(Note 3) The unit number and COM. port number in the above program is applied when the COM.1 port of the
CPU unit is used.
■
Timing chart
■
I/O allocation (CPU Unit)
COM. port no.
Name Description
1 2 0
XC XD XE
Master
communication
Clear to send flag
Turns ON when MODBUS RTU is set for the communication
mode and the unit is in RUN mode.
YC YD YE
Master
communication
Sending active flag
Turns ON during transmission using SEND/RECV
instructions.
Turns OFF when the sending process is completed.
Y0 Y1 Y2
Sending done result
flag
Reports completion result of sending data in general-purpose
communication or master communication.
(Normal completion: 0, Abnormal completion: 1)
■
I/O allocation (For Serial Communication Unit)
COM. port no.
Name Description
1 2 3 4
XC XD XE XF
Master
communication clear
to send flag
Turns ON when MODBUS RTU is set for the communication
mode and the unit is in RUN mode.
YC YD YE YF
Master
communication
sending active flag
Turns ON during transmission using SEND/RECV
instructions.
Turns OFF when the sending process is completed.
Y0 Y1 Y2 Y3
Sending done result
flag
Reports completion result of sending data in general-purpose
communication or master communication.
(Normal completion: 0, Abnormal completion: 1)
(Note 1) Each contact is used for reading the operation status. Do not write over it with a user program.
8.3 MODBUS RTU Master Communication (RECV)
WUME-FP7COM-07 8-5
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