4
- 31
4.11 Diagnostics (FC: 08)
4.11.5 Force listen only mode (sub-function code: 04)
4
MODBUS(R) STANDARD FUNCTIONS
4.11.5 Force listen only mode (sub-function code: 04)
Places a slave into the offline mode.
Used when disconnecting a slave from the network.
When QJ71MB91 is set in the listen only mode, the status is as follows:
• Ignores all request messages except for those of restart communications
option.(
• Stops counting of the diagnostic counter.(
• Continues recording with the communications event log.(
(1) Request message format (Master Slave)
(2) Response message format (Slave Master)
(When completed normally)
No response message is returned because the listen only mode (offline status) is
active.
(When completed with an error)
* 1 Exception and error codes are stored in the buffer memory in the case of error completion.
Refer to the following for storage location, confirmation methods, and detailed contents.
Figure 4.38 Force listen only mode (Request message)
Figure 4.39 Force listen only mode (Exception message)
(L)
Data
(L)
Function code
Function
code
(08
H
)
Sub-function code
Sub-function code
(0004
H
)
(0000
H
)
(H)
(H)
Data
Function code
Function
code
(88
H
)
Exception
code*
1
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