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MELSEC-Q
7 DATA COMMUNICATIONS USING BIDIRECTIONAL PROTOCOL
POINT
(1) Receive data can also be read using interrupt programs.
For more details on reading receive data with interrupt programs, see Chapter
4 of the User's Manual (Application).
Note that if the reading of data received from the same interface is to be
performed, it is not possible to combine the reading of data received by the
main program and reading of data received by the interrupt program.
Accordingly, use one or the other of the above programs to read the data
received.
(2) The SPBUSY instruction is used to read the execution status when using a
dedicated instruction. (See Chapter 9.)
(3) More than one BIDIN instruction cannot be executed simultaneously.
Execute the next BIDIN instruction only after the execution of the first BIDIN
instruction is completed.
(4) If the communication data count is set in byte units and the receive data count
is an odd byte when requesting the reading of receive data to the PLC CPU,
00
H
is stored in the higher byte of the final data storage position in the receive
data storage area.
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