GE 469

10 469 MOTOR MANAGEMENT RELAY – COMMUNICATIONS GUIDE
MODBUS FUNCTIONS COMMUNICATIONS GUIDE
MESSAGE FORMAT AND EXAMPLE:
Request status from slave 11.
Loopback Test
Modbus Implementation: Loopback Test
469 Implementation: Loopback Test
This function is used to test the integrity of the communication link. The 469 will echo the
request.
MESSAGE FORMAT AND EXAMPLE:
Loopback test from slave 11.
Store Multiple Setpoints
Modbus Implementation: Preset Multiple Registers
469 Implementation: Store Multiple Setpoints
This function code allows multiple setpoints to be stored into the 469 memory. Modbus
“registers” are 16-bit (two byte) values transmitted high order byte first. Thus all 469
setpoints are sent as two byte values. The maximum number of setpoints that can be
stored in one transmission is dependent on the slave device. Modbus allows up to a
maximum of 60 holding registers to be stored. The 469 response to this function code is to
echo the slave address, function code, starting address, the number of Setpoints stored,
and the CRC.
Master Transmission Bytes Example Description
Slave Address 1 0B message for slave 11
Function Code 1 07 read device status
CRC (low, high) 2 47 42 computed CRC error code
Slave Response Bytes Example Description
Slave Address 1 0B message from slave 11
Function Code 1 07 read device status
Device Status 1 59 status = 01011001b
CRC (low, high) 2 C2 08 computed CRC error code
Master Transmission Bytes Example Description
Slave Address 1 0B message for slave 11
Function Code 1 08 loopback test
Diagnostic Code 2 00 00 must be 00 00
Data 2 00 00 must be 00 00
CRC (low, high) 2 E0 A1 computed CRC error code
Slave Response Bytes Example Description
Slave Address 1 0B message from slave 11
Function Code 1 08 loopback test
Diagnostic Code 2 00 00 must be 00 00
Data 2 00 00 must be 00 00
CRC (low, high) 2 E0 A1 computed CRC error code