● The case of SCU shows the case that it is used in the following combination.
• COM.0 port equipped in the CPU unit
• Communication cassettes attached to the CPU unit (COM.1 to COM.2 ports)
• Communication cassettes attached to the serial communication unit (COM.1 to COM.4
ports)
● The communication cassette (Ethernet type) does not support MODBUS.
■
I/O allocation (in the case of CPU with built-in SCU)
COM Port No.
Name Description
1 2 0
XC XD XE
Master
communication
clear to send flag
Turns ON when MEWTOCOL-COM, MEWTOCOL7, or MODBUS-
RTU is set for the communication mode, and the unit is in the
RUN mode.
YC YD YE
Master
communication
sending flag
Turns ON during sending data based on SEND/RECV instruction.
Turns OFF when the sending process is completed.
Y0 Y1 Y2 Sent flag
Reports completion result of sending data in genera-purpose
communication or master communication.
(Normal completion: 0, Abnormal completion: 1)
(Note 1) Each contact is used for reading the operation state. Do not write over it with a user program.
■
I/O allocation (in the case of 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 MEWTOCOL-COM, MEWTOCOL7, or
MODBUS-RTU is set for the communication mode, and the unit
is in the RUN mode.
YC YD YE YF
Master
communication
sending flag
Turns ON during sending data based on SEND/RECV
instruction.
Turns OFF when the sending process is completed.
Y0 Y1 Y2 Y3 Sent flag
Reports completion result of sending data in genera-purpose
communication or master communication.
(Normal completion: 0, Abnormal completion: 1)
(Note 1) Each contact is used for reading the operation state. Do not write over it with a user program.
■
Precautions during programming (in the case of SCU)
● Use the UNITSEL instruction immediately before the SEND/RECV instruction to specify a
target port for communication.
● Master communication is only enabled when MEWTOCOL or MODBUS is selected. Confirm
that the "master communication clear to send flags" (XC to XF) are ON for the corresponding
channel, and execute the SEND/RECV instruction.
● Another SEND/RECV instruction cannot be executed for a communication port where master
communication is in progress. Confirm that the "master communication sending flags" (YC to
YF) are OFF, and execute the instruction.
15.6 SEND (MODBUS Master: Function Code Specification)
WUME-FP7CPUPGR-12 15-41
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