08: Loopback Test - GE 239 Instruction Manual

7 COMMUNICATIONS
• Modbus Implementation:Loopback Test
• 239 Implementation:
This function is used to test the integrity of the communication link. The 239 will echo the request.
a) MESSAGE FORMAT AND EXAMPLE
Loopback test from slave 11.
Master Transmission
SLAVE ADDRESS
FUNCTION CODE
DIAG CODE
DATA
CRC
Slave Response
SLAVE ADDRESS
FUNCTION CODE
DIAG CODE
DATA
CRC
7
7-8
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Loopback Test
Bytes
- 1 byte
- 1 byte
- 2 bytes
- 2 bytes
- 2 bytes
Bytes
- 1 byte
- 1 byte
- 2 bytes
- 2 bytes
- 2 bytes
239 Motor Protection Relay
7 COMMUNICATIONS

7.12 08: LOOPBACK TEST

Example (hex)
11 message for slave 11
08 loopback test
00 must be 00 00
00
00 must be 00 00
00
E0 CRC calculated by the master
0B
Example (hex)
11 message from slave 11
08 loopback test
00 must be 00 00
00
00 must be 00 00
00
E0 CRC calculated by slave
0B
GE Multilin