SLSM5 Interface Definition

SLSM5 Interface Definition
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SLSM5 SYNTHESIZER INTERFACE DEFINITION
GENERAL
The SLSM5 synthesizer employs the latest fractional N
technology to realize a high performance versatile frequency
synthesizer. The SLSM5 architecture makes possible for very
wideband synthesizers with 1 kHz step resolution up to 32
GHz. These units offer excellent phase-noise and low spurious
performance.
The SLSM5 is ideal for many applications in communications, radar and
instrumentation. This synthesizer provides outstanding performance and
reliability in a high quality compact unit.
VCO
F0
10 MHz
REFERENCE
MULTIPLIER

OR
INT.
REF
(TCXO)
PLL IC
(OPTION)
P1
COMM. INTERFACE
RX/TX
485
µC
SPEED CONTROL
MASTER RESET
RESET
EEPROM
LOCK MONITOR
LD
DC POWER (+5.5V)
REFERENCE SIGNAL
1. EXTERNAL REFERENCE
The external 10 MHz reference signal should be a good quality signal at a level of 0 dBm ±3dB.
2. INTERNAL REFERENCE
An optional configuration (SLSM5-xxxx-INT) provides an internal 10 MHz TCXO (±0.5ppm -10°C to
+70°C). In this configuration the synthesizer will operate on the internal reference only.
PAGE 1 OF 6
Rev. K 11-13-15
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DC POWER AND FREQUENCY CONTROL
The DC power and frequency control is via P1, a 9 pin (MALE) D-SUB connector. The pin-out for this
connector is given below. The synthesizer has an internal LDR and filtering however the supplied DC
voltage should be from a quality power supply source capable of supplying 650 mA.
Pin Number
1
2
3
4
5
6
7
8
9
CONNECTOR P1
Description
TX+ (out of synthesizer)
TX- (out of synthesizer)
RX- (into synthesizer)
RX+ (into synthesizer)
Speed Select
Internal pull-up (0=115.2K, 1=9600)
+5.5 Vdc ±0.5 V
(LD) Lock Detector (note 3)
/MR (Master Reset) 0-3V
GND
Notes:
1. For 2-wire mode tie together pins 1+4 and 2+3.
2. /MR is the master reset and is active low (0V). Max high (3V)
3. The LD is custom configured for open collector or TTL as indicted on specific product data sheet.
LOCK DETECTOR
The synthesizer status monitoring for phase lock can be done in one of two ways as shown below:
 LD Pin 7 of P1, this lock detector indicates a failed condition and is low when a failure is sensed.
The LD is configured as an open collector and is valid for all fault conditions including no reference
signal.
 Through polling via the serial interface. However this would not be responsive if the reference is
removed.
Please note that monitoring pin 7 does not add noise to the output, while polling via the serial
interface can result in spectral degradation.
NON-VOLATILE MEMORY
The SLSM5 has an internal non-volatile memory (EEPROM) device which retains the settings of the
last commanded state. The frequency and mute state are saved to this memory. At power up turn on
the synthesizer will be restored to the last saved state.
The non-volatile memory (EEPROM) is limited to 1,000,000 write cycles.
HOP MODE FOR CONTINUOUS FREQUENCY ADDRESSING
For applications that require unlimited tuning cycles like continuous band sweeping or random
continuous address of the frequency, a hop-frequency command is provided. The hop-frequency
command does not save the commanded frequency to the non-volatile memory (EEPROM).
PAGE 2 OF 6
Rev. K 11-13-15
20 N. Tyson Ave, Floral Park, NY 11001 Tel. (516) 358-2880 Fax (516) 358-2757 Email: sales@luffresearch.com Web: www.luffresearch.com
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SERIAL INTERFACE PROTOCOL
Luff Research’s Model SLSM5 frequency synthesizers are monitored and controlled through an
asynchronous serial interface (UART). The electrical interface is RS485 and can be wired in two or
four wire mode. The serial communications operates at either 9600 Baud or 115200 Baud selectable
through the interface connector. Additional specifications for the interface are 8 data bits, 1 stop bit,
no parity, and no flow control. The protocol is addressable allowing multi-drop communications. The
address is selectable through a rotary switch on the unit.
Serial communication occurs only with either an external 10 MHz reference or an internal TCXO. The
synthesizer serial interface shall operate in a command/response mode. The remote host shall
provide the desired frequency setting in ASCII values and the synthesizer shall respond with a
command accepted or rejected response. An ASCII 'A' shall be returned if the command is accepted
and an ASCII 'R' shall be returned if the command is rejected. The ACK/NACK response shall be
followed by a carriage return. The synthesizer output can be turned off or on (mute) through the serial
interface. Current status of the synthesizer can also be obtained via the serial interface. Two ASCII
characters representing the address setting allow multiple synthesizers to be connected together in
RS-422/RS-485 mode. The synthesizer shall only accept & respond to commands that include
address values that match the rotary switch (S1) setting (Refer to Figure 1).
Address 0xFF is used as a global address and the unit will always respond to this address. The
address in the response will correspond to the actual setting. This feature allows the user to
determine the rotary switch setting via the serial interface. This feature cannot be used in multi-drop
mode. The unit is shipped with the address set to 01. Care should be taken in setting S1 since it is a
plastic screw and can be damaged with an inappropriate metal screw driver.
S1
FIGURE 1
There are three independent commands available to control the synthesizer. Please note that at
power turn-on, the synthesizer returns to the last state saved in the non-volatile memory.
DEFINITIONS:
All characters are ASCII characters
 >Start of Message HOST to SYNTH
 <Start of message SYNTH to HOST
 ? is the status
PAGE 3 OF 6
Rev. K 11-13-15
20 N. Tyson Ave, Floral Park, NY 11001 Tel. (516) 358-2880 Fax (516) 358-2757 Email: sales@luffresearch.com Web: www.luffresearch.com
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







F is the frequency command; the frequency value is saved to non-volatile memory.
H is the hop-frequency command; the frequency value is NOT saved to non-volatile memory.
n1n2 represents address ‘00’ to ‘0F’ as set by S1
fffffff represents the current frequency in 1 kHz steps.
L is the lock/unlock condition of the synthesizer, ‘L’=Locked; ‘U’ = Unlocked; ‘M’ =Muted
 is the carriage return.
M is the mute command
m is a value of ‘0’ or ‘1’
‘0’=synthesizer output is OFF
‘1’= synthesizer output is ON
 A = accepted
 R = rejected
FREQUENCY COMMAND:
Command:
>n1n2Ffffffff
Response:
<n1n2A
Examples:
Tune to 3.3 GHz and at address 01:
Command:
>01F3300000
Response:
<01A
Error Frequency:
Command:
Response:
>01F3300
<01R
HOP FREQUENCY COMMAND:
Command:
>n1n2Hfffffff
Response:
<n1n2A
Examples:
Tune to 3.3 GHz and at address 01:
Command:
>01H3300000
Response:
<01A
Error Frequency:
Command:
Response:
>01H3300
<01R
MUTE COMMAND:
Command:
>n1n2Mm
Response:
<n1n2A
Example:
Command: >01M1
Response: <01A
STATUS REQUEST:
Command:
>n1n2?
Response:
< n1n2FfffffffL
Example:
Command: >01?
Response: <01F3300000L
PAGE 4 OF 6
Rev. K 11-13-15
20 N. Tyson Ave, Floral Park, NY 11001 Tel. (516) 358-2880 Fax (516) 358-2757 Email: sales@luffresearch.com Web: www.luffresearch.com
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TYPICAL TEST SET-UP
FREQ.
ADJ.
RF OUT
USA
XXXX
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DATE CODE
RF Output
www.luffre sea rch.com
P1
RS485
(4 wire
operation)
SLSM5-XXXX
RS232
or USB
**Appropriate
Converter
Adapter Cable
Or
***Adapter PCB
XXXX
PC Running
Luff Supplied
*Tuner
SERIAL No.
+5.5 Vdc ±0.5 V
REF IN
10 MHz
Reference
* SLSM5 TUNER (on disc supplied with the unit)
** For RS232 to RS485 - B&B Electronics P/N: 485TBLED or P/N 4WSD9R (along with 485PS) is suggested.
** For USB to RS485 - B&B Electronics P/N: 485USB9F-4W is suggested.
*** Optional PCB adapter (SLSM5-ADP)
Typical SLSM5 Test Setup
PAGE 5 OF 6
Rev. K 11-13-15
20 N. Tyson Ave, Floral Park, NY 11001 Tel. (516) 358-2880 Fax (516) 358-2757 Email: sales@luffresearch.com Web: www.luffresearch.com
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SUPPLIED TUNER SOFTWARE
The synthesizer is supplied with a windows based graphic user interface (GUI) that allows the user to
execute frequency control of the synthesizer. The .Net Framework is required for operation of the
GUI. Since most PC’s and Laptops are provided with a RS232 COM port or USB port the user must
provide an appropriate converter for the RS485 transceiver.
SLSM5 Tuner
ADDITIONAL NOTES
The SLSM5 is the most current synthesizer implementation of the fractional-N architecture. The
resulting design offers many advantages in performance, size and cost. The following two points are
noted:
(1) The output frequency accuracy varies slightly, for example at 4 GHz the output frequency
accuracy is actually +2.9 Hz.
(2) This design utilizes techniques which result in <-60 dBc spurious through most of the band. There
may be a small set of frequencies (out of millions) where due to an anomaly in the fractional N
process the spurs are >-60 dBc. At these locations for the most part the <-60 dBc level can be
realized by shifting the frequency by 1 or 2 kHz.
For technical support please contact Luff Research directly at:
Phone: 516-358-2880 or E-mail to: sales@luffresearch.com
PAGE 6 OF 6
Rev. K 11-13-15
20 N. Tyson Ave, Floral Park, NY 11001 Tel. (516) 358-2880 Fax (516) 358-2757 Email: sales@luffresearch.com Web: www.luffresearch.com
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