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WHEN COMMUNICATING DATA USING THE MC PROTOCOL9
9 - 2
9
MELSEC-F
(2) When an external device writes data to the PLC
1) Area C indicates transmission from the external device to the PLC.
2) The program of the external device is generated so that the data is
transmitted sequentially from left to right. (For example: in case of
area C, data should be sequentially sent from Header to the right.)
POINT
When the PLC receives a command message from an external device, it
completes processing of the data in area A/C, then sends a response message
and waits for the next command message (neutral state).
External
device side
(Command message)
PLC side
Header
Subheader
PC No.
Monitoring
timer
Area C
Header
Subheader
Complete code
(Response message)