Function Code 08H - GE 345 Communications Manual

MODBUS FUNCTIONS

Function Code 08H

1–174
The master/slave packets have the following format:
Table 37: Function code 7 bitmask
Bit
0
1
2
3
4
5
6
7
Table 38: MASTER/SLAVE PACKET FORMAT FOR FUNCTION CODE 07H
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
CRC
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
DEVICE STATUS (see definition
above)
CRC
Modbus Implementation: Loopback
Test 345 Implementation: Loopback Test
This function is used to test the integrity of the communication link. The 345 will echo the
request.
For example, consider a loopback test from slave 17:
Table 39: MASTER/SLAVE PACKET FORMAT FOR FUNCTION CODE 08H
MASTER TRANSMISSION
SLAVE ADDRESS
FUNCTION CODE
DIAG CODE
DATA
CRC
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
DIAG CODE
DATA
CRC
CHAPTER 1: COMMUNICATIONS GUIDE
Function
Alarm
Trip
Self Test
Breaker Connected
52a Contact
52b Contact
Maintenance
Relay in Service
BYTES EXAMPLE
1 11
1 07
2 4C 22
BYTES EXAMPLE
1 11
1 07
1 2C
2 22 28
BYTES EXAMPLE
1 11
1 08
2 00 00
2 00 00
2 E0 0B
BYTES EXAMPLE
1 11
1 08
2 00 00
2 00 00
2 E0 0B
345 TRANSFORMER PROTECTION SYSTEM – COMMUNICATIONS GUIDE
DESCRIPTION
message for slave 17
read device status
CRC error code
DESCRIPTION
message from slave
17
read device status
status = 00101100
(in binary)
CRC error code
DESCRIPTION
message for slave 17
loopback test
must be 00 00
must be 00 00
CRC error code
DESCRIPTION
message from slave
17
loopback test
must be 00 00
must be 00 00
CRC error code