129. TAM Handset Record OGM (Continued)
AT+VRX
CONNECT
Trigger receive operation. The first byte
after the newline character following the
CONNECT message will be the first data
stream byte.
Receive OGM voice stream. During voice
stream capture, the user can adjust the
UC0 value via the <DLE><u> and
[Voice Stream] <DLE><d> commands. The host voice
driver will need track the number of adjustments and update the +VGR value for
future use.
<DLE><!>
<DLE><ETX>
OK
Terminate the receive operation. The
modem will respond with <DLE><ETX> to
mark the end of the data stream. The OK
denotes the return to command mode. A
Handset Lowered Event, timeout, or silence
event can trigger the <DLE><!> transmission.
AT:U0B1,0
OK
Disable Si3000-to-DAA transmit gain path.
This ensures codec tones are not sent to
the FDV and DTMF.
AT:U199|A
OK
Mute the microphone and speaker paths to
the codec.
OK
Configure Si3000 Register 1:
Disable speaker driver
Enable line output driver
Disable telephone instrument driver
Disable MBIAS output
OK
Configure Si3000 Register 5:
20 dB Line In gain
Enable Line In
20 dB MIC input gain
Mute MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Enable Line Out
Disable telephone instrument output
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0108
AT:U72,05D7
AT:U72,065E
AT:U72,075E
Rev. 1.3
205
AN93
Table 129. TAM Handset Record OGM (Continued)
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT:U199&FFF7
OK
Enable speaker for local ring tone/alert
tones.
7.6.3.2. Review OGM
The host will prompt the user to lift the handset to begin OGM review. The procedure restores the TAM Hands-Free
settings before completion. The host will need to ensure the Handset Lowered Event is received before
Table 130. TAM Handset Review OGM
Host to Modem Commands / Data
Modem to
Host Result
Codes/Data
AT:U199|A
OK
Mute the microphone and speaker paths to
the codec.
OK
Configure Si3000 Register 1:
Enable speaker driver
Disable line output driver
Disable telephone instrument driver
Enable MBIAS output
OK
Configure Si3000 Register 5:
10 dB Line In gain
Mute Line In
20 dB MIC input gain
Enable MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Disable Line Out
Disable telephone instrument output
AT:U72,075E
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT+VGT=128
OK
Set the RS232-to-Si3000 transmit gain
(UB8) for TAM Hands-Free.
AT:U72,0110
AT:U72,05B3
AT:U72,065C
206
Rev. 1.3
Local Modem Actions
AN93
Table 130. TAM Handset Review OGM (Continued)
Select G.711U -law PCM, 8-bit, 64 kbps
format. The voice driver will need to track
the OGM format with the OGM PCM file.
AT+VSM=4
OK
AT+VTX
CONNECT
Trigger transmit operation.
<DLE><u>
TX Underrun. Appears at the start of +VTX
before transmit data are seen.
Transmit OGM voice stream. During voice
stream capture, the user can adjust the UB8
value via the <DLE><u> and <DLE><d>
commands. The host voice driver will need
track the number of adjustments and update
the +VGT value for future use.
[Voice Stream]
<DLE><ETX>
OK
Terminate the transmit operation. The
modem will respond with OK to denote the
return to command mode.
AT:U199|A
OK
Mute the microphone and speaker paths to
the codec.
OK
Configure Si3000 Register 1:
Disable speaker driver
Enable line output driver
Disable telephone instrument driver
Disable MBIAS output
OK
Configure Si3000 Register 5:
20 dB Line In gain
Enable Line In
20 dB MIC input gain
Mute MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Enable Line Out
Disable telephone instrument output
AT:U72,075E
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT:U199&FFF7
OK
Enable speaker for local ring tone/alert
tones.
AT:U72,0108
AT:U72,05D7
AT:U72,065E
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7.6.3.3. Record Local ICM
The Record Local ICM is identical to the Record OGM procedure provided in Table 129 on page 204. The main
difference is that one of the ADPCM formats is generally used and the PCM file is stored with the other ICM files
recorded from the PSTN.
7.6.3.4. Review ICM
The Review ICM is identical to the Review OGM procedure provided in Table 130 on page 206. The main
difference is that one of the ADPCM formats is generally used to conserve message space.
7.6.4. TAM PSTN
This system voice mode differs from the TAM Hands-Free and TAM Handset modes in that the modem is off-hook
and connected to the PSTN. Due to the paired nature of the +VGR and +VGT, the voice driver should maintain two
copies of each: one for RS232-to-Si3000 and another for RS232-to-DAA. See Figure 29 on page 188 for details.
7.6.4.1. Normal Answer – OGM Playback with ICM Record
Table 131. TAM PSTN Normal Answer – OGM Playback with ICM Record
Host to Modem Commands / Data
Modem to Host Result
Codes/Data
<DLE><R>
AT+VTS=[700,500,80]
OK
Local Modem Actions
Ring Detection
Play local ring tone.
<DLE><X>
CIDM
DATE=0101
TIME=0110
Receive Type I CID DLE complex report.
NMBR=102
NAME=JONES JENNIFER
<DLE><.>
<DLE><R>
AT+VTS=[700,500,80]
OK
<DLE><R>
208
Ring Detection.
Play local ring tone.
Ring Detection. The voice driver will use a
rings-to-answer count. This example uses
three rings before answer.
AT+VTS=[700,500,80]
OK
Play local ring tone.
AT:U199|8
OK
Mute the speaker so the OGM is not heard
locally. The user may remove this command to allow local review.
AT+VGR=128
OK
Set the DAA-to-RS232 receive gain register (UBF) for TAM PSTN.
AT+VGT=128
OK
Set the RS232-to-DAA transmit gain register (UB3) for TAM PSTN.
AT+VSD=129
OK
Set sensitivity level for ICM recording
silence detection.
AT+VSM=4
OK
Select G.711U -law PCM, 8-bit, 64 kbps
format. The voice driver will need to track
the OGM format with the OGM PCM file.
Rev. 1.3
AN93
Table 131. TAM PSTN Normal Answer – OGM Playback with ICM Record (Continued)
AT+VLS=0
OK
Disable voice mode. Used as a transition
point between non-zero +VLS voice
modes.
AT+VLS=15
OK
Setup off-hook voice to PSTN. See
Table 117 on page 190 for details.
AT+VTX
CONNECT
Trigger transmit operation.
<DLE><u>
TX Underrun. Appears at the start of +VTX
before transmit data are seen.
Transmit OGM voice stream. During voice
stream capture, the user can adjust the
UB3 value via the <DLE><u> and
<DLE><d> commands. The host voice
driver will need track the number of adjustments and update the +VGT value for
future use.
[Voice Stream]
<DLE><ETX>
OK
Terminate the transmit operation. The
modem will respond with OK to denote the
return to command mode.
AT+VSM=131
OK
Select G.726 ADPCM, 4-bit, 32 kbps format.
AT+VTS=[1000,0,100]
OK
Play user record tone prompt.
AT:U0B5,0200
OK
Restore DAA-to-Si3000 receive gain path.
This will allow call screening of the ICM.
AT:U199&FFF7
OK
Enable speaker for call screening of the
ICM.
CONNECT
Trigger receive operation. The first byte
after the newline character following the
CONNECT message will be the first data
stream byte.
AT+VRX
<DLE><!>
[Voice Stream]
Receive ICM voice stream. During voice
stream capture, the user can adjust the
UBF value via the <DLE><u> and
<DLE><d> commands. The host voice
driver will need track the number of adjustments and update the +VGR value for
future use.
<DLE><ETX>
OK
Terminate the receive operation. The
modem will respond with <DLE><ETX> to
mark the end of the data stream. The OK
denotes the return to command mode. A
loss of loop current, parallel phone detect,
timeout, or silence event can trigger the
<DLE><!> transmission.
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Table 131. TAM PSTN Normal Answer – OGM Playback with ICM Record (Continued)
AT:U0B5,0
OK
Disable DAA-to-Si3000 receive gain path.
This ensures line events such as CID and
ring tone are not heard via the codec.
AT:U199|2
OK
Mute the microphone.
AT:U199&FFF7
OK
Enable speaker for local ring tone/alert
tones.
AT+VLS=0
OK
Disable voice mode. Used as a transition
point between non-zero +VLS voice
modes. This will hang-up the call.
AT+VLS=14
OK
Setup on-hook TAM voice mode. See
Table 117 on page 190 for details.
7.6.4.2. Interrupted Answer – OGM Playback with DTMF Menu Entry
The procedure listed in Table 132 uses a remote-access password of 1234. DTMF decoding is asynchronous. The
host voice driver will need to employ a timer or timestamp to validate the consecutive DTMF digits that comprise
the remote password.
Table 132. TAM PSTN Interrupted Answer – OGM Playback with DTMF Menu Entry
Host to Modem Commands / Data
Modem to Host Result
Codes/Data
<DLE><R>
AT+VTS=[700,500,80]
OK
Local Modem Actions
Ring Detection
Play local ring tone.
<DLE><X>
CIDM
DATE=0101
TIME=0110
Receive Type I CID DLE complex report.
NMBR=102
NAME=JONES JENNIFER
<DLE><.>
<DLE><R>
AT+VTS=[700,500,80]
OK
<DLE><R>
210
Ring Detection.
Play local ring tone.
Ring Detection. The voice driver will use a
rings-to-answer count. This example uses
three rings before answer.
AT+VTS=[700,500,80]
OK
Play local ring tone.
AT:U199|8
OK
Mute the speaker so the OGM is not heard
locally. The user may remove this command to allow local review.
AT+VGR=128
OK
Set the DAA-to-RS232 receive gain register (UBF) for TAM PSTN.
Rev. 1.3
AN93
Table 132. TAM PSTN Interrupted Answer – OGM Playback with DTMF Menu Entry (Continued)
Host to Modem Commands / Data
Modem to Host Result
Codes/Data
Local Modem Actions
AT+VGT=128
OK
Set the RS232-to-DAA transmit gain register (UB3) for TAM PSTN.
AT+VSD=129
OK
Set sensitivity level for ICM recording
silence detection.
AT+VSM=4
OK
Select G.711U -law PCM, 8-bit, 64 kbps
format. The voice driver will need to track
the OGM format with the OGM PCM file.
AT+VLS=0
OK
Disable voice mode. Used as a transition
point between non-zero +VLS voice
modes.
AT+VLS=15
OK
Setup off-hook voice to PSTN. See
Table 117 on page 190 for details.
AT+VTX
CONNECT
Trigger transmit operation.
<DLE><u>
TX Underrun. Appears at the start of +VTX
before transmit data are seen.
Transmit OGM voice stream. During voice
stream capture, the user can adjust the
UB3 value via the <DLE><u> and
<DLE><d> commands. The host voice
driver will need track the number of adjustments and update the +VGT value for
future use.
[Voice Stream]
<DLE><ETX>
<DLE><~>
<DLE><1>
<DLE></>
DTMF 1 digit detected.
<DLE><~>
<DLE><2>
<DLE></>
DTMF 2 digit detected.
<DLE><~>
<DLE><3>
<DLE></>
DTMF 3 digit detected.
<DLE><~>
<DLE><4>
<DLE></>
DTMF 4 digit detected. The password of
1234 has been matched. Abort answer
sequence.
OK
Rev. 1.3
Terminate the transmit operation. The
modem will respond with OK to denote the
return to command mode.
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Table 132. TAM PSTN Interrupted Answer – OGM Playback with DTMF Menu Entry (Continued)
Host to Modem Commands / Data
Modem to Host Result
Codes/Data
AT+VTS=[500,0,100]
OK
Local Modem Actions
Play special administrator tone.
Using the +VTX command, the voice driver
can playback a menu and monitor DTMF
digit events to perform operations
remotely.
[Playback Menu Options]
7.6.4.3. Speakerphone Transition
A SP Button On Event will trigger the transition to Speakerphone system voice mode. Based upon the point at
which the event is received, the voice driver will vector to a user answer state to gracefully exit the TAM PSTN
mode.
7.6.4.4. Handset Transition
A Handset Raised Event will trigger the transition to Handset system voice mode. Based upon the point at which
the event is received, the voice driver will vector to a user answer state to gracefully exit the TAM PSTN mode.
7.7. Speakerphone
7.7.1. Overview
The Si2494/39 speakerphone consists of the following function components as shown in Figure 29 on page 188:






Acoustical echo canceller (AEC)
Acoustical echo suppressor (AES)
AEC double-talk detector (DTD)
Line echo canceller (LEC)
Howling controller (HC)
High-pass filter (HPF)
7.7.2. Simplex Speakerphone
Simplex Speakerphone (SSP) is a special case of speakerphone operation. Like Speakerphone, it allows two-way
hands-free voice communication over a telephone line, but SSP allows communication in only one direction at a
time. The direction of voice transmission can be done automatically, based on the presence of local and remote
speech at the modem, or manually using a push-to-talk function. Simplex and full-duplex speakerphone modes are
mutually exclusive. SSP supports the Ademco Contact ID and SIA security protocols. It also supports DTMF
generation and detection. DTMF detection is enabled only during +VTR. Commonality in control registers between
SSP and full duplex facilitates programming across platforms. SSP supports Type II Caller ID, but Caller ID is
disabled during +VRX. A DLE<R> event report is sent to the DTE when a SAS Call Waiting tone is detected. If a
CAS tone is detected, the modem mutes the Si3000 speaker while Caller ID Type II data are being captured. It
then reports Caller ID info to the DTE as a DLE-shielded complex event. This happens automatically, without the
need for an AT+VCIDR? command.
1. The microphone sample is taken after U19D; the speaker sample is taken after U19C. However, the scale
factors are set to 1.0 internally, so U19C and U19D will not affect the SSP.
2. To mute the local talker, set U199 [1] to 1 and MUTE_DAA_TO_MIXER=1. To mute the remote talker, set
U199 [3] to 1 and MUTE_MIXER_TO_DAA to 1.
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Table 133. Simplex Speakerphone U Registers
Register
Name
Description
Default Value
U1D5
SSPHLDTIM
Extra time SSP stays in RX or TX mode to prevent frequent switching 0x0000
U1D6
SSPLTHRSH Local talker threshold
0x0000
U1D7
SSPRTHRSH Remote talker threshold
0x0000
U1D8
SSPBKTHRU Break-through threshold for speaker in auto-switch mode.
Disable feature by setting this to 7FFFh.
0x7FFF
7.7.3. External Microphone/Speaker Calibration
The Si2494/39 speakerphone calibration is required for a new external speaker and microphone pair to work
properly with the speakerphone code. This section covers the following procedures:

To calibrate the speaker and microphone module from a commercial reference platform to have the same
speaker loudness and microphone sensitivity relative to those of the active reference system.
 To calibrate the speakerphone gains so that the AEC/DTD input signal levels are ensured for optimal AEC/AES/
DTD performance.
The external analog gains on the Si24xx-VMB should be finalized before the performing the speakerphone
calibration.
7.7.3.1. Transmit Gain Calibration—Speakerphone Disabled
Figure 32 illustrates the reference setup where the commercial speakerphone is active with default settings. Using
the reference commercial speakerphone, call the remote telephone and establish a voice call. Place a sound
source such as a PC speaker at a distance of one foot from the speakerphone’s microphone. Play out white noise
as the near-end speech through the sound source, and adjust the white noise level so that the level at the
speakerphone’s Tip/Ring is -15 dBm. Record the white noise level and disconnect the call.
Figure 32. Transmit Gain Reference Measurements
Figure 33 illustrates the setup used to set the transmit gain. Here the modem has the AEC/AES disabled with
AT+VSP=0. Using the Si24xx-VMB, call the remote phone and establish a voice call. Use the command sequence
in Table 134. Place the same sound source at a distance of one foot from the speakerphone’s microphone. Play
out the same white noise as the near-end speech through the sound source, and adjust the transmit gain UB1 so
that the level at the Si24xx Tip/Ring is –15 dBm. Record the calibrated UB1 value.
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Figure 33. Transmit Gain Configuration
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Rev. 1.3
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Table 134. Transmit/Receive Gain Calibration – Dial Remote Telephone
Host to Modem Commands Modem to Host Result
/ Data
Codes/Data
Local Modem Actions
ATZ
OK
Reset the modem.
AT+FCLASS=8
OK
Enter voice mode.
AT:U199|4
OK
Set SPCAL (U199 [2]) to enable calibration.
AT*Y254:W59|1
OK
Enable the SSI interface to the Si3000.
OK
Configure Si3000 Register 1:
Disable speaker driver
Enable line output driver
Disable telephone instrument driver
Disable MBIAS output
OK
Configure Si3000 Register 5:
10 dB Line In gain
Enable Line In
20 dB MIC input gain
Mute MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Enable Line Out
Disable telephone instrument output
AT:U72,075E
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
OK
Setup off-hook voice mode. See Table 115 on page 186
for details. This command will switch the modem to offhook state. The default value is +VSP=0 for disabled
speakerphone.
AT:U72,0108
AT:U72,0597
AT:U72,065E
AT+VLS=13
[Dial Number]
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7.7.3.2. Receive Gain Calibration—Speakerphone Disabled
Figure 34 illustrates the reference setup where the commercial speakerphone is active with speaker set to
maximum volume. Using the reference commercial speakerphone, call the remote telephone and establish a voice
call. Place a sound source such as a PC speaker at a distance of one foot from the remote telephone microphone.
Play out white noise as the far-end speech through the sound source, and adjust the white noise level so that the
level at the speakerphone’s Tip/Ring is -15 dBm. Next, measure the speaker loudness by using a sound meter
(preferred) or a PC microphone to record the sound level at a distance of one foot from the speakerphone’s
speaker. Record the white noise level and speaker level loudness, and then disconnect the call.
Figure 34. Receive Gain Reference Measurements
Figure 35 illustrates the setup used to set the transmit gain. Here the modem has the AEC/AES disabled with
AT+VSP=0. Using the Si24xx-VMB, call the remote phone and establish a voice call. Use the command sequence
in Table 135. Send the same white noise as the far-end speech from the remote phone, and adjust the receive gain
UB5 so that the speaker loudness is the same as that of the reference speakerphone. Record the calibrated UB5
value.
Figure 35. Receive Gain Configuration
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7.7.3.3. Speakerphone Calibration—AEC Gain Calibration
Figure 36 illustrates the setup used to set AEC speaker reference gain (U19C) and the AEC microphone input
signal gain (U19D). Here the modem has the AEC/AES enabled (AT+VSP=1) with the calibrated UB1 and UB5
values, which where obtained from the two previous sections. Using the Si24xx-VMB, call the remote phone and
establish a voice call. Use the command sequence in Table 135.
The AECREF (U19E) contains the energy information of both the AEC speaker reference signal (SPKREF) and the
microphone signal (MICREF). The SPKREF bits represent the AEC speaker reference energy, and MICREF bits
represent the AEC microphone input energy. The energy value is computed from average(s[t]^2).
Reg.
Name
U19E
AECREF
Bit
15
Bit
14
Bit
13
Bit
12
Bit
11
Bit
10
Bit
9
Bit
8
Bit
7
Bit
6
SPKREF
Bit
5
Bit
4
Bit
3
Bit
2
Bit
1
Bit
0
MICREF
Send the white noise from the remote phone so that the energy level at the meter (Tip and Ring) is -15dBm. Use
the AT:R19E command to read the contents of the U19E register. Adjust the AEC gain (U19C) of the speaker
reference signal until SPKREF reaches a value as close to 0x38 as possible. Adjust the AEC gain (U19D) of the
microphone input signal until MICREF has a value as close as possible to 0x38.
U19C and U19D are calibrated when the AT:R19E reading is close to 0x3838, with a power-level difference of less
than 2dB. Record these values and use them in the initialization sequence defined in Table 119, “Initialization
Sequence,” on page 194.
Figure 36. AEC Gain Calibration
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Table 135. AEC Gain Calibration – Dial Remote Telephone
Host to Modem
Commands / Data
Modem to Host Result
Codes/Data
ATZ
OK
Reset the modem.
AT+FCLASS=8
OK
Enter voice mode.
AT:U199|4
OK
Set SPCAL (U199 [2]) to enable calibration.
AT*Y254:W59|1
OK
Enable the SSI interface to the Si3000.
OK
Configure Si3000 Register 1:
Disable speaker driver
Enable line output driver
Disable telephone instrument driver
Disable MBIAS output
OK
Configure Si3000 Register 5:
10 dB Line In gain
Enable Line In
20 dB MIC input gain
Mute MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Enable Line Out
Disable telephone instrument output
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT:UB1,xxxx
OK
Use calibrated value from “Transmit Gain Calibration –
Speakerphone Disabled” section.
AT:UB5,xxxx
OK
Use calibrated value from “Receive Gain Calibration –
Speakerphone Disabled” section.
AT+VLS=13
OK
Setup off-hook voice mode. See Table 122 on page 198
for details. This command will switch the modem to offhook state.
AT+VSP=1
OK
Enable speakerphone voice path. See Table 136 for
details.
AT:U72,0108
AT:U72,0597
AT:U72,065E
AT:U72,075E
Local Modem Actions
[Dial Number]
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7.7.4. Speakerphone Configuration
This section covers the speakerphone call and answer cases, and the switching between the handset mode and
speakerphone mode. Table 136 contains the initial configuration that is used by all dialing use cases. The
sequence is also sent for the answer case. The user will have been notified of the incoming call through a local
+VTS ring tone and a SP Button On Event would prompt the Speakerphone Configuration sequence to answer the
call. The UB1, UB5, UB6, and Si3000 register configurations vary with the customer’s production hardware. The
UB5 register serves as the general volume control in this mode.
Table 136. Speakerphone Configuration
Host to Modem Commands / Data
Modem to Host
Result Codes/
Data
Local Modem Actions
AT:U199|A
OK
Mute the microphone and speaker paths to
the codec.
AT+VLS=0
OK
Disable voice mode. Used as a transition
point between non-zero +VLS voice modes.
AT+VLS=13
OK
Setup off-hook voice mode. See Table 117
on page 190 for details. This command will
switch the modem to off-hook state.
AT:U0B1,0500
OK
Restore Si3000-to-DAA transmit gain path.
AT:U0B5,0200
OK
Restore DAA-to-Si3000 receive gain path.
OK
Configure Si3000 Register 1:
Disable speaker driver
Enable line output driver
Disable telephone instrument driver
Disable MBIAS output
OK
Configure Si3000 Register 5:
10 dB Line In gain
Enable Line In
20 dB MIC input gain
Mute MIC input
Mute telephone instrument input
Enable IIR filter
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Enable Line Out
Disable telephone instrument output
OK
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AT:U72,0108
AT:U72,0597
AT:U72,065E
AT:U72,075E
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Table 136. Speakerphone Configuration (Continued)
Host to Modem Commands / Data
Modem to Host
Result Codes/
Data
Local Modem Actions
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT+VSP=1
OK
Enable speakerphone voice path. See Figure 29
on page 188 for details.
AT:U199&FFF5
OK
Enable the microphone and speaker paths
to the codec.
7.7.5. Simplex Speakerphone Configuration
Configuring the modem to automatically switch between local talker and remote talker is as follows:

For the SSP auto-switch (VOX) function, set SSP_FLAG to 1 (U199 [6] = 1) and SSP_PTT to 0 (U199 [7] = 0).
Set the speaker and microphone level thresholds, which determine whether remote speech or local speech is
active. The thresholds are defined in U19C and U19D. Typical values for the speaker and microphone
thresholds are 0x700 and 0x600, respectively. These thresholds are not affected by the speaker and
microphone control gains UB5 and UB1.
 Set the holding time, which is the time that the SSP holds the current mode after the signal level falls below the
threshold. Holding time prevents frequent mode switching between RX and TX. A typical value for holding time
is 0xC8 (200 ms).
For manual operation (push-to-talk):


Set SSP_FLAG to 1 (U199 [6] = 1) and SSP_PTT to 1 (U199 [7] = 1).
 Use the SSP_LOCTALK bit (U199 [8]) to set the speech direction: U199 [8] = 1 for local talker; U199 [8] = 0 for
remote talker.
U1D8 is the break-through threshold for the speaker signal in SSP auto-switch mode. If the speaker signal is above
the threshold U1D8 and holds at least for the holding time, the direction is switched to remote talker, no matter how
strong the signal in the microphone is. To disable break-through, set the threshold to 7FFFh (AT:U1D8,7FFF).

U1D8 greater than U1D6: when the speaker signal is greater than or equal to U1D8, the microphone is muted
and speaker unmuted immediately, regardless of the microphone holding time. When the speaker signal is
greater than U1D6 but less than U1D8, the speaker signal goes through after the expiration of the microphone
holding time.
 U1D8 less than U1D6: the break-through threshold U1D8 takes over and the speaker level threshold U1D6
becomes inactive.
 The default value for U1D8 is 7FFFh. A typical value for U1D8 is 0x1000. Adjust U1D8 according to the needs
of the application.
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Table 137. Simplex Speakerphone Configuration
Host to Modem Command
Modem to Host
Result Code
Local Modem Actions
AT:U1CD,40,10
OK
Set LEC Filter Length
Set LEC Delay
AT:U1D5,C8,400,400,7FFF
OK
Set Holding Time (ms)
Set Speaker Threshold
Set Microphone Threshold
Disable break-through
AT:U199|40
OK
Enable SSP, configure for automatic switch mode
7.7.6. Call—Automatic Tone Dial
Table 138 lists the commands that occur after the configuration defined in Table 136.
Table 138. Speakerphone Automatic Tone Dial
Host to Modem
Commands / Data
Modem to Host Result
Codes/Data
Local Modem Actions
OK
Perform automatic tone dial of 102. Modem will return
OK. The user will not receive <DLE> events for dial
tone, ring-back, busy, and quiet since the detectors are
disabled. See Table 117 for details on active detectors.
ATDT102
7.7.7. Call—Manual Off-Hook Tone Dial
Table 139 lists the commands that occur after the configuration defined in Table 136.
Table 139. Speakerphone Manual Off-Hook Dial
Host to Modem Commands
/ Data
Modem to Host Result
Codes/Data
AT+VTS=[697,1209,20]
OK
AT+VTS=[941,1336,20]
OK
AT+VTS=[697,1336,20]
OK
Local Modem Actions
The user is free to dial manually using the +VTS commands to create the DTMF digits.
Generate DTMF 1 digit for 200 ms.
Generate DTMF 0 digit for 200 ms.
Generate DTMF 2 digit for 200 ms.
The user will not receive <DLE> events for dial tone,
ring-back, busy, and quiet since the detectors are disabled. See Table 117 on page 190 for details on active
detectors.
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7.7.8. Call—Automatic Pulse Dial
Table 140 lists the commands that occur after the configuration defined in Table 136.
Table 140. Speakerphone Automatic Pulse Dial
Host to Modem
Commands / Data
Modem to Host Result
Codes/Data
ATDP102
OK
Local Modem Actions
Perform automatic pulse dial of 102. Modem will return
OK. The user will not receive <DLE> events for dial
tone, ring-back, busy, and quiet since the detectors are
disabled. See Table 122 on page 198 for details on
active detectors.
7.7.9. Answer
A ring event will prompt the user to press the speakerphone button. This will generate a SP Button On Event and
the Speakerphone Configuration procedure defined in Table 136 on page 219 should be used to answer the call.
For ring detection and local ring tone/melody generation, see "7.6.2. TAM Hands-Free—Idle".
7.7.10. Handset Transition
For a SP Button Off Event (Handset Off-Hook), the voice driver should use the command sequence in Table 141 to
return to the Handset mode. Note the voice driver is responsible for tracking the handset hook switch state.
Table 141. Speakerphone to Handset Transition
Host to Modem Commands / Data
Modem to Host
Result Codes/
Data
Local Modem Actions
AT:U199|A
OK
Mute the microphone and speaker paths to
the codec.
OK
Configure Si3000 Register 1:
Enable speaker driver
Disable line output driver
Disable telephone instrument driver
Enable MBIAS output
OK
Configure Si3000 Register 5:
10 dB Line In gain
Mute Line In
20 dB MIC input gain
Enable MIC input
Mute telephone instrument input
Enable IIR filter
AT:U72,065C
OK
Configure Si3000 Register 6:
0 dB RX PGA gain
Disable Line Out
Disable telephone instrument output
AT:U72,075E
OK
AT:U72,0110
AT:U72,05B3
222
Rev. 1.3
Configure Si3000 Register 7:
0 dB RX PGA gain
Enable SPKRL
Mute SPKRR
AN93
Table 141. Speakerphone to Handset Transition (Continued)
AT:U72,0900
OK
Configure Si3000 Register 9:
0 dB Line Out attenuation
0 dB Speaker output attenuation
AT+VSP=0
OK
Select handset voice path. See Figure 29 on
page 188 for details.
AT:U199&FFF5
OK
Enable the microphone and speaker paths
to the codec.
7.7.11. Termination
A SP Button Off Event (Handset On-Hook) will cause the system to return to the TAM Hands-Free mode. Use the
same configuration listed in Table 124 on page 199. Note the voice driver is responsible for tracking the handset
hook-switch state.
7.8. Glossary















AEC
AES
Convergence Rate
DCE
DLE
DTE
DTD
Double-Talk
ETX
ICM
LEC
OGM
PSTN
Single-Talk
TAM
Acoustical Echo Canceller of speakerphone
Acoustical Echo Suppressor of speakerphone
Rate at which AEC or LEC converges
Data Circuit-terminating Equipment
Data Link Escape (0x10)
Data Terminal Equipment
Double talk detector of AEC or LEC
Both the near-end and far-end users talk
End of Text (0x03)
Incoming Message
Line Echo Canceller of speakerphone
Outgoing Message
Public Switch Telephone Network
Either the near-end or far-end user talks
Telephone Answering Machine
7.9. References

ITU-T G.711
 ITU-T G.726
 ITU-T V.253
Pulse code modulation (PCM) of voice frequencies – 11/1998
40, 32, 24, 16 kbit/s adaptive differential pulse code modulation (ADPCM) – 12/1990
Control of voice-related functions in a DCE by an asynchronous DTE - 02/1998.
Rev. 1.3
223
AN93
8. Security Protocols
The Si24xx ISOmodem can handle a variety of security protocols. Two are specifically described here. The
"Ademco® Contact ID Protocol" and the SIA protocol.
8.1. Implementing the SIA Protocol
The SIA protocol defines communication between an alarm panel and a central station. In a traditional security
system, the alarm panel always calls the central station and sends data; the central station only acknowledges its
readiness to receive data and that data has been received. For this reason, the communication part of the alarm
panel has been called the transmitter; the communication part of the central station has been called the receiver.
With the SIA protocol, the central station can also send data to the alarm panel; since data is sent using FSK, the
communication can be half-duplex or full-duplex. Nevertheless, the traditional nomenclature of transmitter for the
alarm panel and receiver for the central station is still used for the SIA protocol.
The communication session consists of four elements:

The Handshake Tone (a single tone)
The Speed Synchronization Signal (two tones)
 Data Blocks and Control Signals (transmitted using Bell 103 FSK encoded data)
 Acknowledgement Blocks (can be either single tones or Bell 103 FSK encoded data, according to the
capabilities of the transmitter)

8.1.1. Modem-Specific Implementation Details
8.1.1.1. Listen-In and V-channel Periods (Voice Pass-Through)
This can be accomplished with the following procedure using standard voice modem commands:
1. Prior to making the call, the host issues AT+VNH=2 to modem. This will keep the modem off-hook when the
host clears down the FSK data connection using ATH.
2. After the modem has negotiated a Listen-in period using the SIA protocol in Bell 103, the host clears down the
FSK data link with ATH.
3. The host issues AT+VNH=2 to the modem again to maintain off-hook status for next cleardown.
4. The host then issues AT+FCLASS=8 followed by the usual Si3000 voice pass-through command sequence. (To
minimize the transition time, the host should set up the Si3000, TX/RX voice filters and all gain stages before
the call.)
5. AT+VLS=5 starts the Si3000 pass through, which supports Listen-in as well as V-Channel (bi-directional voice)
operation. Use +VLS=13, +VSP=1 etc. if speakerphone is desired.
6. When voice period is over, the host puts the modem back in data mode using AT+FCLASS=0. This will
terminate voice operation as well as going to +FCLASS=0. ATH and +VLS=0 must not be used in +FCLASS=8
to terminate the voice session because they override +VNH=2 (per V.253 standard).
7. The host again issues AT+VNH=2 to the modem to keep it off-hook for the next cleardown.
8. AT+F0 puts the transmitter in Bell 103, SIA mode to resume SIA protocol communication.
8.1.1.2. Inserting a V.32bis period (e.g., SIA Level-3 Video Block Support)
This can be accomplished with the following procedure using standard voice modem commands:
1. After clearing down the SIA FSK link, the host issues AT+VNH=2 to the modem to maintain off-hook status for
the next cleardown.
2. The host sets the modem to V.32bis; i.e., AT&H4, AT\N3 (if error correction is desired)
3. The host selects V.32bis originate or answer mode: AT%O2 if the transmitter should assume the handshake
mode of an originating V.32bis modem; AT%O1 if it should assume the handshake mode of an answering
modem.
224
Rev. 1.3
AN93
4. Issuing ATO to modem will start the V.32bis handshake. The host then waits for the CONNECT message before
sending data. (For an originating modem, the ATO command must be sent as soon as possible so the modem
will be ready when the remote answering modem starts. For an answering modem, the ATO should be delayed
a little to give the remote originating modem a chance to get ready first.)
5. The host disconnects the V.32bis session (using either +++ followed by ATH, or with DTR, if it has previously
been enabled with AT&D2).
6. The host issues AT+VNH=2 to the modem again to maintain off-hook status for next cleardown.
7. AT\N0 removes error-correction, if it was used during the V.32bis period.
8. SIA protocol communication resumes by starting up the transmitter in Bell 103, SIA mode with AT+F0.
8.1.1.3. Considerations when Disconnecting the Session
Because AT+VNH=2 keeps the modem off-hook during a cleardown, the first ATH or DTR desertion will not put
modem back on-hook but only force AT+VNH=0 (per V.253). The host must issue a second ATH to put the modem
back in on-hook idle state. Alternatively the host could issue a AT+VNH=0, then ATH (or AT+VNH=0;H)
Table 142 lists the AT Commands provided to support SIA Level-3 Protocol communication.
Table 142. AT Commands Provided to Support SIA Level-3 Protocol Communication
AT Command AT+F0
Modem Function
Remarks
Enable B103 Transmitter for Data Block Modem turns on FSK transmitter and starts marking
transmission.
for the minimum duration required by standard.
Sends CONNECT message to DTE when that is
accomplished.
Modem will then interpret the first character from
DTE as Block Header and use the byte count to
allow transmission of the specified number of characters to the remote modem and then send OK
message to DTE to indicate ready for next AT command.
Note1: FSK transmitter remains on. DTE is
expected to issue either a +F2 (detect ACK/NACK)
or another +F0 (to send another data block) command to the modem.
Note2: The “+++” escape sequence can be used to
abort the data block transmission and return the
modem to AT command mode.
Note3: The +F0 command can be used to resume
SIA protocol communication after a voice listen-in or
V.32bis interruption.
Rev. 1.3
225
AN93
Table 142. AT Commands Provided to Support SIA Level-3 Protocol Communication (Continued)
AT Command AT+F1
Modem Function
Remarks
Enable B103 Receiver for Data Block
reception.
Modem enables FSK receiver, waits for >12T marks
to be detected, then sends CONNECT message to
DTE to indicate a received Data Block follows.
Modem will stay in this mode indefinitely until an AT
command is issued by DTE. It is usually a
+F3(ACK), +F4(NACK) or +F5(ACK followed by
Data Block transmission) command.
Note1: Modem will wait for up to 1 second to detect
>12T marks before unclamping RXD. After 1 second RXD will be unclamped regardless.
Note 2: The +F1 command can be used to resume
SIA protocol communication after a voice listen-in or
V.32bis interruption.
AT+F2
Enable tonal ACK/NACK detection.
Detect and report ACK or NACK to DTE.
‘OK’ for ACK and ‘ERROR’ for NACK.
A NACK will be reported if no valid signal is
detected within 2.5 seconds.
AT+F3
Transmit Tonal ACK
Transmit Space for 600 ms. Send ‘OK’ prompt to
DTE when done.
AT+F4
Transmit Tonal NACK
Transmit Mark for 600 ms. Send ‘OK’ prompt to
DTE when done.
AT+F5
Transmit Tonal ACK with reverse chan- Transmit Space for 600 ms, followed by Mark for
nel command.
180 ms. Then send CONNECT to DTE to indicate
modem is ready to accept data.
AT+F6
Abort current Data Block Reception or
Transmission.
226
Rev. 1.3
This command is useful for exception handling,
such as timeout. If the FSK transmitter was on, +F6
shuts it off. FSK reception is aborted and modem
returns to the AT command mode.
AN93
Table 143 lists the definitions of result codes typically expected in an SIA session.
Table 143. Definitions of Result Codes Typically Expected in an SIA Session
Result Code
Meaning
Remarks
OK
Ready for next command
(or ACK)
When it comes as a response to the +F2 command,
“OK” means ACK
CONNECT
Physical handshake is completed.
In SIA FSK mode, CONNECT means that the
modem is in the data passing state ready to receive
or transmit data.
Note: there is an extra space character between the
letter T and the carriage return delimiter.
In V.32bis mode, CONNECT is followed by the DCE
connection speed: e.g., CONNECT 14400
RING
Incoming ring
Modem should answer the incoming call; the host
can command this with ATA.
NO CARRIER
ERROR
Connection is terminated
Invalid AT command
(or NACK)
As a response to the +F2 command, “ERROR”
means NACK; otherwise, it means invalid command.
BUSY
Dialed number is Busy.
Rev. 1.3
227
AN93
8.2. Implementing the Ademco® Contact ID Protocol
Contact ID is a communications protocol for security applications. It is a de facto standard which was developed
and is owned by the Ademco Group. The following is a brief overview of the Contact ID protocol. The complete
standard is available at the following web site:
http://webstore.ansi.org/RecordDetail.aspx?sku=SIA+DC-05-1999.09
Communication is between an alarm panel and a central station. The part of the alarm panel that handles
communication has the following functions:

Call the central station
Wait for the central station to indicate that it is ready for data
 Send data
 Wait for the central station to indicate that data was received
The central station also has a block that handles communication. Its functions are:


Answer calls
 Acknowledge that it is ready to receive data
 Receive data
 Acknowledge that data was received
While performing their security functions, the communication part of the alarm panel always sends data, while the
communication part of the central station always receives data. They are called the transmitter and receiver,
respectively. (Data could flow the other way, for instance to download new firmware to the alarm panel, but this isn't
covered by the Contact ID Protocol.)
A transaction begins with the transmitter calling the receiver. The receiver goes off-hook and acknowledges that it
is ready to receive data by producing the handshake tone sequence:

1400 Hz tone for 100 ms
Pause for 100 ms
 2300 Hz tone for 100 ms
The frequency tolerance on the handshake tones is ±3%. The tolerance on tone and pause times is ±5%.
Transmitters have a frequency tolerance of ±5% to account for older receivers.

After the communication channel has been established, the transmitter sends data to the receiver in Message
Blocks. Data is transmitted as DTMF codes. The frequency tolerance of the DTMF tones is ±1.5%. Twist is not
specified by the Contact ID protocol standard.
After sending the message, the transmitter waits for the receiver to send an acknowledgement (Kissoff) tone. The
Kissoff tone is a 1400 Hz tone that lasts for at least 750 ms and at most 1 second. The frequency tolerance of the
Kissoff tone is ±3%; transmitters have a frequency tolerance of ±5% for back compatibility with old receivers. The
receiver must detect at least 400 ms of the Kissoff tone for it to be considered valid.
The transmitter waits for the Kissoff tone to end, then waits an additional 250 to 300 ms before sending another
Message Block. If no Kissoff tone is received after 1.25 s, the transmitter sends the message again. Up to four
retries are attempted per Message Block. After the last message block has been acknowledged, the transmitter
hangs up.
228
Rev. 1.3
AN93
8.2.1. Modem Specific Implementation Details
The DTMF transmitters and receivers are used to send and receive data. Voice mode operation documented in
chapter X is used to transmit and receive the tones.
A summary of the necessary tone transmission AT commands is shown in Table 144.
The procedure is as follows:
Modem Initialization: (host sends to modem ):
AT+FCLASS=8
(enters voice mode)
AT+VLS=15:
(goes off hook and starts tone detection)
Send and receive tones example:
AT+VTS=[941,1336,10]
Host commands modem to send DTMF digit 0.
0x10, 0x2F, 0x31, 0x32, 0x7E
Modem responds with 5 characters as it receives two DTMF tones:
1 and 2. There are 2 preamble and 1 postamble characters
in this example.
Table 144. Ademco® Contact ID Protocol Tone Transmission AT Commands
DTMF Digit
Low Tone (Hz)
High Tone (Hz)
Contact ID
Digit
Contact ID
Digit Value
AT Command
0
941
1336
0
10
AT+VTS=[941.1336. 10]
1
697
1209
1
1
AT+VTS=[697.1209. 10]
2
697
1336
2
2
AT+VTS=[697.1336. 10]
3
697
1477
3
3
AT+VTS=[697.1447. 10]
4
770
1209
4
4
AT+VTS=[770.1209. 10]
5
770
1336
5
5
AT+VTS=[770.1336. 10]
6
770
1477
6
6
AT+VTS=[770.1477. 10]
7
852
1209
7
7
AT+VTS=[852.1209. 10]
8
852
1336
8
8
AT+VTS=[852.1336. 10]
9
852
1477
9
9
AT+VTS=[852.1477. 10]
*
941
1209
B
11
AT+VTS=[941.1209. 10]
#
941
1477
C
12
AT+VTS=[941.1477. 10]
A
697
1633
D
13
AT+VTS=[697.1633. 10]
B
770
1633
E
14
AT+VTS=[770.1633. 10]
C
852
1633
F
15
AT+VTS=[852.1633. 10]
D
941
1633
not used
N/A
N/A
1400
----
KISSOFF
AT+VTS=[1400,0,85]
Rev. 1.3
229
AN93
8.2.1.1. Handshake Tone Detection
Two tone detectors are reconfigured for detection of the 1400Hz and 2300Hz tones. When a valid tone burst is
detected the modem reports it to the host DTE in the V.253 event format as follows.
Event
Modem-to-DTE indication
Remarks
1400 Hz tone burst detected
0x10, 0x63
Character pair <DLE><c> is sent to DTE
at the end of the valid tone burst.
2300 Hz tone burst detected
0x10, 0x65
Character pair <DLE><e> is sent to DTE
at the end of the valid tone burst.
8.2.1.2. Session Example
Table 145. Ademco® Mode of Operation
Step
1
2
3
DTE-to-Modem Command
Remarks
AT*y254:w8686,1AA,CCDF,C73B,C001,0
AT*y254:w868B,1AA,D3D1,C39A,3FFF,DDD
AT*y254:w8690,1AA,C34B,C35F,3FFF,54A0
AT*y254:w8695,C,400
AT*y254:w8697,7BE,E050,CC04,3FFF,345F
AT*y254:w869C,7BE,BF39,CA8D,3FFF,37B5
AT*y254:w86A1,C,300,C00,CCD
OK
OK
OK
OK
OK
OK
OK
Initialize 2300 Hz tone detector.
AT*y254:w86A5,100,2A44,C480,C001,0
AT*y254:w86AA,167,25BC,C22F,3FFF,EC95
AT*y254:w86AF,167,303D,C21E,3FFF,BEF2
AT*y254:w86B4,C,400
AT*y254:w86B6,812,1E2F,C772,3FFF,D55F
AT*y254:w86BB,939,3394,C6FC,3FFF,D345
AT*y254:w86C0,1000,0,0,0,0
AT*y254:w86C5,C,140,8c0,CCD
OK
OK
OK
OK
OK
OK
OK
OK
Initialize 1400 Hz tone detector.
ATE0:UAD|40
OK
AT:UAD&FF7F
OK
Set UAD.6 to enable Ademco
mode tone detections.
Clear UAD.7 to disable SIA
mode.
5
AT:R48
6
AT+FCLASS=8
230
Modem-to-DTE
Indication
0064
OK
Rev. 1.3
Note: This step must be done
after a reset or ATZ. But it is not
needed for every call.
This step must be done after a
reset or ATZ. But it is not needed
for every call.
DTE reads and records what is
the normal “tone off” duration for
DTMF dialing. This parameter is
country dependent. This parameter will be modified for Data
Tones transmission later.
Put modem into V.253 voice
mode.
AN93
Table 145. Ademco® Mode of Operation (Continued)
Step
DTE-to-Modem Command
Modem-to-DTE
Indication
Remarks
7
AT:U181,78,0,0,1C
OK
Set up 1400 Hz detector to
detect 100 ms Handshake tone
burst.
8
ATDnnnnnnn
OK
Call RECEIVER station.
9
AT+VTD=5;:U48,32
OK
Change DTMF on off time to prepare for Data Tones transmission.
10
Wait for RECEIVER to answer with handshake tones
11
12
<DLE><c>
1400 Hz tone burst detected
i.e. 0x10, 0x63
Note: First part of Handshake
Tones detected.
<DLE><e>
2300 Hz tone burst detected
i.e. 0x10, 0x65
Notes: Second part of Handshake Tones detected.
Since there is a 100 ms silence
between the 1400 Hz and
2300 Hz tones, the <DLE><e>
message should come nominally 200msec after the previous
<DLE><c> message.
It is the responsibility of the host
DTE driver to measure and validate this time period.
13
AT:U181,334,0,0,12C
OK
14
Delay 250 ms before transmitting Data Tones
message.
Rev. 1.3
Change 1400 Hz detector to
detect 800 ±300 ms tone burst,
i.e. Kissoff tone.
Host DTE should adjust this
delay so that the following +VTS
DTMF transmission will start
between 250 to 300 ms after the
reception of <DLE><e> above.
231
AN93
Table 145. Ademco® Mode of Operation (Continued)
Step
15
DTE-to-Modem Command
Modem-to-DTE
Indication
AT+VTS=9,9,9,9,1,8,1,*,#,A,0,0,0,0,0,3
OK
Remarks
First Data Block is transmitted.
Note: Data octets are placed
after the “=” and separated by
commas.
Note: Host DTE driver must perform these substitutions,
Octet B as *
Octet C as #
Octet D as A
Octet E as B
Octet F as C
Note: OK is sent at end of transmission.
16
Wait for Kissoff tone
17
18
1.25 s has elapsed. But modem
still has not reported <DLE><c>
to DTE
AT*Y254:Q83FB
01AF
Check to see if start of a Kissoff
Tone has been detected?
A non zero response (i.e. not
0000) from modem denotes start
of tone is detected. Modem will
send <DLE><c> to DTE after it
has verified that the Kissoff Tone
burst duration is valid.
19
<DLE><c>
Acknowledgement from
RECEIVER detected.
Note: <DLE><c> is sent at end
of tone burst.
20
Delay 250 ms before sending next Data Tone
Message.
Repeat from Step 15 for sending more Data
Codes
ATH
232
OK
Rev. 1.3
Hang up at end of session.
AN93
Table 145. Ademco® Mode of Operation (Continued)
Step
DTE-to-Modem Command
Modem-to-DTE
Indication
AT:U48,64
OK
Remarks
Restore DTMF parameters to
comply with normal dialing
requirements.
Repeat from Step 6 for next call
Rev. 1.3
233
AN93
9. Chinese ePOS SMS
9.1. Introduction
An ePOS transaction normally begins with the ePOS terminal calling the server and transmitting data first. In this
instance the terminal initiates the call, so it is known as the Originate modem, while the server is the Answer
modem. After the modems connect, go through handshake and complete the first data transmission, the two
modems alternate being the transmitter and receiver until the completion of the call.
The Si24xx ISOmodems support SMS (Short Message Service) in an ePOS (electronic point of sale) connection.
An SMS message is delivered in frames, using the format shown in Figure 37.
Data Frame
Channel Seizure
Mark Signal
Protocol 1: 0 bits
Protocol 2: 300 bits
Protocol 1: 80 bits +/-25
Protocol 2: 80 bits +/- 25
Mark
Signal
Type
Length
Payload
Checksum
Figure 37. SMS Message Format
As shown in the figure, an SMS frame follows one of two protocols, Protocol 1 or Protocol 2. Protocol 1 frames
begin with the Mark signal, while Protocol 2 frames start with the Channel Seizure (CS) signal. Otherwise the two
protocols are identical. The Originate modem is configured to transmit in one of the two protocols at the beginning
of a call. The Answer modem recognizes which protocol is being sent and processes the incoming message
accordingly.
The modem strips off the Channel Seizure and Marks at the beginning and end of the data and provides the Data
Frame to the host processor. It does not provide frame content verification of any kind.
234
Rev. 1.3
AN93
9.2. SMS AT Command Set
Table 146 shows the AT commands that the host (DTE) uses to control the transmission or reception of SMS
messages.
Table 146. AT Commands for SMS
AT Command
ISOmodem Response
Description
&D1
OK
ESC (pin 22) escapes to command mode from data
mode if also enabled by HES (Enable Hardware
Escape Pin): U70, bit 15.
&D2
OK
ESC (pin 22) assertion during a modem connection
causes the modem to go on-hook and return to command mode. The escape pin must be enabled by setting bit HES: U70, bit 15.
+FCLASS=256
OK
Enables SMS mode
DTXXXX;
OK
Originate modem dials XXXX, then goes back into
command mode.
DT;
OK
Answer modem picks up the line and goes back into
command mode.
+FRM=200
CONNECT 1 or
CONNECT 2
Receive modem goes into data mode and waits for
FSK data from Transmit modem; response is determined by whether a Protocol 1 or 2 message was
received.
+FTM=201
CONNECT
Transmit modem goes into data mode and waits for
data from the DTE. Sends marks when first data byte is
received, followed by data.
+FTM=202
CONNECT
Transmit modem goes into data mode and waits for
data from the DTE. When first data byte is received,
modem sends Channel Seizure and marks followed by
data.
Rev. 1.3
235
AN93
9.2.1. SMS User Registers
User registers that set up SMS operations are shown in Table 147. The default settings are shown in bold.
Table 147. User Registers for SMS Operations
Register
Bits
Name
U70
15
HES
UAA
2
RUDE
UCA
0
SMSMOD
UCB
15:0
TXCS
Number of channel seizure bits
0 = no Channel Seizure
1 to 65535 = number of continuous alternating
spaces and marks in Channel Seizure.
2580
UCC
7:0
TXMK
Number of mark bits in message header
2580
UCD
0
CASRPT
UD1
11:0
TXDEL
Time the Originate modem waits before transmitting a
frame, in 10 ms units. Timed from the termination of the
previous signal.
0000
UD2
11:0
RXTO
Time that the Answer modem waits for the received signal after it receives the +FRM command; in 10 ms units
0000
UD3
15:0
V.29FC Answer Tone Detector Threshold (in ms).
Range = 50–180 ms
0000
UD4
14:0
CAS Tone Detector Threshold
0000
UD7
15:0
SMS Mark Length Threshold
0578
236
CTDT
Description
Default
(Hex)
Enables ESC (pin 22)
0 = Disabled
1 = Enabled
0
0 = Disables rude disconnect
1 = Enables rude disconnect
0
Modulation for SMS data
0: Bell202
1: V.23
0
Respond to CAS, don’t report to the host (Auto) or do
report to the host (Manual)
0 = Auto Mode
1 = Manual Mode
Rev. 1.3
0
AN93
9.2.2. Procedure
To enable the SMS features on the Si24xx, the host sends “AT+FCLASS=256” to the modem prior to an SMS call.
To enable the hardware escape pin functions, the host would set HES with the command “AT:U70|8000”.
After setting the other U-registers according to the configurations of the Originate and Answer modems, the host
can dial an SMS call using the command “ATDTxxxx;” (where xxxx is the number to be dialed) or answer an SMS
call with “ATDT;”. The semi-colon at the end of the command places the modem into command mode after dialing.
The modem responds to the host with “OK”. The host then puts the modem into transmit or receive SMS data
mode.
Many SMS POS protocols perform handshaking using CAS and CAS ACK. CAS is a two-tone signal (2130 Hz /
2750 Hz); CAS ACK is a DTMF ‘D’. The terminal modem connects to the server, which sends CAS tones until it
times out or the terminal modem replies to the server with CAS ACK. The threshold for the modem’s CAS tone
energy detector is set by CTDT, which has a default value of 500h. The CAS tone must have a minimum duration
of 30 ms to guarantee detection.
CAS detection is enabled by setting the detector threshold UD4 to a value other than 7FFFh. When the CAS
detector is enabled, FSK CS/MARK detection will run after CAS is detected. The modem will time out if CAS is not
detected. (When implementing SMS POS protocols that don’t use CAS and CAS ACK, the CAS tone detector must
be disabled with the command AT:UD4,7FFF.)
Once CAS is detected, the modem responds with CAS ACK. The duration of CAS ACK is 60 ms.
CASRPT selects Auto or Manual mode for transmitting CAS ACK.
Auto mode (CASRPT = 0): Auto mode reduces the delay between CAS and CAS ACK. After an AT+FRM=200
command, the modem detects the CAS tones and sends CAS ACK without reporting CAS detection to the host.
Manual mode (CASRPT = 1): Manual mode allows the host processor to have more control. A modem reports to its
host with the string "CAS" when it detects CAS tones. The modem waits for the host to reply with the ASCII
character 'D', then it responds to the other modem with CAS ACK. If the host sends any character other than 'D',
the modem returns to the command mode immediately without sending CAS ACK and replies to the host with
<DLE><ETX>. This allows the host to send any DTMF digit. The host can then send an AT+FTM command or an
AT+FRM command. If the host doesn't send any characters or commands, the modem will time out (as set by UD2)
and go back on-hook without sending CAS ACK.
9.2.2.1. Example
The host could use this sequence to set up the modem for Protocol 1 SMS:
AT:UCA,1,0,4E
This sets up the modem for V.23 modulation, Protocol 1, 78
Mark bits in the message header.
AT+FTM=201
Transmit a Protocol 1 SMS frame
<CR><LF>CONNECT <CR><LF>
Modem response to the host
To set up the modem for Protocol 2 SMS:
AT:UCA,0,12C,4E
This sets up the modem for Bell 103 modulation, Protocol 2,
300 bit Channel Seizure, 78 Mark bits in the message header.
AT+FTM=202
Transmit a Protocol 2 SMS frame
<CR><LF>CONNECT <CR><LF>
Modem response to the host
In either protocol, the host must wait for the “CONNECT” response before it sends data. Transmission of data
before this message can result in loss of information.
Rev. 1.3
237
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After the host receives “CONNECT “, it sends the frame data followed by <DLE><ETX>. A frame includes type,
length, payload and checksum. The frame data can contain anything, including <DLE><ETX>. No DLE shielding
is needed. <DLE><ETX> with no data for about 8ms is treated as the end of frame.
After a frame has been sent, the modem response will be: <CR><LF>OK<CR><LF>
On the answer modem side, the command AT+FRM=200 causes the receiver to look for at least 32 bits of CS and
for at least 60 bits of marks. The answer modem detects the protocol of the transaction by whether CS comes
before the marks.
AT+FRM=200
Receive an SMS frame
AT:UD2,<RxTimeout>
Set RxTimeout:
There can be several responses to AT+FRM=200, depending on the received data.
9.2.2.2. Response 1
If the frame had not been received within the time specified in RxTimeout, the modem response to the host would
be:
<DLE><ETX><CR><LF>NO CARRIER<CR><LF>
9.2.2.3. Response 2
If the frame had been received with a mark segment at beginning of frame, the modem would respond to the host
with:
CONNECT 1<CR><LF>
<Frame Data Received><DLE><ETX>
<CR><LF>OK <CR><LF>
No frame checking would be done by the modem; all of that would be left to the host. As shown above,
<DLE><ETX> marks the end of frame. After sending OK to the host, the modem goes back into command mode.
9.2.2.4. Response 3
If the frame had been received with channel seizure and mark segment detected at beginning of frame, the modem
would send one of the responses below to the host:
CONNECT 2<CR><LF>
<Frame Data Received><DLE><ETX>
<CR><LF>OK <CR><LF>
The Host does all upper level frame validations, since the modem does not do any frame checking. As shown
above, <DLE><ETX> signifies the end of frame. After the modem sends OK, it goes back to command mode.
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9.3. Example Session
The example below shows a typical session. The user determines the values of the U-registers.
transmit "AT+FCLASS=256<CR>"
;Enable SMS POS mode
waitfor "OK"
transmit "AT:UCA,0,12C,4E<CR>" ;Set SMS POS parameters
waitfor "OK"
transmit "ATD<phone number here>;<CR>"
;dial out
waitfor "OK`x0d`x0a"
The ’;’ at the end of the dial string returns the modem to command mode after dialing. The modem will issue an
OK after dialing.
transmit "AT:UD1,3C<CR>"
; Set TxDelay = 600ms
waitfor "OK"
transmit "AT:UD2,3E8<CR>"
; Wait 10 s for an answer.
waitfor "OK"
transmit "AT+FRM=200<CR>"
; Go into data mode and wait for Originate modem
The length of the timeout is dependent on the host called. Once the connection is made, the answer modem’s host
expects to receive a frame such as:
0x81 0x00 0x05 0x13 0xcd 0xaa 0xa4 0x00 0x4c
Followed by:
<DLE><ETX><CR><LF>OK<CR><LF>
Once a frame has been received, the receive modem becomes the transmit modem. The server returns a frame of
data to the terminal.
transmit "AT+FTM=202<CR>"; Use Protocol 2
waitfor "CONNECT `x0d`x0a"
Transmit a frame such as:
0x82 0x00 0x05 0x6c 0xea 0x50 0x6b 0x00 0x68
transmit "`x10`x03"
; Send <DLE><ETX> at the end of frame
waitfor "OK`x0d`x0a"
Rev. 1.3
239
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POS
Server
TS1
TS 2
CAS
TS3
CAS Ack
(Complete the CAS Handshake)
TD1
Send FSK Packet
TS5
TD3
Send FSK Packet
TS4
TD2
Send FSK Packet
Figure 38. Diagram of Handshake (Using CAS/CAS ACK) and Message Packet Exchange
240
Rev. 1.3
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For Figure 39, assume that the originating modem transmits first and that the two modems alternate transmitting
and receiving. For simplicity, this figure does not show the provisions for timeout cases.
H ES = 1
AT+FCLASS = 2 56
(V.2 3 h alf -du ple x )
O
ATD Txxxx ;
Orig ina te
?
A
ATDT ;
OK
1
N
Pr otocol
?
OK
2
AT +FRM =2 00
AT+FTM =20 1
AT+FTM =202
CONN ECT
CONNEC T
N
Da ta recei ved
from Host
?
Data re ceive d
fro m Ho st
?
Y
30 0 bits chan nel
se izure
( altern atin g 1 's &
0 's)
Ho st sen ds
messa ge fol low ed
by 15 0 ms o f
si len ce , then ESC
Se nd Ma rks
R ecei ve messag e ,
send to Ho st
Y
80 bi ts of ma rk
N CONN ECT n
n = 1 or 2
OK
8 0 b its of mark
Host send s
messag e fo ll owe d
by 15 0 ms of
sil en ce , th en ESC
ESC to
Co mmand
Mod e
?
Y
Sen d Marks
N
ESC to
Co mma nd
Mo de
?
Y
Implicit +FRM Figure 39. SMS Process in Host and Modem
Rev. 1.3
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10. Testing and Diagnostics
10.1. Prototype Bring-Up (Si3018/10)
10.1.1. Introduction
This section provides tips for the debugging of initial prototypes. Although most ISOmodem prototype designs
function as expected, there is the potential for layout errors, omitted or incorrect components used in the initial
assembly run, and host software problems. If the prototype modem does not function correctly, the techniques
outlined in this guide will help quickly isolate the problem and get the prototype functioning correctly. A functional
ISOModem evaluation board and data sheet and a computer with HyperTerminal are required for some of the
troubleshooting steps. It is assumed that the designer has read the data sheet, implemented the reference design
using the recommended bill of materials, and carefully followed the layout guidelines presented in "4.4. Layout
Guidelines" on page 49. Troubleshooting begins with system-level checks and then proceeds all the way down to
the component level. In this chapter, all system-side pin numbers refer to the 24-pin TSSOP package and all lineside pin numbers refer to the 16-pin version.
10.1.2. Visual Inspection
Before troubleshooting, be certain that the circuit boards and components are clean. Carefully wash the boards to
remove all solder flux and solder flakes. Inspect the modem circuitry to ensure all components are installed, and
inspect all solder joints for incomplete connections, cold solder joints, and solder bridges. Check all polarized
components, such as diodes and capacitors, for correct orientation. Thoroughly clean the circuit board after
replacing a component or soldering any connection.
Reset the Modem
Make sure the modem is reset after the power and clocks are applied and stable.
10.1.3. Basic Troubleshooting Steps

Check the Power
With power off, use an ohmmeter to verify that the system ground is connected to ISOmodem pin 6. Turn on
system power and measure the voltage between pin 5 and pin 6 and between pin 21 and pin 6 on the
ISOmodem. In both cases, the voltage should be 3.3 V. If this is not the case, check the power routing. If power
is present, go to the next step.
 Check the Phone Line
Check the phone line with a manual telephone to be sure that there is a dial tone and that dialing is possible.
The dc voltage across Tip and Ring should read approximately 40–52 V with the phone on-hook.
 Reset the Modem
Do a manual reset on the modem. Hold ISOmodem pin 12 (RESET) low for at least 5 ms, return to VDD (3.3 V),
and wait for at least 300 ms before executing the first AT command.
 Check the DTE Setup (UART Mode)
Be sure the DTE (host) serial port is configured the same as the modem. The default condition is eight data bits,
no parity-bit, one stop-bit, and a DTE rate of 19.2 kbps.
 Check the DTE Connection (UART Mode)
Check the DTE interface connection. Be sure the RTS (ISOmodem pin 8) and CTS (ISOmodem pin 11) signals
are low.
 Check the Pulldown Configuration Resistors
 Check the Modem Configuration
Read back the modem register settings and correct any inconsistencies. The ATS$ command lists the contents of
all S registers, and the AT:R command lists the contents of all U registers.
If the problem was not located with these basic troubleshooting steps, it is time to narrow the problem down to the
host system (hardware and software), the ISOmodem chip and associated components, or the Si3018/10 and
associated components.
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






AT OK?
The modem responds with an OK to the command AT<CR>. This indicates that the host processor/software is
communicating with the modem controller, and problems are in one of the following areas:
Inappropriate Commands
Verify that all AT commands used are supported by the ISOmodem and comply with the proper format. Be sure
each command and argument is correct. Do not mix upper- and lower-case alpha characters in an AT
command. An AT command string must contain 48 or fewer characters followed by a carriage return. Command
strings greater than 48 characters are ignored.
Command Timing
The execution time for an AT command is approximately 200 ms. Execution is complete when OK is received.
Subsequent AT commands should wait for the OK message, which appears within 200 ms after the carriage
return. The reset recovery time (the time between the rising edge of a hardware reset or the carriage return of
an ATZ command and the time the next AT command can be executed) is approximately 300 ms. When a data
connection is being established, do not try to escape to the command mode until after the protocol message.
Register Configurations
The ATS$ command lists the contents of all S registers, and the AT:R command lists the contents of all U
registers.
Si3018/10 and/or Associated Components
If the modem goes off-hook and draws loop current as a result of giving the ATH1 command, go to "10.1.6.
Si3018/10 Troubleshooting".
If the modem does not go off-hook and draw loop current as a result of giving the ATH1 command and receiving
an OK message, begin troubleshooting with the isolation capacitor at the ISOmodem. First, check all solder
joints on the isolation capacitors, Si3018/10, and associated external components. If no problems are found,
proceed to "10.1.5. Isolation Capacitor Troubleshooting" to verify whether the problem is on the ISOmodem or
the Si3018/10 side of the isolation capacitor. If the problem is found to be on the ISOmodem side, check C50,
C51, C53, the corresponding PCB traces, and the ISOmodem pins. Correct any problem found. If no problems
are found with the external components, replace the ISOmodem. If the problem is found to be on the Si3018/10
side of the isolation capacitor, go to "Si3018/10 Troubleshooting".
If the modem does not respond with an OK to the command AT<CR>, this indicates that the host processor/
software is not communicating with the modem controller, and the problem can be isolated as follows:
ISOmodem Clock is Oscillating
First, be sure the ISOmodem is properly reset and RESET, pin 12, is at 3.3 V. Next, check the DTE connection
with the host system. If this does not isolate the problem, go to "10.1.4. Host Interface Troubleshooting".
ISOmodem Clock is Not Oscillating
Check the voltage on the ISOmodem, pins 5 and 21, to be sure the chip is powered. Also, check that pins 6 and
20 are grounded. Next, check the solder joints and connections (PCB traces) on C40, C41, Y1, and the
ISOmodem Pin 1 and Pin 2. Measure C26 and C27 (or replace them with known good parts) to ensure that they
are the correct value. If these steps do not isolate the problem, replace the ISOmodem.
10.1.4. Host Interface Troubleshooting
The methods described in this section are useful as a starting point for debugging a prototype system or as a
continuation of the troubleshooting process described previously. The procedures presented in this section require
a known good ISOModem evaluation board and data sheet. This section describes how to substitute the evaluation
board for the entire modem circuitry in the prototype system. Substituting a known operational modem can help
isolate problems quickly. The first step is to substitute the evaluation board for the complete modem solution in the
prototype system. This immediately demonstrates whether any modem functionality problems are in the prototype
modem circuitry or in the host processor, interface, or software.

Verify ISOModem Evaluation Board Functionality
Connect the evaluation board to a PC and a phone line or telephone line simulator. Using a program, such as
HyperTerminal, make a data connection between the evaluation board and a remote modem. Remove power
and the RS232 cable from the evaluation board and proceed to the next step.
Rev. 1.3
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
Connect Evaluation Board to Prototype System
Completely disconnect the embedded modem from the host interface in the prototype system. Connect the
ISOModem evaluation board to the host interface using JP3 as described in the ISOModem evaluation board
data sheet section titled Direct Access Interface. This connection is illustrated in Figure 40. Be sure to connect
the evaluation board ground to the prototype system ground. Power up and manually reset the evaluation
board, then power up the prototype system and send AT<CR>. If an OK response is received, make a
connection to the remote modem as in the previous step. If no OK response is received, debug host interface
and/or software. If a connection is successful, go to the next step to isolate the problem in the prototype
modem.
An alternative approach is to connect the prototype modem to the ISOModem EVB motherboard in place of the
daughter card and use a PC and HyperTerminal to test the prototype modem. See Figure 41 for details.
10.1.5. Isolation Capacitor Troubleshooting
Connect the evaluation board isolation capacitor to Prototype Modem Si3018/10. Remove C1 on the evaluation
board and on the prototype system. Solder one end of the evaluation board, C1, to the ISOmodem-side pad
leaving the other end of C1 unconnected. Next, solder a short jumper wire from the unconnected side of C1 on the
evaluation board to the Si3018/10-side C1 pad on the prototype system. This connection is illustrated in Figure 42.
Connect the phone line to the prototype system RJ-11 jack.
Power up and manually reset the evaluation board, then power up the prototype system. Attempt to make a
connection using the host processor and software, the evaluation board ISOmodem, and the prototype system
Si3018/10 and associated external components. If this connection is successful, the problem lies with the PCB
layout, the external components associated with the ISOmodem or the ISOmodem device itself.
If the connection attempt is not successful, the problem lies with the Si3018/10 and/or associated components.
Proceed to “Si3018/10 Troubleshooting”.
This diagnosis can be validated by connecting the Host ISOcap capacitors to the Si3018/10 on the evaluation
board as shown in Figure 43.
10.1.6. Si3018/10 Troubleshooting
Start by measuring the on-hook and off-hook voltages at the Si3018/10 pins with respect to IGND (pin 15).
Compare these voltages to those in Figure 44. This may indicate an area of circuitry to investigate further using the
Component Troubleshooting techniques in the following section. The voltages measured should be reasonably
close to those in the figure.
If any of the on-hook or off-hook Si3018/10 pin voltages are significantly different than those in Figure 44 and
nothing seems wrong with the external circuitry after using the Component Troubleshooting techniques, replace
the Si3018/10.
10.1.7. Component Troubleshooting
A digital multimeter is a valuable tool for verifying resistances across components, diode directions, transistor
polarities and node voltages. During this phase of troubleshooting, it is very useful to have a known, good
ISOModem evaluation board to compare against measurements taken from the prototype system. The resistance
values and voltages listed in Tables 148, 149, and 150 will generally be enough to troubleshoot all but the most
unusual problems.
Start with power off and the phone line disconnected. Measure the resistance of all Si3018/10 pins with the
Ohmmeter’s black lead on pin 15 (IGND). Compare these measurements with the values in Table 148. Next,
measure the resistance across the components listed in Table 149 and compare the readings to the values listed in
the table. Finally, using the diode checker function on the multimeter, check the polarities of the transistors and
diodes as described in Table 150. The combination of these measurements should indicate the faulty component
or connection. If none of the measurements appears unusual and the prototype modem is not working, replace the
Si3018/10.
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Prototype System
Host
Controller
Host
UART
RS232
Transceiver
Si24xx
Si3018
Discretes
Si24xx
Si3018
Discretes
EVB




To
Phone
Line
Connect prototype system ground to EVB ground
Disable RS232 transceiver outputs (check evaluation board data sheet)
Disconnect prototype modem interface
Connect the evaluation board to the target system
Figure 40. Test the Host Interface
Prototype System
Host
Controller
PC
Host
UART
RS232
Transceiver
Si24xx
Si3018
Discretes
Si24xx
Si3018
Discretes
To
Phone
Line
EVB





Connect prototype system ground to EVB ground
Remove modem module from EVB
Disconnect host outputs from prototype modem
Connect EVB RS232 transceivers to prototype modem
Use PC with HyperTerminal to test prototype modem
Figure 41. Test the Prototype Modem
Rev. 1.3
245
AN93
Prototype System
C1
Host
Controller
Host
UART
Si24xx
Si3018
Discretes
Si3018
Discretes
C2
To
Phone
Line
C1
PC
RS232
Transceiver
Si24xx
C2
EVB





Connect the prototype ground to the EVB ground.
Lift prototype C1 and C2 and EVB C1 and C2 so the Si3018 is disconnected from the Si24xx on both modems.
Connect EVB C1 and C2 to the Si3018 pad of prototype system C1 and C2.
Connect the phone line to the RJ11 jack on the prototype system.
Use PC and HyperTerm and attempt to establish a modem connection.
Figure 42. Test the Prototype Si3018/10 Circuitry
Prototype System
C1
Host
Controller
Host
UART
Si24xx
Si3018
Discretes
Si3018
Discretes
C2
C1
RS232
Transceiver
EVB





Si24xx
C2
Connect the prototype ground to the EVB ground
Lift prototype and EVB C1 and C2 to decouple the line side from the DSP side. Do same on evaluation board.
Connect prototype system C1 and C2 to the Si3018 pad of EVB C1 and C2
Connect the phone line to the RJ11 jack on the EVB
Run the prototype system software to attempt a modem connection
Figure 43. Verify Prototype Si3018/10 Failure
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Line
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On-Hook
Off-Hook
0V
QE
DCT2
0V
DCT
IGND
0V
RX
DCT3
0V
IB
0.5 V
0.9 V
1.6 V
QE
DCT2
2.2 V
3.4 V
DCT
IGND
0V
2.5 V
RX
DCT3
1.6 V
QB
0V
0V
0V
FB
QB
2.8 V
C1B
QE2
0V
0.5 V
CIB
QE2
2.1 V
C2B
S2
0V
0.9 V
C2B
SC
0V
2.3 V
VREG
VREG2
1.8 V
~1.0 V
1.0 V
RNG1
RNG2
0.9 V
~2.3 V
VREG
VREG2
~1.0 V
RNG1
RNG2
0V
0V
Voltages measured with respect to IGND (Si3018 pin 15)
Figure 44. Si3018/10 Typical Voltages
Table 148. Resistance to Si3018/10 Pin 15
Si3018/10
Resistance
Pin 1
> 6 M
Pin 2
> 5 M
Pin 3
> 2 M
Pin 4
1 M
Pin 5
> 5 M
Pin 6
> 5 M
Pin 7
> 1 M
Pin 8
> 2 M
Pin 9
> 2 M
Pin 10
> 1 M
Pin 11
0
Pin 12
> 2 M
Pin 13
> 5 M
Pin 14
> 14 M
Pin 16
> 5 M
Rev. 1.3
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Table 149. Resistance across Components
Si3018/10
Resistance
FB1
<1
FB2
<1
RV1
> 20 M
R1
1.07 k
R2
150 
R3
3.65 k
R4
2.49 k
R5
100 k
R6
100 k
R7
4.5 or 16 M
R8
4.5 or 16 M
R9
> 800 k
R10
536 
R11
73 
R12
<1
R13
<1
R15
<1
R16
<1
C1
> 20 M
C2
> 20 M
C3
> 3 M
C4
3.5 M or 9.7 M
C7
2 M or 5 M
C8
> 20 M
C9
> 20 M
Note: If two values are given, the resistance measured is dependent on polarity.
Table 150. Voltages across Components with Diode Checker
Component
Q1, Q3, Q4, Q5:
Base (red lead) to Emitter (black lead)
Base (red lead) to Collector (black lead)
(Verifies transistors are NPN)
0.6 V
0.6 V
Q2:
Emitter (red lead) to Base (black lead)
Collector (red lead) to Base (black lead)
(Verifies transistor is PNP)
0.6 V
0.6 V
Collector of Q2 (red lead)
to pin 1 of Si3018/10 (black lead)
If test fails, Z1 is reversed.
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10.2. Self Test
The Si24xx ISOmodem’s advanced design provides the system manufacturer with an enhanced ability to
determine system functionality during production tests and to support end-user diagnostics. In addition to local
echo, a loopback mode allows increased test coverage of system components. For the loopback test mode, a lineside power source is required. While a standard phone line can be used, the test circuit shown in Figure 45 is
adequate.
TIP
+
600 
Si3018
VTR
RING
IL
10 F
>20 mA
–
Figure 45. Loop Test Circuit
The AT&Tn command, in conjunction with the AT&Hn command, performs a loopback self test of the modem.
AT&Hn determines the modulation used for the test (V.22bis, V.32bis, etc). If an AT&Hn command is not issued just
prior to the start of the test, the default or previously-selected modulation is used. The modulation options and
defaults are listed in Table 40 on page 77. The test is started with an AT&T2 or AT&T3 command. During the test,
the modem is in data mode. To end the test, escape data mode using one of the “Escape” methods, such as +++,
and end the test with ATH.
The AT&T2 command initiates a test loop from the DSP through the DAA interface circuit of the ISOmodem.
Transmit data are returned to the DSP through the receive channel. In the parallel or SPI mode, the transmit data
are passed to the receiver via Hardware Interface Register 0. AT&T2 tests only the Si24xx chip, not the Si3018/10.
The AT&T3 command initiates a test loop from the DSP through the DAA interface, the ISOcap interface, the
Si3018/10, and the hybrid circuit. This test exercises the Si24xx, the Si3018/10, and many external components. A
phone line termination with loop current and no dial tone is required for this test since it involves the line-side chip
(Si3018/10) and the hybrid. The modem is off-hook during this test. The AT&T3 mode is useful during emitted and
conducted radiation testing. To test the ISOcap link only, set U62 (DL) [1] = 1 and issue the AT&T3 command.
The AT\U command is also useful as a production test. This command places a 25 ms low pulse on the RI and
DCD pins. It also makes INT the inverse of ESC and RTS the inverse of CTS. Sending the AT\U command can be
used to verify the connection of these pins to the circuit board. This command is terminated by resetting the
ISOmodem.
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10.3. Board Test
The modem and DAA chips come from Silicon Laboratories 100% functionally tested on automatic test equipment
to guarantee compliance with the published chip specifications. The functionality of a finished product containing
an ISOmodem chipset depends not only on the functionality of the modem chipset after assembly but also on
discrete components and product-related software. Finished product test requirements and procedures depend on
the manufacturer and on the product. Consequently, no universal final test procedure can be defined.
Testing the modem in a finished product is done for several reasons. First, it is important to be sure the modem
chipset and peripheral components were installed correctly during assembly and were not damaged. Second, it is
necessary to be sure the correct component values were installed and that there are no manufacturing problems,
such as solder bridges, cold solder joints, or missing components.
Functional testing can be used to test special features, such as intrusion detection, Caller ID, and overcurrent
detection. An intrusion can be simulated by placing a 1 k resistor across Tip and Ring through a relay. Caller ID
testing requires special test equipment, such as the Rochelle 3500 or Advent AI-150.
Many manufacturers choose to use built-in self-test features, such as the &T3 Loopback test described above.
Others do a complete functional test of the modem by originating and answering a call and successfully passing a
data file in each direction. This process tests the modem and line-side chip functionality, the associated external
components, and the software controlling the modem. This test can be done with a modem under test (MUT) and a
known-good reference modem, or between two modems under test. Testing two modems under test at once
reduces test and setup times. Modem operational testing is time consuming and adds to product cost. It is up to the
manufacturer to determine whether operational testing is warranted.
Analog modems (Bell 103 through V.34) can be tested by connecting the modems through a telephone line
simulator, such as Teltone TLS-3. A call can be placed or received in either direction at the speed set in the
modems. A test script must be written for a computer to control the dialing, monitor the call progress, send a file,
and compare the received and sent file. Figure 46 illustrates this test configuration.
Reference Modem
Test
Computer
Teltone TLS 3
Modem Under
Test
Figure 46. Bell 103–V.34 Modem Functional Test Connection
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V.90 modems must be tested with a digital modem, such as the USR Courier I. If a digital modem isn’t used as
illustrated in Figure 47, the highest connection speed a V.90 modem will support is 33.6 kbps. A call can be placed
or received in either direction at the speed set in the modems. A test script must be written for a computer to control
the dialing, monitor the call progress, send a file, and compare the received and sent files. Figure 47 illustrates this
test configuration.
Teltone
ILS 2000
ISDN
ISDN Modem
Test
Computer
ISDN
ISDN
Terminal
Adaptor
Analog
Modem Under Test
Figure 47. V.90 Modem Functional Test Connection
Table 151 compares the coverage of &T2, &T3, and full bidirectional functional testing.
Table 151. Test Coverage
Circuit or Function
&T2
&T3
Functional Test
Si24xx chip
Yes
Yes
Yes
ISOcap Operation
Yes
Yes
Yes
Si3018/10 Operation
Yes
Yes
Hookswitch
Yes
Yes
dc Termination
Yes
Yes
Bridge
Yes
Yes
AC Termination
Yes
Yes
Line Voltage Monitor
Yes
Ringer Network
Yes
Intrusion Detection
Yes
Caller ID
Yes
Overcurrent Detection
Yes
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10.4. Compliance Testing
Regulatory compliance testing requires the modem to be configured in specific ways and controlled to perform
specific operations necessary to make required measurements. Compliance testing commands and configuration
information are provided.
Some helpful commands for conducting compliance testing on the ISOmodem are listed in Table 152. The modem
register defaults configure the modem for FCC operation.
Table 152. AT Commands for Compliance Testing
AT Command/Test Method
Desired Response
ATH1
Continuous off-hook
ATH0
Return on-hook
AT&Hn (see command description for n)
Set modulation
AT&T3 (requires load and loop current)
Turn on carrier (originate)
Set S10 = 255 to keep the modem under test from hanging up after the
remote modem is unplugged. Connect with another modem (Si24xx in Turn on carrier (answer)
answer mode); then, unplug the other modem.
AT&T4
Initiate transmit as originating modem
with automatic data generation
AT&T5
Initiate transmit as answering modem
with automatic data generation
ATX0
Blind dial (no dial tone)
AT*Y1D<digit> (example: AT*Y1D1 for DTMF1)
Send continuous DTMF digit
ATM2
Speaker on continuously
ATM0
Turn off speaker
AT:Uhh,xxxx (hh is U register and xxxx is the hex value to be written)
Write a U register
AT:Rhh (hh is U register)
Read a U register
AT:R
Read all U registers
ATA
Send Answer Tone for 3 seconds
AT:U4D,0008 ATX0 ATDT
Send Calling Tone
Connect test modem and remote modem through a telephone line simulator. Configure test modem without protocol. Set test modem
S10 = 255. Connect phone in parallel to remote modem. Set remote
Transmit a specific modulation
modem to desired modulation. Dial remote modem and connect. Take
parallel phone off-hook. Remove power from remote modem. Test
modem transmits indefinitely.
Homologation testing requires that the ISOmodem signal output be measured for each modulation and data rate.
The AT&T3 command establishes an analog loopback connection to the phone line and places the modem in data
mode. The modulation is controlled by the &H command. This command is insufficient for homologation for several
reasons:

It is not possible to configure the output tone to be as if from the answering or originating modem.
It is not possible to configure the data rate used in an analoop connection within a given modulation.
 Three data patterns need to be sent during output testing: all marks, all spaces, and random data.
Once transmission with automatic data generation is initiated, the modem goes off-hook and begins to transmit the
data in the modulation selected by the existing &H command. Transmission continues until the ATH command is
sent after escape.

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The data sent during &T4 and &T5 transmission tests is controlled by the S40 register. The data rate for &T4 and
&T5 commands is controlled by the existing &G command. In V.34 cases, where a data rate may use multiple
symbol rates, the symbol rate is controlled by the S41 register. If an invalid combination of data/symbol rate is
selected, the modem chooses a valid symbol rate. It is the responsibility of the operator to select valid
combinations for testing.
Table 153. Symbol/Data Rate
S41
V.34 Symbol Rate
Allowable Data Rates
0 (default)
2400 symbols/second
2400–21600
1
2743 symbols/second
4800–26400
2
2800 symbols/second
4800–26400
3
3000 symbols/second
4800–28800
4
3200 symbols/second
4800–31200
5
3429 symbols/second
7200–33600
After the &T4 or &T5 command is issued and the modulation output has begun, a result code stating CONNECT
followed by the data rate (as if the output were an actual connection) is sent. The 300 bps rate does not give the
speed after CONNECT. The &G4 command allows V.34/2400bps operation, and &G3 allows V.22bis/1200 bps
operation.
The answer tone output must also be measured during homologation testing. A bit in memory allows a continuous
answer tone to be output in the same way as a continuous DTMF tone through the AT*Y1 command. After issuing
the commands AT&H10 and AT*Y2A, a constant answer tone is produced, and the modem is returned to command
mode. Both AT commands need to be sent for each and every tone to be produced. Each of the two commands
need to be on its own command line. The tone continues until a character is received or the S7 timer expires. After
the command has been terminated, the modem returns on-hook and sends the NO CARRIER message.
For homologation testing, it may be necessary to output the V.29 modulation with transmit data. The +FTM
command includes additional codes given in Table 154 to initiate output with the transmit data specified in S40.
Table 154. V.29 Data Rate
+FTM=
Transmit Modulation
Data Rate
53
V.29
7200
55
V.29
9600
The AT+FCLASS=0 command must be sent before any other analoop test or connection is made. The modem
must remain on-hook for a time programmed in S-register 50. Any attempt to go off-hook is delayed by this time in
1 s units. S-50 default is 3 seconds.
There is a double CONNECT message for analoop in B1O3, V.21, and V.23 for all options except \V0.
10.4.1. EMI
The ISOmodem chipset and recommended DAA schematic are fully compliant with and pass all international
electromagnetic emissions and conducted immunity tests (including FCC parts 15 and 68; EN50082–1). Careful
attention to the ISOmodem schematic (page 47), bill of materials (page 48), and layout guidelines ensure
compliance with these international standards. In designs with difficult layout constraints, the addition of R12 and
R13 to the C8 and C9 recommended capacitors may improve modem performance on emissions and conducted
immunity. For such designs, a population option for R12 and R13 may allow additional flexibility for optimization
after the printed circuit board has been completed. Also, under some layout conditions, C8 and C9 may improve
the immunity to telephone-line transients.
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10.4.2. Safety
Designs using the ISOmodem pass all overcurrent and overvoltage tests for UL1950 3rd Edition with the addition
of a 1.25 A Fuse or PTC, as shown in Figure 48. In a cost-optimized design, compliance to UL1950 does not
always require overvoltage tests. In the design cycle, it is important to plan ahead and know which overvoltage
tests will apply. System-level elements in the construction, such as fire enclosure or spacing requirements, need to
be considered during the design stages. Consult with a testing agency during product design to determine which
tests will apply.
1000  @ 100 MHz, 200 mA
C8
1.25 A
FB1
TIP
Fuse/PTC
RV1
1000  @ 100 MHz, 200 mA
FB2
RING
C9
Figure 48. Circuits that Pass All UL1950 Overvoltage Tests
10.4.3. Surges
Use the reference design described in "4. Hardware Design Reference" on page 43 with through-hole Y1
capacitors for C1, C2, C8, and C9. Use spacing between the capacitor leads, between any line-side (high voltage)
component or trace and system side (low voltage) component or trace greater than 8 mm. Also, the spacing
between any line-side component or trace (or through-hole lead extending through the PCB) and the chassis (or
anything connected to the chassis or low voltage circuitry) must be greater than 8 mm or protected with insulating
material capable of withstanding a voltage greater than 8 kV. Additionally, slots cut through the PCB are
recommended between the leads of C1, C2, C8, and C9 for increased creepage. The PCB and components should
be clean and free of contamination, such as solder flux or other residue. The design engineer must verify the
spacing indicated above meets or exceeds any specifications with which they wish to comply. The ISOmodem,
used with the components and techniques described above, offers the highest reliability and lowest cost of any
available solution. The use of supplemental surge-suppression components is not recommended.
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10.5. AM-Band Interference
In certain areas, AM-band interference causes poor connectivity rates and error rates. A good EMI common-mode
filter may be necessary in some situations. An example of an off-the-shelf unit designed to plug directly into the
phone line is the Coilcraft TRF-RJ11, which can be used for debugging or fixing problem locations.
Figure 49. Published Coilcraft TRF-RJ11 Filter Performance
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10.6. Debugging the DTE interface
A hardware-based serial RS232 monitoring product, such as the Parascope Plus, is an invaluable tool for
debugging the DTE/DCE Interface. It captures and records details of DTE - DCE interaction. Hexadecimal and bitshifted views are possible, and it timestamps every character exchanged with much greater precision than a
software-based monitor. It is sold by FETEST at http://www.fetest.com.
To
DCE
To
Power
To PC
Printer Port
Silabs IsoModem eval. board
Timestamp of highlighted char.
Feline WinXL serial transaction log.
Figure 50. Debugging the DTE Interface
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APPENDIX A—EPOS APPLICATIONS
EPOS applications generally require nearly flawless call connection reliability and a very short overall transaction
time. The message length of a typical EPOS terminal is between 120 to 260 bytes of information. Due to the
relatively small message length, the need for reliable connections under all line conditions, and short connection
times, the preferred modulations have traditionally been variations of V.22 (1200 bps) or Bell 212 (1200 bps).
EPOS servers do not strictly follow ITU standards. Despite the informal use of the term “V.22 fast connect”, there is
no ITU “fast connect” standard. De-facto standards with modifications of ITU standards, such as V.22 Fast
Connect, have been adopted to reduce the transaction time. Some server manufacturers make changes to the
modem with the intent of making it difficult for competing terminals to connect. Many EPOS servers have out-ofspecification clocks and use reduced handshake timing. V.22bis (2400 bps) is occasionally used in EPOS
terminals as well. The primary method by which V.22bis terminals achieve a shorter connection time has been
through the use of a shorter answer tone. V.29 FastPOS is a Hypercom proprietary protocol based on the V.29 Fax
standard. For these reasons, EPOS applications often require some amount of reverse engineering and fine tuning
of the ISOmodem performance, typically with a patch.
Recently, improvements to the overall user experience have necessitated the storage of transaction information
within the EPOS terminal based on some predefined criteria. These stored transactions are typically sent as part of
a larger transaction at a later time. This effectively increases the message length to over 2 kB, necessitating the
use of higher-speed modulations, such as V.29 FastPOS or V.32bis.
The choice of either V.29 FastPOS versus V.32bis is a tradeoff between transaction message length and
connection times. It is common for a terminal to support both of these modulations.
Modulation
Typical Connect Time (Sec)*
V.90
25
V.34
10.7
V.32b
7.8
V.22b
5.0
V.22
3.0
V.22 FastConnect
0.6
V.29 FastPOS
0.5
*Note: Does not include dial delay.
VISA II (7E1)
Terminal
Host
Dials host
ENQ (0x05)
STX <data>ETX, LRC
ACK (0x06)
STX <data>ETX, LRC
ACK (0x06)
EOT (0x04)
Disconnects
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Another consideration for EPOS applications is the method of error detection and error correction. Early EPOS
terminals adopted the Zilog 85C30 Serial Communications Controller (SCC) in conjunction with a synchronous
modem to implement an HDLC/SDLC-based data link layer. The complexities of the HDLC handling is done by the
SCC, while the modem performs strict data pump function. However, given the broad availability of UARTs, HDLC
handling can be performed by the modem also. To facilitate this system partitioning, the V.80 protocol is used. V.80
allows the multiplexing of data, control, and status information so that the host processor can specifically control
what frames are sent to, or received from, the modem across the asynchronous UART (DTE) interface. The host
performs much of the other layers of the protocol stack beyond this Data Link Layer. A discussion of host software
is beyond the scope of this appendix.
Recommendation V.80
The goal of V.80 is the concept of “abstracting hardware circuits”. This is achieved by the addition of a control and
status channel alongside the main data channel. The main data channel is effectively the information transfer
across the UART TX and RX lines. The control/status channel that runs alongside the main data channel is
signaled by the use of EM shielding. This means a “special character” is chosen to signify the beginning of the
control/status channel. In its simplest form, this “special character,” in conjunction with the “next” character, is taken
together as a single nugget of information denoting a special control message or a special status.
V.80 uses <0x19> as a special control character. The next question becomes how to send the character 0x19 as
data? This is accommodated by the concept of transparency, in which the host is required to send a special
sequence to signify its desire to send 0x19 as data rather than a control character.
The concept could have been very simple, but there are additional complications:

The desire to support 7-bit data and 1-bit parity asynchronous protocols
 The desire to support XON and XOFF handshaking
 The desire to limit bandwidth usage
The desire to support 7 data bits and 1 parity bit creates the possibility that the host would be sending <0x99>
when the intention is to be sending the <0x19> special character. The <EM> character is really a shortcut for
saying <0x19> or <0x99>.
The XON and XOFF characters are <0x11> and <0x13>, respectively. These characters are treated in a special
way by many UARTs, and, therefore, V.80 must ensure that neither <0x11> or <0x13> occur in the data stream so
that a lower protocol layer will not need to be rewritten. Hence, the final “special character set” for V.80 includes
<0x19>, <0x99>, <0x11>, and <0x13>.
What happens if the data file being sent is a constant stream of <0x19> bytes? By the single-transparency rules,
one would then argue that the number of bytes sent across the DTE would effectively be doubled. In order to
ensure that the throughput does not become bloated by the EM Shielding, provisions for all combinations of two
special character combinations are created. This adds yet another sixteen EM Shielding cases since there are 4 x
4 matrix of combinations of these special characters.
At this point, the transparency cases for EM Shielding can thus guarantee the ability to send “anything” over the
DTE with the special considerations of 7 vs 8 data bits, XON and XOFF characters and throughput considerations.
However, once the data channel has been architected, the rest of the unused EM codes can be used for the
primary purpose of V.80, which is the concept of hardware abstraction.
In EPOS applications, there is little value in abstracting pins such as RI or RTS. The value comes in abstracting the
TXCLK and RXCLK of the Synchronous UART. The Synchronous UART is the primary method of connecting to the
Zilog 85C30 SCC. V.80 allows the interface between the host and the modem to be a simple asynchronous DTE,
while allowing for synchronous operation performed by the modem itself.
The purpose of going through this explanation is to allow the easier reading of the V.80 standard and to provide the
proper framing of the use of V.80 in an EPOS application. It is important to note that the usage of V.80 for HDLC
function does not use many of the other aspects of V.80.
For example, the data transferred across the UART is assumed to be 8 bits, even though V.80 also provides the
ability to transfer 7-bit ASCII data. Also, it is rare for XON/XOFF handshaking to be used in an EPOS application,
but the transparency rules of EM Shielding are burdened with these extra EM codes in any case.
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In the end, the only thing that matters in an EPOS application is the ability to send and receive HDLC frames
across the DTE. For this, the ability of the host to tell the modem “end of transmit frame” and the ability for the
modem to tell the host “CRC successful” is, in essence, the kernel of V.80 use in an EPOS application.
One final note before showing an example… the V.80 standard refers to a “Transparent Sub-Mode” and a “Framed
Sub-Mode”. The main idea behind the Transparent Sub-Mode is to allow the host to specifically decide what bits
are being sent across the DCE. In the Transparent Sub-Mode, nothing is left out, and the host is responsible for
every single bit that is transmitted to and from the modem. In the Framed Sub-mode, the HDLC handling is
performed by the modem, and, therefore, there are actions taken by the modem that the host assumes and does
not worry about. In EPOS applications, only the “Framed Sub-Mode” is of importance.
Example:sending an HDLC Frame containing the following bytes:
0xFF 0x11
The host will transmit the following byte stream. Note that the 0x11 is sent as an <EM><t3> or 0x19 0xA0. An
<EM><flag> or 0x19 0xB1 denotes the end of frame.
0xFF 0x19 0xA0 0x19 0xB1
At the UART interface at TXD, the bit-representation is:
strt
1
0xFF
0
stp stp
11111111 1
0x19
0
stp strt
10001001
1
0xA0
0
stp strt
00000101 1
0x19
0
stp strt
10001001
1
0
0xB1
10001101
The modem strips off the start and stop bits and reconstructs the original bytes:
0xFF 0x19 0xA0 0x19 0xB1
The transparency characters are resolved, and, since the <EM><flag> is present, the Frame Check Sequence is
calculated. Let us assume that the FCS is 0xC00F:
16-bit FCS
0xFF 0x11 0xC0 0x0F
Adding the HDLC flags and zero-stuffing, the bit stream is shown as follows. The bit stream containing the 0xFF
and 0x0F bytes have inserted zero bits. The algorithm is fairly simple in that whenever there are five ones in a row,
a bit is inserted. The inserted bits are shown in red. This bit stream is then modulated and transmitted out to the
DCE.
16-bit FCS
Flag
0xFF
0x11
0xC0
0x0F
Flag
01111110 111110111 10001000 00000011 111010000 01111110
The receive process reverses the above steps. The receiver hunts for HDLC flags and synchronizes to the HDLC
flag stream. It then extracts the frame between the HDLC Flags and performs zero-bit deletion on the payload. The
receiver also calculates the CRC and matches with the 16-bit FCS of the frame. Then, the <EM> transparency is
added, and finally, the <EM><flag> is sent as an indication that the calculated CRC of the frame matches the FCS.
Rev. 1.3
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Isomodem with V.80
UART
Data
DataBlock
Data
Block
Block
V.80
Transparency
Encode
Transmit
Path
HDLC
FLAG
Insertion
TXD
CTS*
Insert V.80
EM<FLAG>
between blocks
MODEM
UART
V.80
Transparency
Decode
Zero-Bit
Stuffing
TX Bit
Clock
PLL
XTAL
Modulate
g
Frame Check
Sequence
Generate
DCE
V.80 Handler
Data
DataBlock
Data
Block
Block
EM<FLAG> if good
RX frame, EM<ERR>
if bad RX frame
RX Bit Clock
Recovery
HDLC
FLAG
Detection
V.80
Transparency
Decode
Receive
Path
RXD
MODEM
UART
V.80
Transparency
Encode
Zero-Bit
Deletion
Add EM<FLAG>
or EM <ERR>
nCRC
Check
Demodulate
Figure 51. ISOmodem V.80 Protocol HDLC Framing in Framed Sub-Mode
The ISOmodem in EPOS Applications

The Rev D Si2493/57/34/15/04 and Rev A Si2494/39 include all Rev B and C patches.
AT:U87 [10] must be set when using Rev B silicon.
 A V.80 interface to V.29 Fast Connect is not supported on Rev B silicon and can be accomplished only as a
patch on Rev C. Please contact Silicon Laboratories, Inc. for latest patch. "5.8. Firmware Upgrades" on page
121 outlines how to use this patch.
 When operating as V.22 Fast Connect (+MS=V22, AT:U7A,3), the register U80 can be modified to account for
unusual server timings. The value in U80 should reflect the expected answer tone duration of the NAC. The
units are in 1/600 s. For example, if the answer tone duration of the server is 500 ms, AT:U80,012C.
 When operating as V.22 Fast Connect (+MS=V22, AT:U7A,3), a short answer tone of at least 300 ms is required
for proper operation. This answer tone can be 2100 Hz, 2225 Hz, or a V.22 Unscrambled Binary Ones (USB1).
If the server NAC does not have any of these answer tones prior to scrambled data or HDLC flags, it is possible
to command the modem to operate without these tones by setting bit 15 of U80. The modem then begins
transmitting scrambled data (or HDLC Flags) some time after the end of dialing, based on the value in
U80 [14:0]. The units are in 1/600 s. For example, to command the modem to begin transmitting 3 s after the
end of dialing, set AT:U80,8708.

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A V.29 FastPOS Sample Program
Introduction
In previous versions of the interface to V.29 FastPOS, the HDLC layer was assumed to be implemented by the host
software. Another issue was the case where the EPOS Terminal was calling a server that could answer either as
V.29 FastPOS or V.22bis; it was not possible for the modem to “train down” to V.22bis.
To address these issues, a new interface has been implemented in the Rev D Si2493/57/34/15 and Rev A Si2494/
39 and is available as a patch in the RevC ISOmodem. This interface allows the call to start as a V.29 FastPOS
and can train down to V.22bis if the server NAC can answer as either a V.29 FastPOS or V.22bis. Please contact
Silicon Laboratories, Inc. for the latest patch.
One of the improved aspects of this interface technique is to use two control lines: (RTS and DTR); RTS controls
direction of transfer, while the DTR hangs up the line. The tradeoff here is that RTS can no longer be used as a
method of stopping the modem from sending data to the host.
This is generally not an issue as long as the DTE rate is greater than the DCE rate and the host can keep up with
the receiver without having to resort to the negation of RTS.
The data are in V.80 format. Just read and write data while toggling RTS as needed. Assert RTS to transmit and
de-assert to receive. This is called a push-to-talk paradigm.
The description here shows how to set up and use the modem for V.29 FastPOS and also provides a sample
program along with both a DTE trace and WAV files that capture what is happening at both ends of the modem.
The only critical signals that are not recorded below but obviously controlled in the program are the RTS and DTR
lines.
The hardware used was the Engineering Eval. Board Rev 3.2 and a 24xx2G-DC Rev 1.2 module containing a 24
pin 2457 Rev C ISOmodem chip plus a 3018 DAA chip. JP6 was strapped {1-2, 4-5, 7-8, 10-11, 13-14}. JP5 was
unstrapped.
Setup procedure:
1. Host DTE Rate must be greater than 19200.
2. Host DTE must be configured for 8N1 CTS-only flow control
3. Load Patch “rc_p71_bcd8.txt”
AT+GCI=xxxxxxx
AT&D2
Enables escape pin (U70 HES bit needs to be set also.)
AT+IFC=0,2
Flow control setup
AT:U87,050A
V.80 Setup
AT\N0
Wire Mode
AT+FCLASS=1
AT:U7A,1
AT:UAA,8004
AT+ES=6,,8
Synch access mode
AT+ESA=0,0,0,,1
Synch access mode control
4. Make Sure RTS is negated (voltage high)
5. Make Sure DTR is asserted (voltage low)
6. Send ATDT###
Notes:
1. Patch is “Originate Only”
2. RTS is used as DIRECTION of transfer. Think “push-to-talk” paradigm. Assert RTS PRIOR to transmission.
Negate RTS after frame has been sent. The modem will guarantee that the carrier is turned off after all
current frames have been completed.
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3. DTR is assumed to be connected to the ESC pin of the modem. It has been programmed to HANG UP when
DTR is negated.
4. When the modem is in RECEIVE operation (RTS negated), it is not possible to communicate with the
modem. The only control is to hang up using DTR.
5. The modem “automatically” takes care of figuring out if it is supposed to be in “V.29 Long Train” vs. “V.29
Short Train”. The primary host responsibility is to take care of RTS.
6. Data to/from the modem is expected to be in V.80 format.
Example Program in C/C++
This program shows how to establish an SDLC V.29 FastPOS link and keep the loop alive.
How to use the program:
This program is meant to run for only a few minutes for testing. It is run after a reset is done, loads a patch from
“patch.txt” and calls using the atdt line it finds in “tel_no.txt”. Both files need to terminate in CR LF.
The tel_no.txt file must contain a complete telephone number dialing line followed by a CR, e.g. ATDT8,5551212.
// V29_test.cpp : Defines the entry point for the console application.
// Copyright 2005 Silicon Labs Inc. All rights reserved.
// Rev 0.0602
#include
#include
#include
#include
#include
char
char
char
char
void
void
void
void
bool
void
"stdafx.h"
"windows.h"
"stdlib.h"
<stdio.h>
<time.h>
fnamePatch[]=".\\patch.txt";
fnameTelno[]=".\\Tel_no.txt";
*SendAndWaitFor(char *cpCommand, char *cpInBuffRd,
char *cpResponse, int iTimeoutMs);
*WaitForResponse(char *cpResponse, char *cpInputBuffer,
int iTimeOutInMs);
SetupSerPort(void);
AssertRTS(bool bAssert);
AssertDTR(bool bAssert);
Delay(long iMs) ;
GetFileTextLine(char *cpIn);
LoadAndSendPatch(void);
char
char
char
char
*cpInBuffer;
*cpOutBuffer;
*cpInputWr;
*cpErrorString;
FILE
FILE
*hpPatchFile;
*hpTelNoFile;
DCB
HANDLE
char
COMMTIMEOUTS
int
char
dcb;
hCom;
*pcCommPort = "COM1";
sCOMMTIMEOUTS;
iCharCount;
*cpInputRd, *cpInputRd_temp, cpInput_test[255];
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char
caUA_PKT_STR[] = {(char)0x30, (char)0x73, (char)0x19, (char)0xb1, (char)0 };
char caRR_PKT_STR[] = {(char)0x30, (char)0x19, (char)0xa0, (char)0x19, (char)0xb1, (char)0 };
char caSNRM_PKT_STR[] = {(char)0x30, (char)0x93, (char)0x19, (char)0xb1, (char)0 };
char caRX_PKT_STR[]
= {(char)0x19, (char)0xb1, (char)0 };
void AlternateCall(void);
int main(int argc, char* argv[])
{
// Initialize these buffers.
cpInBuffer = (char *)malloc(100000);
cpOutBuffer = (char *)malloc(100000);
cpErrorString = (char *)malloc(100000);
for (int i= 0; i< 10000; i++)
{
cpInBuffer[i]
= 0;
cpOutBuffer[i]
= 0;
cpErrorString[i] = 0;
}
cpInputRd = cpInBuffer;
cpInputWr = cpInBuffer;
unsigned long
ulNoOfbytes;
SetupSerPort();
LoadAndSendPatch();
AssertDTR(true);// Leave DTR asserted for calling
cpInputRd = SendAndWaitFor("atz\r", cpInputRd, "OK\r\n", 300); // A soft reset Just in case
Delay(300); // Important, AN93 implies this delay must be done after an ATZ.
cpInputRd = SendAndWaitFor("ATE0\r", cpInputRd, "OK\r\n", 300);
cpInputRd_temp = SendAndWaitFor("AT&T6\r", cpInputRd, "OK\r\n", 300);// Get the patch CRC
printf ("%s \n", cpInputRd); cpInputRd=cpInputRd_temp;
// Display the patch CRC
// setup county of operation
********************MODIFY to your locality******************
//
cpInputRd = SendAndWaitFor("at+gci=B5\r", cpInputRd, "OK\r\n", 300);
// &D2 enables escape pin,
// X4 enable extended result codes
// \V2 report connect message only // %c0 disable data compression
// %V1 Auto line status detection mode is the fixed method
// +IFC=0,2 No data flow control, Hardware flow control
cpInputRd = SendAndWaitFor("AT&D2x4\\V2%c0%V1+IFC=0,2\r", cpInputRd, "OK\r\n", 300);
// \N0
wire mode,
// +FCLASS=1
HDLC mumbo jumbo
cpInputRd = SendAndWaitFor("AT\\N0+FCLASS=1\r", cpInputRd, "OK\r\n", 300);
cpInputRd = SendAndWaitFor("AT:UAA,8004\r", cpInputRd, "OK\r\n", 300);
// +ES=6,,8
enabled synch access, //
6,, enables synch access on initiating a connect
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AN93
// ,,8
enables synch access on answering a connect
cpInputRd = SendAndWaitFor("AT+ES=6,,8\r", cpInputRd, "OK\r\n", 300);
// AT+ESA=0,0,0,,1 synch access mode control
// 0,,,, modem transmits SYN if underrun during transparent mode
// ,0... modem tx's flags after underrun after flag happens in framed sub mode
// ,,0,, modem tx's abort on underrun in frame middle during framed sub mode
// ,,,,1 enables CRC generation and checking
cpInputRd = SendAndWaitFor("AT+ESA=0,0,0,,1\r", cpInputRd, "OK\r\n", 300);
// "AT:U87,010A Synch access mode config
// 0x0400 bit 10
Minimal transparency <EM><T1 thru
// 0x0100 bit 8
Upon connection immediately enter
// 0x000A bits 3:0 Wait for 10 bytes before starting
cpInputRd = SendAndWaitFor("AT:U87,050A\r", cpInputRd,
T4> during Rx
framed sub mode
xmission.
"OK\r\n", 300);
// :U7A,1 Fast connect
cpInputRd = SendAndWaitFor("AT:U7A,1\r", cpInputRd, "OK\r\n", 300);
AssertRTS(false);
if ((hpTelNoFile = fopen(fnameTelno, "rb")) == NULL)
{
fprintf(stderr, "The Tel. Number File is missing.\n");
exit(1);
}
char caOutGoing[256];
bool bValidLine = GetFileTextLine(caOutGoing);
printf("Phone Number: %s\n",caOutGoing);
if(bValidLine)
cpInputRd = SendAndWaitFor(caOutGoing, cpInputRd, "CONNECT\r\n", 120000);
else
{
fprintf(stderr, "The Tel. Number File is incorrect.\n");
exit(1);
}
int iLength;
iCharCount = 0;
//
//
//reset the total chars to 0 for data mode.
Skip waiting for the speed packet.
cpInputRd = WaitForResponse("\0x19\0xbe\0x24\0x24\0x19\0xb1", cpInputRd, 6000);
// Long training happens now!
cpInputRd = WaitForResponse(caSNRM_PKT_STR, cpInputRd, 6000);
Delay(50);
//Delay to allow the line to turn around
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// ???
AN93
AssertRTS(true); //RTS=1 for transmitting
Delay(300); //Delay to allow the line to turn around
//
iLength = strlen(caUA_PKT_STR);
WriteFile(hCom, caUA_PKT_STR, iLength, &ulNoOfbytes, 0);
Delay(100);
Alternatively use USE CTS
// Tx UA messge
while(1)
// Short training happens now!
{
AssertRTS(false); printf("RTS=0 Rx ");
//RTS=0 for receiving
cpInputRd=WaitForResponse(caRX_PKT_STR,cpInputRd,3000);//Rx RR message
iLength = strlen(cpInput_test);
for (int i=0; i<iLength; i++)
printf("%02x ", (unsigned char)cpInput_test[i]);printf("**%d ", *cpInputRd);
//Alternatively use CTS
Delay(150);
do{ // flush out the bytes for last RX packets.
BOOL bError = !ReadFile(hCom, cpInputWr, 1, &ulNoOfbytes, 0); //ulNoOfbytes=1
printf("%02x ", (unsigned char)cpInputWr[0]);
}while (ulNoOfbytes); printf("\n");
AssertRTS(true); printf("RTS=1 Tx ");
//RTS=1 for transmitting
Delay(50); // morrie 01/20/06
iLength = strlen(caRR_PKT_STR);
for (i=0; i<iLength; i++)printf("%02x ", (unsigned char)caRR_PKT_STR[i]); printf("\n");
WriteFile(hCom, caRR_PKT_STR, iLength, &ulNoOfbytes,0); //Tx RR message
Delay(100); //Delay x ms to complete TX sending before set RTS=0 for RX
}
return;
}
// ------------------------------------------------------------------------------------// Use this call to check CTS status
// DWORD iEVentMAsk;
// wait for EV_CTS
// BOOL WaitCommEvent(HANDLE hFile, &iEVentMAsk, LPOVERLAPPED lpOverlapped);
// ---------------------------------------------------------------void SetupSerPort()
{
BOOL
bSuccess;
hCom = CreateFile(pcCommPort, GENERIC_READ | GENERIC_WRITE, 0,
NULL, OPEN_EXISTING, 0, NULL);
if (hCom == INVALID_HANDLE_VALUE)
{
// Handle the error.
printf ("CreateFile failed with error %d.\n", GetLastError());
exit(1);
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}
// Build on the current configuration, and skip setting the size
// of the input and output buffers with SetupComm.
bSuccess = GetCommState(hCom, &dcb);
if (!bSuccess)
{
// Handle the error.
printf ("GetCommState failed with error %d.\n", GetLastError());
exit(1);
}
// Fill in DCB: 57,600 bps, 8 data bits, no parity, and 1 stop bit.
dcb.fBinary
= TRUE;
// Binary mode; no EOF check
dcb.fOutxCtsFlow
= FALSE;
// No CTS output flow control
dcb.fOutxDsrFlow
= FALSE;
// No DSR output flow control
dcb.fDtrControl
= DTR_CONTROL_ENABLE;
// DTR flow control type
dcb.fDsrSensitivity = FALSE;
// DSR sensitivity
dcb.fTXContinueOnXoff= TRUE;
// XOFF continues Tx
dcb.fOutX
= FALSE;
// No XON/XOFF out flow control
dcb.fInX
= FALSE;
// No XON/XOFF in flow control
dcb.fErrorChar
= FALSE;
// Disable error replacement
dcb.fNull
= FALSE;
// Disable null stripping
dcb.fRtsControl
= RTS_CONTROL_ENABLE;
// assert RTS
dcb.fAbortOnError
= FALSE;
// Do not abort rds/wr on error
dcb.BaudRate
= CBR_115200;
// set the baud rate
dcb.ByteSize
= 8;
// data size, xmit, and rcv
dcb.Parity
= NOPARITY;
// no parity bit
dcb.StopBits
= ONESTOPBIT;
// one stop bit
bSuccess = SetCommState(hCom, &dcb);
if (!bSuccess)
{
// Handle the error.
printf ("SetCommState failed with error %d.\n", GetLastError());
exit(1);
}
printf ("Serial port %s successfully initialized.\n", pcCommPort);
return;
}
// ------------------------------------------------------------------------------char *SendAndWaitFor(char *cpCommand, char *cpInBuffRd,
char *cpResponse, int iTimeoutMs)
{
unsigned long ulNoOfbytes;
strcpy(cpOutBuffer, cpCommand);
WriteFile(hCom, (long *)cpOutBuffer, strlen((char *)cpOutBuffer),
&ulNoOfbytes, 0);
if(iTimeoutMs)
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Rev. 1.3
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cpInBuffRd = WaitForResponse(cpResponse, cpInBuffRd, iTimeoutMs);
if(!cpInBuffRd)
exit(0);
return cpInBuffRd;
}
// Check for a specific response in the input buffer, and return ptr to what
// follows. If this times out or ERRORs before the response is found then a
// NULL is returned; It keeps reading the ser channel while waiting
char *WaitForResponse(char *cpResponse, char *cpInputBuffer, int iTimeOutInMs)
{
unsigned long ulNoOfbytes;
clock_t
sStartTime
= clock();
clock_t
sCurrentTime;
// covert wait time in ms's to clock_t by mutiplying by CLOCKS_PER_SEC/1000
clock_t
sWaitTime = (clock_t)(iTimeOutInMs*CLOCKS_PER_SEC)/1000;
int iPasses = 0;
int iCharCnt =0;
// set to 0
while(1)
{
char cTemp = *cpInputWr;
*cpInputWr = 0;
char *cpFound = strstr(cpInputBuffer, cpResponse);
*cpInputWr = cTemp;
if(cpFound)
{//copy the received bytes for late display
strncpy(cpInput_test, cpInputBuffer, iCharCnt);cpInput_test[iCharCnt]='\0';
return cpFound + strlen(cpResponse);
}
// Setup a 50 ms timeout for reads
sCOMMTIMEOUTS.ReadIntervalTimeout
sCOMMTIMEOUTS.ReadTotalTimeoutMultiplier
sCOMMTIMEOUTS.ReadTotalTimeoutConstant
sCOMMTIMEOUTS.WriteTotalTimeoutMultiplier
sCOMMTIMEOUTS.WriteTotalTimeoutConstant
SetCommTimeouts(hCom,
&sCOMMTIMEOUTS);
=
=
=
=
=
0;
0;
50;
0;
0;
// Read the serial port
//cpInputWr has char from the port
BOOL bError = !ReadFile(hCom, cpInputWr, 1, &ulNoOfbytes, 0);
iCharCount += ulNoOfbytes; iCharCnt+=ulNoOfbytes;
if(bError)
{
strcat(cpErrorString, "Read Error\r\n");
exit(10); // implement a write to file before exit(0)
}
cpInputWr += ulNoOfbytes;
// check for a timeout
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AN93
sCurrentTime = clock();
iPasses++;
if( sCurrentTime > (sStartTime + sWaitTime) )
{
strcat(cpErrorString, "Timeout of "); strcat(cpErrorString, cpResponse);
printf ("\n%s\n", cpErrorString);
strncpy(cpInput_test, cpInputBuffer, iCharCnt);
cpInput_test[iCharCnt]='\0'; //copy the received bytes for late display
return cpInputBuffer;
// we exit with the same input string we came in with
// because we time out.
}
}
};
// ------------------------------------------------------------------------void AssertRTS(bool bAssert)
{
BOOL
bSuccess;
if(bAssert)
dcb.fRtsControl
= RTS_CONTROL_ENABLE;
// assert RTS
else
dcb.fRtsControl
= RTS_CONTROL_DISABLE;
// dis-assert RTS
bSuccess = SetCommState(hCom, &dcb);
if (!bSuccess)
{
// Handle the error.
printf ("SetCommState failed with error %d.\n", GetLastError());
exit(1);
}
else
return;
}
void AssertDTR(bool bAssert)
{
BOOL
bSuccess;
if(bAssert)
dcb.fDtrControl
= RTS_CONTROL_ENABLE;
// assert RTS
else
dcb.fDtrControl
= RTS_CONTROL_DISABLE;
// dis-assert RTS
bSuccess = SetCommState(hCom, &dcb);
if (!bSuccess)
{
// Handle the error.
printf ("SetCommState failed with error %d.\n", GetLastError());
exit(1);
}
268
Rev. 1.3
AN93
return;
}
void Delay(long iMs)
{
clock_t wait;
// covert ms's to clock_t by mutiplying by CLOCKS_PER_SEC/1000
wait = (clock_t)(iMs*CLOCKS_PER_SEC)/1000;
clock_t goal;
goal = wait + clock();
while( goal > clock() )
;
}
void LoadAndSendPatch(void)
{
char caOutGoing[256];
cpInputRd_temp = SendAndWaitFor("AT&T7\r", cpInputRd, "OK\r\n", 300); // Reset the modem
printf ("Current %s \n", cpInputRd); cpInputRd=cpInputRd_temp;
printf ("Loading patch:%s...\n", fnamePatch);
if ((hpPatchFile = fopen(fnamePatch, "rb")) == NULL)
{
fprintf(stderr, "The Patch File is missing.\n");
exit(1);
}
AssertRTS(true );
cpInputRd=SendAndWaitFor("ATE1\r", cpInputRd, "OK\r\n", 300);
bool bValidLine = true;
while(bValidLine)
{
bValidLine = GetFileTextLine(caOutGoing);
if(bValidLine)
cpInputRd
= SendAndWaitFor(caOutGoing, cpInputRd, "OK\r\n", 3000);
}
cpInputRd = SendAndWaitFor("ATE1\r", cpInputRd, "OK\r\n", 300);
cpInputRd_temp = SendAndWaitFor("AT&T6\r", cpInputRd, "OK\r\n", 300);
printf ("Finish Loading, %s \n", cpInputRd); cpInputRd=cpInputRd_temp;
fclose(hpPatchFile);
}
// Returns FALSE when at end of file
// Stops after first LF.
bool GetFileTextLine(char *cpIn)
{
*cpIn = 0; char cpInChar[8]; cpInChar[1] = 0;
while(!feof(hpPatchFile))
Rev. 1.3
269
AN93
{
cpInChar[0] = fgetc(hpPatchFile);
strcat(cpIn, cpInChar);
if(*cpInChar == '\n')
return TRUE;
}
return FALSE;
}
270
Rev. 1.3
AN93
V.29 FastPOS Detailed Wave Files
The following is a wave file that shows a V.29 FastPOS SDLC transaction. It was captured with the program listed
above with a keep-alive loop. See "Appendix B—Line Audio Recording" on page 273 for details on how to capture
wave files.
RTS (not RTS) signal
V.29 Calling Tone
Answer Tone
(2225 Hz)
Repeat
DTE sends the calling
modem a UA packet
to transmit:
<0x30>(0x73><EM><0xB1>
Calling modem is receiving
and sends to the DTE:
“Connect Packet” :
<EM><0xBE><0x24><0x24><EM><B1>
Then the SNRM Packet:
<0x30><0x93><EM><0xB1>
DTE sends the calling modem
an RR packet to transmit:
<30><EM><0xA0><EM><B1>
Calling modem is receiving.
Sends a Tx abort to DTE:
<EM><0xB2>
Then the received RR packet:
<30><EM><0xA0><EM><B1>
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271
AN93
V.29 FastPOS DTE Trace
This is recorded while the program listed above is running. The patch load is left out for brevity.
DCE
DTE
DCE
DTE
DCE
DTE
CR LF CR LF O
K
CR LF
a
a
A
E
0
CR
b
c
d
8
T
E
0
t
z
CR CR LF O
CR LF CR LF O
K
t
K
&
T
y
0
CR
A
T
T
*
CR LF O
K
CR LF
+
g
c
i
=
B
5
CR
DCE
DTE
V
2
%
c
0
%
V
1
+
I
F
C
=
0
DCE
DTE
T
\
N
0
+
F
C
L
A
S
S
=
1
CR
DCE
DTE
CR LF O
K
CR LF
A
A
,
8
0
0
4
CR
DCE
DTE
CR LF O
K
CR LF
CR
,
2
LF O
K
6
A
T
CR LF C
:
CR
CR LF O
K
CR LF
&
4
D
2
x
CR LF O
K
CR LF
\
A
K
CR LF
A
T
:
U
8
A
T
+
E
S
=
6
,
,
,
0
,
,
1
CR
CR LF O
K
CR LF
CR
T
+
E
S
A
=
0
,
0
U
8
7
,
0
5
0
A
CR
CR LF O
K
CR LF
A
T
D
T
8
,
0
1
1
CR LF C
O
N
N
E
C
T
CR LF
0
EM A0
0
EM A0
CR LF
A
T
:
:
U
7
A
,
1
CR
DCE
DTE
5
1
1
5
8
5
3
2
EM BE $
$
EM B1 0
EM B2 0
CR LF
A
T
EM B1
K
CR
CR LF O
DCE
DTE
272
t
A
t
DCE
DTE
a
CR LF
a
DCE
DTE
CR CR LF O
CR LF
DCE
DTE
DCE
DTE
z
CR
5
0
7
CR LF
0
s
93 EM B1
EM B2 0
EM B2 0
EM A0 EM B1
Rev. 1.3
5
EM A0 EM B1
EM B1
EM A0 EM B1
0
A
EM A0 EM B1
AN93
APPENDIX B—LINE AUDIO RECORDING
Recording and examining the audio signals on the phone line is one of the best debugging techniques for PSTN
modems. Virtually all the relevant signals are in the audio spectrum and are easy to acquire using a standard PC
sound card and accessory hardware and software that is especially designed for music creation and analysis.
The required hardware is a Radio Shack Catalog No. 43-228A “Recorder Control”. It can be used with any
computer equipped with a 3.5 mm audio-input jack.
The resulting wave can usually be recorded in the field using the computer’s operating-system resources, but for
analysis, a software package capable of showing the spectral contents as they change over time is recommended.
The two most widely used ones are Adobe Audition, a commercial product, and WaveSurfer, which is a free opensource product that runs on Windows, Linux, OS X and Unix. This audio-recording technique does not replace
sophisticated test equipment, but it is quite useful in showing up some faults in the line and in the modem's (DUT)
negotiation with the device on the other side of the phone line.
When to Use Audio Recording
This technique is best used when the modem appears to connect normally against some servers but does not
connect well when calling a specific server or modem. This implies the hardware is functional and the issues most
likely involve the negotiations between the modems during connect and retrain. One way to rule out the possibility
of a hardware problem is to call the server or modem where the connect issue is found using the Silicon Labs EVB
module.
Times When Audio Recording May Not Help
Some signals are exceptions and cannot be monitored in this way due to the limits of the bandwidth examined.
Examples are the dc voltage and currents that exist during both on- and off-hook conditions, precise details of the
pulse dialing waveforms, and most EMI signals. EMI signals, which are not visible during the recordings, may
produce in-band demodulated and cross-product signals in the modem.
Some in-band signals cannot easily be monitored this way because they are common-mode signals. While they
may be less visible to the recording apparatus, they can be received by the modems in some cases. An example of
this is a strong common-mode 50 or 60 Hz hum with its harmonics (a 50 or 60 Hz buzz).
Hardware Setup
The Radio Shack Recorder Control contains a transformer that bridges the phone line with a dc-blocking capacitor,
plus a voice-operated switch output that starts and stops a recording device. We only use one of the output
connectors since we are not interested in the VOX mechanism. Connect the audio output connector (a 3.5 mm
O.D. connector) to the microphone input socket at the back of the computer. The RJ11 connector from the
Recorder Control should be connected to the Tip and Ring of the phone line being monitored.
Rev. 1.3
273
AN93
The larger of the
two jacks (3.5 mm)
carries audio to
the PC
Connect the R11
jack in parallel
with Tip/Ring of
modem
Figure 52. Hardware Setup
Setting PC Microphone Input for Recording (Windows NT)
Use the following procedure:
1. Click Start->Settings->Control Panel->Sounds and Multimedia to open the “Sounds and Multimedia Properties”
window.
2. Click Audio Tab; click Volume to open the “Recording Control” window.
3. Select Microphone as input; adjust balance and volume.
274
Rev. 1.3
AN93
Figure 53. Sounds and Multimedia Properties
Setting PC Microphone Input for Recording (Windows 98)
Use the following procedure:
1. Select Start->Settings->Control Panel->Multimedia Properties to open the Multimedia Properties window.
2. Select the “Audio” tab and then the “Recording” icon to open the Recording Control window.
3. Select Microphone as input, and adjust the balance and volume.
Rev. 1.3
275
AN93
Figure 54. Multimedia Properties
Setting PC Microphone Input for Recording (Windows XP)
Use the following procedure:
1. Select Start->Control Panel->Multimedia Properties to open the Sounds and Audio Devices Properties window.
2. Select the Audio tab and then the Sound Recording volume button to open the Recording Control window.
3. Select Microphone as input, and adjust balance and volume.
4. Select Advanced to open the Advanced Controls for Microphone screen.
5. Deselect the “1 Mic Boost” radio button (Mic. Boost is essentially an AGC mechanism that can spoil the audio
recordings.)
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Figure 55. Sounds and Audio Devices Properties
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277
AN93
Making the Recording with Windows Sound Recorder (Windows XP, NT or Windows 98)
Use the following procedure:
1. Click Start->Programs->Accessories->Entertainment->Sound Recorder to open “Sound Recorder” window
2. Select the red record button to start recording, then File->Save when done.
Figure 56. Sound Recorder
Making the Recording with Adobe Audition or WaveSurfer
These applications provide more recording options than the Window Sound Recorder application. They should be
set up for monophonic recordings at a sample rate of about 11,000 samples per second in order to save recording
space while still retaining reasonable fidelity. The number of bits per word should be 16 bits to allow the full
dynamic range available in the sound card. The larger resolution size of 32 bits floating point would be a waste of
space and computing power.
Figure 57. Adobe Audition Example
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Rev. 1.3
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Audio Playback and Analysis
Below are two displays showing the results of recording a good V.22 transaction using Adobe Audition. We need to
examine the signal both in the time domain and the frequency domain, with the frequency domain being a much
more useful view. The graphs below show time on the horizontal axis and either wave energy in dB or Frequency in
Hz on the vertical scale. In the frequency display, the color of the wave indicates the energy at that combination of
elapsed time and frequency. The color scheme is programmable. It is typical in the temporal view to see a dc offset
until one applies a high-pass filter, a step that is rarely necessary.
Figure 58. Adobe Audition Temporal View of a Good V.22 Transaction
Rev. 1.3
279
AN93
Figure 59. Adobe Audition Spectral View of a Good V.22 Transaction
An important parameter that is not obvious at first glance is the resolution in “bands” of the spectral display. There
is a tradeoff that must always be considered. This is set up in the Options->Settings Display tab in the Adobe
Audition product. This parameter allows for finer and coarser vertical (frequency) resolution at the cost of timedomain uncertainty. Figures 60 and 61 depict the same wave files but with 256 bands versus 2048 bands. One can
see better timing details in one graph compared with the other. The 256-band spectral display shown in Figure 60
shows the fine timing details of the protocol, but with poor frequency resolution. The 2048-band spectral display
shown in Figure 61 allows more precise frequency measurements and signal separation, but at the cost of
obtaining a coarser time resolution.
280
Rev. 1.3
AN93
Figure 60. 256 Band Spectral Display
Figure 61. 2048 Band Spectral Display
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281
AN93
Audio-Recording Pitfalls
To facilitate communications protocol debugging, it is imperative that audio recordings be made properly. The two
most common conditions that degrade the quality of audio recordings are:
 "Waveform clipping due to excessive recording level
 "Time-varying levels due to use of AGC (automatic gain control)
Figure 62. Recording Made at Excessive Level
The above recording was made at an excessively high level. One can see clipping in the time domain and
numerous distortion products in the frequency domain.
Figure 63. Recording Made with AGC Noise Reduction
The above recording was made with AGC "Noise Reduction" still enabled, as can be seen from the gradual level
drop in the time domain graph at the start of V.22 negotiations. It also shows evidence of a microphone being used
instead of the Radio Shack adapter. This is visible in the frequency-domain graph as horizontal striations (an
undulating frequency response) during the scrambled portion of the V.22 communication. One can also see thirdharmonic distortion.
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Details of Some Low-Speed Protocols
The following annotated recordings give basic ideas of what to expect the EPOS modem transactions will look like.
There are many possible variations of these examples, both in and out of compliance with published standards, in
common use. There are also very unusual variations that Silicon Labs has made efforts to support in order to allow
customers to connect to non-standard and essentially broken modems. Some of these are described in a later
section.
Answering modem’s
Scambled Binary
Ones and Scrambled
Data; visually indistinguishable from
each other.
Bell 212 (2225 Hz
Answer Tone)
Calling modem’s
Scrambled Binary
Ones and Scrambled
Data; visually indistinguishable from
each other.
DTMF dialing
Figure 64. Appearance of Bell 212 Protocol
Unscrambled Binary
Ones (USB1) signal.
Two tones at 2250 and
2850 Hz.
2100 Hz
Answer Tone
Scrambled Binary
Ones and Scrambled
Data; visually indistinguishable from each
other.
DTMF dialing
Calling modem’s
Scrambled Binary
Ones and Scrambled
Data; visually indistinguishable from
each other.
Figure 65. Appearance of V.22 Protocol
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AN93
Answering modem’s
scrambled binary
ones and scrambled
data; visually indistinguishable from
each other.
Unscrambled Binary
Ones (USB1) signal.
Two tones at 2250
and 2850 Hz.
2100 Hz Answer Tone.
The three short horizontal
lines are the S1 signal
that triggers V.22bis training. The S1 signal is an
unscrambled double
digit 00 – 01.
Calling modem’s
Scrambled Binary
Ones and Scrambled Data; visually
indistinguishable
from each other.
Figure 66. Appearance of V.22 bis Protocol
This looks the same as the V.22 bis protocol above except for S1 signal used for signaling V.22 bis(ness) and for
start of retrains.
Caller Responds with
SB1s and scrambled
data.
2100 Hz Answer Tone.
DTMF dialing.
Caller sends SB1s
immediately.
Figure 67. Appearance of V.22 Fast Connect Protocols
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As shown in Figure 68, the V.29 FastPOS protocol looks different than the older, slower V.22-like protocols. It is
also half-duplex, and each participating modem uses the entire spectral space available on the telephone line.
A receiving modem recognizes that the calling modem is V.29-capable by detecting the V.29 calling tone at 980 Hz.
Another example with some more SDLC-oriented data is provided later in this document.
DTMF dialing.
V.29 Calling
Tone (980 Hz).
Answer Tone
(2225 or 2100 Hz).
Answering modem
sends training patterns and packet(s).
Calling modem sends
training patterns and
packet(s).
Modem exchange packets.
Figure 68. Appearance of V.29 FastPOS Protocol
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A V.22 bis server
with unpredictable
and undesirable
gaps during the
USB1 signal.
A V.22 bis server
with a 2225 answer
tone instead of
2100 Hz.
Figure 69. Examples of EPOS Server Misbehavior
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The Answer Tone
is too short at
400 ms.
Innocent, answer
modem generated,
guard tone.
Figure 70. Example of EPOS Server Misbehavior
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Examples of Line Impairments
DTMF Distorted by Low Line Level
Figure 71. Defective DTMF
Figure 72. Normal DTMF
Solutions:

Fix the telephone line.
 Lower the DTMF level with AT:U46, 0BD0 or AT:U46, 0CF0
 Check the loop-current level with AT:R79 and AT:R6C.
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Power Line Related Noise
Figure 73. Odd Harmonics of 50 Hz Manifest as Horizontal Lines Spaced at 100 Hz
Causes:

Unbalanced phone line
High ac leakage supply
 Poor CMR in modem
Solutions:


Fix the telephone line.
 Ground the system to earth or float completely using a battery.
 Use an analog supply with lower ac Leakage
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APPENDIX C—PARALLEL/SPI INTERFACE SOFTWARE IMPLEMENTATION
This appendix describes the software interface requirements for communication with the ISOmodem in parallel or
SPI mode. Sample code was developed to run on the Silicon Labs C8051F12xx platform to allow basic
communication between the modem and a PC using the parallel or SPI interface. Figure 74 shows a typical
connection between a PC and the modem using the MCU C8051F12xx demo board as interface:
Figure 74. PC to Modem Connection through a C8051F12xx Demo Board
A typical application is structured in four software layers:
1. Hardware access: where the MCU performs all the basic I/O accesses to and from the modem
2. Interrupt service or polling: depending on the mode of access (polling or interrupt), this layer contains the
algorithms that determine when the host and the modem exchange data.
3. Data buffer management, status and control: this portion of the code contains the circular buffers that relay data
between the UART and the modem in both directions. Access functions are provided for the application to set
the software interrupt mask and the escape bit, and to query the status of software interrupts.
4. The application layer: this code depends on the application. An example application main() block is provided
in this document. An optional diagnostic console-level command set is also available to run on the application
layer. This command set is enabled using compiler options in the MCU development environment. Refer to
"Compiler Option: Dot Commands" on page 299 for details.
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Figure 75 illustrates the MCU software architecture, and the MCU and modem hardware connections.
(Optional)
Dot‐command shell
Application layer
modem_main.c
dot_command_loop.c
Buffer management layer
status_control.c
application_buffers.c
test_code.c
Interrupt service and/or polling
ISR_and_polling.c
Hardware access layer
modem_hardware.c
MCU
MCU_hardware.c
Parallel interface
SPI master
Parallel interface
SPI slave
Hardware Interface Register 1 (HIR1)
Transmit and receive FIFOs
MCU hardware (UART, timers, etc.)
UART interface
Modem
Figure 75. MCU Software and Modem Interface
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Software Description
Hardware Access Layer
This layer contains all the routines to access the MCU and modem hardware at the most basic level. The
application layer typically does not need to access these functions directly. It consists of two source files:

MCU_hardware.c
 modem_hardware.c
MCU_hardware.c
This sample code will work only on the Silicon Labs MCU C8051F12xx platform used for this example. This file
contains code specific to the MCU hardware configuration such as port configuration, oscillator configuration,
timers, UART, GPIOs, etc.
modem_hardware.c
This code can be ported to other applications with minimal changes needed to compile on a given host platform.
This file contains code to read from or write to the modem. The two functions below provide basic access to the
modem's Hardware Interface Registers:
char readModem( tHIRREG eHIR ): This is the main access point for unconditionally reading the modem's
data and status registers in parallel or SPI mode. The function reads the HIR0 when eHIR is HIR0 (0) and the
HIR1 when eHIR is HIR1 (1).
void writeModem( tHIRREG eHIR, char val, char mask ): This is the main access point for
unconditionally writing the modem's data and control registers in parallel or SPI mode. The parameter eHIR can be
HIR0 (0) or HIR1 (1). When writing to the HIR1, an optional mask value allows first reading the HIR1 from the
modem by calling readModem(), and then setting or clearing only those bits that are high in mask. Defined values
for mask are:
#define SiCTSb 0x01 // Clear to send (active low)
#define SiRTSb 0x02 // Request to send (active low)
#define SiESC
0x04 // Escape to command mode
#define SiINT
0x08 // Software interrupt
#define SiINTM 0x10 // Enable software interrupt
#define SiREM
0x20 // Receive FIFO empty
#define SiTXE
0x40 // Transmit FIFO almost empty interrupt
#define SiRXF
0x80 // Receive FIFO almost full interrupt
Boolean-OR combinations of the above are possible. This allows setting and/or clearing several bits
simultaneously. Thus a mask value of 0xFF results in all bits of val being written to the HIR1, and a mask value of
zero reads the HIR1 and simply rewrites the value just read, ignoring val. The mask parameter is ignored when
writing to the HIR0.
Interrupt Service and Polling Layer
Sample code for this layer can be found in the ISR_and_Polling.c file. This code can be ported to other
applications with minimal changes needed to compile on the host platform. This block contains the interrupt service
routines for both modem access and MCU to PC UART access. Except for modemCommunicationUpdate(), the
application layer typically does not need to access these functions directly. The access mode is interrupt driven by
default. In order to select polling mode, the system must set the global variable pollingNotInterruptMode to a
nonzero value. The software is designed to allow switching back and forth between polling and interrupt modes. If
only one mode is ever used, the code can be simplified accordingly. The next two sections detail out the functioning
of the polling and interrupt modes.
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Polling HIR1 Method
Transmitting and receiving data to and from the modem is accomplished by polling HIR1 status bits TXE and REM.
Polling is implemented by the following code fragment, excerpted from modemCommunicationUpdate(), which
must run in an infinite loop:
static char bytesToSend == 12;
// Declared in modemCommunicationUpdate()
if ( ( readModem( HIR1 ) & SiREM ) == 0
&& rxBufferSize < MODULUS_MASK )
{
readModemByte;
}
if ( gUARTToModemBufferSize > 0 )
// If there are data to be sent
{
if ( bytesToSend == 12 )
// Check TXE only every twelve bytes sent
{
status = readModem( HIR1 ) & SiTXE;
if ( status )
// If transmit FIFO empty
{
writeModem( HIR0, pullByteForModem(), 0xFF );
bytesToSend--;
}
}
else
// No need to check TXE because transmit FIFO is twelve deep
{
writeModem( HIR0, pullByteForModem(), 0xFF );
bytesToSend--;
// If the bytes to send count = 0, reset the count
if ( bytesToSend == 0 )
{
bytesToSend = 12;
}
}
}
Interrupt Service Routine (ISR) Method
Transmitting and receiving data to and from the modem is accomplished by servicing the interrupts generated by
the modem. The interrupt sources are described below. Whenever new communication is initiated after a period of
idling with respect to the TXE interrupt, the interrupt must be "jump-started" by calling the interrupt service routine
manually.
RXF Interrupt: Receive FIFO Almost Full
The RXF bit indicates the status of the receive FIFO. If this bit is set, the FIFO is either full (contains 12 bytes) or
almost full (contains 10 or 11 bytes). There are two ways to clear this interrupt: the RXF bit in HIR1 can be cleared
by the host, or enough bytes can be read from the receive FIFO to leave 9 bytes or less, thus removing the
condition for the interrupt. If the host clears the RXF bit, the interrupt is disabled. The interrupt can be rearmed only
when the receive FIFO drops below the ten-byte threshold. The interrupt can then trigger again when the receive
FIFO fills up to ten bytes or more.
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TXE Interrupt: Transmit FIFO Almost Empty
This interrupt occurs when only two bytes or fewer remain in the modem's transmit FIFO. The interrupt can be
cleared by writing more data to the FIFO to clear the interrupt condition, or by clearing the TXE bit in the HIR1.
However, if the FIFO is emptied by the modem faster than it is being filled, the TXE interrupt will either persist or
trigger again. If the TXE bit is cleared, the interrupt is disabled and can be rearmed only when three bytes have
been placed into the transmit FIFO. The TXE interrupt may then trigger again when the transmit FIFO drops below
the three-byte threshold. If the transmit FIFO is empty and new data need to be transmitted after the TXE interrupt
has been cleared, the TXE interrupt needs to be jump-started by calling modemCommunicationUpdate().
Timer Interrupt: Receive FIFO Not Empty
This interrupt occurs whenever some data remained in the modem's receive FIFO without the FIFO being read for
a period of time set in register U6F. This happens typically at the end of a data burst, when there aren't enough
bytes in the receive FIFO to cause an RXF interrupt, and no more data are received. A timer interrupt can also
occur when the receive FIFO is full if the RXF interrupt was disabled by clearing the RXF bit. The timer is also reset
when new received data are added to the receive FIFO.
The reset value of U6F is 1 ms. The timer interrupt can only be cleared by reading at least one byte from the
receive FIFO. If there remain bytes in the receive FIFO after servicing a timer interrupt, the timer will trigger another
interrupt after the same amount of time specified in the U6F register.
U70 Interrupt
This interrupt is analogous to the interrupt pin when operating in UART mode. It is the result of a condition set in
the U70 register being met, e.g. a parallel phone detection if bit PPDM was set in U70.
The U70 interrupt, indicated by the INT bit in HIR1, can be enabled and disabled using the INTM bit in the same
register. The only way to clear this interrupt is by sending the AT:I command to the modem. Typically, this requires
the application layer to send an ESC control word to place the modem in command mode before sending AT:I. The
response from the AT:I reports the cause of the interrupt. Refer the programmer's guide for more information.
Figure 76 shows the ISR implementation for modem-originated interrupts. The interrupt service routine keeps
running in a loop until all interrupt conditions are cleared. The modemInterrupt() sample code on page 300
shows the full ISR implementation. Refer to the #define statements to see how the different interrupt conditions
are inferred.
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Figure 76. Parallel- or SPI-Port Interrupt-Service Flowchart
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Buffer Management, Status and Control Layer
Buffer Management
Sample code for this layer can be found in the application_buffers.c file. This code can be ported to other
applications with minimal changes needed to compile on the host platform. This block contains the buffermanagement routines for both modem and UART access. The buffer structure consists of two circular buffers
implemented as the following array variables:
char gModemToUARTBuffer[ BUFFERSIZE ];
The above buffer is typically filled by modemInterrupt() and emptied by UART0Interrupt(). Once the buffer
is empty, subsequent TI0 (UART) interrupts have no effect. If the buffer is filled again after all TI0 interrupts have
been serviced, the TI0 interrupt needs jump starting. This is accomplished by calling
UARTCommunicationUpdate() after filling the buffer.
char gUARTToModemBuffer[ BUFFERSIZE ];
The above buffer is typically filled by UART0Interrupt() and emptied by modemInterrupt(). Once the buffer
is empty, subsequent TXE (modem) interrupts have no effect. If the buffer is filled again after all TXE interrupts
have been serviced, the TXE interrupt needs jump starting. This is accomplished by calling
modemCommunicationUpdate() after filling the buffer.
The two arrays above must be sized by choosing a power of two for the value of BUFFERSIZE, defined in
modem_80C51.h. This is because keeping track of the circular-buffer indexes requires modulus operations.
Instead of costly integer divisions with remainder, the modulus operation is achieved by bit masking using the allone bit pattern equal to BUFFERSIZE minus one. For example, if BUFFERSIZE is 1024 (210), the bit mask
(MODULUS_MASK) used for updating buffer pointers modulo BUFFERSIZE must be 1023 (0011 1111 1111). When a
buffer index reaches the value 1024 (0100 0000 0000), a bitwise-AND operation with MODULUS_MASK will reset the
index value to zero. If the value of BUFFERSIZE is changed in the header file, then the value of MODULUS_MASK
must be set to the same value minus one. The following global variables track the state of the buffers. A value of
zero indicates an empty buffer.
int gModemToUARTBufferSize;
int gUARTToModemBufferSize;
Read and write addresses to the above buffers are tracked by the following pointers:
int gLastFromUART;
// The last byte that was added to gUARTToModemBuffer[]
int gNextToModem;
// The first byte that will be taken out of gUARTToModemBuffer[]
int gLastFromModem; // The last byte that was added to gModemToUARTBuffer[]
int gNextToUART;
// The first byte that will be taken out of gModemToUARTBuffer[]
The flow of data between the modem and the UART is managed by the following functions:
char pullByteForModem( void );
// Remove a byte from gUARTToModemBuffer[]
char pullByteForUART( void );
// Remove a byte from gModemToUARTBuffer[]
void pushByteToModem( char byteToSend ); // Add a byte to gUARTToModemBuffer[]
void pushByteToUART( char byteToSend );
// Add a byte to gModemToUARTBuffer[]
Figure 77 summarizes the interactions between the function calls, pointers and buffers described above.
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Figure 77. Circular-Buffer Flowchart
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Status and Control
Sample code for this layer can be found in status_control.c file. This code can be ported to other applications with
minimal changes needed to compile on the host platform. The modem status may be queried, and modem control
flags may be set using the two functions below:
void setControl( char controlCode, char action, char condition ): Set modem control.
Possible control codes are:
SiESC: Set or clear escape flag.
SiINTM: Enable or disable U70 interrupt.
The action may be ENABLE or DISABLE. Control takes effect upon one of two conditions:
NOW: Unconditionally upon entering the function call.
WHEN_TX_BUF_EMPTY: The setControl() function loops until the gUARTToModemBuffer[] is empty. This
enables, for instance, setting the escape code after a given data set has been transmitted, prior to sending AT
commands. It is up to the application to ensure the buffer empties within a reasonable amount of time.
char queryU70IntStatus( void ): Returns the INT flag from the ISOmodem at the same bit position as in
the HIR1 register.
The Application Layer: Sample Application
Sample code for an application can be found in the modem_main.c and modem_80C51.h files. This code is
application and host platform specific. By default, the program simply passes data back and forth between the
modem and the UART using the buffers and function calls described above. The minimal application is shown
below:
char gPollingNotInterruptMode = 0;
// Interrupt mode by default
void main( void )
{
EA = 0;
// Disable global interrupt
EA = 0;
// Dummy, as per MCU data sheet
initApplicationBuffers();
initHardware();
setControl( SiESC, DISABLE, NOW );
IT1 = 1;
// External interrupt 1 is edge triggered
EX1 = 1;
// Enable external interrupt 1
PS = 1;
// High interrupt priority for UART0
PX1 = 0;
// Low interrupt priority for modem side
EA = 1;
// Enable global interrupt
while ( 1 )
{
modemCommunicationUpdate();
UARTCommunicationUpdate();
}
}
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The infinite loop has two functions depending on the use of interrupts or polling for modem communication:
1. In interrupt mode, the TXE (modem) and TI0 (UART) interrupts are always jump-started by making periodic
calls to modemCommunicationUpdate() and to UARTCommunicationUpdate(), respectively. The calls
are necessary only to jump-start the modem and UART transmit interrupts. A system that is aware of the
transmit activity for both the modem and the UART can reduce the number of calls, thereby freeing MCU
bandwidth for other tasks.
2. In polling mode, only TI0 (UART) interrupts need jump-starting using periodic calls to
UARTCommunicationUpdate(), and repeated calls to modemCommunicationUpdate() are necessary to
poll the modem's HIR1 and determine the status of the transmit and receive FIFOs. An obvious limitation of the
polling method is the need to constantly poll the modem for a change of FIFO state, which uses up MCU
bandwidth.
Compiler Option: Dot Commands
To include diagnostic (dot command) functions, define DIAGNOSTICS by removing the comment slashes (//) at
the appropriate line in the modem_80C51.h header file, and include the files dot_command_loop.c and
test_code.c in the project build. Contact Silicon Labs for more details on diagnostic commands.
Modem Operation
Initialization
After reset, the ISOmodem does not by default have all the required features enabled. When using the parallel or
SPI mode, Silicon Labs recommends the following initialization steps:
1. Push the command AT:U70,8F00 followed by carriage return into the transmit buffer. The setting of U70 can
vary, but it is recommended that bit 15 (HES) be set to enable escape.
2. Monitor the receive buffer for OK, indicating that the command was successful.
3. If a firmware upgrade needs to be programmed into the part, push the upgrade into the transmit buffer one line
at a time. The OK prompt must be received after each line.
4. Once the patch is written to the ISOmodem, other commands can be pushed into the transmit buffer.
5. If software interrupts are required, enable them by calling:
setControl( SiINTM, ENABLE, NOW ).
Silicon Labs also recommends the use of any firmware upgrade (provided by Silicon Labs) if called for in the errata
for that revision. Firmware upgrades address known problems with a given revision.
Making a Connection
Making a connection in parallel or SPI mode is no different than in UART mode. The application layer should keep
track of whether the ISOmodem is in command mode or data mode to determine whether to send an escape
before sending commands. The steps for making a connection are as follows:
1. Clear the HIR1 ESC bit by calling setControl( SiESC, DISABLE, NOW ).
2. Push the dial string into the transmit buffer, and begin monitoring for the CONNECT response.
3. The ISOmodem is now in data mode when the connect/protocol response is received.
4. The application layer can begin pushing data to the modem for transmission over the phone line. Received data
will accumulate in the receive buffer as a result of polling or interrupts.
Data Bursts
The ISOmodem has internal buffering of approximately one kilobyte in each of the receive and transmit directions.
The modem attempts to empty and fill these buffers as quickly as possible. This results in transmit and receive data
bursts at a much faster rate than the modem connection. The receive bursts are limited by the V.42 frame size and
the V.42bis data compression ratio. The higher the compression ratio, the longer the burst will be. The transmit
bursts can be as large as one kilobyte when transmission first begins. Once the buffer is full, the transmit bursts are
also limited by the V.42 frame size and compression ratio.
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Modem Interrupt Service Sample Code
The following is the C code for the modem ISR. Also refer to "Figure 76. Parallel- or SPI-Port Interrupt-Service
Flowchart" for more explanations. Please contact Silicon Labs to obtain a complete C8051F12xx project bundle.
// Macros for modem ISR readability
#define RXFInterrupt
( modem_status & SiRXF )
#define TXEInterrupt
( modem_status & ( SiTXE & modem_control ) )
#define TimerInterrupt ( !( modem_status & SiREM ) && !RXFInterrupt && !rxf_processed )
#define U70Interrupt
( modem_status & ( SiINT & ( modem_status >> 1 ) ) )
#define RTSIsSet
( modem_status & SiRTSb )
#define ClearRTS
( modem_control &= ~SiRTSb )
#define ClearRXF
( modem_control &= ~SiRXF )
#define ClearTXE
( modem_control &= ~SiTXE )
#define ClearINTM
( modem_control &= ~SiINTM )
#define rxBufferSize
gModemToUARTBufferSize
#define ReadModemStatus
modem_status = readModem( HIR1 )
#define readModemByte
pushByteToUART( readModem( HIR0 ) )
//----------------------------------------------------------------------------// Interrupt service routine
//----------------------------------------------------------------------------// modemInterrupt()
//----------------------------------------------------------------------------// Invoked whenever the modem issues an interrupt: this is meant as reference
// code for parallel-port/SPI interrupt service.
//
// Parameters:
None
// Return value: None
//----------------------------------------------------------------------------void modemInterrupt( void ) interrupt 2
{
char modem_status;
char modem_control; // Modem control before writing (written only if modifed)
char control_update = 0; // Tracks whether control register was modified, needs updating
char rxf_processed = 0;
int BytesSent;
int BytesReceived = 0;
char SFRPAGE_SAVE;
EA = 0;
EA = 0;
SFRPAGE_SAVE = SFRPAGE;
ReadModemStatus;
//
//
//
//
Disable global interrupt
Dummy operation required by MCU, as per MCU data sheet
Save Current SFR page
Read HIR1 to get current status
// Set default write value. Always write the RXF and TXE bits to 1 by default
// to avoid inadvertently clearing those interrupts
modem_control = modem_status | SiTXE | SiRXF;
//
//
//
if
{
Clear the RTS bit if it's set. The part comes out of reset with RTS set.
RTS will have no effect unless the modem gets the AT\Q3 command.
If RTS isn't needed this code can be removed.
( RTSIsSet )
ClearRTS;
// Clear the RTSb so data enters FIFO
control_update = 1;
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}
// This is the main ISR handler loop: stay in it until all interrupts are cleared
while ( RXFInterrupt || TXEInterrupt || TimerInterrupt || U70Interrupt )
{
// ***RXF INTERRUPT***
// Separate RXF interrupt from timer interrupt to reduce the number of HIR1 reads.
if ( RXFInterrupt )
{
// MODULUS_MASK is BUFFERSIZE - 1
while ( ( rxBufferSize < MODULUS_MASK ) && ( BytesReceived < 10 ) )
{
readModemByte;
// Set a flag to know that RXF was serviced
rxf_processed = 1;
BytesReceived++;
}
// Clear the RXF interrupt if fewer than 3 bytes were read. If more than 3 bytes
// were read from the FIFO the interrupt will be cleared automatically.
if (BytesReceived < 3)
{
ClearRXF;
// Clear RXF since we didn't empty the FIFO
control_update = 1;
}
}
// ***TIMER INTERRUPT***
// If there wasn't an RXF interrupt, but the receive FIFO isn't empty,
// the interrupt may have been caused by the receive timer interrupt.
// Note: If the host cannot empty its queue fast enough to keep up with the
// modem or if it is going to have a long period of time (>:U6F setting) where
// there won't be room in the FIFO, it would be better to completely disable
// the interrupt until the host has made room for more data. The timer interrupt
// can only be cleared by reading a byte from the FIFO; if there is no room
// in the FIFO, the interrupt will not be cleared. Alternatively, the routine
// could read a byte to clear the interrupt and then discard the data.
// MODULUS_MASK is BUFFERSIZE - 1
while ( TimerInterrupt && ( rxBufferSize < MODULUS_MASK ) )
{
// Read a byte
readModemByte;
BytesReceived++;
// Check the status to see if the FIFO is empty
ReadModemStatus;
}
// ***U70 INTERRUPT***
// Check for a "software" interrupt. "software" refers to any of the interrupts
// described in U70 in the modem datasheet. Only do this if the
// software interrupt is not masked. This is the reason for the bit shift.
if ( U70Interrupt )
{
// Mask the interrupt so that it doesn't cause another interrupt
// until the host software clears it with AT:I and tells us to
// turn it back on
ClearINTM;
control_update = 1;
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// Insert code here to inform the host of the U70 interrupt
// or service it application dependent), e.g.
gU70Interrupt = 1;
}
// ***TXE INTERRUPT***
if ( TXEInterrupt )
{
// Clear the data sent counter
BytesSent = 0;
// The transmit FIFO is fourteen bytes deep, therefore upon TXE interrupts
// (two bytes or fewer in the transmit FIFO), it is possible to send up to
// twelve bytes to the part without risking overflow.
while ( ( gUARTToModemBufferSize > 0 ) && ( BytesSent < 12 ) )
{
writeModem( HIR0, pullByteForModem(), 0xFF );
BytesSent++;
}
// If there weren't enough data sent to clear the interrupt, clear it manually.
if ( BytesSent < 3 )
{
// Clear the TXE bit to clear the interrupt
ClearTXE;
control_update = 1;
}
}
// Check if the status register needs to be written
if ( control_update )
{
writeModem( HIR1, modem_control, 0xFF );
control_update = 0;
}
// Read register 1 to get current status
ReadModemStatus;
// Reset receiver counter for a subsequent RXF condition in this loop
BytesReceived = 0;
}
SFRPAGE = SFRPAGE_SAVE;
EA = 1;
// Restore SFR page
// Enable global interrupt
}
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DOCUMENT CHANGE LIST
Revision 0.9 to Revision 1.0

Revision 0.5 to Revision 0.6













Added Si2493 to title.
Added V.92 information.
Added V.44 information.
Added and expanded several AT+ commands.
Added U71 and U9F-UAA registers.
Corrected CTS* trigger points.
Added note for U70 configuration for Australia and
Brazil
Expanded "5.14. Legacy Synchronous DCE Mode/
V.80 Synchronous Access Mode".
Added "2.5. PCM/Voice Mode (24-Pin TSSOP and
38-Pin QFN Only)".
Added "6.4. SMS Support".
Added "6.5. Type II Caller ID/SAS Detection".
Added "6.7. Modem-On-Hold".
Added "6.12. V.92 Quick Connect".
Added “Appendix D—Si3006/3009 Supplement” for
for 3006 and 3009 DAA support.
Revision 1.0 to Revision 1.1

Major revision to reflect the latest Si24xx ISOmodem
product offerings.
 Added support for new product features: SPI
interface and 32.768 kHz clock input.
 Added software support for parallel and SPI
interfaces.
Revision 1.1 to Revision 1.2





Correction to SPI and 32.768 kHz and SPI strapping
tables.
Added several registers.
Removed Appendix D.
Updated for Si2493/57/34/15/04 Revision D.
Added Si2493 and Si2439 configuration and voice
functions.
Revision 0.6 to Revision 0.7
Revision 1.2 to Revision 1.3











Added V.29 FC to Table 1.
Updated part numbers in "4.3. Bill of Materials".
Updated EE section and example code.
Updated Table 46, “U-Register Descriptions,” on
page 91.
Updated U63 bit map.
Updated U7D bit map
Updated “22.1. Country Register Settings for CTR/
TBR21 ATAAB and CTR21 Type Countries” on page
138.
Corrected New Zealand Pulse dial settings in “22.20
Country Register Settings for New Zealand” on page
147.
Updated Table 102 on page 163.
Deleted references to U69 (now for internal use
only).

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
Added Si2494 and Si2439 configuration and voice
functions.
Added "2.5. SSI/Voice Mode (24-Pin TSSOP and 38Pin QFN Only)" on page 30.
Added "5.13. EPOS (Electronic Point of Sale)
Applications" on page 125.
Added "7. Handset, TAM, and Speakerphone
Operation" on page 173.
Added "8. Security Protocols" on page 224.
Added "9. Chinese ePOS SMS" on page 234.
Revision 0.7 to Revision 0.8

Updates to Registers CALT and GEND.
Revision 0.8 to Revision 0.9
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Document format changes.
Minor text edits.
Deleted Legacy-Synchronous mode.
Updated layout guidelines.
Updated country configuration tables.
Added “Appendix C—Si3008 Supplement”.
Added “Appendix D—EPOS Application”.
Rev. 1.3
303
AN93
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304
Rev. 1.3
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