28-6 9440300990
Modbus
®
Communication DECS-250
CRC Hi error check
CRC Lo error check
Return Query Data
This query contains data to be returned (looped back) in the response. The response and query
messages should be identical. If the query is a broadcast (device address = 0), no response message is
returned.
Device Address
Function Code = 08 (hex)
Subfunction Hi = 00 (hex)
Subfunction Lo = 00 (hex)
Data Hi = xx (don't care)
Data Lo = xx (don't care)
CRC Hi error check
CRC Lo error check
Restart Communications Option
This query causes the remote communications function of the DECS-250 to restart, terminating an active
listen only mode of operation. No effect is made upon primary relay operations. Only the remote
communications function is affected. If the query is a broadcast (device address = 0), no response
message is returned.
If the DECS-250 receives this query while in the listen only mode, no response message is generated.
Otherwise, a response message identical to the query message is transmitted prior to the
communications restart.
Device Address
Function Code = 08 (hex)
Subfunction Hi = 00 (hex)
Subfunction Lo = 01 (hex)
Data Hi = xx (don't care)
Data Lo = xx (don't care)
CRC Hi error check
CRC Lo error check
Listen Only Mode
This query forces the addressed DECS-250 to the listen only mode for Modbus communications, isolating
it from other devices on the network. No responses are returned.
While in the listen only mode, the DECS-250 continues to monitor all queries. The DECS-250 does not
respond to any other query until the listen only mode is removed. All write requests with a query to Preset
Multiple Registers (Function Code = 16) are also ignored. When the DECS-250 receives the restart
communications query, the listen only mode is removed.
Device Address
Function Code = 08 (hex)
Subfunction Hi = 00 (hex)
Subfunction Lo = 04 (hex)
Data Hi = xx (don't care)
Data Lo = xx (don't care)
CRC Hi error check
CRC Lo error check
Preset Multiple Registers
A preset multiple registers query could address multiple registers in one slave or multiple slaves. If the
query is a broadcast (device address = 0), no response message is returned.
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