GE b30 Communications Guide

2-6 UR FAMILY – COMMUNICATIONS GUIDE
MODBUS FUNCTION CODES CHAPTER 2: MODBUS COMMUNICATION
2
Table 2-8: Master and slave device packet transmission example
2.2.5 Store multiple settings (function code 10h)
This function code allows the master to modify the contents of a one or more consecutive setting registers in a relay.
Setting registers are 16-bit (two byte) values transmitted high order byte first. The maximum number of setting registers
that can be stored in a single packet is 123. The following table shows the format of the master and slave packets in
Modbus RTU. Modbus TCP/IP ADUs have a MBAP instead of slave address, and CRC is in another stack layer. The example
shows a master device storing the value 200 at memory map address 4051h, and the value 1 at memory map address
4052h to slave device 11h (17 decimal).
Table 2-9: Master and slave device packet transmission example
2.2.6 Exception responses
Programming or operation errors usually happen because of illegal data in a packet. These errors result in an exception
response from the slave. The slave detecting one of these errors sends a response packet to the master with the high order
bit of the function code set to 1.
The following table shows the format of the master and slave packets in Modbus RTU. Modbus TCP/IP ADUs have a MBAP
instead of slave address, and CRC is in another stack layer. The example shows a master device sending the unsupported
function code 39h to slave device 11h.
Master transmission Slave response
Packet format Example (Hex) Packet format Example (Hex)
SLAVE ADDRESS 11 SLAVE ADDRESS 11
FUNCTION CODE 06 FUNCTION CODE 06
DATA STARTING ADDRESS - high 40 DATA STARTING ADDRESS - high 40
DATA STARTING ADDRESS - low 51 DATA STARTING ADDRESS - low 51
DATA - high 00 DATA - high 00
DATA - low C8 DATA - low C8
CRC - low CE CRC - low CE
CRC - high DD CRC - high DD
Master transmission Slave response
Packet format Example (Hex) Packet format Example (Hex)
SLAVE ADDRESS 11 SLAVE ADDRESS 11
FUNCTION CODE 10 FUNCTION CODE 10
DATA STARTING ADDRESS - hi 40 DATA STARTING ADDRESS - hi 40
DATA STARTING ADDRESS - lo 51 DATA STARTING ADDRESS - lo 51
NUMBER OF SETTINGS - hi 00 NUMBER OF SETTINGS - hi 00
NUMBER OF SETTINGS - lo 02 NUMBER OF SETTINGS - lo 02
BYTE COUNT 04 CRC - lo 07
DATA #1 - high order byte 00 CRC - hi 64
DATA #1 - low order byte C8
DATA #2 - high order byte 00
DATA #2 - low order byte 01
CRC - low order byte 12
CRC - high order byte 62

GE b30 Specifications

General

Brand	GE
Model	b30
Category	Relays
Language	English