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Slave Modbus Send Event
This type of event byte is stored by the slave when it finishes processing a query
message.
It is stored if the slave returned a normal or exception response, or no response.
Bit
Contents
0
Read Exception Sent (Exception Codes 1-3)
1
Slave Abort Exception Sent (Exception Code 4)
2
Not used
3
Not used
4
Write Timeout Error Occurred
5
Currently in Listen Only Mode
6
1
7
0
Slave Entered Listen Only Mode
This type of event byte is stored by the slave when it enters the Listen Only Mode.
The event is defined by a content of '04' hex.
Slave Initiated Communication Restart
This type of event byte is stored by the slave when its communications port is restarted.
The slave can be restarted by the Diagnostics function (code 08), with subfunction
Restart Communications Option (code 01).
The event is defined by a contents of '00' hex.
3.7 Diagnostics function and subfunctions (function 8)
The format of a diagnostics (08) function query is as follows:
QUERY
Slave address
Function
Subfunction
Data field
Error check field CRC
The format of a response to a diagnostics function query is an echo of the query itself.
If the request is directed to a counter, however, the slave returns the counter's value in
the data field.
00 Return Query Data
The data in the query data field is to be returned (looped back) in the response. The
entire response should be identical to the query.
01 Restart Communication Option
18 Modbus function codes ç RVT communication
1 byte
1 byte
2 bytes
2 bytes
2 bytes
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