Mitsubishi MELSEC-A series, Programming Manual

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7. APPLICATION INSTRUCTIONS
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MELSEC-A
(3) Though the data specified at (D3) is dummy data which calls for no processing
in the program, specify any output (Y) number at this. Devices specified at (D3)
can be freely used in the program.
(4) Data communication is performed according to the data in the communication
request registration areas which are registered by executing the FROM(P) and
DFRO(P) instructions, as shown below. Execution of these instructions is
completed when data are registered in the communication request registration
areas. And then, following instructions are executed.
Once registration is completed by execution of an instruction, communication
processing is executed to the end even though the condition signal before the
FROM(P)/DFRO(P) instructions is turned OFF.
(5) The device number specified at (D2) is checked. If the same device number
was already specified to execute a processing, registration is not processed
after execution of the FROM(P)/DFRO(P) instructions.
(6) After completion of a processing which is executed according to registered data,
the bit device specified at (D2) is turned ON and deleted from the
communication request registration areas.
(7) The communication request registration areas can hold data for up to 32
requests. If the number of registration data exceeds 32, operation error occurs
and registration processing is not executed.
A2C/A52G
Remote terminal
module
I/O module
Remote terminal
module
I/O module
Registration of
communication request
Communication request
registration areas
K K K
FROM 1 18 D10 1
PRC M0 Y000