7-8 239 Motor Protection Relay GE Multilin
7 COMMUNICATIONS 7 COMMUNICATIONS
7
7.12 08: LOOPBACK TEST
• Modbus Implementation:Loopback Test
• 239 Implementation: Loopback Test
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 Bytes Example (hex)
SLAVE ADDRESS - 1 byte 11 message for slave 11
FUNCTION CODE - 1 byte 08 loopback test
DIAG CODE - 2 bytes 00 must be 00 00
00
DATA - 2 bytes 00 must be 00 00
00
CRC - 2 bytes E0 CRC calculated by the master
0B
Slave Response Bytes Example (hex)
SLAVE ADDRESS - 1 byte 11 message from slave 11
FUNCTION CODE - 1 byte 08 loopback test
DIAG CODE - 2 bytes 00 must be 00 00
00
DATA - 2 bytes 00 must be 00 00
00
CRC - 2 bytes E0 CRC calculated by slave
0B
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