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7. DIAGNOSTICS
Modbus Function 08, as implemented in the RVS-AXO supports only Sub-function $0000.
It provides for "loopback" (Return Query Data) feature, for checking the Communication
Serial Link between the master and the RVS-AXO.
To request RVS-AXO # 18 to return Query data, the master should send following Query
frame:
Byte 1: Serial Link No.
($01)
Byte 2: Function
($08)
Byte 3: Sub-function High
($00)
Byte 4: Sub-function Low
($00)
Byte 5: Data High
($A5)
Byte 6: Data Low
($37)
Byte 7: CRC_Low
($XX)
Byte 8: CRC_High
($XX)
The normal (if no exception) response is the echo of the Query:
Byte 1: Serial Link No.
($12)
Byte 2: Function
($08)
Byte 3: Sub-function High
($00)
Byte 4: Sub-function Low
($00)
Byte 5: Force Data High
($A5)
Byte 6: Force Data Low
($37)
Byte 7: CRC_Low
($XX)
Byte 8: CRC_High
($XX)
