Mitsubishi Electric MELSEC iQ-RJ71C24-R4 - Force Listen Only Mode (Sub-Function Code: 04 H)

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3 MODBUS STANDARD FUNCTION DETAILS
3.8 Diagnostics (FC: 08H)
Force listen only mode (sub-function code: 04H)
Operation description
Places a slave into the offline mode.
Used when disconnecting a slave from the network.
When C24 is set in the listen only mode, the status is as follows:
• Ignores all request messages except for those of restart communications option. (Page 23 Restart communications
option (sub-function code: 01H))
• Stops counting of the diagnostic counter. (Page 21 Checking communication conditions using a diagnostic counter)
• Continues recording with the communications event log. (Page 39 Get Communications Event Log (FC: 0CH))
Request message format (from master to slave)
Response message format (from slave to master)
■ When completed successfully
No response message is returned because the listen only mode (offline status) is active.
■ When completed with an error
Whether the C24 has been switched to listen only mode or not can be checked in the 'Communications mode'
of the buffer memory (Un\G32525/32589).
• 0000H: Online mode
• 0001H: Listen only mode
The listen only mode can be changed to online mode by either of the following:
• Restart communications option (Page 23 Restart communications option (sub-function code: 01H))
• Turn the power OFF and ON, or reset the programmable controller CPU.
(H) (L)
08H (0004H) (0000H)
(H) (L)
DataFunction code Sub-function code
88H
Data
Exception code
Function code