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MEWTOCOL Master/Slave Communication
Timing chart
Master communication
Clear to send flag
(XC)
Master communication
Sending active flag
(YC)
Execute RECV
Master communication
Sending done result flag
(Y0)
Sending data
Response reception
processing
I/O allocation
COM port no. 1
XC
YC
Y0
(Note 1) Each contact is used for reading the operation status. Do not write over it with a user program.
KEY POINTS
Specify the port targeted for communication, using UNITSEL instruction
immediately before SEND/RECV instruction.
Master communication is only valid when MEWTOCOL is selected. Confirm
that the "Master communication Clear to send flag" (XC) for the targeted
channel is ON, and execute SEND/RECV instruction.
You cannot execute other SEND/RECV instruction for a communication port
in master communication. Confirm that the "Master communication Sending
active flag" (YC) is OFF, and execute instruction.
You cannot execute SEND/RECV instruction for a port in slave
communication.
If no response is received, the "Master communication Sending active flag"
(YC) remains ON throughout the timeout setting time specified in CPU
configuration.
Up to 16 SEND/RECV instructions can be executed simultaneously for
different COM. ports.
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Confirm ON
Confirm OFF
Name
Explanation
Master
Turns ON when MEWTOCOL-COM or MEWTOCOL7 is set for
communication Clear
the communication mode, and the unit is in the RUN mode.
to send flag
Master
Turns ON during sending data based on SEND/RECV
communication
instruction.
Sending active flag
Turns OFF when the sending process is completed.
Reports completion result of sending data in general-purpose
Sending done result
communication or master communication.
flag
(Normal completion: 0, Abnormal completion: 1)
Conditions to enable execution of RECV
instruction
Clear to send flag (XC): ON
Sending active flag (YC): OFF
Sending active flag (YC):
Sending data: ON, Sending done: OFF
Sending done result flag (Y0):
Normal completion: OFF
Abnormal completion: ON
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