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COMMUNICATION USING MC PROTOCOL8
8 - 2
8
MELSEC-F
(2) Remote control of the PLC
This function executes remote RUN/STOP operations.
Remote operations of the PLC can be performed from the external device side.
*1 Time required for communication in binary code is shorter because the amount of communication data is
approximately a half of what is required for communication in ASCII code data.
8.1.2 How to Read the Control Procedures of the MC Protocol
This section explains the control procedures when an external device accesses the
PLC using MC protocol.
(1) Transmission of command messages
Data communication through the MC protocol is performed using half-duplex
communication.
When accessing the PLC, send the next command message after receiving a
response message from the PLC side for the previous command message
transmission.
(2) When a normal completion response message to a command
message cannot be received
1) If an abnormal completion response message is received
Handle the case according to the error code in the response message.
2) If the response message cannot be received or nothing can be received
Send the command message again after the monitoring time of the response
monitor timer.
* Modify the value of the monitoring time as needed.
Send frame Communication data code Function
Communication
using MC protocol
A compatible 1E
frame.
ASCII code or binary code
*1
Device memory read/
write
Batch read/write in bit/
word units
Remote control of the
PLC
Remote RUN
Remote STOP
External device side
PLC side
(Command message) (Command message)
(Response message) (Response message)