Read Relay Coil / Digital Input Status; Message Format And Example, Function 01; Modbus Functions Supported Functions - GE 469 Communications Manual

COMMUNICATIONS GUIDE
Modbus Functions
Supported Functions

Read Relay Coil / Digital Input Status

469 MOTOR MANAGEMENT RELAY – COMMUNICATIONS GUIDE
The following functions are supported by the 469:
Modbus Function Code 01: Read Relay Coil
Modbus Function Code 02: Read Digital Input Status
Modbus Function Code 03: Read Setpoints and Actual Values
Modbus Function Code 04: Read Setpoints and Actual Values
Modbus Function Code 05: Execute Operation
Modbus Function Code 06: Store Single Setpoint
Modbus Function Code 07: Read Device Status
Modbus Function Code 08: Loopback Test
Modbus Function Code 16: Store Multiple Setpoints
Modbus implementation: Read Coil and Input Status
469 Implementation: Read Relay Coil and Digital Input Status
For the 469 implementation of Modbus, these commands can be used to read Relay Coil
Status or Digital Input Status.

MESSAGE FORMAT AND EXAMPLE, FUNCTION 01:

The standard implementation requires the following: slave address (one byte), function
code (one byte), starting relay coil (two bytes), number of coils to read (two bytes), and CRC
(two bytes). The slave response is the slave address (one byte), function code (one byte),
relay coil mask byte count (one byte; always 01 since only six relay coils), bit mask
indicating the status of requested relay coils (one byte), and CRC (two bytes).
Request slave 11 to respond with status of relay coil 3 to 5:
Relay
1 TRIP Energized
2 AUXILIARY De-energized
3 AUXILIARY De-energized
4 ALARM De-energized
5 BLOCK START Energized
6 SERVCE Energized
Bit Mask 0011 0001 (0 × 31)
Master Transmission
Slave Address
Function Code
Starting Relay Coil
Number of Relays
CRC
Slave Response
Slave Address
Status
Bytes Example
1 0B
1 01
2 00 03
2 00 03
2 8C A1
Bytes Example
1 0B
MODBUS FUNCTIONS
Description
message for slave 11
read relay coil status
starting relay coil 3
3 relay coils (relays 3 AUXILIARY,
4 AUXILIARY, and 5 BLOCK START)
computed CRC error code
Description
message from slave 11
5