Texas Instruments | TRF7970A Multiprotocol Fully Integrated 13.56-MHz RFID and Near Field Communication (NFC) Transceiver IC (Rev. L) | Datasheet | Texas Instruments TRF7970A Multiprotocol Fully Integrated 13.56-MHz RFID and Near Field Communication (NFC) Transceiver IC (Rev. L) Datasheet

Texas Instruments TRF7970A Multiprotocol Fully Integrated 13.56-MHz RFID and Near Field Communication (NFC) Transceiver IC (Rev. L) Datasheet
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TRF7970A
SLOS743L – AUGUST 2011 – REVISED MARCH 2017
TRF7970A Multiprotocol Fully Integrated 13.56-MHz RFID and Near Field Communication
(NFC) Transceiver IC
1 Device Overview
1.1
Features
1
• Supports Near Field Communication (NFC)
Standards NFCIP-1 (ISO/IEC 18092) and NFCIP‑2
(ISO/IEC 21481)
• Completely Integrated Protocol Handling for
ISO/IEC 15693, ISO/IEC 18000-3, ISO/IEC 14443
A and B, and FeliCa™
• Integrated Encoders, Decoders, and Data Framing
for NFC Initiator, Active and Passive Target
Operation for All Three Bit Rates (106 kbps,
212 kbps, 424 kbps), and Card Emulation
• RF Field Detector With Programmable Wake-up
Levels for NFC Passive Transponder Emulation
Operation
• RF Field Detector for NFC Physical Collision
Avoidance
• Integrated State Machine for ISO/IEC 14443 A
Anticollision (Broken Bytes) Operation
(Transponder Emulation or NFC Passive Target)
• Input Voltage Range: 2.7 VDC to 5.5 VDC
1.2
•
•
•
•
Applications
Mobile Devices (Tablets, Handsets)
Secure Pairing ( Bluetooth®, Wi-Fi®, Other Paired
Wireless Networks)
Public Transport or Event Ticketing
Passport or Payment (POS) Reader Systems
1.3
• Programmable Output Power: +20 dBm (100 mW),
+23 dBm (200 mW)
• Programmable I/O Voltage Levels From 1.8 VDC
to 5.5 VDC
• Programmable System Clock Frequency Output
(RF, RF/2, RF/4) from 13.56-MHz or 27.12-MHz
Crystal or Oscillator
• Integrated Voltage Regulator Output for Other
System Components (MCU, Peripherals,
Indicators), 20 mA (Max)
• Programmable Modulation Depth
• Dual Receiver Architecture With RSSI for
Elimination of "Read Holes" and Adjacent Reader
System or Ambient In-Band Noise Detection
• Programmable Power Modes for Ultra Low-Power
System Design (Power Down <1 µA)
• Parallel or SPI Interface (With 127-Byte FIFO)
• Temperature Range: –40°C to 110°C
• 32-Pin QFN Package (5 mm × 5 mm)
•
•
•
•
•
Short-Range Wireless Communication Tasks
(Firmware Updates)
Product Identification or Authentication
Medical Equipment or Consumables
Access Control, Digital Door Locks
Sharing of Electronic Business Cards
Description
The TRF7970A device is an integrated analog front end (AFE) and multiprotocol data-framing device for a
13.56-MHz NFC/RFID system supporting all three NFC operation modes – reader/writer, peer-to-peer, and
card emulation according to ISO/IEC 14443 A and B, Sony FeliCa, ISO/IEC 15693, NFCIP-1
(ISO/IEC 18092), and NFCIP-2 (ISO/IEC 21481). Built-in programming options make the device suitable
for a wide range of applications for NFC, proximity, and vicinity identification systems.
The device is configured by selecting the desired protocol in the control registers. Direct access to all
control registers allows fine tuning of various reader parameters as needed.
The TRF7970A device supports data rates up to 848 kbps with all framing and synchronization tasks for
the ISO protocols onboard. The TRF7970A device also supports reader and writer mode for NFC Forum
tag types 1, 2, 3, 4, and 5. Other standards and even custom protocols can be implemented by using one
of the direct modes the device offers. These direct modes let the user fully control the AFE and also gain
access to the raw subcarrier data or the unframed, but already ISO-formatted, data and the associated
(extracted) clock signal.
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
TRF7970A
SLOS743L – AUGUST 2011 – REVISED MARCH 2017
www.ti.com
The receiver system has a dual-input receiver architecture to maximize communication robustness. The
receivers also include various automatic and manual gain control options. The received signal strength
from transponders, ambient sources, or internal levels is available in the RSSI register.
A SPI or parallel interface can be used for the communication between the MCU and the TRF7970A
device. When the built-in hardware encoders and decoders are used, transmit and receive functions use a
127-byte FIFO register. For direct transmit or receive functions, the encoders or decoders can be
bypassed so the MCU can process the data in real time.
The TRF7970A device supports a wide supply voltage range of 2.7 V to 5.5 V and data communication
levels from 1.8 V to 5.5 V for the MCU I/O interface.
The transmitter has selectable output power levels of 100 mW (+20 dBm) or 200 mW (+23 dBm)
equivalent into a 50-Ω load when using a 5-V supply and supports OOK and ASK modulation with
selectable modulation depth.
The built-in programmable auxiliary voltage regulator delivers up to 20 mA to supply an MCU and
additional external circuits within the reader system.
Integrated RF field detector with programmable wake-up levels, eight selectable power modes, and ultralow power operation enable easy development of robust and cost-efficient designs for long battery life.
Start evaluating the TRF7970A multiprotocol transceiver IC with the TRF7970AEVM, TRF7970ATB, or
DLP-7970ABP.
Device Information
PART NUMBER
TRF7970ARHB
2
PACKAGE
BODY SIZE
VQFN (32)
5 mm × 5 mm
Device Overview
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1.4
SLOS743L – AUGUST 2011 – REVISED MARCH 2017
Functional Block Diagram
Figure 1-1 shows the block diagram.
VDD_I/O
MUX
RX_IN1
Phase and
Amplitude
Detector
Gain
RSSI
(AUX)
RF Level
Detector
RX_IN2
RSSI
(External)
Filter
and AGC
Digitizer
ISO
Protocol
Handling
Transmitter
Analog Front End
I/O_1
(Control
Registers and
Command
Logic)
I/O_3
Gain
VDD_PA
TX_OUT
I/O_0
State
Control
Logic
MCU
Interface
Bit
Framing
127-Byte
FIFO
I/O_5
I/O_6
I/O_7
SYS_CLK
DATA_CLK
VIN
Serial
Conversion
CRC and Parity
VSS_PA
I/O_4
IRQ
Decoder
Framing
I/O_2
Level Shifter
Phase and
Amplitude
Detector
RSSI
(Main)
Logic
VDD_A
BAND_GAP
EN
EN2
ASK/OOK
VSS_A
Digital Control
State Machine
MOD
VDD_RF
Voltage Supply Regulator Systems
(Supply Regulators and Reference Voltages)
VSS_RF
VDD_X
OSC_IN
OSC_OUT
VSS
Crystal or Oscillator
Timing System
VSS_D
Copyright © 2017, Texas Instruments Incorporated
Figure 1-1. Block Diagram
Device Overview
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Table of Contents
1
Device Overview ......................................... 1
6
4
6.10
TRF7970A IC Communication Interface ............ 31
Functional Block Diagram ............................ 3
6.11
6.12
TRF7970A Initialization ............................. 49
Special Direct Mode for Improved MIFARE™
Compatibility ......................................... 50
6.13
NFC Modes.......................................... 50
6.14
Direct Commands from MCU to Reader ............ 52
6.15
Register Description ................................. 56
Applications ........................................... 1
1.3
Revision History ......................................... 5
Device Characteristics .................................. 7
Related Products ..................................... 7
Terminal Configuration and Functions .............. 8
.......................................... 8
4.2
Signal Descriptions ................................... 8
Specifications ........................................... 10
5.1
Absolute Maximum Ratings ........................ 10
5.2
ESD Ratings ........................................ 10
5.3
Recommended Operating Conditions ............... 10
5.4
Electrical Characteristics ............................ 11
5.5
Thermal Resistance Characteristics ................ 12
5.6
Switching Characteristics ........................... 12
Detailed Description ................................... 13
6.1
Overview ............................................ 13
6.2
System Block Diagram .............................. 16
6.3
Power Supplies ...................................... 16
6.4
Receiver – Analog Section .......................... 22
6.5
Receiver – Digital Section ........................... 23
6.6
Oscillator Section ................................... 28
6.7
Transmitter – Analog Section ....................... 29
4.1
5
Description ............................................ 1
1.2
3.1
4
Transmitter – Digital Section ........................ 30
Transmitter – External Power Amplifier and
Subcarrier Detector ................................. 31
Features .............................................. 1
1.4
2
3
6.8
6.9
1.1
Pin Diagram
7
Applications, Implementation, and Layout........ 76
7.1
8
9
TRF7970A Reader System Using SPI With SS
Mode ................................................ 76
..............................
......
7.4
Reader Antenna Design Guidelines ................
Device and Documentation Support ...............
8.1
Getting Started and Next Steps .....................
8.2
Device Nomenclature ...............................
8.3
Tools and Software .................................
8.4
Documentation Support .............................
8.5
Community Resources ..............................
8.6
Trademarks..........................................
8.7
Electrostatic Discharge Caution .....................
8.8
Glossary .............................................
7.2
Layout Considerations
77
7.3
Impedance Matching TX_Out (Pin 5) to 50 Ω
77
78
79
79
79
80
80
81
81
81
81
Mechanical, Packaging, and Orderable
Information .............................................. 82
Table of Contents
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2 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from April 18, 2014 to March 27, 2017
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Corrected the designation of ISO/IEC standards throughout document; for example, changed ISO14443 to
ISO/IEC 14443 ........................................................................................................................ 1
Changed the contents of Section 1.3, Description ............................................................................... 1
Added Section 3.1, Related Products ............................................................................................. 7
Moved TSTG from Section 5.2 to Section 5.1, Absolute Maximum Ratings .................................................. 10
Moved Section 5.2 and changed title from Handling Ratings to ESD Ratings .............................................. 10
Added VOL and VOH to Section 5.4, Electrical Characteristics ................................................................ 11
Changed the TYP value of the fD_CLKmax parameter from 8 to 4 MHz in Section 5.4, Electrical Characteristics ....... 11
Throughout document, removed support for application control of Automatic Gain Control (AGC) and Receiver
Gain Adjust, because these features were designed for test functionality and not for production use .................. 13
Added NFC Type 5 tags to supported list in Section 6.1.1, RFID and NFC Operation – Reader and Writer ........... 13
Removed the paragraph that started "The desired system of operation (bit rate) is achieved by..." from
Section 6.1.2, NFC Device Operation – Initiator ................................................................................ 14
Removed the paragraph that started "The desired system of operation (bit rate) is achieved by..." from
Section 6.1.3, NFC Device Operation – Target ................................................................................. 14
Throughout document, changed "tag" emulation or emulator to "card" emulation or emulator ........................... 14
Added the sentence that starts "For interoperability purposes, TI recommends..." in the first bulleted list item in
Section 6.1.3, NFC Device Operation – Target ................................................................................. 15
Changed POLLING to SENSF_REQ in the bulleted list item that starts "If the first command is a
SENSF_REQ..." and deleted the sentence that started "The POLLING response is sent in..." in Section 6.1.3,
NFC Device Operation – Target................................................................................................... 15
Updated the bulleted list item that starts "If the first command is ATR_REQ..." in Section 6.1.3, NFC Device
Operation – Target ................................................................................................................. 15
Changed "coded as ISO14443" to "SENSB_REQ" in the bulleted list item that starts "If the first command is a
SENSB_REQ..." in Section 6.1.3, NFC Device Operation – Target .......................................................... 15
Changed "FeliCa" to "peer-to-peer" in Section 6.1.3.1, Active Target, and Section 6.1.3.2, Passive Target ........... 15
Updated the paragraph that starts "The transmission of a response must occur after RF collision avoidance..." in
Section 6.1.3.1, Active Target .................................................................................................... 15
Updated the paragraph that starts "The transmit system in passive target mode..." in Section 6.1.3.2, Passive
Target ................................................................................................................................. 15
Updated the description in Section 6.1.3.3, Card Emulation .................................................................. 16
Added the sentence that starts "For applications in which the TRF7970A may be subjected..." in the second
paragraph of Section 6.3, Power Supplies ....................................................................................... 16
Changed VDD_A to VDD_X in the last sentence that reads "The VDD_X output current should not exceed 20 mA." in
the NOTE in Analog Supply Regulator: VDD_A ................................................................................... 17
Removed the paragraph that started "The RF power amplifier regulator..." from Digital Supply Regulator: VDD_X .... 17
Changed 250 mV to 400 mV in "...a "Delta Voltage" of 400 mV below VIN..." .............................................. 17
Added the paragraph that starts "As VDD_RF is increased, the system..." in Section 6.3.2, Supply Regulator
Settings .............................................................................................................................. 19
Removed the paragraphs that started "The main receiver also has..." and "By default, the AGC window
comparator..." from Section 6.4.2, Receiver Gain and Filter Stages ........................................................ 22
Changed Table 6-5 to match Table 6-37......................................................................................... 23
Updated Section 6.5, Receiver – Digital Section, to clarify and remove duplicate content................................ 23
Updated the description in Section 6.5.1.2, External RSSI .................................................................... 27
Removed "Equivalent Series Resistance" from Table 6-9, Minimum Crystal Recommendations ........................ 29
Removed mention of 3-wire SPI and replaced "IRQ" with "Slave Select" in the first paragraph of Section 6.10.1,
General Introduction ................................................................................................................ 31
Updated the description of FIFO level interrupts in Section 6.10.1.4, FIFO Operation .................................... 35
Added "but recommended" to "It is optional but recommended to read the FIFO Status register..." in
Section 6.10.3, Reception of Air Interface Data ................................................................................. 37
Changed the title of Section 6.10.4, Data Transmission From MCU to TRF7970A ........................................ 38
Removed the sentence that started "The choice of one of these modes over another..." from Section 6.10.5,
Serial Interface Communication (SPI) ............................................................................................ 38
Updated the paragraph that starts "TI recommends resetting the FIFO after receiving data..." in
Revision History
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SLOS743L – AUGUST 2011 – REVISED MARCH 2017
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Section 6.10.5.1, Serial Interface Mode With Slave Select (SS) ..............................................................
Added the NOTE that starts "An additional direct mode..." in Section 6.10.6, Direct Mode ...............................
Added Section 6.11, TRF7970A Initialization ...................................................................................
Changed the application report that is referenced in Section 6.12, Special Direct Mode for Improved MIFARE™
Compatibility .........................................................................................................................
Changed POLLING to SENSF_REQ and updated description in the list item that starts "If the first command is a
SENSF_REQ..." .....................................................................................................................
Updated the description in the list item that starts "If the first command is ATR_REQ..." .................................
Corrected description of B1 Irq_col in Table 6-18, IRQ Status Register (0x0C) for NFC and Card Emulation
Operation: changed from "(as defined in register 0x01)" to "(as defined in register 0x10)" ..............................
Removed mention of collision avoidance commands from Section 6.13.2, Initiator........................................
Added and updated comments in Table 6-19, Address and Command Word Bit Distribution ............................
Removed command code 0x15, Close Slot Sequence, from Table 6-19, Address and Command Word Bit
Distribution ..........................................................................................................................
Added the sentence that starts "This command should be sent after a Software Initialization command..." in
Section 6.14.1.1, Idle (0x00) .......................................................................................................
Changed the description in Section 6.14.1.3, Initial RF Collision Avoidance (0x04) .......................................
Changed the description in Section 6.14.1.4, Response RF Collision Avoidance (0x05) .................................
Changed the description in Section 6.14.1.5, Response RF Collision Avoidance (0x06, n = 0) .........................
Added "This is used by the ISO/IEC 15693 protocol" to Section 6.14.1.11, Transmit Next Time Slot (0x14) ..........
Corrected description of B1 Irq_col in Table 6-43, IRQ Status Register (0x0C): changed from "(as defined in
register 0x01)" to "(as defined in register 0x10)" ...............................................................................
Changed the description of B5:B3 in Table 6-47 from "...Auxiliary RSSI represents the signal level at RX_IN2" to
"...Auxiliary RSSI represents the signal level at RX_IN1" ......................................................................
Removed former Section 7.1, TRF7970A Reader System Using Parallel Microcontroller Interface .....................
Changed Figure 7-1, Application Schematic – SPI With SS Mode MCU Interface ........................................
Updated the description in Section 7.1.2, Schematic ..........................................................................
Added Section 8.1, Getting Started and Next Steps ...........................................................................
Added Section 8.2, Device Nomenclature .......................................................................................
Added Section 8.3, Tools and Software ..........................................................................................
Updated Section 8.4, Documentation Support ..................................................................................
Revision History
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3 Device Characteristics
Table 3-1 lists the supported modes of operation for the TRF7970A device.
Table 3-1. Supported Modes of Operation
P2P INITIATOR OR READER/WRITER
TECHNOLOGY
BIT RATE
(kbps)
NFC-A and NFC-B
(ISO/IEC 14443 A and B)
(1)
3.1
CARD EMULATION
P2P TARGET
TECHNOLOGY
BIT RATE
(kbps)
TECHNOLOGY
BIT RATE
(kbps)
106, 212, 424,
848 (1)
NFC-A, NFC-B
106
NFC-A
106
NFC-F (JIS: X6319-4)
212, 424
N/A
N/A
NFC-F
212, 424
NFC-V (ISO/IEC 15693)
6.7, 26.7
N/A
N/A
N/A
N/A
848 kbps applies to reader/writer mode only.
Related Products
For information about other devices in this family of products or related products, see the following links.
Products for TI Wireless Connectivity Connect more with the industry’s broadest wireless connectivity
portfolio.
Products for NFC / RFID TI provides one of the industry’s most differentiated NFC and RFID product
portfolios and is your solution to meet a broad range of NFC connectivity and RFID
identification needs.
Companion Products for TRF7970A Review products that are frequently purchased or used with this
product.
Reference Designs for TRF7970A The TI Designs Reference Design Library is a robust reference
design library that spans analog, embedded processor, and connectivity. Created by TI
experts to help you jump start your system design, all TI Designs include schematic or block
diagrams, BOMs, and design files to speed your time to market. Search and download
designs at ti.com/tidesigns.
Device Characteristics
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4 Terminal Configuration and Functions
4.1
Pin Diagram
Figure 4-1 shows the pinout for the 32-pin RHB package.
VDD_X
OSC_IN
OSC_OUT
VSS_D
EN
SYS_CLK
DATA_CLK
EN2
32
31
30
29
28
27
26
25
VDD_A
1
24
I/O_7
VIN
2
23
I/O_6
VDD_RF
3
22
I/O_5
VDD_PA
4
21
I/O_4
TX_OUT
5
20
I/O_3
VSS_PA
6
19
I/O_2
VSS_RX
7
18
I/O_1
RX_IN1
8
17
I/O_0
Pad
11
12
13
14
RX_IN2
VSS
BG
ASK/OOK
IRQ
MOD
15
16
VDD_I/O
10
VSS_A
9
Figure 4-1. 32-Pin RHB Package (Top View)
4.2
Signal Descriptions
Table 4-1 describes the signals.
Table 4-1. Terminal Functions
TERMINAL
NAME
NO.
VDD_A
1
VIN
VDD_RF
TYPE
(1)
DESCRIPTION
OUT
Internal regulated supply (2.7 V to 3.4 V) for analog circuitry
2
SUP
External supply input to chip (2.7 V to 5.5 V)
3
OUT
Internal regulated supply (2.7 V to 5 V), normally connected to VDD_PA (pin 4)
VDD_PA
4
INP
Supply for PA; normally connected externally to VDD_RF (pin 3)
TX_OUT
5
OUT
RF output (selectable output power, 100 mW or 200 mW, with VDD = 5 V)
VSS_PA
6
SUP
Negative supply for PA; normally connected to circuit ground
VSS_RX
7
SUP
Negative supply for RX inputs; normally connected to circuit ground
RX_IN1
8
INP
Main RX input
RX_IN2
9
INP
Auxiliary RX input
VSS
10
SUP
Chip substrate ground
BAND_GAP
11
OUT
Bandgap voltage (VBG = 1.6 V); internal analog voltage reference
ASK/OOK
12
BID
(1)
8
Selection between ASK and OOK modulation (0 = ASK, 1 = OOK) for direct mode 0 or 1.
Can be configured as an output to provide the received analog signal output.
SUP = Supply, INP = Input, BID = Bidirectional, OUT = Output
Terminal Configuration and Functions
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Table 4-1. Terminal Functions (continued)
TERMINAL
NAME
IRQ
NO.
13
TYPE
(1)
DESCRIPTION
OUT
Interrupt request
INP
External data modulation input for direct mode 0 or 1
OUT
Subcarrier digital data output (see registers 0x1A and 0x1B)
MOD
14
VSS_A
15
SUP
Negative supply for internal analog circuits; connected to GND
VDD_I/O
16
INP
Supply for I/O communications (1.8 V to VIN) level shifter. VIN should be never exceeded.
I/O_0
17
BID
I/O pin for parallel communication
I/O_1
18
BID
I/O pin for parallel communication
I/O_2
19
BID
I/O_3
20
BID
I/O_4
21
BID
I/O_5
22
BID
I/O pin for parallel communication
TX enable (in special direct mode)
I/O pin for parallel communication
TX data (in special direct mode)
I/O pin for parallel communication
Slave select signal in SPI mode
I/O pin for parallel communication
Data clock output in direct mode 1 and special direct mode
I/O pin for parallel communication
I/O_6
23
BID
MISO for serial communication (SPI)
Serial bit data output in direct mode 1 or subcarrier signal in direct mode 0
I/O pin for parallel communication.
I/O_7
24
BID
EN2
25
INP
Selection of power down mode. If EN2 is connected to VIN, then VDD_X is active during power
down mode 2 (for example, to supply the MCU).
DATA_CLK
26
INP
Data clock input for MCU communication (parallel and serial)
OUT
If EN = 1 (EN2 = don't care) the system clock for MCU is configured. Depending on the crystal
that is used, options are as follows (see register 0x09):
13.56-MHz crystal: Off, 3.39 MHz, 6.78 MHz, or 13.56 MHz
27.12-MHz crystal: Off, 6.78 MHz, 13.56 MHz, or 27.12 MHz
SYS_CLK
27
MOSI for serial communication (SPI)
If EN = 0 and EN2 = 1, then system clock is set to 60 kHz
EN
28
INP
Chip enable input (If EN = 0, then chip is in sleep or power-down mode).
VSS_D
29
SUP
Negative supply for internal digital circuits
OSC_OUT
30
OUT
Crystal or oscillator output
OSC_IN
31
VDD_X
Thermal Pad
INP
Crystal or oscillator input
OUT
Crystal oscillator output
32
OUT
Internally regulated supply (2.7 V to 3.4 V) for digital circuit and external devices (for example,
an MCU)
PAD
SUP
Chip substrate ground
Terminal Configuration and Functions
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5 Specifications
Absolute Maximum Ratings (1)
5.1
(2)
over operating free-air temperature range (unless otherwise noted)
VIN
Input voltage range
IIN
Maximum current VIN
TJ
Maximum operating virtual junction temperature
TSTG
Storage temperature
(1)
(2)
(3)
5.3
6
UNIT
V
150
mA
Any condition
140
°C
Continuous operation, long-term reliability (3)
125
°C
150
°C
–55
ESD Ratings
V(ESD)
(2)
MAX
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions are not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values are with respect to substrate ground terminal VSS.
The maximum junction temperature for continuous operation is limited by package constraints. Operation above this temperature may
result in reduced reliability or lifetime of the device.
5.2
(1)
MIN
–0.3
Electrostatic discharge
VALUE
UNIT
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins (1)
±2000
V
Charged-device model (CDM), per JEDEC specification JESD22-C101, all
pins (2)
±500
V
Machine model (MM)
±200
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Pins listed as ±2000
V may actually have higher performance.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Pins listed as ±500 V
may actually have higher performance.
Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
TYP
MAX
UNIT
VIN
Operating input voltage
2.7
5
5.5
V
TA
Operating ambient temperature
–40
25
110
°C
TJ
Operating virtual junction temperature
–40
25
125
°C
VIL
Input voltage, logic low
I/O lines, IRQ, SYS_CLK, DATA_CLK,
EN, EN2, ASK/OOK, MOD
VIH
Input voltage threshold, logic high
I/O lines, IRQ, SYS_CLK, DATA_CLK,
EN, EN2, ASK/OOK, MOD
10
Specifications
0.2 ×
VDD_I/O
0.8 ×
VDD_I/O
V
V
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5.4
SLOS743L – AUGUST 2011 – REVISED MARCH 2017
Electrical Characteristics
TYP operating conditions are TA = 25°C, VIN = 5 V, full-power mode (unless otherwise noted)
MIN and MAX operating conditions are over recommended ranges of supply voltage and operating free-air temperature
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
0.2 ×
UNIT
VOL
Low-level output voltage
V
VOH
High-level output voltage
IPD1
Supply current in power down mode 1
All building blocks disabled, including
supply-voltage regulators; measured after
500-ms settling time (EN = 0, EN2 = 0)
0.5
5
µA
IPD2
Supply current in power down mode 2
(sleep mode)
The SYS_CLK generator and VDD_X
remain active to support external circuitry;
measured after 100-ms settling time
(EN = 0, EN2 = 1)
120
200
µA
ISTBY
Supply current in stand-by mode
Oscillator running, supply-voltage
regulators in low-consumption mode
(EN = 1, EN2 = x)
1.9
3.5
mA
ION1
Supply current without antenna driver
current
Oscillator, regulators, RX and AGC
active, TX is off
10.5
14
mA
ION2
Supply current, TX (half power)
Oscillator, regulators, RX and AGC and
TX active, POUT = 100 mW
70
78
mA
ION3
Supply current, TX (full power)
Oscillator, regulators, RX and AGC and
TX active, POUT = 200 mW
130
150
mA
VPOR
Power-on-reset voltage
Input voltage at VIN
1.4
2
2.6
V
VBG
Bandgap voltage (pin 11)
Internal analog reference voltage
1.5
1.6
1.7
V
VDD_A
Regulated output voltage for analog
circuitry (pin 1)
VIN = 5 V
3.1
3.4
3.8
V
VDD_X
Regulated supply for external circuitry
Output voltage pin 32, VIN = 5 V
3.1
3.4
3.8
V
IVDD_Xmax
Maximum output current of VDD_X
Output current pin 32, VIN = 5 V
20
mA
RRFOUT
Antenna driver output resistance
RRFIN
RX_IN1 and RX_IN2 input resistance
VRF_INmax
Maximum RF input voltage at RX_IN1
and RX_IN2
VRF_INmin
VDD_I/O
0.8 ×
VDD_I/O
(1)
V
Half-power mode, VIN = 2.7 V to 5.5 V
8
12
Full-power mode, VIN = 2.7 V to 5.5 V
4
6
10
20
4
VRF_INmax should not exceed VIN
3.5
Minimum RF input voltage at RX_IN1
and RX_IN2 (input sensitivity) (2)
fSUBCARRIER = 424 kHz
1.4
2.5
fSUBCARRIER = 848 kHz
2.1
3
fSYS_CLK
SYS_CLK frequency
In power mode 2, EN = 0, EN2 = 1
60
120
fC
Carrier frequency
Defined by external crystal
tCRYSTAL
Crystal run-in time
Time until oscillator stable bit is set
(register 0x0F) (3)
fD_CLKmax
Maximum DATA_CLK frequency (4)
Depends on capacitive load on the I/O
lines, TI recommends 2 MHz (4)
ROUT
RSYS_CLK
(1)
(2)
(3)
(4)
25
kΩ
Vpp
13.56
mVpp
kHz
MHz
3
2
Ω
ms
4
10
MHz
Output resistance I/O_0 to I/O_7
500
800
Ω
Output resistance RSYS_CLK
200
400
Ω
Antenna driver output resistance
Measured with subcarrier signal at RX_IN1 or RX_IN2 and measured the digital output at MOD pin with register 0x1A bit 6 = 1.
Depends on the crystal parameters and components
TI recommends a DATA_CLK speed of 2 MHz. Higher data clock depends on the capacitive load. Maximum SPI clock speed should not
exceed 10 MHz. This clock speed is acceptable only when external capacitive load is less than 30 pF. MISO driver has a typical output
resistance of 400 Ω (12-ns time constant when 30-pF load used).
Specifications
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5.5
(1)
(2)
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Thermal Resistance Characteristics
PACKAGE
θJC
θJA (1)
RHB (32 pin)
31°C/W
36.4°C/W
POWER RATING (2)
TA ≤ 25°C
TA ≤ 85°C
2.7 W
1.1 W
This data was taken using the JEDEC standard high-K test PCB.
Power rating is determined with a junction temperature of 125°C. This is the temperature at which distortion starts to increase
substantially. Thermal management of the final PCB should strive to keep the junction temperature at or below 125°C for best
performance and long-term reliability.
5.6
Switching Characteristics
TYP operating conditions are TA = 25°C, VIN = 5 V, full-power mode (unless otherwise noted)
MIN and MAX operating conditions are over recommended ranges of supply voltage and operating free-air temperature
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
Depends on capacitive load on the
I/O lines (1)
250
62.5
50
UNIT
tLO/HI
DATA_CLK time high or low, one half of DATA_CLK at
50% duty cycle
tSTE,LEAD
Slave select lead time, slave select low to clock
200
ns
tSTE,LAG
Slave select lag time, last clock to slave select high
200
ns
tSTE,DIS
Slave select disable time, slave select rising edge to
next slave select falling edge
tSU,SI
ns
300
ns
MOSI input data setup time
15
ns
tHD,SI
MOSI input data hold time
15
ns
tSU,SO
MISO input data setup time
15
ns
tHD,SO
MISO input data hold time
15
ns
tVALID,SO
MISO output data valid time
(1)
12
DATA_CLK edge to MISO valid,
CL ≤ 30 pF
30
50
75
ns
TI recommends a DATA_CLK speed of 2 MHz. Higher data clock depends on the capacitive load. Maximum SPI clock speed should not
exceed 10 MHz. This clock speed is acceptable only when external capacitive load is less than 30 pF. MISO driver has a typical output
resistance of 400 Ω (12-ns time constant when 30-pF load used).
Specifications
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6 Detailed Description
6.1
6.1.1
Overview
RFID and NFC Operation – Reader and Writer
The TRF7970A is a high-performance 13.56-MHz HF RFID and NFC transceiver IC composed of an
integrated analog front end (AFE) and a built-in data framing engine for ISO/IEC 15693, ISO/IEC 14443 A
and B, and FeliCa. This includes data rates up to 848 kbps for ISO/IEC 14443 with all framing and
synchronization tasks on board (in default mode). The TRF7970A also supports NFC tag type 1, 2, 3, 4,
and 5 operations. This architecture lets the customer build a complete cost-effective yet high-performance
multiprotocol 13.56-MHz RFID and NFC system together with a low-cost microcontroller.
Other standards and even custom protocols can be implemented by using either of the direct modes that
the device offers. These direct modes (0 and 1) allow the user to fully control the analog front end (AFE)
and also gain access to the raw subcarrier data or the unframed but already ISO formatted data and the
associated (extracted) clock signal.
The receiver system has a dual input receiver architecture. The receivers also include various automatic
and manual gain control options. The received input bandwidth can be selected to cover a broad range of
input subcarrier signal options.
The received signal strength from transponders, ambient sources, or internal levels is available through
the RSSI register. The receiver output is selectable among a digitized subcarrier signal and any of the
integrated subcarrier decoders. The selected subcarrier decoder delivers the data bit stream and the data
clock as outputs.
The TRF7970A also includes a receiver framing engine. This receiver framing engine performs the CRC
or parity check, removes the EOF and SOF settings, and organizes the data in bytes for ISO/IEC 14443 A
and B, ISO/IEC 15693, and FeliCa protocols. Framed data is then accessible to the microcontroller (MCU)
through a 127-byte FIFO register.
VDD
VDD_X
VDD
VDD_I/O
TX_OUT
Matching
TRF7970A
RX_IN 1
RX_IN2
VSS
Crystal
13.56 MHz
MCU
(MSP430 or ARM)
Parallel
or SPI
VIN
XIN
Supply: 2.7 V to 5.5 V
Figure 6-1. Application Block Diagram
A parallel or serial interface (SPI) can be used for the communication between the MCU and the
TRF7970A reader. When the built-in hardware encoders and decoders are used, transmit and receive
functions use a 127-byte FIFO register. For direct transmit or receive functions, the encoders and
decoders can be bypassed so that the MCU can process the data in real time. The TRF7970A supports
data communication voltage levels from 1.8 V to 5.5 V for the MCU I/O interface. The transmitter has
selectable output-power levels of 100 mW (+20 dBm) or 200 mW (+23 dBm) equivalent into a 50-Ω load
when using a 5-V supply.
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The transmitter supports OOK and ASK modulation with selectable modulation depth. The TRF7970A also
includes a data transmission engine that comprises low-level encoding for ISO/IEC 15693, ISO/IEC 14443
A and B, and FeliCa. Included with the transmit data coding is the automatic generation of Start Of Frame
(SOF), End Of Frame (EOF), Cyclic Redundancy Check (CRC), and parity bits.
Several integrated voltage regulators ensure a proper power-supply noise rejection for the complete
reader system. The built-in programmable auxiliary voltage regulator VDD_X (pin 32), is able to deliver up to
20 mA to supply a microcontroller and additional external circuits within the reader system.
6.1.2
NFC Device Operation – Initiator
The transmitting system includes an RF level detector (programmable level) which is used for initial (or
response) RF collision avoidance. The RF collision avoidance sequence is started by sending a direct
command. If successful, the NFC initiator can send the data or commands, the MCU has loaded in the
FIFO register. The coding of this data is done by hardware coders in ISO/IEC 14443 A and B, or FeliCa
format. The coders also provide CRC and parity bits (if required) and automatically add preambles, SOF,
EOF, and synchronization bytes as defined by selected protocol.
The receiver system offers the same analog features (AGC, AM or PM, bandwidth selection, and so on)
as described previously in RFID and NFC reader and writer description. The system comprises integrated
decoders for passive targets (ISO/IEC 14443 A or ISO/IEC 14443 B tag or FeliCa) or active targets
(ISO/IEC 14443 A or ISO/IEC 14443 B reader or FeliCa). For all this options, the system also supports
framing including CRC and parity check and removal of SOF, EOF, and synchronization bytes as
specified by the selected protocol.
6.1.3
NFC Device Operation – Target
The activation of NFC target is done when a sufficient RF field level is detected on the antenna. The level
needed for wake-up is selectable and is stored in a nonvolatile register.
When the activation occurs, the system performs automatic power-up and waits for the first command to
be received. Based on this command, the system knows if it should operate as passive or active target
and at what bit rate. After activation, the receiver system offers the same analog features (for example,
AGC, AM/PM, and bandwidth selection) as in the case of an RFID reader.
When used as the NFC target, the chip is typically in a power down or standby mode. If EN2 = H, the chip
keeps the supply system on. If EN2 = L and EN = L, the chip is in complete power down. To operate as
NFC target or card emulator, the MCU must load a value different from zero (0) in the Target Detection
Level register (B0-B2) to enable the RF measurement system (supplied by VEXT, so it can also operate
during complete power down and consume only 3.5 µA). The RF measurement constantly monitors the
RF signal on the antenna input. When the RF level on the antenna input exceeds the level defined in the
in Target Detection Level register, the chip is automatically activated (EN is internally forced high).
When the voltage supply system and the oscillator are started and are stable, osc_ok goes high (B6 of
RSSI Level and Oscillator Status register) and IRQ is sent with bit B2 = 1 of IRQ register (field change).
Bit B7 NFC Target Protocol in register directly displays the status of RF level detection (running constantly
also during normal operation). This informs the MCU that the chip should start operation as NFC TARGET
device. When the first command from the INITIATOR is received, another IRQ sent with B6 (RX start) set
in the IRQ register. The MCU must set EN = H (confirm the power up) in the time between the two IRQs,
because the internal power-up ends after the second IRQ. The type and coding of the first initiator (or
reader in the case of a card emulator) command defines the communication protocol type that the target
must use. Therefore, the communication protocol type is available in the NFC Target Protocol register
immediately after receiving the first command.
14
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Based on the first command from the INITIATOR, the following actions are taken:
• If the first command is SENS_REQ or ALL_REQ, the TARGET must enter the SDD protocol for 106kbps passive communication to begin; afterward, the baud rate can be changed to 212 kbps or 424
kbps, which is determined by the NFC initiator device. If bit B5 in the NFC Target Detection Level
register is not set, the MCU handles the SDD and the command received is send to FIFO. For
interoperability purposes, TI recommends allowing the MCU to handle the SDD process rather than
use the TRF7970A Auto-SDD feature to ensure interoperability with other NFC devices. If the RF field
is turned off (B7 in NFC Target Protocol register is low) at any time, the system sends an IRQ to the
MCU with bit B2 (RF field change) in the IRQ register set high. This informs the MCU that the
procedure was aborted and the system must be reset. The clock extractor is automatically activated in
this mode.
• If the command is SENS_REQ or ALL_REQ and the card emulation bit in ISO Control register is set,
the system emulates an ISO/IEC 14443 A or ISO/IEC 14443 B tag. The procedure does not differ from
the one previously described for the case of a passive target at 106 kbps. The clock extractor is
automatically activated in this mode.
• If the first command is a SENSF_REQ, the system becomes the TARGET in passive communication
using 212 kbps or 424 kbps. The SDD is relatively simple and is handled by the MCU directly.
• If the first command is ATR_REQ, the system operates as an active TARGET using the same
communication speed and bit coding as used by the INITIATOR. Again, all of the replies are handled
by the MCU. The MCU should handle the timing requirements for collision avoidance. This is done by
using external RSSI to detect external RF fields before enabling RF on the TRF7970A.
• If the first command is a SENSB_REQ request and the card emulation bit is set in the ISO Control
register, the system enters ISO/IEC 14443 B emulation mode. The anticollision must be handled by the
MCU, and the chip provides all physical level coding, decoding, and framing for this protocol.
6.1.3.1
Active Target
If the first command received by the RF interface defines the system as an active target, then the receiver
selects the appropriate data decoders (ISO/IEC 14443 A or ISO/IEC 14443 B reader or peer-to-peer) and
framing option. Only the raw (decoded) data is forwarded to the MCU through the FIFO. SOF, EOF,
preamble, sync bytes, CRC, and parity bytes are checked by the framer and discarded.
The transmission of a response must occur after RF collision avoidance has been processed. The
recommended method for RF collision avoidance is to use external RSSI to detect any external RF field. If
successful, the NFC initiator can send the data that the MCU has loaded in the FIFO register. The coding
of this data is done by hardware coders either in ISO/IEC 14443 A format (106-kbps system) or in peer-topeer format for (212-kbps and 424-kbps systems). The coders also provide CRC and parity bits (if
required) and automatically add preambles, SOF, EOF, and synchronization bytes as defined by selected
protocol.
6.1.3.2
Passive Target
If the first command received by the RF interface defines the system as a passive target, then the receiver
selects the appropriate data decoders (ISO/IEC 14443 A or ISO/IEC 14443 B reader or peer-to-peer) and
framing option. Again, only the raw (decoded) data is forwarded to the MCU through the FIFO; SOF, EOF,
preamble, sync bytes, CRC, and parity bytes are checked by the framer and discarded. The receiver
works same as in the case of an active target.
The transmit system in passive target mode differs from active target and operates similar to the standard
tag. There is no RF collision avoidance sequence, and encoders are used to code the data for
ISO/IEC 14443 A or ISO/IEC 14443 B tag (at 106 kbps, to start) or peer-to-peer (at 212 kbps, to start)
format. The coding system adds all of the SOF, EOF, CRC, parity bits, and synchronization bytes that are
required by protocol. The response is transmitted over-the-air with a method known as load modulation.
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6.1.3.3
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Card Emulation
The chip can enter this mode by setting appropriate option bits. The chip can emulate ISO/IEC 14443 A
and B card types. For ISO/IEC 14443 A and B, the emulation supports 106-kbps data rate to start. For
ISO/IEC 14443 A, the anticollision algorithm can be performed using an internal state machine, which
relieves the MCU of any real-time tasks; however, this method can present interoperability challenges with
other NFC devices due to timing requirements. To ensure best interoperability, TI recommends allowing
the MCU to manage the anticollision process, instead. The unique ID required for anticollision is provided
by the MCU after wakeup of the system.
6.2
System Block Diagram
Figure 6-2 shows a block diagram of the TRF7970A.
VDD_I/O
MUX
Phase and
Amplitude
Detector
RX_IN1
Gain
Logic
I/O_0
State
Control
Logic
I/O_1
(Control
Registers and
Command
Logic)
I/O_3
RSSI
(AUX)
RF Level
Detector
RSSI
(External)
RX_IN2
Gain
Filter
and AGC
Digitizer
MCU
Interface
VDD_PA
ISO
Protocol
Handling
Transmitter
Analog Front End
TX_OUT
Bit
Framing
127-Byte
FIFO
I/O_5
I/O_6
I/O_7
SYS_CLK
DATA_CLK
VIN
Serial
Conversion
CRC and Parity
VSS_PA
I/O_4
IRQ
Decoder
Framing
Level Shifter
Phase and
Amplitude
Detector
RSSI
(Main)
I/O_2
VDD_A
BAND_GAP
EN
VSS_A
EN2
Digital Control
State Machine
ASK/OOK
MOD
VDD_RF
Voltage Supply Regulator Systems
(Supply Regulators and Reference Voltages)
VSS_RF
VDD_X
OSC_IN
OSC_OUT
VSS
Crystal or Oscillator
Timing System
VSS_D
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Figure 6-2. System Block Diagram
6.3
Power Supplies
The TRF7970A positive supply input VIN (pin 2) sources three internal regulators with output voltages
VDD_RF, VDD_A and VDD_X. All regulators use external bypass capacitors for supply noise filtering and must
be connected as indicated in reference schematics. These regulators provide a high power supply reject
ratio (PSRR) as required for RFID reader systems. All regulators are supplied by VIN (pin 2).
The regulators are not independent and have common control bits in register 0x0B for output voltage
setting. The regulators can be configured to operate in either automatic or manual mode (register 0x0B,
bit 7). The automatic regulator setting mode ensures an optimal compromise between PSRR and the
highest possible supply voltage for RF output (to ensure maximum RF power output). The manual mode
allows the user to manually configure the regulator settings. For applications in which the TRF7970A may
be subjected to external noise, manually reducing the regulator settings can improve RF performance.
16
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6.3.1
SLOS743L – AUGUST 2011 – REVISED MARCH 2017
Supply Arrangements
Regulator Supply Input: VIN
The positive supply at VIN (pin 2) has an input voltage range of 2.7 V to 5.5 V. VIN provides the supply
input sources for three internal regulators with the output voltages VDD_RF, VDD_A, and VDD_X. External
bypass capacitors for supply noise filtering must be used (per reference schematics).
NOTE
VIN must be the highest voltage supplied to the TRF7970A.
RF Power Amplifier Regulator: VDD_RF
The VDD_RF (pin 3) regulator is supplying the RF power amplifier. The voltage regulator can be set for
either 5-V or 3-V operation. External bypass capacitors for supply noise filtering must be used (per
reference schematics). When configured for 5-V manual-operation, the VDD_RF output voltage can be set
from 4.3 V to 5 V in 100-mV steps. In 3-V manual-operation, the output can be programmed from 2.7 V to
3.4 V in 100-mV steps. The maximum output current capability for 5-V operation is 150 mA and for 3-V
operation is 100 mA.
Analog Supply Regulator: VDD_A
Regulator VDD_A (pin 1) supplies the analog circuits of the device. The output voltage setting depends on
the input voltage and can be set for 5-V and 3-V operation. When configured for 5-V manual-operation,
the output voltage is fixed at 3.4 V. External bypass capacitors for supply noise filtering must be used (per
reference schematics). When configured for 3-V manual-operation, the VDD_A output can be set from 2.7 V
to 3.4 V in 100-mV steps (see Table 6-2).
NOTE
The configuration of VDD_A and VDD_X regulators are not independent from each other. The
VDD_X output current should not exceed 20 mA.
Digital Supply Regulator: VDD_X
The digital supply regulator VDD_X (pin 32) provides the power for the internal digital building blocks and
can also be used to supply external electronics within the reader system. When configured for 3-V
operation, the output voltage can be set from 2.7 to 3.4 V in 100-mV steps. External bypass capacitors for
supply noise filtering must be used (per reference schematics).
NOTE
The configuration of the VDD_A and VDD_X regulators are not independent from each other.
The VDD_X output current should not exceed 20 mA.
By default, the regulators are set in automatic regulator setting mode. In this mode, the regulators are
automatically set every time the system is activated by setting EN input High or each time the automatic
regulator setting bit, B7 in register 0x0B is set to a 1. The action is started on the 0 to 1 transition. This
means that, if the user wants to rerun the automatic setting from a state in which the automatic setting bit
is already high, the automatic setting bit (B7 in register 0x0B) should be changed: 1-0-1.
By default, the regulator setting algorithm sets the regulator outputs to a "Delta Voltage" of 400 mV below
VIN, but not higher than 5 V for VDD_RF and 3.4 V for VDD_A and VDD_A.
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Power Amplifier Supply: VDD_PA
The power amplifier of the TRF7970A is supplied through VDD_PA (pin 4). The positive supply pin for the
RF power amplifier is externally connected to the regulator output VDD_RF (pin 3).
I/O Level Shifter Supply: VDD_I/O
The TRF7970A has a separate supply input VDD_I/O (pin 16) for the built-in I/O level shifter. The supported
input voltage ranges from 1.8 V to VIN, not exceeding 5.5 V. Pin 16 is used to supply the I/O interface pins
(I/O_0 to I/O_7), IRQ, SYS_CLK, and DATA_CLK pins of the reader. In typical applications, VDD_I/O is
directly connected to VDD_X, while VDD_X also supplies the MCU. This ensures that the I/O signal levels of
the MCU match the logic levels of the TRF7970A.
Negative Supply Connections: VSS, VSS_TX, VSS_RX, VSS_A, VSS_PA
The negative supply connections VSS_X of each functional block are all externally connected to GND.
The substrate connection is VSS (pin 10), the analog negative supply is VSS_A (pin 15), the logic negative
supply is VSS_D (pin 29), the RF output stage negative supply is VSS_PA (pin 6), and the negative supply for
the RF receiver VSS_RX (pin 7).
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6.3.2
SLOS743L – AUGUST 2011 – REVISED MARCH 2017
Supply Regulator Settings
The input supply voltage mode of the reader needs to be selected. This is done in the Chip Status Control
register (0x00). Bit 0 in register 0x00 selects between 5-V or 3-V input supply voltage. The default
configuration is 5 V, which reflects an operating supply voltage range of 4.3 V to 5.5 V. If the supply
voltage is below 4.3 V, the 3-V configuration should be used.
As VDD_RF is increased, the system can become more susceptible to noise coupling on the RX lines. For
minimum noise coupling, TI recommends using the value of 0x00. For improved range, higher VDD_RF
voltages may be set, but complete system testing is required to determine the value which provides
optimal performance.
The various regulators can be configured to operate in automatic or manual mode. This is done in the
Regulator and I/O Control register (0x0B), as shown in Table 6-1 and Table 6-2.
Table 6-1. Supply Regulator Setting: 5-V System
REGISTER
ADDRESS
(hex)
OPTION BITS SETTING IN REGULATOR CONTROL REGISTER
B7
(1)
COMMENTS
B6
B5
B4
B3
B2
B1
B0
1
x
x
x
x
x
0
0
Automatic regulator setting 400-mV difference
0B
0
x
x
x
x
1
1
1
VDD_RF = 5 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
1
1
0
VDD_RF = 4.9 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
1
0
1
VDD_RF = 4.8 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
1
0
0
VDD_RF = 4.7 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
0
1
1
VDD_RF = 4.6 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
0
1
0
VDD_RF = 4.5 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
0
0
1
VDD_RF = 4.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
0
0
0
VDD_RF = 4.3 V, VDD_A = 3.4 V, VDD_X = 3.4 V
Automatic Mode (default)
0B
Manual Mode
(1)
x = Don't care
Table 6-2. Supply Regulator Setting: 3-V System
REGISTER
ADDRESS
(hex)
OPTION BITS SETTING IN REGULATOR CONTROL REGISTER
B7
(1)
COMMENTS
B6
B5
B4
B3
B2
B1
B0
1
x
x
x
x
x
0
0
Automatic regulator setting 400-mV difference
0B
0
x
x
x
x
1
1
1
VDD_RF = 3.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
x
x
x
x
1
1
0
VDD_RF = 3.3 V, VDD_A = 3.3 V, VDD_X = 3.3 V
0B
0
x
x
x
x
1
0
1
VDD_RF = 3.2 V, VDD_A = 3.2 V, VDD_X = 3.2 V
0B
0
x
x
x
x
1
0
0
VDD_RF = 3.1 V, VDD_A = 3.1 V, VDD_X = 3.1 V
0B
0
x
x
x
x
0
1
1
VDD_RF = 3.0 V, VDD_A = 3.0 V, VDD_X = 3.0 V
0B
0
x
x
x
x
0
1
0
VDD_RF = 2.9 V, VDD_A = 2.9 V, VDD_X = 2.9 V
0B
0
x
x
x
x
0
0
1
VDD_RF = 2.8 V, VDD_A = 2.8 V, VDD_X = 2.8 V
0B
0
x
x
x
x
0
0
0
VDD_RF = 2.7 V, VDD_A = 2.7 V, VDD_X = 2.7 V
Automatic Mode (default)
0B
Manual Mode
(1)
x = Don't care
The regulator configuration function adjusts the regulator outputs by default to 400 mV below VIN level, but
not higher than 5 V for VDD_RF, 3.4 V for VDD_A and VDD_X. This ensures the highest possible supply
voltage for the RF output stage while maintaining an adequate PSRR (power supply rejection ratio).
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6.3.3
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Power Modes
The chip has several power states, which are controlled by two input pins (EN and EN2) and several bits
in the chip status control register (0x00) (see Table 6-3 and Table 6-4).
Table 6-3. 3.3-V Operation Power Modes (1)
EN2
EN
CHIP
STATUS
CONTROL
REGISTER
(0x00)
REGULATOR
CONTROL
REGISTER
(0x0B)
TRANSMITTER
RECEIVER
SYS_CLK
(13.56 MHz)
SYS_CLK
(60 kHz)
VDD_X
Power down
0
0
XX
XX
OFF
OFF
OFF
OFF
OFF
<0.001
-
Sleep mode
1
0
XX
XX
OFF
OFF
OFF
ON
ON
0.120
-
Standby mode at +3.3 VDC
X
1
80
00
OFF
OFF
ON
X
ON
2
-
Mode 1 at +3.3 VDC
X
1
00
00
OFF
OFF
ON
X
ON
3
-
Mode 2 at +3.3 VDC
X
1
02
00
OFF
ON
ON
X
ON
9
-
Mode 3 (half power) at
+3.3 VDC
X
1
30
07
ON
ON
ON
X
ON
53
14.5
Mode 4 (full power) at
+3.3 VDC
X
1
20
07
ON
ON
ON
X
ON
67
17
MODE
(1)
TYPICAL
TYPICAL
CURRENT
POWER
(mA)
OUT (dBm)
X = Don't care
Table 6-4. 5-V Operation Power Modes (1)
EN2
EN
CHIP
STATUS
CONTROL
REGISTER
(0x00)
REGULATOR
CONTROL
REGISTER
(0x0B)
TRANSMITTER
RECEIVER
SYS_CLK
(13.56 MHz)
SYS_CLK
(60 kHz)
VDD_X
Power down
0
0
XX
XX
OFF
OFF
OFF
OFF
OFF
<0.001
-
Sleep mode
1
0
XX
XX
OFF
OFF
OFF
ON
ON
0.120
-
Standby mode at +5 VDC
X
1
81
07
OFF
OFF
ON
X
ON
3
-
Mode 1 at +5 VDC
X
1
01
07
OFF
OFF
ON
X
ON
5
-
Mode 2 at +5 VDC
X
1
03
07
OFF
ON
ON
X
ON
10.5
-
Mode 3 (half power) at
+5 VDC
X
1
31
07
ON
ON
ON
X
ON
70
20
Mode 4 (full power) at
+5 VDC
X
1
21
07
ON
ON
ON
X
ON
130
23
MODE
(1)
TYPICAL
TYPICAL
CURRENT
POWER
(mA)
OUT (dBm)
X = Don't care
Table 6-3 and Table 6-4 show the configuration for the different power modes when using a 3.3-V or 5-V
system supply, respectively. The main reader enable signal is pin EN. When EN is set high, all of the
reader regulators are enabled, the 13.56-MHz oscillator is running and the SYS_CLK (output clock for
external microcontroller) is also available.
The input pin EN2 has two functions:
• A direct connection from EN2 to VIN to ensure the availability of the regulated supply VDD_X and an
auxiliary clock signal (60 kHz, SYS_CLK) for an external MCU. This mode (EN = 0, EN2 = 1) is
intended for systems in which the MCU is also being supplied by the reader supply regulator (VDD_X)
and the MCU clock is supplied by the SYS_CLK output of the reader. This allows the MCU supply and
clock to be available during sleep mode.
• EN2 enables the start-up of the reader system from complete power down (EN = 0, EN2 = 0). In this
case the EN input is being controlled by the MCU (or other system device) that is without supply
voltage during complete power down (thus unable to control the EN input). A rising edge applied to the
EN2 input (which has an approximately 1-V threshold level) starts the reader supply system and 13.56MHz oscillator (identical to condition EN = 1).
When user MCU is controlling EN and EN2, a delay of 1 ms between EN and EN2 must be used. If the
MCU controls only EN, TI recommends connecting EN2 to either VIN or GND, depending on the
application MCU requirements for VDD_X and SYS_CLK.
20
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VIN
SS
EN2
EN
2 ms
5 ms
6 ms
Figure 6-3. Nominal Start-up Sequence Using SPI With SS (MCU Controls EN2)
VIN
5 ms
EN2
EN
6 ms
Figure 6-4. Nominal Start-up Sequence Using Parallel (MCU Controls EN2)
This start-up mode lasts until all of the regulators have settled and the 13.56-MHz oscillator has stabilized.
If the EN input is set high (EN = 1) by the MCU (or other system device), the reader stays active. If the EN
input is not set high (EN = 0) within 100 µs after the SYS_CLK output is switched from auxiliary clock (60
kHz) to high-frequency clock (derived from the crystal oscillator), the reader system returns to complete
Power-Down Mode 1. This option can be used to wake-up the reader system from complete Power Down
(PD Mode 1) by using a pushbutton switch or by sending a single pulse.
After the reader EN line is high, the other power modes are selected by control bits within the chip status
control register (0x00). The power mode options and states are listed in Table 6-3.
When EN is set high (or on rising edge of EN2 and then confirmed by EN = 1) the supply regulators are
activated and the 13.56-MHz oscillator is started. When the supplies are settled and the oscillator
frequency is stable, the SYS_CLK output is switched from the auxiliary frequency of 60 kHz to the 13.56MHz frequency derived from the crystal oscillator. At this point, the reader is ready to communicate and
perform the required tasks. When this occurs, osc_ok (B6) of the RSSI Level and Oscillator Status register
is set. The MCU can then program the Chip Status Control register 0x00 and select the operation mode
by programming the additional registers.
• Standby Mode (bit 7 = 1 of register 0x00), the reader is capable of recovering to full operation in
100 µs.
• Mode 1 (active mode with RF output disabled, bit 5 = 0 and bit 1 = 0 of register 0x00) is a low power
mode which allows the reader to recover to full operation within 25 µs.
• Mode 2 (active mode with only the RF receiver active, bit 1 = 1 of register 0x00) can be used to
measure the external RF field (as described in RSSI measurements paragraph) if reader-to-reader
anticollision is implemented.
• Modes 3 and 4 (active modes with the entire RF section active, bit 5 = 1 of register 0x00) are the
normal modes used for normal transmit and receive operations.
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6.4
6.4.1
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Receiver – Analog Section
Main and Auxiliary Receivers
The TRF7970A has two receiver inputs: RX_IN1 (pin 8) and RX_IN2 (pin 9). Each of the input is
connected to an external capacitive voltage divider to ensure that the modulated signal from the tag is
available on at least one of the two inputs. This architecture eliminates any possible communication holes
that may occur from the tag to the reader.
The two RX inputs (RX_IN1 and RX_IN2) are multiplexed into two receivers - the main receiver and the
auxiliary receiver. Only the main receiver is used for reception, the auxiliary receiver is used for signal
quality monitoring. Receiver input multiplexing is controlled by bit B3 in the Chip Status Control register
(address 0x00).
After start-up, RX_IN1 is multiplexed to the main receiver which is composed of an RF envelope detection,
first gain and band-pass filtering stage, second gain and filtering stage with AGC. Only the main receiver
is connected to the digitizing stage which output is connected to the digital processing block. The main
receiver also has an RSSI measuring stage, which measures the strength of the demodulated signal
(subcarrier signal).
The primary function of the auxiliary receiver is to monitor the RX signal quality by measuring the RSSI of
the demodulated subcarrier signal (internal RSSI). After start-up, RX_IN2 is multiplexed to the auxiliary
receiver. The auxiliary receiver has an RF envelope detection stage, first gain and filtering with AGC stage
and finally the auxiliary RSSI block.
The default MUX setting is RX_IN1 connected to the main receiver and RX_IN2 connected to the auxiliary
receiver. To determine the signal quality, the response from the tag is detected by the "main" (pin RX_IN1)
and "auxiliary" (pin RX_IN2) RSSI. Both values measured and stored in the RSSI Levels and Oscillator
Status register (address 0x0F). The MCU can read the RSSI values from the TRF7970A RSSI register
and make the decision if swapping the input- signals is preferable or not. Setting B3 in Chip Status Control
register (address 0x00) to 1 connects RX_IN1 (pin 8) to the auxiliary received and RX_IN2 (pin 9) to the
main receiver.
The main and auxiliary receiver input stages are RF envelope detectors. The RF amplitude at RX_IN1 and
RX_IN2 should be approximately 3 VPP for a VINsupply level greater than 3.3 V. If the VIN level is lower,
the RF input peak-to-peak voltage level should not exceed the VINlevel.
6.4.2
Receiver Gain and Filter Stages
The first gain and filtering stage has a nominal gain of 15 dB with an adjustable band-pass filter. The
band-pass filter has programmable 3-dB corner frequencies between 110 kHz to 450 kHz for the highpass filter and 570 kHz to 1500 kHz for the low-pass filter. After the band-pass filter, there is another gainand-filtering stage with a nominal gain of 8 dB and with frequency characteristics identical to the first bandpass stage.
The internal filters are configured automatically depending on the selected ISO communication standard in
the ISO Control register (address 0x01). If required, additional fine tuning can be done by writing directly
to the RX Special Setting registers (address 0x0A).
Table 6-5 shows the various settings for the receiver analog section. Setting B4, B5, B6, and B7 to 0
results in a band-pass characteristic of 240 kHz to 1.4 MHz, which is appropriate for ISO/IEC 14443 B
106 kbps, ISO/IEC 14443 A and B data rates of 212 kbps and 424 kbps, and FeliCa 424 kbps.
22
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Table 6-5. RX Special Setting Register (0x0A)
Function: Sets the gains and filters directly
Default: 0x40 at POR = H or EN = L, and at each write to the ISO Control register (0x01). When bits B7, B6, B5 and B4 are all zero, the
filters are set for ISO/IEC 14443 B (240 kHz to 1.4 MHz).
Bit
Name
B7
C212
Band-pass 110 kHz to 570 kHz
Appropriate for 212-kHz subcarrier system (FeliCa)
B6
C424
Band-pass 200 kHz to 900 kHz
Appropriate for 424-kHz subcarrier used in ISO/IEC 15693
B5
M848
Band-pass 450 kHz to 1.5 MHz
Appropriate for Manchester-coded 848-kHz subcarrier used in
ISO/IEC 14443 A and B
B4
hbt
Band-pass 100 kHz to 1.5 MHz
Gain reduced for 18 dB
Appropriate for highest bit rate (848 kbps) used in high-bit-rate
ISO/IEC 14443
B3
gd1
B2
gd2
00
01
10
11
Sets the RX gain reduction and reduces sensitivity
B1
Reserved
B0
Reserved
6.5
Function
= Gain
= Gain
= Gain
= Gain
reduction
reduction
reduction
reduction
Description
0 dB
for 5 dB
for 10 dB
for 15 dB
Receiver – Digital Section
The output of the TRF7970A analog receiver block is a digitized subcarrier signal and is the input to the
digital receiver block, which consists of two sections that partly overlap. The digitized subcarrier signal is a
digital representation of the modulation signal on the RF envelope. The two sections of the digital receiver
block are the protocol bit decoder section and the framing logic section.
The protocol bit decoder section converts the subcarrier coded signal into a serial bit stream and a data
clock. The decoder logic is designed for maximum error tolerance. This tolerance lets the decoder section
successfully decode even partly corrupted subcarrier signals that would otherwise be lost due to noise or
interference.
The framing logic section formats the serial bit stream data from the protocol bit decoder stage into data
bytes. During the formatting process, special signals such as the start of frame (SOF), end of frame
(EOF), start of communication, and end of communication are automatically removed. The parity bits and
CRC bytes are also checked and removed. The end result is "clean or raw" data that is sent to the 127byte FIFO register where it can be read by the external microcontroller system. Providing the data this
way, in conjunction with the timing register settings of the TRF7970A, means that the firmware developer
does not need to know the finer details of the ISO protocols to create a very robust application, especially
in low-cost platforms in which code space is at a premium and high performance is still required.
The start of the receive operation (successfully received SOF) sets the IRQ flags in the IRQ Status
register (0x0C). The end of the receive operation is signaled to the external system MCU by setting pin 13
(IRQ) to high. When data is received in the FIFO, an interrupt is sent to the MCU to signal that there is
data to be read from the FIFO. The FIFO Status register (0x1C) should be used to provide the number of
bytes that should be clocked out during the actual FIFO read. Additionally, an interrupt is sent to the MCU
when the received data occupies 75% of the FIFO capacity to signal that the data should be removed
from the FIFO. By default, that interrupt is triggered once the received data packet is longer than 124
bytes. This setting can be modified in the Adjustable FIFO IRQ Levels register (0x14).
Any error in the data format, parity, or CRC is detected and notified to the external system by setting pin
13 (IRQ) to high. The source condition of the interrupt is available in the IRQ Status register (0x0C).
Section 6.15.3.3.1 describes the bit coding description of this register. The information in the IRQ Status
register differs if the chip is configured as an RFID reader or as an NFC device (including card emulation).
Section 6.13 describes NFC operation.
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The framing section also supports bit-collision detection as specified in ISO/IEC 14443 A and
ISO/IEC 15693. When a bit collision is detected, an interrupt request is sent and a flag is set in the IRQ
Status register (0x0C). For ISO/IEC 14443 A specifically, the position of the bit collision is written in two
registers: partly in the Collision Position register (0x0E) and partly in the Collision Position and Interrupt
Mask register (0x0D) (bits B6 and B7).
This collision position is presented as sequential bit number, where the count starts immediately after the
start bit. This means a collision in the first bit of a UID would give the value 00 0001 0000 in these
registers when their contents are combined after being read (the count starts with 0 and the first 16 bits
are the command code and the number of valid bits [NVB] byte).
The receive section also contains two timers.
The RX wait time timer is controlled by the value in the RX Wait Time register (0x08). This timer defines
the time interval after the end of the transmit operation during which the receive decoders are not active
(held in reset state). This prevents false detections resulting from transients following the transmit
operation. The value of the RX Wait Time register (0x08) defines the time in increments of 9.44 µs. This
register is preset at every write to the ISO Control register (0x01) according to the minimum tag response
time defined by each standard.
The RX no response timer is controlled by the RX No Response Wait Time register (0x07). This timer
measures the time from the start of the slot in the anticollision sequence until the start of tag response. If
there is no tag response in the defined time, an interrupt request is sent and a flag is set in the IRQ Status
register (0x0C). This enables the external controller to be relieved of the task of detecting empty slots. The
wait time is stored in the register in increments of 37.76 µs. This register is also preset automatically for
every new protocol selection.
The main register controlling the digital part of the receiver is the ISO Control register (0x01). By writing to
this register, the user selects the protocol to be used. With each new write in this register, all related
registers are preset to their defaults for the protocol, so no further adjustments in other registers are
needed for proper operation. Table 6-6 describes the bit fields of the ISO Control register (0x01).
NOTE
If changes to other registers are needed to fine-tune the system, those changes must be
made after setting the ISO Control register (0x01).
24
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Table 6-6. Coding of the ISO Control Register
BIT
SIGNAL NAME
B7
rx_crc_n
FUNCTION
COMMENTS
1 = No RX CRC
Receiving without CRC
0 = RX CRC
B6
dir_mode
0 = Output is subcarrier data
Direct mode type
1 = Output is bit stream and clock from decoder selected by ISO bits
B5
rfid
0 = RFID reader mode
RFID mode
1 = NFC or card emulator mode
RFID: Mode selection
B4
iso_4
NFC:
RFID protocol, NFC target
0 = NFC target
1 = NFC initiator
RFID: Mode selection (see Table 6-7)
B3
iso_3
NFC:
RFID protocol, NFC mode
0 = Passive mode
1 = Active mode
RFID: Mode selection
B2
iso_2
RFID protocol, Card Emulation
NFC:
0 = NFC normal modes
1 = Card emulation mode
B1
iso_1
RFID protocol, NFC bit rate
RFID: Mode selection
NFC: Bit rate selection or Card Emulation selection (see Table 6-8)
B0
iso_0
RFID protocol, NFC bit rate
RFID: Mode selection
NFC: Bit rate selection or Card Emulation selection (see Table 6-8)
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Table 6-7. Coding of the ISO Control Register For RFID Mode (B5 = 0)
Iso_4
Iso_3
Iso_2
Iso_1
Iso_0
0
0
0
0
0
ISO/IEC 15693 low bit rate, one subcarrier, 1 out of 4
PROTOCOL
REMARKS
0
0
0
0
1
ISO/IEC 15693 low bit rate, one subcarrier, 1 out of 256
0
0
0
1
0
ISO/IEC 15693 high bit rate, one subcarrier, 1 out of 4
0
0
0
1
1
ISO/IEC 15693 high bit rate, one subcarrier, 1 out of 256
0
0
1
0
0
ISO/IEC 15693 low bit rate, double subcarrier, 1 out of 4
0
0
1
0
1
ISO/IEC 15693 low bit rate, double subcarrier, 1 out of 256
0
0
1
1
0
ISO/IEC 15693 high bit rate, double subcarrier, 1 out of 4
0
0
1
1
1
ISO/IEC 15693 high bit rate, double subcarrier, 1 out of 256
0
1
0
0
0
ISO/IEC 14443 A, bit rate 106 kbps
0
1
0
0
1
ISO/IEC 14443 A high bit rate 212 kbps
0
1
0
1
0
ISO/IEC 14443 A high bit rate 424 kbps
0
1
0
1
1
ISO/IEC 14443 A high bit rate 848 kbps
0
1
1
0
0
ISO/IEC 14443 B, bit rate 106 kbps
0
1
1
0
1
ISO/IEC 14443 B high bit rate 212 kbps
0
1
1
1
0
ISO/IEC 14443 B high bit rate 424 kbps
0
1
1
1
1
ISO/IEC 14443 B high bit rate 848 kbps
1
0
0
1
1
Reserved
1
0
1
0
0
Reserved
1
1
0
1
0
FeliCa 212 kbps
1
1
0
1
1
FeliCa 424 kbps
Default for RFID IC
RX bit rate when TX rate
different from RX rate (see
register 0x03)
RX bit rate when TX rate
different from RX rate (see
register 0x03)
Table 6-8. Coding of the ISO Control Register For NFC
Mode (B5 = 1, B2 = 0) or Card Emulation (B5 = 1,
B2 = 1)
26
NFC (B5 = 1, B2 = 0)
CARD EMULATION
(B5 = 1, B2 = 1)
0
N/A
ISO/IEC 14443 A
1
106 kbps
ISO/IEC 14443 B
1
0
212 kbps
N/A
1
1
424 kbps
N/A
Iso_1
Iso_0
0
0
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6.5.1
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Received Signal Strength Indicator (RSSI)
The TRF7970A incorporates in total three independent RSSI building blocks: Internal Main RSSI, Internal
Auxiliary RSSI, and External RSSI. The internal RSSI blocks measure the amplitude of the subcarrier
signal, and the external RSSI block measures the amplitude of the RF carrier signal at the receiver input.
6.5.1.1
Internal RSSI – Main and Auxiliary Receivers
Each receiver path has its own RSSI block to measure the envelope of the demodulated RF signal
(subcarrier). Internal Main RSSI and Internal Auxiliary RSSI are identical however connected to different
RF input pins. The Internal RSSI is intended for diagnostic purposes to set the correct RX path conditions.
The internal RSSI values can be used to adjust the RX gain settings or determine which RX path (main or
auxiliary) provides the greater amplitude and, hence, to determine if the MUX may need to be
reprogrammed to swap the RX input signal. The measuring system latches the peak value, so the RSSI
level can be read after the end of each receive packet. The RSSI register values are reset with every
transmission (TX) by the reader. This ensures an updated RSSI measurement for each new tag response.
RSSI Levels and Oscillator Status Register Value (0x0F)
The Internal RSSI has 7 steps (3 bit) with a typical increment of approximately 4 dB. The operating range
is between 600 mVPP and 4.2 VPP with a typical step size of approximately 600 mV. Both Internal Main
and Internal Auxiliary RSSI values are stored in the RSSI Levels and Oscillator Status register (0x0F). The
nominal relationship between the input RF peak level and the RSSI value is shown in Figure 6-5.
7
6
5
4
3
2
1
0
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
2.25 2.5 2.75
Input RF Carrier Level (VPP)
3
3.25
3.5
3.75
4
4.25
Figure 6-5. Digital Internal RSSI (Main and Auxiliary) Value vs RF Input Level in VPP (V)
This RSSI measurement is done during the communication to the Tag; this means the TX must be on. Bit
1 in the Chip Status Control register (0x00) defines if Internal RSSI or the External RSSI value is stored in
the RSSI Levels and Oscillator Status register (0x0F). Direct command 0x18 is used to trigger an Internal
RSSI measurement.
6.5.1.2
External RSSI
The external RSSI is mainly used to check for any external 13.56-MHz signals at the receiver RX_IN1
input. The external RSSI measurement should be used before turning on the transmitter to prevent RF
field collisions. This is especially important for active mode, when both devices emit their own RF field.
The level of the RF signal received at the antenna is measured and stored in the RSSI Levels and
Oscillator Status register (0x0F). Figure 6-6 shows the relationship between the voltage at the RX_IN1
input and the 3-bit code.
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7
6
5
4
3
2
1
0
0
25
50
75
100
125
150
175
200
225
250
275
300
325
RF Input Voltage Level at RF_IN1 (mVPP)
Figure 6-6. Digital External RSSI Value vs RF Input Level in VPP (mV)
The relation between the 3-bit code and the external RF field strength (A/m) sensed by the antenna must
be determined by calculation or by experiments for each antenna design. The antenna Q-factor and
connection to the RF input influence the result. Direct command 0x19 is used to trigger an external RSSI
measurement.
For clarity, to check the internal or external RSSI value independent of any other operation, the user must:
1. Set transmitter to desired state (on or off) using Bit 5 of Chip Status Control register (0x00) and enable
receiver using Bit 1.
2. Check internal or external RSSI using direct commands 0x18 or 0x19, respectively. This action places
the RSSI value in the RSSI register.
3. Delay at least 50 µs.
4. Read the RSSI register using direct command 0x0F; values range from 0x40 to 0x7F.
5. Repeat steps 1 to 4 as needed. The register is reset when it is read.
6.6
Oscillator Section
The 13.56-MHz or 27.12-MHz crystal (or oscillator) is controlled by the Chip Status Control register (0x00)
and the EN and EN2 terminals. The oscillator generates the RF frequency for the RF output stage as well
as the clock source for the digital section. The buffered clock signal is available at pin 27 (SYS_CLK) for
any other external circuits. B4 and B5 inside the Modulation and SYS_CLK register (0x09) can be used to
divide the external SYS_CLK signal at pin 27 by 1, 2, or 4.
Typical start-up time from complete power down is in the range of 3.5 ms.
During Power Down Mode 2 (EN = 0, EN2 = 1) the frequency of SYS_CLK is switched to 60 kHz (typical).
The crystal needs to be connected between pin 30 and pin 31. The external shunt capacitors values for C1
and C2 must be calculated based on the specified load capacitance of the crystal being used. The external
shunt capacitors are calculated as two identical capacitors in series plus the stray capacitance of the
TRF7970A and parasitic PCB capacitance in parallel to the crystal.
The parasitic capacitance (CS, stray and parasitic PCB capacitance) can be estimated at 4 to 5 pF
(typical).
As an example, using a crystal with a required load capacitance (CL) of 18 pF, the calculation is shown in
Equation 1.
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C1 = C2 = 2 × (CL– CS) = 2 × (18 pF – 4.5 pF) = 27 pF
(1)
A 27-pF capacitor must be placed on pins 30 and 31 to ensure proper crystal oscillator operation.
CS
TRF7970A
Pin 30
Pin 31
Crystal
C1
C2
Figure 6-7. Crystal Block Diagram
Any crystal used with TRF7970A should meet the minimum characteristics in Table 6-9.
Table 6-9. Minimum Crystal Recommendations
PARAMETER
SPECIFICATION
Frequency
13.56 MHz or 27.12 MHz
Mode of operation
Fundamental
Type of resonance
Parallel
Frequency tolerance
±20 ppm
Aging
< 5 ppm/year
Operation temperature range
–40°C to 85°C
As an alternative, an external clock oscillator source can be connected to pin 31 to provide the system
clock; pin 30 can be left open.
6.7
Transmitter – Analog Section
The 13.56-MHz oscillator generates the RF signal for the PA stage. The power amplifier consists of a
driver with selectable output resistance of nominal 4 Ω or 8 Ω. The transmit power level is set by bit B4 in
the Chip Status Control register (0x00). The transmit power levels are selectable between 100 mW (half
power) or 200 mW (full power) when configured for 5-V automatic operation. The transmit power levels
are selectable between 33 mW (half power) or 70 mW (full power) when configured for 3-V automatic
operation.
The ASK modulation depth is controlled by bits B0, B1, and B2 in the Modulator and SYS_CLK Control
register (0x09). The ASK modulation depth range can be adjusted between 7% to 30% or 100% (OOK).
External control of the transmit modulation depth is possible by setting the ISO Control register (0x01) to
direct mode. While operating the TRF7970A in direct mode, the transmit modulation is made possible by
selecting the modulation type ASK or OOK at pin 12. External control of the modulation type is made
possible only if enabled by setting B6 in the Modulator and SYS_CLK Control register (0x09) to 1.
In normal operation mode, the length of the modulation pulse is defined by the protocol selected in the
ISO Control register (0x01). With a high-Q antenna, the modulation pulse is typically prolonged, and the
tag detects a longer pulse than intended. For such cases, the modulation pulse length needs to be
corrected by using the TX Pulse Length Control register (0x06).
If the register contains all zeros, then the pulse length is governed by the protocol selection. If the register
contains a value other than 0x00, the pulse length is equal to the value of the register multiplied by
73.7 ns; therefore, the pulse length can be adjusted between 73.7 ns and 18.8 µs in 73.7-ns increments.
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Transmitter – Digital Section
The digital part of the transmitter is a mirror of the receiver. The settings controlled the ISO Control
register (0x01) are applied to the transmitter just like the receiver. In the TRF7970A default mode the
TRF7970A automatically adds these special signals: start of communication, end of communication, SOF,
EOF, parity bits, and CRC bytes.
The data is then coded to modulation pulse levels and sent to the RF output stage modulation control unit.
Similar to working with the receiver, this means that the external system MCU must only load the FIFO
with data, and all the microcoding is done automatically, again saving the firmware developer code space
and time. Additionally, all of the registers used for transmit parameter control are automatically preset to
optimum values when a new selection is entered into the ISO Control register (0x01).
NOTE
The FIFO must be reset before starting any transmission with direct command 0x0F.
There are two ways to start the transmit operation:
• Send the transmit command and the number of bytes to be transmitted first, and then start to send the
data to the FIFO. The transmission starts when first data byte is written into the FIFO.
• Load the number of bytes to be sent into registers 0x1D and 0x1E and load the data to be sent into the
FIFO (address 0x1F), followed by sending a transmit command (see Direct Commands section). The
transmission then starts when the transmit command is received.
NOTE
If the data length is longer than the FIFO, the TRF7970A notifies the external system MCU
when most of the data from the FIFO has been transmitted by sending an interrupt request
with a flag in the IRQ register to indicate a FIFO low or high status. The external system
should respond by loading the next data packet into the FIFO.
At the end of a transmit operation, the external system MCU is notified by interrupt request (IRQ) with a
flag in IRQ register (0x0C) indicating TX is complete (example value = 0x80).
The TX Length registers also support incomplete byte transmission. The high two nibbles in register 0x1D
and the nibble composed of bits B4 through B7 in register 0x1E store the number of complete bytes to be
transmitted. Bit B0 in register 0x1E is a flag indicating that there are also additional bits to be transmitted
that do not form a complete byte. The number of bits is stored in bits B1 through B3 of the same register
(0x1E).
Some protocols have options, and there are two sublevel configuration registers to select the TX protocol
options.
• ISO/IEC 14443 B TX Options register (0x02). This register controls the SOF and EOF selection and
EGT selection for the ISO/IEC 14443 B protocol.
• ISO/IEC 14443 A High Bit Rate Options and Parity register (0x03). This register enables the use of
different bit rates for RX and TX operations in the ISO/IEC 14443 high bit rate protocol and also
selects the parity method in the ISO/IEC 14443 A high bit rate protocol.
The digital section also has a timer. The timer can be used to start the transmit operation at a specified
time in accordance with a selected event.
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Transmitter – External Power Amplifier and Subcarrier Detector
The TRF7970A can be used in conjunction with an external TX power amplifier or external subcarrier
detector for the receiver path. In this case, certain registers must be programmed as shown here:
• Bit B6 of the Regulator and I/O Control register (0x0B) must be set to 1. This setting has two functions:
first, to provide a modulated signal for the transmitter if needed, and second, to configure the
TRF7970A receiver inputs for an external demodulated subcarrier input.
• Bit B3 of the Modulation and SYS_CLK Control register (0x09) must be set to 1 (see
Section 6.15.3.2.8). This function configures the ASK/OOK pin for either a digital or analog output
(B3 = 0 enables a digital output, B3 = 1 enables an analog output). The design of an external power
amplifier requires detailed RF knowledge. There are also readily designed and certified high-power HF
reader modules on the market.
6.10 TRF7970A IC Communication Interface
6.10.1 General Introduction
The communication interface to the reader can be configured in two ways: with a eight line parallel
interface (D0:D7) plus DATA_CLK, or with a 4-wire Serial Peripheral Interface (SPI). The SPI interface
uses traditional Master Out/Slave In (MOSI), Master In/Slave Out (MISO), Slave Select, and DATA_CLK
lines.
These communication modes are mutually exclusive; that is, only one mode can be used at a time in the
application.
When the SPI interface is selected, the unused I/O_2, I/O_1, and I/O_0 pins must be hard-wired as shown
in Table 6-10. At power up, the TRF7970A samples the status of these three pins and then enters one of
the possible SPI modes.
The TRF7970A always behaves as the slave device, and the microcontroller (MCU) behaves as the
master device. The MCU initiates all communications with the TRF7970A, and the TRF7970A makes use
of the Interrupt Request (IRQ) pin in both parallel and SPI modes to prompt the MCU for servicing
attention.
Table 6-10. Pin Assignment in Parallel and Serial Interface Connection or Direct Mode
(1)
(2)
(3)
(4)
(5)
PARALLEL (DIRECT MODE)
SPI WITHOUT SS (1)
PIN
PARALLEL
SPI WITH SS
DATA_ CLK
DATA_CLK
DATA_CLK
DATA_CLK from master
DATA_CLK from master
I/O_7
A/D[7]
Not used
MOSI (2) = data in (reader in)
MOSI (2) = data in (reader in)
I/O_6
A/D[6]
Direct mode, data out (subcarrier
MISO (3) = data out (MCU out)
or bit stream)
MISO (3) = data out (MCU out)
I/O_5 (4)
A/D[5]
Direct mode, strobe – bit clock
out
See
See
I/O_4
A/D[4]
Not used
SS – slave select (5)
Not used
I/O_3
A/D[3]
Not used
Not used
Not used
I/O_2
A/D[2]
Not used
At VDD
At VDD
I/O_1
A/D[1]
Not used
At VDD
At VSS
I/O_0
A/D[0]
Not used
At VSS
At VSS
IRQ
IRQ interrupt
IRQ interrupt
IRQ interrupt
IRQ interrupt
(4)
.
(4)
.
FIFO is not accessible in SPI without SS mode. See the TRF7970A Silicon Errata for detailed information.
MOSI = master out, slave in
MISO = master in, slave out
I/O_5 pin is used only for information when data is put out of the chip (for example, reading 1 byte from the chip). It is necessary first to
write in the address of the register (8 clocks) and then to generate another 8 clocks for reading out the data. The I/O_5 pin goes high
during the second 8 clocks. But for normal SPI operations, I/O_5 pin is not used.
Slave select pin is active low
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Communication is initialized by a start condition, which is expected to be followed by an
Address/Command word (Adr/Cmd). The Adr/Cmd word is 8 bits long, and Table 6-11 shows its format.
Table 6-11. Address and Command Word Bit Distribution
BIT
DESCRIPTION
BIT FUNCTION
ADDRESS
COMMAND
B7
Command control bit
0 = Address
1 = Command
0
1
B6
Read/Write
0 = Write
1 = Read
R/W
0
B5
Continuous address mode
1 = Continuous mode
R/W
0
B4
Address/Command bit 4
Adr 4
Cmd 4
B3
Address/Command bit 3
Adr 3
Cmd 3
B2
Address/Command bit 2
Adr 2
Cmd 2
B1
Address/Command bit 1
Adr 1
Cmd 1
B0
Address/Command bit 0
Adr 0
Cmd 0
The MSB (bit 7) determines if the word is to be used as a command or as an address. The last two
columns of Table 6-11 show the function of the separate bits if either address or command is written. Data
is expected once the address word is sent. In continuous-address mode (Cont. mode = 1), the first data
that follows the address is written (or read) to (from) the given address. For each additional data, the
address is incremented by one. Continuous mode can be used to write to a block of control registers in a
single stream without changing the address; for example, setup of the predefined standard control
registers from the MCU nonvolatile memory to the reader. In noncontinuous address mode (simple
addressed mode), only one data word is expected after the address.
Address Mode is used to write or read the configuration registers or the FIFO. When writing more than 12
bytes to the FIFO, the Continuous Address Mode should be set to 1.
Command Mode is used to enter a command resulting in reader action (for example, initialize
transmission, enable reader, and turn reader on or off).
The following sections give examples of the expected communications between an MCU and the
TRF7970A.
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6.10.1.1 Continuous Address Mode
Figure 6-8 summarizes the continuous address mode communication. Figure 6-8 and Figure 6-9 show the
signals between the MCU and the TRF7970A.
Table 6-12. Continuous Address Mode
Start
Adr x
Data(x)
Data(x+1)
Data(x+2)
Data(x+3)
Data(x+4)
...
Data(x+n)
StopCont
Figure 6-8. Continuous Address Register Write Example Starting With Register 0x00 Using SPI With SS
Figure 6-9. Continuous Address Register Read Example Starting With Register 0x00 Using SPI With SS
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6.10.1.2 Noncontinuous Address Mode (Single Address Mode)
Table 6-13 summarizes the noncontinuous address (single address) mode communication. Figure 6-10
and Figure 6-11 show the signals between the MCU and the TRF7970A.
Table 6-13. Noncontinuous Address Mode (Single Address Mode)
Start
Adr x
Data(x)
Adr y
Data(y)
...
Adr z
Data(z)
StopSgl
Figure 6-10. Single Address Register Write Example of Register 0x00 Using SPI With SS
Figure 6-11. Single Address Register Read Example of Register 0x00 Using SPI With SS
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6.10.1.3 Direct Command Mode
Table 6-14 summarizes the direct command mode communication. Figure 6-12 shows the signals
between the MCU and the TRF7970A.
Table 6-14. Direct Command Mode
Start
Cmd x
(Optional data or command)
Stop
Figure 6-12. Direct Command Example of Sending 0x0F (Reset) Using SPI With SS
Section 6.14 describes the other direct command codes from the MCU to the TRF7970A IC.
6.10.1.4 FIFO Operation
The FIFO is a 127-byte register at address 0x1F with byte storage locations 0 to 126. FIFO data is loaded
in a cyclical manner and can be cleared by a reset command (0x0F) (see Figure 6-12 showing this direct
command).
Associated with the FIFO are two counters and three FIFO status flags. The first counter is a 7-bit FIFO
byte counter (bits B0 to B6 in register 0x1C) that tracks the number of bytes loaded into the FIFO. If the
number of bytes in the FIFO is n, the register value is n (number of bytes in FIFO register). For example, if
8 bytes are in the FIFO, the FIFO counter (Register 0x1C) has the hexadecimal value of 0x08 (binary
value of 00001000).
A second counter (12 bits wide) indicates the number of bytes being transmitted (registers 0x1D and
0x1E) in a data frame. An extension to the transmission-byte counter is a 4-bit broken-byte counter also
provided in register 0x1E (bits B0 to B3). Together these counters make up the TX length value that
determines when the reader generates the EOF byte.
During transmission, the FIFO is checked for an almost-empty condition, and during reception for an
almost-full condition. The maximum number of bytes that can be loaded into the FIFO in a single
sequence is 127 bytes.
NOTE
The number of bytes in a frame, transmitted or received, can be greater than 127 bytes.
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During transmission, the MCU loads the TRF7970A FIFO (or during reception the MCU removes data
from the FIFO), and the FIFO counter counts the number of bytes being loaded into the FIFO. Meanwhile,
the byte counter keeps track of the number of bytes being transmitted. An interrupt request is generated if
the number of bytes in the FIFO triggers the watermark levels, which are configured in the Adjustable
FIFO IRQ Levels register (0x14). The default setting is for the interrupt to be triggered when receiving
124 bytes during RX or having 4 bytes remaining during TX. These watermark levels are used so that
MCU can send new data or read the data as necessary. The MCU must also validate the number of data
bytes to be sent, so as to not surpass the value defined in the TX Length Byte registers (0x1D and 0x1E).
The MCU also signals the transmit logic when the last byte of data is sent or was removed from the FIFO
during reception.
Figure 6-13 shows an example of checking the FIFO Status register using SPI with SS.
Figure 6-13. Example of Checking the FIFO Status Register Using SPI With SS
6.10.2 Parallel Interface Mode
In parallel mode, the start condition is generated on the rising edge of the I/O_7 pin while the CLK is high.
This is used to reset the interface logic. Figure 6-14, Figure 6-15, and Figure 6-16 show the sequence of
the data, with an 8-bit address word first, followed by data.
Communication is ended by:
• The StopSmpl condition, where a falling edge on the I/O_7 pin is expected while CLK is high.
• The StopCont condition, where the I/O_7 pin must have a successive rising and falling edge while CLK
is low to reset the parallel interface and be ready for the new communication sequence.
• The StopSmpl condition is also used to terminate the direct mode.
Start
Condition
StopSmpl
Condition
CLK
50 ns
I/O_[7]
I/O_[6:0]
a1 [7]
d1 [7]
a2 [7]
d2 [7]
aN [7]
dN [7]
a1 [6:0]
d1 [6:0]
a2 [6:0]
d2 [6:0]
aN [6:0]
dN [6:0]
Figure 6-14. Parallel Interface Communication With Simple Stop Condition (StopSmpl)
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Start
Condition
StopCont
Continuous Mode
CLK
50 ns
I/O_[7]
I/O_[6:0]
xx
a0 [7]
d0 [7]
d1 [7]
d2 [7]
d3 [7]
dN [7]
a0 [6:0]
d0 [6:0]
d1 [6:0]
d2 [6:0]
d3 [6:0]
dN [6:0]
xx
Figure 6-15. Parallel Interface Communication With Continuous Stop Condition (StopCont)
Figure 6-16. Example of Parallel Interface Communication With Continuous Stop Condition
6.10.3 Reception of Air Interface Data
At the start of a receive operation (when SOF is successfully detected), B6 is set in the IRQ Status
register. An RX complete interrupt request is sent to the MCU at the end of the receive operation if the
receive data string is shorter than or equal to the number of bytes configured in the Adjustable FIFO IRQ
Levels register (0x14). An IRQ_FIFO interrupt request is sent to the MCU during the receive operation if
the data string is greater than the level set in the Adjustable FIFO IRQ Levels register (0x14). After
receiving an IRQ_FIFO or RX complete interrupt, the MCU must read the FIFO Status register (0x1C) to
determine the number of bytes to be read from the FIFO. Next, the MCU must read the data in the FIFO.
It is optional but recommended to read the FIFO Status register (0x1C) after reading FIFO data to
determine if the receive is complete. In the case of an IRQ_FIFO, the MCU should expect either another
IRQ_FIFO or RX complete interrupt. This is repeated until an RX complete interrupt is generated. The
MCU receives the interrupt request, then checks to determine the reason for the interrupt by reading the
IRQ Status register (0x0C), after which the MCU reads the data from the FIFO.
If the reader detects a receive error, the corresponding error flag is set (framing error, CRC error) in the
IRQ Status register, indicating to the MCU that reception was not completed correctly.
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6.10.4 Data Transmission From MCU to TRF7970A
Before beginning data transmission, the FIFO should always be cleared with a reset command (0x0F).
Data transmission is initiated with a selected command (see Section 6.14). The MCU then commands the
reader to do a continuous write command (0x3D) starting from register 0x1D. Data written into register
0x1D is the TX Length Byte 1 (upper and middle nibbles), while the following byte in register 0x1E is the
TX Length Byte 2 (lower nibble and broken byte length) (see Table 6-57 and Table 6-58) . Note that the
TX byte length determines when the reader sends the end of frame (EOF) byte. After the TX length bytes
are written, FIFO data is loaded in register 0x1F with byte storage locations 0 to 127. Data transmission
begins automatically after the first byte is written into the FIFO. The loading of TX length bytes and the
FIFO can be done with a continuous-write command, as the addresses are sequential.
At the start of transmission, the flag B7 (IRQ_TX) is set in the IRQ Status register, and at the end of the
transmit operation, an interrupt is sent to inform the MCU that the task is complete.
6.10.5 Serial Interface Communication (SPI)
When an SPI interface is used, I/O pins I/O_2, I/O_1, and I/O_0 must be hard wired according to Table 610. On power up, the TRF7970A looks for the status of these pins and then enters into the corresponding
mode.
The serial communications work in the same manner as the parallel communications with respect to the
FIFO, except for the following condition. On receiving an IRQ from the reader, the MCU reads the
TRF7970A IRQ Status register to determine how to service the reader. After this, the MCU must to do a
dummy read to clear the reader's IRQ status register. The dummy read is required in SPI mode because
the reader's IRQ status register needs an additional clock cycle to clear the register. This is not required in
parallel mode because the additional clock cycle is included in the Stop condition. When first establishing
communications with the TRF7970A, the SOFT_INIT (0x03) and IDLE (0x00) commands should be sent
first from the MCU (see Table 6-19).
The procedure for a dummy read is as follows (see Figure 6-17 and Figure 6-18):
1. Start the dummy read:
(a) When using slave select (SS): set SS bit low.
(b) When not using SS: start condition is when Data Clock is high (see Table 6-10).
2. Send address word to IRQ status register (0x0C) with read and continuous address mode bits set to 1
(see Table 6-10).
3. Read 1 byte (8 bits) from IRQ status register (0x0C).
4. Dummy-read 1 byte from register 0x0D (collision position and interrupt mask).
5. Stop the dummy read:
(a) When using slave select (SS): set SS bit high.
(b) When not using SS: stop condition when Data Clock is high.
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Write Address
Byte (0x6C)
Read Data in
IRQ Status Register
Dummy Read
DATA_CLK
MOSI
MISO
B7
B6
B5
B4
B3
B2
Don’t Care
B1
B0
No Data Transitions (All High or Low)
B7
B6
B5
B4
B3
B2
B1
No Data Transitions (All High or Low)
B0
Ignore
Slave
Select
Figure 6-17. Procedure for Dummy Read
Figure 6-18. Example of Dummy Read Using SPI With SS
6.10.5.1 Serial Interface Mode With Slave Select (SS)
The serial interface is in reset while the Slave Select signal is high. Serial data in (MOSI) changes on the
rising edge, and is validated in the reader on the falling edge, as shown in Figure 6-19. Communication is
terminated when the Slave Select signal goes high.
All words must be 8 bits long with the MSB transmitted first.
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t STE,LEAD
Slave Select
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Write
Read
MOSI Transitions on Data Clock
Rising Edge
MOSI Valid on Data Clock Falling Edge
Data Transition is on Data Clock
Rising Edge
MISO Valid on Data Clock Falling Edge
t STE,LAG
1/f UCxCLK
t STE,DIS
DATA_CLK
t LO/HI
MOSI
t LO/HI
t SU,SI
b6…b1
b7
t HD,SI
No Data Transitions
(All High or Low)
b0
t SU,SO
MISO
t HD,SO
t VALID,SO
b0
b6...b1
b7
Don’t Care
Figure 6-19. SPI With Slave Select Timing Diagram
The read command is sent out on the MOSI pin, MSB first, in the first eight clock cycles. MOSI data
changes on the rising edge, and is validated in the reader on the falling edge, as shown in Figure 6-19.
During the write cycle, the serial data out (MISO) is not valid. After the last read command bit (B0) is
validated at the eighth falling edge of SCLK, valid data can be read on the MISO pin at the falling edge of
SCLK. It takes eight clock edges to read out the full byte (MSB first). See Section 5.4 for electrical
specifications related to Figure 6-19.
Figure 6-20 and Figure 6-21 show the continuous read operation.
Write
Address Byte
Read Data
Byte 1
Read Data
Byte n
No Data Transitions (All High or Low)
No Data Transitions (All High or Low)
B7 B6 B5 B4
B7 B6 B5 B4
DATA_CLK
MOSI
B7 B6 B5 B4
MISO
B3 B2
Don’t Care
B1 B0
B3 B2
B1 B0
B3 B2
B1 B0
Slave
Select
Figure 6-20. Continuous Read Operation Using SPI With Slave Select
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Figure 6-21. Continuous Read of Registers 0x00 to 0x05 Using SPI With SS
Figure 6-22 shows an example of performing a single slot inventory command. Reader registers (in this example)
are configured for 5 VDC in and default operation.
Figure 6-22. Inventory Command Sent From MCU to TRF7970A
The TRF7970A takes these bytes from the MCU and then send out Request Flags, Inventory Command,
and Mask over the air to the ISO/IEC 15693 transponder. After these three bytes have been transmitted,
an interrupt occurs to indicate back to the reader that the transmission has been completed. In the
example in Figure 6-23, this IRQ occurs approximately 1.6 ms after the SS line goes high after the
Inventory command is sent out.
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Figure 6-23. IRQ After Inventory Command
The IRQ status register read (0x6C) yields 0x80, which indicates that TX is indeed complete. This is
followed by a dummy clock. Then, if a tag is in the field and no error is detected by the reader, a second
interrupt is expected and occurs (in this example) approximately 4 ms after first IRQ is read and cleared.
In the continuation of the example (see Figure 6-24), the IRQ Status Register is read using method
previously recommended, followed by a single read of the FIFO Status register, which indicates that there
are 10 bytes to be read out.
Figure 6-24. Read IRQ Status Register After Inventory Command
This is then followed by a continuous read of the FIFO (see Figure 6-25). The first byte is (and should be)
0x00 for no error. The next byte is the DSFID (usually shipped by manufacturer as 0x00), then the UID,
shown here up to the next most significant byte, the MFG code [shown as 0x07 (TI silicon)].
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Figure 6-25. Continuous Read of FIFO After Inventory Command
TI recommends resetting the FIFO after receiving data. Additionally, the RSSI value of the tag can be read
out at this point. In the example in Figure 6-26, the transponder is very close to the antenna, so value of
0x7F is recovered.
Figure 6-26. Reset FIFO and Read RSSI
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6.10.6 Direct Mode
Direct mode allows the user to configure the reader in one of two ways. Direct mode 0 (bit 6 = 0, as
defined in ISO Control register) allows the user to use only the front-end functions of the reader,
bypassing the protocol implementation in the reader. For transmit functions, the user has direct access to
the transmit modulator through the MOD pin (pin 14). On the receive side, the user has direct access to
the subcarrier signal (digitized RF envelope signal) on I/O_6 (pin 23).
Direct mode 1 (bit 6 = 1, as defined in ISO Control register) uses the subcarrier signal decoder of the
selected protocol (as defined in ISO Control register). This means that the receive output is not the
subcarrier signal but the decoded serial bit stream and bit clock signals. The serial data is available on
I/O_6 (pin 23) and the bit clock is available on I/O_5 (pin 22). The transmit side is identical; the user has
direct control over the RF modulation through the MOD input. This mode is provided so that the user can
implement a protocol that has the same bit coding as one of the protocols implemented in the reader, but
needs a different framing format.
To select direct mode, the user must first choose which direct mode to enter by writing B6 in the ISO
Control register. This bit determines if the receive output is the direct subcarrier signal (B6 = 0) or the
serial data of the selected decoder. If B6 = 1, then the user must also define which protocol should be
used for bit decoding by writing the appropriate setting in the ISO Control register.
The reader actually enters the direct mode when B6 (direct) is set to 1 in the chip status control register.
Direct mode starts immediately. The write command should not be terminated with a stop condition (see
communication protocol), because the stop condition terminates the direct mode and clears B6. This is
necessary as the direct mode uses one or two I/O pins (I/O_6, I/O_5). Normal parallel communication is
not possible in direct mode. Sending a stop condition terminates direct mode.
NOTE
An additional direct mode known as special direct mode can be used to communicate with
certain tags not compliant with ISO standards. For full details on how to use this feature, see
Using Special Direct Mode With the TRF7970A.
Figure 6-27 shows the different configurations available in direct mode.
• In mode 0, the reader is used as an AFE only, and protocol handling is bypassed.
• In mode 1, framing is not done, but SOF and EOF are present. This allows for a user-selectable
framing level based on an existing ISO standard.
• In mode 2, data is ISO-standard formatted. SOF, EOF, and error checking are removed, so the
microprocessor receives only bytes of raw data through a 127-byte FIFO.
Analog Front End (AFE)
Direct Mode 0:
Raw RF Subcarrier
Data Stream
ISO Encoders and Decoders
14443A
14443B
15693
FeliCa
Direct Mode 1:
Raw Digital ISO Coded
Data Without
Protocol Frame
Packetization and Framing
Microcontroller
ISO Mode:
Full ISO Framing
and Error Checking
(Typical Mode)
Figure 6-27. User-Configurable Modes
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The steps to enter direct mode are listed below, using SPI with SS communication method only as one
example, as direct modes are also possible with parallel and SPI without SS. The must enter direct mode
0 to accommodate card type communications that are not compliant with ISO standards. Direct mode can
be entered at any time, so if a card type started with ISO standard communications, then deviated from
the standard after being identified and selected, the ability to go into direct mode 0 is very useful.
Step 1: Configure Pins I/O_0 to I/O_2 for SPI with SS
Step 2: Set Pin 12 of the TRF7970A (ASK/OOK pin) to 0 for ASK or 1 for OOK
Step 3: Program the TRF7970A registers
The following registers must be explicitly set before going into the direct mode.
1. ISO Control register (0x01) to the appropriate standard
– 0x02 for ISO/IEC 15693 High Data Rate
– 0x08 for ISO/IEC 14443 A (106 kbps)
– 0x1A for FeliCa 212 kbps
– 0x1B for FeliCa 424 kbps
2. Modulator and SYS_CLK register (0x09) to the appropriate clock speed and modulation
– 0x21 for 6.78 MHz Clock and OOK (100%) modulation
– 0x20 for 6.78 MHz Clock and ASK 10% modulation
– 0x22 for 6.78 MHz Clock and ASK 7% modulation
– 0x23 for 6.78 MHz Clock and ASK 8.5% modulation
– 0x24 for 6.78 MHz Clock and ASK 13% modulation
– 0x25 for 6.78 MHz Clock and ASK 16% modulation
(See register 0x09 definition for all other possible values)
Example register setting for ISO/IEC 14443 A at 106 kbps:
• ISO Control register (0x01) to 0x08
• RX No Response Wait Time register (0x07) to 0x0E
• RX Wait Time register (0x08) to 0x07
• Modulator control register (0x09) to 0x21 (or any custom modulation)
• RX Special Settings register (0x0A) to 0x20
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Step 4: Entering Direct Mode 0
The following registers must be programmed to enter direct mode 0:
1. Set bit B6 of the Modulator and SYS_CLK Control register (0x09) to 1.
2. Set bit B6 of the ISO Control (Register 01) to 0 for direct mode 0 (default its 0)
3. Set bit B6 of the Chip Status Control register (0x00) to 1 to enter direct mode
4. Send extra eight clock cycles (see Figure 6-28, this step is TRF7970A specific)
NOTE
•
•
It is important that the last write is not terminated with a stop condition. For SPI, this
means that Slave Select (I/O_4) stays low.
Sending a Stop condition terminates the direct mode and clears bit B6 in the Chip Status
Control register (0x00).
NOTE
Access to Registers, FIFO, and IRQ is not available during direct mode 0.
The reader enters the direct mode 0 when bit 6 of the Chip Status Control register (0x00) is set to a 1 and
stays in direct mode 0 until a stop condition is sent from the microcontroller.
NOTE
The write command should not be terminated with a stop condition (for example, in SPI
mode this is done by bringing the Slave Select line high after the register write), because the
stop condition terminates the direct mode and clears bit 6 of the Chip Status Control register
(0x00), making it a 0.
Figure 6-28. Entering Direct Mode 0
46
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Step 5: Transmit Data Using Direct Mode
The application now has direct control over the RF modulation through the MOD input (see Figure 6-29).
TRF7970A
Microcontroller
MOD
(Pin 14)
Drive the MOD pin
according to the data coding
specified by the standard
I/O_6
(Pin 23)
Decode the subcarrier
information according
to the standard
Figure 6-29. Direct Control Signals
The microcontroller is responsible for generating data according to the coding specified by the particular
standard. The microcontroller must generate SOF, EOF, Data, and CRC. In direct mode, the FIFO is not
used and no IRQs are generated. See the applicable ISO standard to understand bit and frame
definitions. Figure 6-30 shows an example of what the developer sees when using DM0 in an actual
application. This figure clearly shows the relationship between the MOD pin being controlled by the MCU
and the resulting modulated 13.56-MHz carrier signal.
Figure 6-30. TX Sequence Out in DM0
Step 6: Receive Data Using Direct Mode
After the TX operation is complete, the tag responds to the request and the subcarrier data is available on
pin I/O_6. The microcontroller needs to decode the subcarrier signal according to the standard. This
includes decoding the SOF, data bits, CRC, and EOF. The CRC then needs to be checked to verify data
integrity. The receive data bytes must be buffered locally.
As an example of the receive data bits and framing level according to the ISO/IEC 14443 A standard is
shown in Figure 6-31 (taken from ISO/IEC 14443 specification and TRF7970A air interface).
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?
?
?
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128/fc = 9.435 µs = tb (106-kbps data rate)
64/fc = 4.719 µs = tx time
32/fc = 2.359 µs = t1 time
tb = 9.44 µs
tx = 4.72 µs
Sequence Y = Carrier for 9.44 µs
t1 = 2.48 µs
Sequence Z = Pause for 2 to 3 µs,
Carrier for Remainder of 9.44 µs
Figure 6-31. Receive Data Bits and Framing Level
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Figure 6-32 shows an example of what the developer should expect on the I/O_6 line during the RX
process while in direct mode 0.
Figure 6-32. RX Sequence on I/O_6 in DM0 (Analog Capture)
Step 7: Terminating Direct Mode 0
After the EOF is received, data transmission is over, and direct mode 0 can be terminated by sending a
Stop Condition (in the case of SPI, make the Slave Select go high). The TRF7970A is returned to default
state.
6.11 TRF7970A Initialization
To properly initialize the TRF7970A, perform these steps:
1. Raise the EN, EN2, and SS lines at the correct intervals after power up (for timing diagrams, see
Figure 6-3 and Figure 6-4).
2. Issue a Software Initialization direct command (0x03), followed by an Idle direct command (0x00) to
soft reset the TRF7970A.
NOTE
Table 6-21 lists the initial register settings for the TRF7970A after the Software Initialization
command.
3. Delay 1 ms to allow the TRF7970A to fully process the soft reset.
4. Issue a Reset FIFO direct command (0x0F).
5. Write the Modulator and SYS_CLK Control register (0x09) with the appropriate application-specific
setting for the crystal and system clock settings.
6. (Optional) Write the Regulator and I/O Control register (0x0B) with the appropriate application-specific
setting.
7. Write the NFC Target Detection Level register (0x18) with the value of 0x00. For details on this
requirement, see the TRF7970A Silicon Errata.
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6.12 Special Direct Mode for Improved MIFARE™ Compatibility
See Using Special Direct Mode With the TRF7970A.
6.13 NFC Modes
6.13.1 Target
When used as the NFC target, the chip is typically in a power down or standby mode. If EN2 = H, the chip
keeps the supply system on. If EN2 = L and EN = L the chip is in complete power down. To operate as
NFC target or card emulator, the MCU must load a value different from zero (0) in Target Detection Level
register (b0-b2) which enables the RF measurement system (supplied by VEXT, so it can operate also
during complete power down and consumes only 3.5 µA). The RF measurement constantly monitors the
RF signal on the antenna input. When the RF level on the antenna input exceeds the level defined in the
in Target Detection Level register, the chip is automatically activated (EN is internal forced high). The
typical RF value that causes power-up for each value of B0 to B2 and the function of Target Detection
Level register is listed in Table 6-15.
NFC Target Detection Level Register (0x18) – defines level for RF level for wake-up and gives
information of NFCID size. This register is directly supplied by VEXT to ensure data retention during
complete power down.
Table 6-15. NFC Target Detection Level Register
BIT
SIGNAL NAME
B7
Id_s1
B6
Id_s0
B5
Sdd_en
B4
(1)
FUNCTION
COMMENTS
NFCID1 size used in 106 kbps passive target SDD
Automatic SDD using internal state machine and ID
stored in NFCID Number register (1)
1 = Enables internal SDD protocol
N/A
B3
Hi_rf
B2
Rfdet_h2
B1
Rfdet_h1
B0
Rfdet_h0
Extended range for RF measurements
RF field level required for system wake-up. If all
bits are 0, the RF level detection is switched off.
Comparator output is displayed in NFC Target
Protocol register B7 (rf_h)
See the TRF7970A Silicon Errata for details on automatic SDD dependencies.
Default: reset to 00 at POR on VEXT (not on POR based on VDD_X), not reset at EN = 0
Table 6-16. Bits B0 to B3 of the NFC Target Detection Level Register
B0 B1 B2
000
001
010
011
100
101
110
111
B3 = 0
RF Vpp
Not active
480 mV
350 mV
250 mV
220 mV
190 mV
180 mV
170 mV
B3 = 1
RF Vpp
Not active
1500 mV
700 mV
500 mV
450 mV
400 mV
320 mV
280 mV
When the voltage supply system and the oscillator are started and is stable, the osc_ok goes high (B6 of
RSSI Level and Oscillator Status register) and IRQ is sent with bit B2 = 1 of IRQ register (field change).
Bit B7 NFC Target Protocol in register directly displays the status of RF level detection (running constantly
also during normal operation). This informs the MCU that the chip should start operation as an NFC
TARGET device.
When the first command from the INITIATOR is received another IRQ sent with B6 (RX start) set in IRQ
register. The MCU must set EN = H (confirm the power-up) in the time between the two IRQs as the
internal power-up ends after the second IRQ. The type and coding of the first initiator (or reader in the
case of a card emulator) command define the communication protocol type which the target must use. So
the communication protocol type is available in the NFC Target Protocol register immediately after
receiving the first command. The coding of the NFC Target Protocol register is described next.
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NFC Target Protocol Register (0x19) – displays the bit rate and protocol type (active or passive)
transmitted by initiator in the first command. It also displays the comparator outputs of both RF level
detectors.
Table 6-17. NFC Target Protocol Register
BIT
NAME
FUNCTION
DESCRIPTION
B7
Rf_h
1 = RF level is above the set wake-up level
The wake-up level is defined by bits b0-b3 of NFC
Target Detection Level register
B6
Rf_l
1 = RF level is above the RF collision avoidance level
The collision avoidance level is defined by bits b0b2 of NFC Low Field Detection Level register
B5
N/A
B4
FeliCa
1 = FeliCa type
0 = ISO/IEC 14443 A type
The first initiator command had physical level
coding like FeliCa or like ISO/IEC 14443 A
B3
Pas106
Passive target 106 kbps or card emulation
The first initiator/reader command was
SENS_REQ or ALL_REQ
B2
Pas14443B
Card emulation ISO/IEC 14443 B
The first reader command was of ISO/IEC 14443 B
type
B1
Nfcbr1
Bit rate of first received command
00
01
10
11
B0
Nfcbr0
= N/A
= 106 kbps
= 212 kbps
= 424 kbps
Default: reset to 00 at POR and EN = L. B0 to B4 are automatically reset after MCU read operation. B6
and B7 continuously display the RF level comparator outputs.
Based on the first command from INITIATOR following actions are taken:
• If the first command is SENS_REQ or ALL_REQ, the TARGET must enter the SDD protocol for 106
kbps passive communication. If bit B5 in NFC Target Detection Level register is not set, the MCU
handles the SDD and the command received is send to FIFO. If the RF field is turned off (B7 in the
NFC Target Protocol register goes low) at any time, the system sends an IRQ to the MCU with bit B2
(RF field change) in the IRQ register set high. This informs the MCU that the procedure was aborted
and the system must be reset. The clock extractor is automatically activated in this mode.
• If the command is SENS_REQ or ALL_REQ and the card emulation bit in the ISO Control register is
set, the system emulates an ISO/IEC 14443 A card. The procedure does not differ from the one
previously described for a passive target at 106 kbps. The clock extractor is automatically activated in
this mode.
• If the first command is a SENSF_REQ, the system becomes a TARGET in passive communication
using 212 kbps or 424 kbps. The SDD is relatively simple and is handled by the MCU directly.
• If the first command is ATR_REQ, the system operates as an active TARGET using the same
communication speed and bit coding as used by the INITIATOR. Again, all of the replies are handled
by the MCU. The MCU should check for collision avoidance by checking the external RSSI as
described in Section 6.5.1.2. When no RF field is detected from the external RSSI result, then the
MCU can begin the process to send the reply.
• If the first command is coded as ISO/IEC 14443 B and the card emulation bit is set in the ISO Control
register, the system enters ISO/IEC 14443 B emulator mode. The anticollision must be handled by the
MCU, and the chip provides all physical level coding, decoding, and framing for this protocol.
Table 6-18 shows the function of the IRQ Status register in NFC and card emulation. This register is
preset to 0 at POR = H or EN = L and at each write to ISO Control. It is also automatically reset at the end
of read phase. The reset also removes the IRQ flag.
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Table 6-18. IRQ Status Register (0x0C) for NFC and Card Emulation Operation
BIT
NAME
DESCRIPTION
B7
Irq_tx
IRQ set due to end of TX
Signals that TX is in progress. The flag is set at the start of
TX but the interrupt request (IRQ = 1) is sent when TX is
finished.
B6
Irg_srx
IRQ set due to RX start
Signals that RX SOF was received and RX is in progress.
The flag is set at the start of RX but the interrupt request
(IRQ = 1) is sent when RX is finished.
B5
Irq_fifo
Signals the FIFO level
Signals FIFO high or low as set in the Adjustable FIFO IRQ
Levels (0x14) register
B4
Irq_err1
CRC error
Indicates receive CRC error only if B7 (no RX CRC) of ISO
Control register is set to 0.
B3
Irq_err2
Parity error
Indicates parity error for ISO/IEC 14443 A
B2
Irq_err3
Byte framing or EOF error
Indicates framing error
Collision error
Collision error for ISO/IEC 14443 A and ISO/IEC 15693
single subcarrier. Bit is set if more than 6 or 7 (as defined in
register 0x10) are detected inside 1 bit period of
ISO/IEC 14443 A 106 kbps. Collision error bit can also be
triggered by external noise.
No-response time interrupt
No response within the "No-response time" defined in RX
No-response Wait Time register (0x07). Signals the MCU
that next slot command can be sent. Only for
ISO/IEC 15693.
B1
Irq_col
B0
(1)
FUNCTION
(1)
Irq_noresp
Displays the cause of IRQ and TX/RX status
6.13.2 Initiator
The chip is fully controlled by the MCU as in RFID reader operation. The MCU activates the chip and
writes the mode selection in the ISO Control register. The normal transmit and receive procedure (through
the FIFO) are used to communicate with the TARGET device as described in Section 6.10.
6.14 Direct Commands from MCU to Reader
6.14.1 Command Codes
Table 6-19 summarizes the command codes.
Table 6-19. Address and Command Word Bit Distribution
COMMAND
CODE
52
COMMAND
COMMENTS
0x00
Idle
0x03
Software initialization
Same as Power on Reset
0x04
Perform RF collision avoidance
Does not function as expected. See the TRF7970A
Errata for details.
0x05
Perform response RF collision avoidance
Does not function as expected. See the TRF7970A
Errata for details.
0x06
Perform response RF collision avoidance (n = 0)
Does not function as expected. See the TRF7970A
Errata for details.
0x0F
Reset FIFO
0x10
Transmission without CRC
0x11
Transmission with CRC
0x12
Delayed transmission without CRC
0x13
Delayed transmission with CRC
0x14
End of frame and transmit next time slot
0x16
Block receiver
0x17
Enable receiver
0x18
Test internal RF (RSSI at RX input with TX off)
Detailed Description
Used for ISO/IEC 15693 only
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Table 6-19. Address and Command Word Bit Distribution (continued)
COMMAND
CODE
0x19
COMMAND
COMMENTS
Test external RF (RSSI at RX input with TX on)
The command code values from Table 6-19 are substituted in Table 6-20, bits 0 through 4. Also, the mostsignificant bit (MSB) in Table 6-20 must be set to 1. (Table 6-20 is same as Table 6-11, shown here again
for easy reference).
Table 6-20. Address and Command Word Bit Distribution
BIT
DESCRIPTION
BIT FUNCTION
ADDRESS
COMMAND
B7
Command control bit
0 = Address
1 = Command
0
1
B6
Read/Write
0 = Write
1 = Read
R/W
0
B5
Continuous address mode
1 = Continuous mode
R/W
0
B4
Address/Command bit 4
Adr 4
Cmd 4
B3
Address/Command bit 3
Adr 3
Cmd 3
B2
Address/Command bit 2
Adr 2
Cmd 2
B1
Address/Command bit 1
Adr 1
Cmd 1
B0
Address/Command bit 0
Adr 0
Cmd 0
The MSB determines if the word is to be used as a command or address. The last two columns of
Table 6-20 show the function of each bit, depending on whether address or command is written.
Command mode is used to enter a command resulting in reader action (initialize transmission, enable
reader, and turn reader on or off).
6.14.1.1 Idle (0x00)
This command issues dummy clock cycles. In parallel mode, one cycle is issued. In SPI mode, eight
cycles are issued. This command should be sent after a Software Initialization command to allow the
command to finish operation.
6.14.1.2 Software Initialization (0x03)
This command starts a power-on reset. After sending this command, the register values change as shown
in Table 6-21.
Table 6-21. Register Values After Sending Software
Initialization (0x03)
ADDRESS
(1)
REGISTER
VALUE
0x00
Chip status control
0x01
ISO control
0x01
0x02
ISO/IEC 14443 B TX options
0x03
ISO/IEC 14443 A high bit rate options
0x04
TX timer high byte control
0xC1 (1)
0x05
TX timer low byte control
0xC1 (1)
0x06
TX pulse length control
0x00
0x07
RX no response wait time
0x0E
0x08
RX wait time
0x09
Modulator and SYS_CLK control
0x0A
RX special setting
0x21 (1)
0x00
0x00
0x07 (1)
0x91
0x10 (1)
Differs from default at POR
Detailed Description
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Table 6-21. Register Values After Sending Software
Initialization (0x03) (continued)
ADDRESS
(2)
REGISTER
VALUE
0x0B
Regulator and I/O control
0x87
0x0C
IRQ status
0x00
0x0D
Collision position and interrupt mask
0x3E
0x0E
Collision position
0x00
0x0F
RSSI levels and oscillator status
0x40
0x10
Special function
0x00
0x11
Special function
0x00
0x12
RAM
0x00
0x13
RAM
0x00
0x14
Adjustable FIFO IRQ levels
0x00
0x15
Reserved
0x00
0x16
NFC low field detection level
0x00
0x18
NFC target detection level
0x00 (2)
0x19
NFC target protocol
0x00
0x1A
Test
0x00
0x1B
Test
0x00
0x1C
FIFO status
0x00
Default value may not always be 0x00. See the TRF7970A Errata for
details.
6.14.1.3 Initial RF Collision Avoidance (0x04)
See the TRF7970A Errata.
6.14.1.4 Response RF Collision Avoidance (0x05)
See the TRF7970A Errata.
6.14.1.5 Response RF Collision Avoidance (0x06, n = 0)
See the TRF7970A Errata.
6.14.1.6 Reset FIFO (0x0F)
The reset command clears the FIFO contents and FIFO Status register (0x1C). It also clears the register
storing the collision error location (0x0E).
6.14.1.7 Transmission With CRC (0x11)
The transmission command must be sent first, followed by transmission length bytes, and FIFO data. The
reader starts transmitting after the first byte is loaded into the FIFO. The CRC byte is included in the
transmitted sequence.
6.14.1.8 Transmission Without CRC (0x10)
Same as Section 6.14.1.7 with CRC excluded.
6.14.1.9 Delayed Transmission With CRC (0x13)
The transmission command must be sent first, followed by the transmission length bytes, and FIFO data.
The reader transmission is triggered by the TX timer.
54
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6.14.1.10 Delayed Transmission Without CRC (0x12)
Same as Section 6.14.1.9 with CRC excluded.
6.14.1.11 Transmit Next Time Slot (0x14)
When this command is received, the reader transmits the next slot command. The next slot sign is defined
by the protocol selection. This is used by the ISO/IEC 15693 protocol.
6.14.1.12 Block Receiver (0x16)
The block receiver command puts the digital part of receiver (bit decoder and framer) in reset mode. This
is useful in an extremely noisy environment, where the noise level could otherwise cause a constant
switching of the subcarrier input of the digital part of the receiver. The receiver (if not in reset) would try to
catch a SOF signal, and if the noise pattern matched the SOF pattern, an interrupt would be generated,
falsely signaling the start of an RX operation. A constant flow of interrupt requests can be a problem for
the external system (MCU), so the external system can stop this by putting the receive decoders in reset
mode. The reset mode can be terminated in two ways. The external system can send the enable receiver
command. The reset mode is also automatically terminated at the end of a TX operation. The receiver can
stay in reset after end of TX if the RX wait time register (0x08) is set. In this case, the receiver is enabled
at the end of the wait time following the transmit operation.
6.14.1.13 Enable Receiver (0x17)
This command clears the reset mode in the digital part of the receiver if the reset mode was entered by
the block receiver command.
6.14.1.14 Test Internal RF (RSSI at RX Input With TX ON) (0x18)
The level of the RF carrier at RF_IN1 and RF_IN2 inputs is measured. Operating range between 300 mVP
and 2.1 VP (step size is 300 mV). The two values are displayed in the RSSI Levels and Oscillator Status
register (0x0F). The command is intended for diagnostic purposes to set correct RF_IN levels. Optimum
RFIN input level is approximately 1.6 VP or code 5 to 6. The nominal relationship between the RF peak
level and RSSI code is shown in Table 6-22 and in Section 6.5.1.1.
NOTE
If the command is executed immediately after power-up and before any communication with
a tag is performed, the command must be preceded by Enable RX command. The Check RF
commands require full operation, so the receiver must be activated by Enable RX or by a
normal Tag communication for the Check RF command to work properly.
Table 6-22. Test Internal RF Peak Level to RSSI Codes
RF_IN1 [mVPP]
300
600
900
1200
1500
1800
Decimal Code
1
2
3
4
5
6
7
001
010
011
001
101
011
111
Binary Code
2100
6.14.1.15 Test External RF (RSSI at RX Input with TX OFF) (0x19)
This command can be used in active mode when the RF receiver is switched on but RF output is switched
off. This means bit B1 = 1 in Chip Status Control Register. The level of RF signal received on the antenna
is measured and displayed in the RSSI Levels and Oscillator Status register (0x0F). The relation between
the 3 bit code and the external RF field strength [A/m] must be determinate by calculation or by
experiments for each antenna type as the antenna Q and connection to the RF input influence the result.
The nominal relation between the RF peak to peak voltage in the RF_IN1 input and RSSI code is shown
in Table 6-23 and in Section 6.5.1.2.
Detailed Description
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NOTE
If the command is executed immediately after power-up and before any communication with
a tag is performed, the command must be preceded by an Enable RX command. The Check
RF commands require full operation, so the receiver must be activated by Enable RX or by a
normal Tag communication for the Check RF command to work properly.
Table 6-23. Test External RF Peak Level to RSSI Codes
RF_IN1 [mVPP]
40
60
80
100
140
180
Decimal Code
1
2
3
4
5
6
7
001
010
011
001
101
011
111
Binary Code
300
6.15 Register Description
6.15.1 Register Preset
After power up and the EN pin low-to-high transition, the reader is in the default mode. The default
configuration is ISO/IEC 15693, single subcarrier, high data rate, 1-out-of-4 operation. The low-level option
registers (0x02 to 0x0B) are automatically set to adapt the circuitry optimally to the appropriate protocol
parameters. When entering another protocol (by writing to the ISO Control register 0x01), the low-level
option registers (0x02 to 0x0B) are automatically configured to the new protocol parameters. After
selecting the protocol, it is possible to change some low-level register contents if needed. However,
changing to another protocol and then back, reloads the default settings, and so then the custom settings
must be reloaded.
The Clo0 and Clo1 register (0x09) bits, which define the microcontroller frequency available on the
SYS_CLK pin, are the only 2 bits in the configuration registers that are not cleared during protocol
selection.
56
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6.15.2 Register Overview
Table 6-24 lists the registers.
Table 6-24. Register Definitions
ADDRESS
REGISTER
READ/WRITE
SECTION
Main Control Registers
0x00
Chip status control
0x01
ISO Control
R/W
Section 6.15.3.1.1
R/W
Section 6.15.3.1.2
Protocol Subsetting Registers
0x02
ISO/IEC 14443 B TX options
R/W
Section 6.15.3.2.1
0x03
ISO/IEC 14443 A high bit rate options
R/W
Section 6.15.3.2.2
0x04
TX timer high byte control
R/W
Section 6.15.3.2.3
0x05
TX timer low byte control
R/W
Section 6.15.3.2.4
0x06
TX pulse length control
R/W
Section 6.15.3.2.5
0x07
RX no response wait time
R/W
Section 6.15.3.2.6
0x08
RX wait time
R/W
Section 6.15.3.2.7
0x09
Modulator and SYS_CLK control
R/W
Section 6.15.3.2.8
0x0A
RX special setting
R/W
Section 6.15.3.2.9
0x0B
Regulator and I/O control
R/W
Section 6.15.3.2.10
0x10
Special function register (preset 0x00)
R/W
Section 6.15.3.3.4
0x11
Special function register (preset 0x00)
R/W
Section 6.15.3.3.5
0x14
Adjustable FIFO IRQ levels
R/W
Section 6.15.3.3.6
0x15
Reserved
R/W
0x16
NFC low field level
R/W
Section 6.15.3.3.7
0x17
NFCID1 number (up to 10 bytes wide)
W
Section 6.15.3.3.8
0x18
NFC target detection level
R/W
Section 6.15.3.3.9
0x19
NFC target protocol
R/W
Section 6.15.3.3.10
0x0C
IRQ status
0x0D
Collision position and interrupt mask register
0x0E
0x0F
Status Registers
R
Section 6.15.3.3.1
R/W
Section 6.15.3.3.2
Collision position
R
Section 6.15.3.3.2
RSSI levels and oscillator status
R
Section 6.15.3.3.3
RAM
0x12
RAM
0x13
RAM
R/W
N/A
R/W
N/A
R/W
Section 6.15.3.4.1
R/W
Section 6.15.3.4.2
R
Section 6.15.3.5.1
Test Registers
0x1A
Test (preset 0x00)
0x1B
Test (preset 0x00)
FIFO Registers
0x1C
FIFO status
0x1D
TX length byte 1
R/W
Section 6.15.3.5.2
0x1E
TX length byte 2
R/W
Section 6.15.3.5.2
0x1F
FIFO I/O register
R/W
N/A
Detailed Description
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6.15.3 Detailed Register Description
6.15.3.1 Main Configuration Registers
6.15.3.1.1 Chip Status Control Register (0x00)
Table 6-25 describes the Chip Status Control register.
Table 6-25. Chip Status Control Register (0x00)
Function: Control of Power mode, RF on or off, Active or Passive mode, Direct mode
Default: 0x01, preset at EN = L or POR = H
Bit
Name
B7
stby
B6
B5
B4
direct
rf_on
Description
1 = Standby mode
Standby mode keeps all supply regulators and the 13.56-MHz SYS_CLK
oscillator running. (Typical start-up time to full operation is 100 µs.)
0 = Active mode
Active mode (default)
1 = Direct mode 0 or 1
Provides user direct access to AFE (direct mode 0) or allows user to add
custom framing (direct mode 1). Bit 6 of the ISO Control register must be set by
user before entering direct mode 0 or 1.
0 = Direct l 2 (default)
Uses SPI or parallel communication with automatic framing and ISO decoders
1 = RF output active
Transmitter on, receivers on
0 = RF output not active
Transmitter off
1 = Half output power
TX_OUT (pin 5) = 8-Ω output impedance P = 100 mW (20 dBm) at 5 V,
P = 33 mW (+15 dBm) at 3.3 V
0 = Full output power
TX_OUT (pin 5) = 4-Ω output impedance P = 200 mW (+23 dBm) at 5 V,
P = 70 mW (+18 dBm) at 3.3 V
1 = Selects aux RX input
RX_IN2 input is used
0 = Selects main RX input
RX_IN1 input is used
1 = Receiver activated for
external field measurement
Forced enabling of receiver and TX oscillator. Used for external field
measurement.
0 = Automatic enable
Allows enable of the receiver by bit 5 of this register (0x00)
1 = 5-V operation
0 = 3-V operation
Selects the VIN voltage range
rf_pwr
B3
pm_on
B2
Reserved
B1
rec_on
B0
Function
vrs5_3
6.15.3.1.2 ISO Control Register (0x01)
Table 6-26 describes the ISO Control register.
Table 6-26. ISO Control Register (0x01)
Function: Controls the selection of ISO standard protocol, direct mode and receive CRC
Default: 0x02 (ISO/IEC 15693 high bit rate, one subcarrier, 1 out of 4); it is preset at EN = L or POR = H
Bit
Name
Function
Description
B7
rx_crc_n
CRC Receive selection
0 = RX CRC (CRC is present in the response)
1 = no RX CRC (CRC is not present in the response) (1)
B6
dir_mode
Direct mode type selection
0 = Direct Mode 0
1 = Direct mode 1
B5
rfid
RFID / Reserved
0 = RFID mode
1 = NFC or card emulation mode
RFID: See Table 6-27 for B0:B4 settings based on ISO protocol in application
B4
(1)
58
iso_4
RFID / NFC Target
NFC:
0 = target
1 = initiator
Only applicable to ISO/IEC 14443 A and ISO/IEC 15693
Detailed Description
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Table 6-26. ISO Control Register (0x01) (continued)
B3
iso_3
RFID / NFC Mode
NFC:
0 = passive mode
1 = active mode
B2
iso_2
RFID / Card Emulation
NFC:
0 = NFC Normal Modes
1 = Card Emulation Mode
B1
iso_1
RFID / NFC bit rate
NFC:
0 = bit rate selection or card emulation selection, see Table 6-28
B0
iso_0
RFID / NFC bit rate
NFC:
0 = bit rate selection or card emulation selection, see Table 6-28
Table 6-27. ISO Control Register ISO_x Settings, RFID Mode
ISO_4
ISO_3
ISO_2
ISO_1
ISO_0
0
0
0
0
0
ISO/IEC 15693 low bit rate, 6.62 kbps, one subcarrier, 1 out of 4
0
0
0
0
1
ISO/IEC 15693 low bit rate, 6.62 kbps, one subcarrier, 1 out of 256
0
0
0
1
0
ISO/IEC 15693 high bit rate, 26.48 kbps, one subcarrier, 1 out of 4
0
0
0
1
1
ISO/IEC 15693 high bit rate, 26.48 kbps, one subcarrier, 1 out of 256
0
0
1
0
0
ISO/IEC 15693 low bit rate, 6.67 kbps, double subcarrier, 1 out of 4
0
0
1
0
1
ISO/IEC 15693 low bit rate, 6.67 kbps, double subcarrier, 1 out of
256
0
0
1
1
0
ISO/IEC 15693 high bit rate, 26.69 kbps, double subcarrier, 1 out of 4
0
0
1
1
1
ISO/IEC 15693 high bit rate, 26.69 kbps, double subcarrier,
1 out of 256
0
1
0
0
0
ISO/IEC 14443 A RX bit rate, 106 kbps
0
1
0
0
1
ISO/IEC 14443 A RX high bit rate, 212 kbps
0
1
0
1
0
ISO/IEC 14443 A RX high bit rate, 424 kbps
0
1
0
1
1
ISO/IEC 14443 A RX high bit rate, 848 kbps
0
1
1
0
0
ISO/IEC 14443 B RX bit rate, 106 kbps
0
1
1
0
1
ISO/IEC 14443 B RX high bit rate, 212 kbps
0
1
1
1
0
ISO/IEC 14443 B RX high bit rate, 424 kbps
0
1
1
1
1
ISO/IEC 14443 B RX high bit rate, 848 kbps
1
0
0
1
1
Reserved
1
0
1
0
0
Reserved
1
1
0
1
0
FeliCa 212 kbps
1
1
0
1
1
FeliCa 424 kbps
(1)
PROTOCOL
REMARKS
Default for reader
RX bit rate
(1)
RX bit rate
(1)
For ISO/IEC 14443 A or B, when bit rate of TX is different from RX, settings can be done in register 0x02 or 0x03.
Table 6-28. ISO Control Register ISO_x Settings,
NFC Mode (B5 = 1, B2 = 0) or Card Emulation (B5 = 1, B2 = 1)
NFC
(B5 = 1, B2 = 0)
CARD EMULATION
(B5 = 1, B2 = 1)
0
N/A
ISO/IEC 14443 A
1
106 kbps
ISO/IEC 14443 B
1
0
212 kbps
N/A
1
1
424 kbps
N/A
ISO_1
ISO_0
0
0
Detailed Description
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6.15.3.2 Control Registers – Sublevel Configuration Registers
6.15.3.2.1 ISO/IEC 14443 TX Options Register (0x02)
Table 6-29 describes the ISO/IEC 14443 TX Options register.
Table 6-29. ISO/IEC 14443 TX Options Register (0x02)
Function: Selects the ISO subsets for ISO/IEC 14443 – TX
Default: 0x00 at POR = H or EN = L
Bit
Name
B7
egt2
TX EGT time select MSB
B6
egt1
TX EGT time select
B5
egt0
TX EGT time select LSB
B4
eof_l0
1 = EOF→ 0 length 11 etu
0 = EOF→ 0 length 10 etu
B3
sof_l1
1 = SOF→ 1 length 03 etu
0 = SOF→ 1 length 02 etu
B2
sof _l0
1 = SOF→ 0 length 11 etu
0 = SOF→ 0 length 10 etu
B1
l_egt
B0
Auto SDD_SAK
Function
Description
Three bit code defines the number of etu (0-7) which separate two characters.
ISO/IEC 14443 B TX only.
ISO/IEC 14443 B TX only
1 = EGT after each byte
0 = EGT after last byte is
omitted
1 = ISO/IEC 14443 A Layer
4 compliant (in SAK
response)
0 = Not Layer 4 compliant
(in SAK response)
For use with Auto SDD configuration, makes B6 in ISO/IEC 14443 A response
1 or 0, indicating Layer 4 compliance (or not), for all other cases, this bit is
unused
6.15.3.2.2 ISO/IEC 14443 High-Bit-Rate and Parity Options Register (0x03)
Table 6-30 describes the ISO/IEC 14443 High-Bit-Rate and Parity Options register.
Table 6-30. ISO/IEC 14443 High-Bit-Rate and Parity Options Register (0x03)
Function: Selects the ISO subsets for ISO/IEC 14443 – TX
Default: 0x00 at POR = H or EN = L, and at each write to ISO Control register
Bit
60
Name
B7
dif_tx_br
B6
tx_br1
Function
Description
TX bit rate different from RX
Valid for ISO/IEC 14443 A or B high bit rate
bit rate enable
tx_br1 = 0, tx_br
tx_br1 = 0, tx_br
tx_br1 = 1, tx_br
tx_br1 = 1, tx_br
TX bit rate
B5
tx_br0
B4
parity-2tx
1 = parity odd except last
byte which is even for TX
B3
parity-2rx
1 = parity odd except last
byte which is even for RX
=0→
=1→
=0→
=1→
106 kbps
212 kbps
424 kbps
848 kbps
For ISO/IEC 14443 A high bit rate, coding and decoding
B2
Unused
B1
Unused
B0
Unused
Detailed Description
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6.15.3.2.3 TX Timer High Byte Control Register (0x04)
Table 6-31 describes the TX Timer High Byte Control register.
Table 6-31. TX Timer High Byte Control Register (0x04)
Function: For Timings
Default: 0xC2 at POR = H or EN = L, and at each write to ISO Control register
Bit
Name
B7
tm_st1
Timer Start Condition
Function
B6
tm_st0
Timer Start Condition
B5
tm_lengthD
Timer Length MSB
B4
tm_lengthC
Timer Length
B3
tm_lengthB
Timer Length
B2
tm_lengthA
Timer Length
B1
tm_length9
Timer Length
B0
tm_length8
Timer Length LSB
Description
tm_st1 = 0, tm_st0 = 0 →
tm_st1 = 0, tm_st0 = 1 →
tm_st1 = 1, tm_st0 = 0 →
tm_st1 = 1, tm_st0 = 1 →
beginning of TX SOF
end of TX SOF
beginning of RX SOF
end of RX SOF
6.15.3.2.4 TX Timer Low Byte Control Register (0x05)
Table 6-32 describes the TX Timer Low Byte Control register.
Table 6-32. TX Timer Low Byte Control Register (0x05)
Function: For Timings
Default: 0x00 at POR = H or EN = L, and at each write to ISO Control register
Bit
Name
Function
Description
B7
tm_length7
Timer Length MSB
B6
tm_length6
Timer Length
B5
tm_length5
Timer Length
B4
tm_length4
Timer Length
B3
tm_length3
Timer Length
Step size is 590 ns
B2
tm_length2
Timer Length
All bits low = timer disabled (0x00)
B1
tm_length1
Timer Length
Preset 0x00 for all other protocols
B0
tm_length0
Timer Length LSB
Defines the time when delayed transmission is started.
RX wait range is 590 ns to 9.76 ms (1 to 16383)
Detailed Description
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6.15.3.2.5 TX Pulse Length Control Register (0x06)
The length of the modulation pulse is defined by the protocol selected in the ISO Control register 0x01.
With a high Q antenna, the modulation pulse is typically prolonged, and the tag detects a longer pulse
than intended. For such cases, the modulation pulse length can be corrected by using the TX Pulse
Length Control register (0x06). If the register contains all zeros, then the pulse length is governed by the
protocol selection. If the register contains a value other than 0x00, the pulse length is equal to the value of
the register in 73.7-ns increments. This means the range of adjustment can be 73.7 ns to 18.8 µs.
Table 6-33 describes the TX Pulse Length Control register.
Table 6-33. TX Pulse Length Control Register (0x06)
Function: Controls the length of TX pulse
Default: 0x00 at POR = H or EN = L and at each write to ISO Control register.
Bit
Name
B7
Pul_p2
Function
B6
Pul_p1
B5
Pul_p0
B4
Pul_c4
The following default timings are preset by the ISO Control register (0x01):
B3
Pul_c3
9.44 µs → ISO/IEC 15693 (TI Tag-It HF-I)
B2
Pul_c2
11 µs → Reserved
B1
Pul_c1
2.36 µs → ISO/IEC 14443 A at 106 kbps
B0
Pul_c0
Pulse length MSB
Description
The pulse range is 73.7 ns to 18.8 µs (1….255), step size 73.7 ns.
All bits low (00): pulse length control is disabled.
1.4 µs → ISO/IEC 14443 A at 212 kbps
Pulse length LSB
737 ns → ISO/IEC 14443 A at 424 kbps
442 ns → ISO/IEC 14443 A at 848 kbps; pulse length control disabled
6.15.3.2.6 RX No Response Wait Time Register (0x07)
The RX No Response timer is controlled by the RX NO Response Wait Time Register 0x07. This timer
measures the time from the start of slot in the anticollision sequence until the start of tag response. If there
is no tag response in the defined time, an interrupt request is sent and a flag is set in IRQ status control
register 0x0C. This enables the external controller to be relieved of the task of detecting empty slots. The
wait time is stored in the register in increments of 37.76 µs. This register is also preset, automatically, for
every new protocol selection. Sending a Reset FIFO (0x0F) direct command after a TX Complete interrupt
will disable this feature.
Table 6-34 describes the RX No Response Wait Time register.
Table 6-34. RX No Response Wait Time Register (0x07)
Function: Defines the time when "no response" interrupt is sent; only for ISO/IEC 15693
Default: 0x0E at POR = H or EN = L and at each write to ISO Control register
Bit
Name
Function
B7
NoResp7
B6
NoResp6
B5
NoResp5
Defines the time when "no response" interrupt is sent. It starts from the end of
TX EOF. RX no response wait range is 37.76 µs to 9628 µs (1 to 255), step
size is: 37.76 µs.
B4
NoResp4
The following default timings are preset by the ISO Control register (0x01):
B3
NoResp3
390 µs → Reserved
B2
NoResp2
529 µs → for all protocols supported, but not listed here
B1
NoResp1
B0
NoResp0
No response MSB
Description
604 µs → Reserved
No response LSB
755 µs → ISO/IEC 15693 high data rate (TI Tag-It HF-I)
1812 µs → ISO/IEC 15693 low data rate (TI Tag-It HF-I)
62
Detailed Description
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6.15.3.2.7 RX Wait Time Register (0x08)
The RX-wait-time timer is controlled by the value in the RX wait time register 0x08. This timer defines the
time after the end of the transmit operation in which the receive decoders are not active (held in reset
state). This prevents incorrect detections resulting from transients following the transmit operation. The
value of the RX wait time register defines this time in increments of 9.44 µs. This register is preset at
every write to ISO Control register 0x01 according to the minimum tag response time defined by each
standard.
Table 6-35 describes the RX Wait Time register.
Table 6-35. RX Wait Time Register (0x08)
Function: Defines the time after TX EOF when the RX input is disregarded for example, to block out electromagnetic disturbance
generated by the responding card.
Default: 0x1F at POR = H or EN = L and at each write toISO control register.
Bit
Name
B7
Rxw7
Function
Description
B6
Rxw6
Defines the time after the TX EOF during which the RX input is ignored. Time
starts from the end of TX EOF.
B5
Rxw5
RX wait range is 9.44 µs to 2407 µs (1 to 255), Step size 9.44 µs.
B4
Rxw4
B3
Rxw3
B2
Rxw2
B1
Rxw1
B1
Rxw0
The following default timings are preset by the ISO Control register (0x01):
RX wait time
9.44 µs → FeliCa
66 µs → ISO/IEC 14443 A and B
180 µs → Reserved
293 µs → ISO/IEC 15693 (TI Tag-It HF-I)
Detailed Description
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6.15.3.2.8 Modulator and SYS_CLK Control Register (0x09)
The frequency of SYS_CLK (pin 27) is programmable by the bits B4 and B5 of this register. The frequency
of the TRF7970A system clock oscillator is divided by 1, 2 or 4 resulting in available SYS_CLK
frequencies of 13.56 MHz or 6.78 MHz or 3.39 MHz.
The ASK modulation depth is controlled by bits B0, B1 and B2. The range of ASK modulation is 7% to
30% or 100% (OOK). The selection between ASK and OOK (100%) modulation can also be done using
direct input OOK (pin 12). The direct control of OOK/ASK using OOK pin is only possible if the function is
enabled by setting B6 = 1 (en_ook_p) in this register (0x09) and the ISO Control Register (0x01, B6 = 1).
When configured this way, the MOD (pin 14) is used as input for the modulation signal.
Table 6-36 describes the Modulator and SYS_CLK Control register.
Table 6-36. Modulator and SYS_CLK Control Register (0x09)
Function: Controls the modulation input and depth, ASK / OOK control and clock output to external system (MCU)
Default: 0x91 at POR = H or EN = L, and at each write to ISO control register, except Clo1 and Clo0.
Bit
Name
B7
27MHz
Enables 27.12-MHz crystal
en_ook_p
1 = Enables external
selection of ASK or OOK
modulation
0 = Default operation as
defined in B0 to B2 (0x09)
B6
Function
Description
Default = 1 (enabled)
Enable ASK/OOK pin (pin 12) for "on the fly change" between any preselected
ASK modulation as defined by B0 to B2 and OOK modulation:
If B6 is 1, pin 12 is configured as follows:
1 = OOK modulation
0 = Modulation as defined in B0 to B2 (0x09)
B5
SYS_CLK output frequency
MSB
Clo0
SYS_CLK output frequency
LSB
B3
en_ana
1 = Sets pin 12 (ASK/OOK)
as an analog output
0 = Default
B2
Pm2
B4
B1
B0
64
Clo1
Pm1
Pm0
Modulation depth MSB
Modulation depth
Modulation depth LSB
SYS_CLK Output SYS_CLK Output
(if 13.56-MHz
(if 27.12-MHz
crystal is used)
crystal is used)
Clo1
Clo0
0
0
Disabled
Disabled
0
1
3.39 MHz
6.78 MHz
1
0
6.78 MHz
13.56 MHz
1
1
13.56 MHz
27.12 MHz
For test and measurement purpose. ASK/OOK pin 12 can be used to monitor
the analog subcarrier signal before the digitizing with DC level equal to AGND.
Pm2
Pm1
Pm0
0
0
0
ASK 10%
0
0
1
OOK (100%)
0
1
0
ASK 7%
0
1
1
ASK 8.5%
1
0
0
ASK 13%
1
0
1
ASK 16%
1
1
0
ASK 22%
1
1
1
ASK 30%
Detailed Description
Mod Type and %
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6.15.3.2.9 RX Special Setting Register (0x0A)
Table 6-37 describes the RX Special Setting register.
Table 6-37. RX Special Setting Register (0x0A)
Function: Sets the gains and filters directly
Default: 0x40 at POR = H or EN = L, and at each write to the ISO Control register 0x01. When bits B7, B6, B5 and B4 are all zero, the
filters are set for ISO/IEC 14443 B (240 kHz to 1.4 MHz).
Bit
Name
Function
B7
C212
Band-pass 110 kHz to 570 kHz
Appropriate for 212-kHz subcarrier system (FeliCa)
B6
C424
Band-pass 200 kHz to 900 kHz
Appropriate for 424-kHz subcarrier used in ISO/IEC 15693
B5
M848
Band-pass 450 kHz to 1.5 MHz
Appropriate for Manchester-coded 848-kHz subcarrier used in
ISO/IEC 14443 A and B
B4
hbt
Band-pass 100 kHz to 1.5 MHz
Gain reduced for 18 dB
Appropriate for highest bit rate (848 kbps) used in high-bit-rate
ISO/IEC 14443
B3
gd1
B2
gd2
00
01
10
11
Sets the RX gain reduction and reduces sensitivity
B1
Reserved
B0
Reserved
= Gain
= Gain
= Gain
= Gain
reduction
reduction
reduction
reduction
Description
0 dB
for 5 dB
for 10 dB
for 15 dB
NOTE
The setting of bits B4, B5, B6 and B7 to 0 selects bandpass characteristic of 240 kHz to 1.4
MHz. This is appropriate for ISO/IEC 14443 B, FeliCa protocol, and ISO/IEC 14443 A higher
bit rates of 212 kbps and 424 kbps.
Detailed Description
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6.15.3.2.10 Regulator and I/O Control Register (0x0B)
Table 6-38 describes the Regulator and I/O Control register.
Table 6-38. Regulator and I/O Control Register (0x0B)
Function: Control the three voltage regulators
Default: 0x87 at POR = H or EN = L
Bit
Name
Function
Description
0 = Manual settings; see B0
to B2 in Table 6-39 and
Auto system sets VDD_RF = VIN – 250 mV and VDD_A = VIN – 250 mV and
Table 6-40
VDD_X= VIN – 250 mV, but not higher than 3.4 V.
1 = Automatic setting (see
Table 6-41 and Table 6-42)
B7
auto_reg
B6
en_ext_pa
Support for external power
amplifier
Internal peak detectors are disabled, receiver inputs (RX_IN1 and RX_IN2)
accept externally demodulated subcarrier. At the same time ASK/OOK pin 12
becomes modulation output for external TX amplifier.
B5
io_low
1 = enable low peripheral
communication voltage
When B5 = 1, maintains the output driving capabilities of the I/O pins connected
to the level shifter under low voltage operation. Should be set 1 when VDD_I/O
voltage is between 1.8 V to 2.7 V.
B4
Unused
No function
Default is 0.
B3
Unused
No function
Default is 0.
B2
vrs2
B1
vrs1
Voltage set MSB voltage
set LSB
Vrs3_5 = L: VDD_RF, VDD_A, VDD_X range 2.7 V to 3.4 V; see Table 6-39 and
Table 6-40
B0
vrs0
Table 6-39. Supply-Regulator Setting – Manual 5-V System
REGISTER
OPTION BITS SETTING IN CONTROL REGISTER
B7
B6
B5
B4
B3
B2
B1
00
ACTION
B0
1
5-V system
0B
0
Manual regulator setting
0B
0
1
1
1
VDD_RF = 5 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
1
1
0
VDD_RF = 4.9 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
1
0
1
VDD_RF = 4.8 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
1
0
0
VDD_RF = 4.7 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
0
1
1
VDD_RF = 4.6 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
0
1
0
VDD_RF = 4.5 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
0
0
1
VDD_RF = 4.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V
0B
0
0
0
0
VDD_RF = 4.3 V, VDD_A = 3.4 V, VDD_X = 3.4 V
Table 6-40. Supply-Regulator Setting – Manual 3-V System
REGISTER
OPTION BITS SETTING IN CONTROL REGISTER
B7
B6
B5
B4
B3
B2
B1
00
66
ACTION
B0
0
3-V system
0B
0
0B
0
1
1
1
Manual regulator setting
VDD_RF = 3.4 V, VDD_A and VDD_X = 3.4 V
0B
0
1
1
0
VDD_RF = 3.3 V, VDD_A and VDD_X = 3.3 V
0B
0
1
0
1
VDD_RF = 3.2 V, VDD_A and VDD_X = 3.2 V
0B
0
1
0
0
VDD_RF = 3.1 V, VDD_A and VDD_X = 3.1 V
0B
0
0
1
1
VDD_RF = 3.0 V, VDD_A and VDD_X = 3.0 V
0B
0
0
1
0
VDD_RF = 2.9 V, VDD_A and VDD_X = 2.9 V
0B
0
0
0
1
VDD_RF = 2.8 V, VDD_A and VDD_X = 2.8 V
0B
0
0
0
0
VDD_RF = 2.7 V, VDD_A and VDD_X = 2.7 V
Detailed Description
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Table 6-41. Supply-Regulator Setting – Automatic 5-V System
OPTION BITS SETTING IN CONTROL REGISTER
REGISTER
B7
B6
B5
B4
B3
B2
B1
x (1)
0
00
0B
(1)
1
ACTION
B0
1
5-V system
0
Automatic regulator setting 400-mV difference
x = don't care
Table 6-42. Supply-Regulator Setting – Automatic 3-V System
OPTION BITS SETTING IN CONTROL REGISTER
REGISTER
B7
B6
B5
B4
B3
B2
B1
x (1)
0
00
0B
(1)
1
ACTION
B0
0
3-V system
0
Automatic regulator setting 400-mV difference
x = don't care
6.15.3.3 Status Registers
6.15.3.3.1 IRQ Status Register (0x0C)
Table 6-43 describes the IRQ Status register.
Table 6-43. IRQ Status Register (0x0C)
Function: Information available about TRF7970A IRQ and TX/RX status
Default: 0x00 at POR = H or EN = L, and at each write to the ISO Control Register 0x01. It is also automatically reset at the end of a read
phase. The reset also removes the IRQ flag.
Bit
Name
Function
Description
B7
Irq_tx
IRQ set due to end of TX
Signals that TX is in progress. The flag is set at the start of TX but the interrupt
request (IRQ = 1) is sent when TX is finished.
B6
Irg_srx
IRQ set due to RX start
Signals that RX SOF was received and RX is in progress. The flag is set at the
start of RX but the interrupt request (IRQ = 1) is sent when RX is finished.
B5
Irq_fifo
Signals the FIFO level
Signals FIFO high or low as set in the Adjustable FIFO IRQ Levels (0x14)
register
B4
Irq_err1
CRC error
Indicates receive CRC error only if B7 (no RX CRC) of ISO Control register is
set to 0.
B3
Irq_err2
Parity error
Indicates parity error for ISO/IEC 14443 A
B2
Irq_err3
Byte framing or EOF error
Indicates framing error
B1
Irq_col
Collision error
Collision error for ISO/IEC 14443 A and ISO/IEC 15693 single subcarrier. Bit is
set if more then 6 or 7 (as defined in register 0x10) are detected in 1 bit period
of ISO/IEC 14443 A 106 kbps. Collision error bit can also be triggered by
external noise.
B0
Irq_noresp
No response time interrupt
No response within the "No-response time" defined in RX No Response Wait
Time register (0x07). Signals the MCU that the next slot command can be sent.
Only for ISO/IEC 15693.
To reset (clear) the register 0x0C and the IRQ line, the register must be read. During Transmit the
decoder is disabled, only bits B5 and B7 can be changed. During Receive only bit B6 can be changed, but
does not trigger the IRQ line immediately. The IRQ signal is set at the end of Transmit and Receive
phase.
Detailed Description
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Table 6-44 describes the IRQ Status register when used for NFC and card emulation operation.
Table 6-44. IRQ Status Register (0x0C) for NFC and Card Emulation Operation
Function: Information available about TRF7970A IRQ and TX/RX status
Default: 0x00 at POR = H or EN = L, and at each write to the ISO Control Register 0x01. It is also automatically reset at the end of a read
phase. The reset also removes the IRQ flag.
Bit
Name
B7
Irq_tx
IRQ set due to end of TX
Signals that TX is in progress. The flag is set at the start of TX but the interrupt
request (IRQ = 1) is sent when TX is finished.
B6
Irg_srx
IRQ set due to RX start
Signals that RX SOF was received and RX is in progress. The flag is set at the
start of RX but the interrupt request (IRQ = 1) is sent when RX is finished.
B5
Irq_fifo
Signals the FIFO level
Signals FIFO high or low as set in the Adjustable FIFO IRQ Levels (0x14)
register
B4
Irq_err1
Protocol error
Any protocol error
B3
Irq_sdd
SDD completed
SDD (passive target at 106 kbps) successfully finished
B2
Irq_rf
RF field change
Sufficient RF signal level for operation was reached or lost
RF collision avoidance
finished
The system has finished collision avoidance and the minimum wait time is
elapsed.
RF collision avoidance not
finished successfully
The external RF field was present so the collision avoidance could not be
carried out.
B1
Irq_col
B0
Irq_col_err
Function
Description
6.15.3.3.2 Interrupt Mask Register (0x0D) and Collision Position Register (0x0E)
Table 6-45 describes the Interrupt Mask register. Table 6-46 describes the Collision Position register.
Table 6-45. Interrupt Mask Register (0x0D)
Default: 0x3E at POR = H and EN = L. Collision bits reset automatically after read operation.
Bit
Name
Function
Description
B7
Col9
Bit position of collision MSB Supports ISO/IEC 14443 A
B6
Col8
Bit position of collision
B5
En_irq_fifo
Interrupt enable for FIFO
Default = 1
B4
En_irq_err1
Interrupt enable for CRC
Default = 1
B3
En_irq_err2
Interrupt enable for Parity
Default = 1
B2
En_irq_err3
Interrupt enable for Framing
Default = 1
error or EOF
B1
En_irq_col
Interrupt enable for collision
error
Default = 1
B0
En_irq_noresp
Enables no-response
interrupt
Default = 0
Table 6-46. Collision Position Register (0x0E)
Function: Displays the bit position of collision or error
Default: 0x00 at POR = H and EN = L. Automatically reset after read operation.
68
Bit
Name
Function
B7
Col7
Bit position of collision MSB
Description
B6
Col6
B5
Col5
B4
Col4
B3
Col3
B2
Col2
B1
Col1
B0
Col0
ISO/IEC 14443 A mainly supported, in the other protocols this register shows
the bit position of error. Frame, SOF, EOF, parity, or CRC error.
Bit position of collision LSB
Detailed Description
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6.15.3.3.3 RSSI Levels and Oscillator Status Register (0x0F)
Table 6-47 describes the RSSI Levels and Oscillator Status register.
Table 6-47. RSSI Levels and Oscillator Status Register (0x0F)
Function: Displays the signal strength on both reception channels and RF amplitude during RF-off state. The RSSI values are valid from
reception start till start of next transmission.
Bit
Name
B7
Unused
Function
Description
B6
osc_ok
B5
rssi_x2
B4
rssi_x1
B3
rssi_x0
B2
rssi_2
MSB RSSI value of main
RX (RX_IN1)
B1
rssi_1
Main channel RSSI
B0
rssi_0
LSB RSSI value of main RX
(RX_IN1)
Crystal oscillator stable
indicator
13.56-MHz frequency stable (approximately 200 µs)
MSB RSSI value of auxiliary
Auxiliary channel is by default RX_IN2. The input can be swapped by B3 = 1
RX (RX_IN2)
(Chip Status Control register 0x00). If "swapped", the Auxiliary channel is
Auxiliary channel RSSI
connected to RX_IN1 and, hence, the Auxiliary RSSI represents the signal level
MSB RSSI value of auxiliary at RX_IN1.
RX (RX_IN2)
Active channel is default and can be set with option bit B3 = 0 of Chip Status
Control register 0x00.
RSSI measurement block is measuring the demodulated envelope signal (except in case of direct
command for RF amplitude measurement described later in direct commands section). The measuring
system is latching the peak value, so the RSSI level can be read after the end of receive packet. The
RSSI value is reset during next transmit action of the reader, so the new tag response level can be
measured. The RSSI levels calculated to the RF_IN1 and RF_IN2 are presented in Section 6.5.1.1 and
Section 6.5.1.2. The RSSI has 7 steps (3 bits) with 4-dB increment. The input level is the peak-to-peak
modulation level of RF signal measured on one side envelope (positive or negative).
6.15.3.3.4 Special Functions Register (0x10)
Table 6-48 describes the Special Functions register at address 0x10.
Table 6-48. Special Functions Register (0x10)
Function: User configurable options for ISO/IEC 14443 A specific operations
Bit
Name
Function
Description
B7
Reserved
Reserved
B6
Reserved
Reserved
B5
par43
Disables parity checking for
ISO/IEC 14443 A
B4
next_slot_37us
B3
Sp_dir_mode
B2
4_bit_RX
B1
B0
0 = 18.88 µs
1 = 37.77 µs
Sets the time grid for next slot command in ISO/IEC 15693
Bit stream transmit for
MIFARE at 106 kbps
Enables direct mode for transmitting ISO/IEC 14443 A data, bypassing the
FIFO and feeding the data bit stream directly onto the encoder.
0 = normal receive
1 = 4-bit receive
Enable 4-bit replay for example, ACK, NACK used by some cards; for example,
MIFARE Ultralight
14_anticoll
0 = anticollision framing
(0x93, 0x95, 0x97)
1 = normal framing (no
broken bytes)
Disable anticollision frames for ISO/IEC 14443 A (this bit should be set to 1
after anticollision is finished)
col_7_6
0 = 7 subcarrier pulses
1 = 6 subcarrier pulses
Selects the number of subcarrier pulses that trigger collision error in
ISO/IEC 14443 A at 106 kbps
Detailed Description
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6.15.3.3.5 Special Functions Register (0x11)
Table 6-49 describes the Special Functions register at address 0x11.
Table 6-49. Special Functions Register (0x11)
Function: Indicate IRQ status for RX operations.
Bit
Name
B7
Reserved
Reserved
B6
Reserved
Reserved
B5
Reserved
Reserved
B4
Reserved
Reserved
B3
Reserved
Reserved
B2
Reserved
Reserved
B1
Reserved
B0
irg_srx
Function
Description
Reserved
Copy of the RX start signal
(Bit 6) of the IRQ Status
register (0x0C)
Signals the RX SOF was received and the RX is in progress. IRQ when RX is
completed.
6.15.3.3.6 Adjustable FIFO IRQ Levels Register (0x14)
Table 6-50 describes the Adjustable FIFO IRQ Levels register.
Table 6-50. Adjustable FIFO IRQ Levels Register (0x14)
Function: Adjusts level at which FIFO indicates status by IRQ
Default: 0x00 at POR = H and EN = L
Bit
Name
B7
Reserved
Reserved
B6
Reserved
Reserved
B5
Reserved
Reserved
B4
Reserved
Reserved
B3
Wlh_1
B2
Wlh_0
B1
Wll_1
B0
70
Wll_0
Function
Description
FIFO high IRQ level (during
RX)
Wlh_1
0
0
1
1
Wlh_0
0
1
0
1
IRQ Level
124
120
112
96
FIFO low IRQ level (during
TX)
Wll_1
0
0
1
1
Wll_0
0
1
0
1
IRQ Level
4
8
16
32
Detailed Description
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6.15.3.3.7 NFC Low Field Level Register (0x16)
Table 6-51 describes the NFC Low Field Level register.
Table 6-51. NFC Low Field Level Register (0x16)
Function: Defines level for RF collision avoidance
Default: 0x00 at POR = H and EN = L.
Bit
Name
B7
Clex_dis
Function
B6
Hash6
N/A
B5
Hash5
N/A
B4
Hash4
N/A
B3
Hash3
N/A
B2
Rfdet_I2
B1
Rfdet_I1
B0
Rfdet_I0
Description
Disable clock extractor
NFC passive 106-kbps and ISO/IEC 14443 A card emulation
RF field level for RF
collision avoidance
Comparator output is displayed in B6 of the NFC Target Protocol register
(0x19)
6.15.3.3.8 NFCID1 Number Register (0x17)
This register is used to hold the ID of the TRF7970A for use during card emulation and NFC peer-to-peer
target operations.
The procedure for writing the ID into register 0x17 is the following:
1. Write bits 5, 6, and 7 in register 0x18 to enable SDD anticollision (bit 5), and set bit 6 and 7 to select
the ID length of 4, 7, or 10 bytes.
2. Write the ID into register 0x17. This should be done using write continuous mode with 4, 7, or 10 bytes
(according to what was set in register 0x18 bits 6 and 7).
6.15.3.3.9 NFC Target Detection Level Register (0x18)
Table 6-52 describes the NFC Target Detection Level register.
Table 6-52. NFC Target Detection Level Register (0x18)
Function: Defines level for RF wake up, enables automatic SDD and gives NFCID size. This register is supplied by Vin to ensure data
retention during complete power down.
Default: 0x00 at POR on Vin (not POR based on VDD_X) and not reset at EN = 0
Bit
B7
Name
Function
Description
Id_s1
NFCID1 size used in 106kbps passive target SDD
B6
Id_s0
B5
Sdd_en
B4
Id_s1
Id_s0
NFCID1 Size
(bytes)
0
0
4
0
1
7
1
0
10
1
1
Not allowed
Automatic SDD using internal state machine and ID stored in the NFCID1
Number register (0x17)
N/A
B3
Hi_rf
B2
Rfdet_h2
B1
Rfdet_h1
B0
Rfdet_h0
Extended range for RF
measurements
RF field level required for
system wakeup. If all bits
are 0, then the RF level
detection is off.
Comparator output is displayed in B7 of the NFC Target Protocol register
(0x19)
Detailed Description
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6.15.3.3.10 NFC Target Protocol Register (0x19)
This register is used (when read) to display the bit rate and protocol type when an NFC/RFID
Initiator/Reader is presented. An example use of this scenario would be when the TRF7970A is placed
into card emulation (Type A or Type B) and another TRF7970A or NFC device (polling for other NFC
devices) is presented to the TRF7970A in card emulation mode. The IRQ indicates that a field was
detected (IRQ Status = 0x04) or that Auto SDD has completed (IRQ Status = 0x08, if configured for
AutoSDD).
If Auto SDD is set and 0x04 is returned in IRQ status, then this register can be read out to see which
commands are coming in for gaining knowledge of the polling cycle sequence. Then, when the correct first
matching command (that is, REQA or REQB) is issued from Reader or Initiator, if AutoSDD is set, the IRQ
fires and the IRQ Status is 0x08, indicating completion of the SDD. The next IRQ should return 0x40 as
status, the Register 0x19 can be checked to make sure it is correct value (that is, 0xC9 for Type A at 106
kbps or 0xC5 for Type B at 106 kbps) indicating there are bytes in the FIFO and a read of the FIFO status
indicates how many bytes to read out. For example, after AutoSDD is completed, there are four bytes in
the FIFO, and these should be the RATS command coming in from the reader, which the MCU controlling
the TRF7970A in Card Emulation mode must respond to. If AutoSDD is not set, as another example with
the TRF7970A in ISO/IEC 14443 B Card Emulation mode, then the field detect happens as previously
described and IRQs also fire to indicate RX is complete (0x40). This register must be checked and
compared against case statement structure that is set up for the value of this register to be 0xC5,
indicating that an ISO/IEC 14443 B command at 106 kbps was issued. When this register (0x19) is 0xC5,
then the FIFO Status can be read and should hold a value of 0x03, and when read, be the REQB
command (0x05, 0x00, 0x00); the controlling MCU must respond with the ATQB response. The next steps
for either of these examples follow the relevant portions of the ISO/IEC 14443-3 or -4 standards, then the
NFC Forum specifications, depending on the system use case or application.
Table 6-53 describes the NFC Target Protocol register.
Table 6-53. NFC Target Protocol Register (0x19)
Function: Displays the bit rate and protocol type (active or passive) transmitted by initiator in first command. It also displays the comparator
outputs of both RF level detectors.
Default: 0x00 at POR = H and EN = L. B0 to B4 are automatically reset after MCU continuous read operation. B6 and B7 continuously
display the RF level comparator outputs.
Bit
Function
Description
B7
Rf_h
RF level is above the wake- The wakeup level is defined by bits B0 to B2 in the NFC Target Detection Level
up level setting
register (0x18)
B6
Rf_l
RF level is above the RF
collision avoidance level
setting
The collision avoidance level is defined by bits B0 – B2 in the register 0x16
(NFC Low Field Detection Level)
B5
Reserved
Reserved
Reserved
B4
FeliCa
1 = FeliCa
0 = ISO/IEC 14443 A
The first initiator command had physical level coding of FeliCa or
ISO/IEC 14443 A
B3
Pas_106
Passive target at 106 kbps
or transponder emulation
The first initiator/reader command was SENS_REQ or ALL_REQ
B2
Pas_14443B
ISO/IEC 14443 B
transponder emulation
The first reader command was ISO/IEC 14443 B
B1
NFCBR1
Bit rate of first received
command
00
01
10
11
B0
72
Name
NFCBR0
= Reserved
= 106 kbps
= 212 kbps
= 424 kbps
Detailed Description
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6.15.3.4 Test Registers
6.15.3.4.1 Test Register (0x1A)
Table 6-54 describes the Test register at address 0x1A.
Table 6-54. Test Register (0x1A) (for Test or Direct Use)
Default: 0x00 at POR = H and EN = L.
Bit
Name
B7
OOK_Subc_In
B6
MOD_Subc_Out
B5
MOD_Direct
B4
o_sel
Function
Description
Subcarrier input
OOK pin becomes decoder digital input
Subcarrier output
MOD pin becomes receiver digitized subcarrier output
Direct TX modulation and
RX reset
MOD pin becomes input for TX modulation control by the MCU
o_sel = L: First stage output used for analog out and digitizing
First stage output selection
o_sel = H: Second Stage output used for analog out and digitizing
B3
low2
Second stage gain –6 dB,
HP corner frequency / 2
B2
low1
First stage gain –6 dB, HP
corner frequency / 2
B1
zun
Input followers test
B0
Test_AGC
AGC test, AGC level is
seen on rssi_210 bits
6.15.3.4.2 Test Register (0x1B)
Table 6-55 describes the Test register at address 0x1B.
Table 6-55. Test Register (0x1B) (for Test or Direct Use)
Default: 0x00 at POR = H and EN = L. When a test_dec or test_io is set IC is switched to test mode. Test Mode persists until a stop
condition arrives. At stop condition the test_dec and test_io bits are cleared.
Bit
Name
Function
Description
B7
B6
B5
test_rf_level
RF level test
B4
B3
test_io1
B2
test_io0
I/O test
Not implemented
B1
test_dec
Decoder test mode
B0
clock_su
Coder clock 13.56 MHz
For faster test of coders
Detailed Description
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6.15.3.5 FIFO Control Registers
Section 6.15.3.5.1 describes the FIFO Status register.
6.15.3.5.1 FIFO Status Register (0x1C)
Table 6-56. FIFO Status Register (0x1C)
Function: Number of bytes available to be read from FIFO (= N number of bytes, in hexadecimal)
74
Bit
Name
Function
B7
Foverflow
B6
Fb6
FIFO bytes fb[6]
B5
Fb5
FIFO bytes fb[5]
B4
Fb4
FIFO bytes fb[4]
B3
Fb3
FIFO bytes fb[3]
B2
Fb2
FIFO bytes fb[2]
B1
Fb1
FIFO bytes fb[1]
B0
Fb0
FIFO bytes fb[0]
FIFO overflow error
Description
Bit is set when FIFO has more than 127 bytes presented to it
Bits B0:B6 indicate how many bytes are in the FIFO to be read out (= N
number of bytes, in hex)
Detailed Description
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6.15.3.5.2 TX Length Byte1 Register (0x1D), TX Length Byte2 Register (0x1E)
Table 6-57 describes the TX Length Byte1 register. Table 6-58 describes the TX Length Byte2 register.
Table 6-57. TX Length Byte1 Register (0x1D)
Function: High 2 nibbles of complete, intended bytes to be transferred through FIFO
Register default is set to 0x00 at POR and EN = 0. It is also automatically reset at TX EOF
Bit
Name
Function
Description
B7
Txl11
Number of complete byte
bn[11]
B6
Txl10
Number of complete byte
bn[10]
B5
Txl9
Number of complete byte
bn[9]
B4
Txl8
Number of complete byte
bn[8]
B3
Txl7
Number of complete byte
bn[7]
B2
Txl6
Number of complete byte
bn[6]
B1
Txl5
Number of complete byte
bn[5]
B0
Txl4
Number of complete byte
bn[4]
High nibble of complete, intended bytes to be transmitted
Middle nibble of complete, intended bytes to be transmitted
Table 6-58. TX Length Byte2 Register (0x1E)
Function: Low nibbles of complete bytes to be transferred through FIFO; Information about a broken byte and number of bits to be
transferred from it
Default: 0x00 at POR and EN = 0. It is also automatically reset at TX EOF
Bit
Name
Function
Description
B7
Txl3
Number of complete byte
bn[3]
B6
Txl2
Number of complete byte
bn[2]
B5
Txl1
Number of complete byte
bn[1]
B4
Txl0
Number of complete byte
bn[0]
B3
Bb2
Broken byte number of bits
bb[2]
B2
Bb1
Broken byte number of bits
bb[1]
B1
Bb0
Broken byte number of bits
bb[0]
B0
Bbf
Broken byte flag
Low nibble of complete, intended bytes to be transmitted
Number of bits in the last broken byte to be transmitted.
Valid only when broken byte flag is set.
B0 = 1 indicates that last byte is not complete 8 bits wide.
Detailed Description
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7 Applications, Implementation, and Layout
NOTE
Information in the following Applications section is not part of the TI component specification,
and TI does not warrant its accuracy or completeness. TI's customers are responsible for
determining suitability of components for their purposes. Customers should validate and test
their design implementation to confirm system functionality.
7.1
7.1.1
TRF7970A Reader System Using SPI With SS Mode
General Application Considerations
Figure 7-1 shows and application schematic optimized for all TRF7970A modes using the Serial Port
Interface (SPI). Short SPI lines, proper isolation of radio frequency lines, and a proper ground area are
essential to avoid interference. The recommended clock frequency on the DATA_CLK line is 2 MHz. This
figure also shows matching to a 50-Ω port, which allows connecting to a properly matched 50-Ω antenna
circuit or RF measurement equipment (for example, a spectrum analyzer or power meter).
7.1.2
Schematic
Figure 7-1 shows a sample application schematic for SPI with an SS mode MCU interface.
Figure 7-1. Application Schematic – SPI With SS Mode MCU Interface
Minimum MCU requirements depend on application requirements and coding style. If only one ISO
protocol or a limited command set of a protocol needs to be supported, MCU Flash and RAM
requirements can be significantly reduced. Recursive inventory and anticollision commands require more
RAM than single slotted operations. For example, an ISO/IEC 15693-only application that supports
anticollision needs approximately 7KB of flash memory and 500 bytes of RAM. In contrast, a full NFC
stack that supports peer-to-peer, card emulation, and reader/writer modes needs 65KB of flash memory
and 4KB of RAM. An MCU that can run its GPIOs at 13.56 MHz is required for direct mode 0 operations.
76
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Layout Considerations
Keep all decoupling capacitors as close to the IC as possible, with the high-frequency decoupling
capacitors (10 nF) closer than the low-frequency decoupling capacitors (2.2 µF).
Place ground vias as close as possible to the ground side of the capacitors and reader IC pins to minimize
possible ground loops.
TI recommends not using any inductor sizes smaller than 0603, as the output power can be compromised.
If smaller inductors are necessary, output performance must be confirmed in the final application.
Pay close attention to the required load capacitance of the crystal, and adjust the two external shunt
capacitors accordingly. Follow the recommendations of the crystal manufacturer for those values.
There should be a common ground plane for the digital and analog sections. The multiple ground sections
or islands should have vias that tie the different sections of the planes together.
Ensure that the exposed thermal pad at the center of the reader IC is properly laid out. It should be tied to
ground to help dissipate any heat from the package.
All trace line lengths should be made as short as possible, particularly the RF output path, crystal
connections, and control lines from the reader to the microprocessor. Proper placement of the TRF7970A,
microprocessor, crystal, and RF connection or connector help facilitate this.
Avoid crossing of digital lines under RF signal lines. Also, avoid crossing of digital lines with other digital
lines when possible. If the crossings are unavoidable, 90° crossings should be used to minimize coupling
of the lines.
Depending on the production test plan, consider possible implementations of test pads or test vias for use
during testing. The necessary pads or vias should be placed in accordance with the proposed test plan to
enable easy access to those test points.
If the system implementation is complex (for example, if the RFID reader module is a subsystem of a
greater system with other modules (Bluetooth, Wi-Fi, microprocessors, and clocks), special considerations
should be taken to ensure that there is no noise coupling into the supply lines. If needed, special filtering
or regulator considerations should be used to minimize or eliminate noise in these systems.
For more information/details on layout considerations, see the TRF796x HF-RFID Reader Layout Design
Guide.
7.3
Impedance Matching TX_Out (Pin 5) to 50 Ω
The output impedance of the TRF7970A when operated at full power out setting is nominally 4 + j0 (4 Ω
real). This impedance must be matched to a resonant circuit and TI recommends matching circuit from
4 Ω to 50 Ω, as commercially available test equipment (for example, spectrum analyzers, power meters,
and network analyzers) are 50-Ω systems. Figure 7-2 shows an impedance-matching reference circuit.
Figure 7-3 shows a Smith chart simulation based on this circuit. This section explains how the values were
calculated.
Starting with the 4-Ω source, the process of going from 4 Ω to 50 Ω can be represented on a Smith Chart
simulator (available from http://www.fritz.dellsperger.net/). The elements are combined where appropriate
(see Figure 7-2).
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L1
TX_OUT
Pin 5
L2
ZL
ZIN
C2 and C3
Combination
256.0 pF
330.0 nH
1.2 nF
150.0 nH
3.0 nF
(4.00 + j0.00) W at 13.6 MHz
C4, C4, and C7
Combination
50 W
C8, C9, C10, and C11
Combination
Figure 7-2. Impedance Matching Circuit
Figure 7-3. Smith Chart Simulation
Resulting power out can be measured with a power meter or spectrum analyzer with power meter function
or other equipment capable of making a "hot" measurement. Observe maximum power input levels on test
equipment and use attenuators whenever available to avoid damage to equipment. Expected output
power levels under various operating conditions are shown in Table 6-25.
7.4
Reader Antenna Design Guidelines
For HF antenna design considerations using the TRF7970A, see these documents:
• Antenna Matching for the TRF7960 RFID Reader
• TRF7960TB HF RFID Reader Module User's Guide
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8 Device and Documentation Support
8.1
Getting Started and Next Steps
For more information on the TI NFC/RFID devices and the tools and software that are available to help
with your development, visit Overview for NFC / RFID.
8.2
Device Nomenclature
To designate the stages in the product development cycle, TI assigns prefixes to the part numbers of
devices. Each commercial family member has one of three prefixes: x, p, or no prefix. These prefixes
represent evolutionary stages of product development from engineering prototypes (with prefix x) through
fully qualified production devices (with no prefix).
Device development evolutionary flow:
xTRF... – Experimental device that is not necessarily representative of the electrical specifications of the
final device
pTRF... – Final device that conforms to the electrical specifications of the final product but has not
completed quality and reliability verification
TRF... – Fully qualified production device
Devices with a prefix of x or p are shipped against the following disclaimer:
"Developmental product is intended for internal evaluation purposes."
Production devices have been characterized fully, and the quality and reliability of the device have been
demonstrated fully. TI's standard warranty applies.
Predictions show that prototype devices have a greater failure rate than the standard production devices.
TI recommends that these devices not be used in any production system because their expected end-use
failure rate still is undefined. Only qualified production devices are to be used.
TI device nomenclature also includes a suffix with the device family name. This suffix indicates the
package type and, optionally, the temperature range. Figure 8-1 provides a legend for reading the
complete device name.
TRF79 70 A RHB R
Device Family
Distribution
Package
Feature Set
Revision
Device Family
TRF79 = NFC/RFID Transceiver
Feature Set
70 = Feature Set
Revision
A = Silicon Revision
Package
See Packaging Information
or www.ti.com/package
Distribution
R = Large Reel
T = Small Reel
Figure 8-1. Device Nomenclature
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8.3
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Tools and Software
Design Kits and Evaluation Modules
NFC Transceiver Add-on Target Board Module The TRF7970ATB Evaluation Module lets the software
application developer get familiar with the functionality of the TRF7970A multiprotocol fully
integrated 13.56-MHz NFC/HF RFID IC on their Texas Instruments embedded
microcontroller platform of choice without having to worry about the RF section.
NFC Transceiver Booster Pack Plug-in Module The third-party provider DLP Design NFC/RFID
BoosterPack plug-in module (DLP-7970ABP) is an add-on board designed to fit all of TI’s
MCU LaunchPad development kits. This BoosterPack plug-in module lets the software
application developer get familiar with the functionality of the TRF7970A multiprotocol fully
integrated 13.56 MHz NFC and HF RFID IC on their TI embedded microcontroller platform of
choice without having to worry about developing the RF section.
NFC Transceiver Evaluation Module The TRF7970AEVM is a self-contained development platform that
can be used to evaluate the performance of NFC Transceiver TRF7970A. TRF7970A is a
multiprotocol fully integrated 13.56-MHz NFC/RFID transceiver IC. Along with the IC, the
evaluation module enables development and evaluation of custom firmware, customer
designed antennas, and potential transponders for a variety of NFC/RFID applications.
8.4
Documentation Support
The following documents describe the TRF7970A device. Copies of these documents are available on the
Internet at www.ti.com.
Receiving Notification of Document Updates
To receive notification of documentation updates—including silicon errata—go to the product folder for
your device on ti.com (for example, TRF7970A). In the upper-right corner, click the "Alert me" button. This
registers you to receive a weekly digest of product information that has changed (if any). For change
details, check the revision history of any revised document.
Errata
TRF7970A Silicon Errata Describes the known exceptions to the functional specifications for the
TRF7970A.
Application Notes
Minimizing TRF79xx Current Use During Power‑‑Down Mode
This application report provides
recommendations on circuit and firmware design to reduce current consumption in powerdown mode for the TRF79xx family of devices (TRF796x, TRF796xA, and TRF7970A).
Various designs are considered, and they are analyzed based on their current consumption.
This application report is particularly targeted for dual-voltage systems that are powered by
battery.
NFC/HF RFID Reader/Writer Using the TRF7970A The near field communication (NFC) market is
emerging into multiple fields including medical, consumer, retail, industrial, automotive, and
smart grid. Reader/writer is one of the three operational modes supported by the TRF7970A.
When using reader/writer mode, the user can configure the TRF7970A to read type 2, type
3, type 4A, type 4B, and type 5 tag platforms, also called transponders. The tags can store
NFC data exchange format (NDEF) messages or proprietary defined data. This application
report describes the fundamental concepts of reader/writer mode and how to properly
configure the TRF7907A transceiver for each supported technology.
TRF7970A NFC Reader Antenna Multiplexing This application report describes the implementation of
multiple reader antennas with a single TRF7970A NFC transceiver IC. For demonstration
purposes, the MSP430F5529 LaunchPad development kit with TRF7970A BoosterPack
plug-in module are used. The demo supports ISO/IEC 15693, and ISO/IEC 14443 A and B
communication protocols.
80
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NFC/RFID Reader Ultra-Low-Power Card Presence Detect With MSP430 and TRF79xxA NFC
and
RFID reader battery-powered applications must have a defined and limited energy
consumption budget as well as low cost for a product to be realized. Techniques and
strategies have emerged over the years for the card presence detection that attempt to
address both concerns. The intent of this application report is to contribute to these
techniques and strategies by offering an advancement expressed by adding a simple circuit
and small firmware control logic loop to an existing design, which offers dramatic
improvement over previously identified card detection solutions.
8.5
Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the
respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views;
see TI's Terms of Use.
TI E2E™ Community
TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At
e2e.ti.com, you can ask questions, share knowledge, explore ideas, and help solve problems with fellow
engineers.
8.6
Trademarks
E2E is a trademark of Texas Instruments.
Bluetooth is a registered trademark of Bluetooth SIG.
MIFARE is a trademark of NXP Semiconductors.
FeliCa is a trademark of Sony Corporation.
Wi-Fi is a registered trademark of Wi-Fi Alliance.
8.7
Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
8.8
Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms and definitions.
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9 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the
most current data available for the designated devices. This data is subject to change without notice and
revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
82
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PACKAGE OPTION ADDENDUM
www.ti.com
24-Oct-2015
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
TRF7970ARHBR
ACTIVE
VQFN
RHB
32
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 110
TRF
7970A
TRF7970ARHBT
ACTIVE
VQFN
RHB
32
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 110
TRF
7970A
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
24-Oct-2015
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
27-Jul-2015
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
TRF7970ARHBR
VQFN
RHB
32
3000
330.0
12.4
5.3
5.3
1.5
8.0
12.0
Q2
TRF7970ARHBT
VQFN
RHB
32
250
180.0
12.4
5.3
5.3
1.5
8.0
12.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
27-Jul-2015
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
TRF7970ARHBR
VQFN
RHB
32
3000
367.0
367.0
35.0
TRF7970ARHBT
VQFN
RHB
32
250
210.0
185.0
35.0
Pack Materials-Page 2
GENERIC PACKAGE VIEW
RHB 32
VQFN - 1 mm max height
PLASTIC QUAD FLATPACK - NO LEAD
5 x 5, 0.5 mm pitch
Images above are just a representation of the package family, actual package may vary.
Refer to the product data sheet for package details.
4224745/A
www.ti.com
PACKAGE OUTLINE
RHB0032E
VQFN - 1 mm max height
SCALE 3.000
PLASTIC QUAD FLATPACK - NO LEAD
5.1
4.9
A
B
PIN 1 INDEX AREA
(0.1)
5.1
4.9
SIDE WALL DETAIL
OPTIONAL METAL THICKNESS
20.000
C
1 MAX
SEATING PLANE
0.05
0.00
0.08 C
2X 3.5
(0.2) TYP
3.45 0.1
9
EXPOSED
THERMAL PAD
16
28X 0.5
8
17
2X
3.5
SEE SIDE WALL
DETAIL
SYMM
33
32X
24
1
PIN 1 ID
(OPTIONAL)
32
0.3
0.2
0.1
0.05
C A B
C
25
SYMM
32X
0.5
0.3
4223442/B 08/2019
NOTES:
1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.
www.ti.com
EXAMPLE BOARD LAYOUT
RHB0032E
VQFN - 1 mm max height
PLASTIC QUAD FLATPACK - NO LEAD
( 3.45)
SYMM
32
25
32X (0.6)
1
24
32X (0.25)
(1.475)
28X (0.5)
33
SYMM
(4.8)
( 0.2) TYP
VIA
8
17
(R0.05)
TYP
9
(1.475)
16
(4.8)
LAND PATTERN EXAMPLE
SCALE:18X
0.07 MIN
ALL AROUND
0.07 MAX
ALL AROUND
SOLDER MASK
OPENING
METAL
SOLDER MASK
OPENING
METAL UNDER
SOLDER MASK
NON SOLDER MASK
DEFINED
(PREFERRED)
SOLDER MASK
DEFINED
SOLDER MASK DETAILS
4223442/B 08/2019
NOTES: (continued)
4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature
number SLUA271 (www.ti.com/lit/slua271).
5. Vias are optional depending on application, refer to device data sheet. If any vias are implemented, refer to their locations shown
on this view. It is recommended that vias under paste be filled, plugged or tented.
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EXAMPLE STENCIL DESIGN
RHB0032E
VQFN - 1 mm max height
PLASTIC QUAD FLATPACK - NO LEAD
4X ( 1.49)
(0.845)
(R0.05) TYP
32
25
32X (0.6)
1
24
32X (0.25)
28X (0.5)
(0.845)
SYMM
33
(4.8)
17
8
METAL
TYP
16
9
SYMM
(4.8)
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
EXPOSED PAD 33:
75% PRINTED SOLDER COVERAGE BY AREA UNDER PACKAGE
SCALE:20X
4223442/B 08/2019
NOTES: (continued)
6. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
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IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD
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