Download Type A1FXCPU Module User`s Manual (Function description)

7. COMMUNICATION WITH SPECIAL MODULE/SPECIAL BLOCK
MELSEC-A
7. COMMUNICATION WITH SPECIAL MODULE/SPECIAL BLOCK
This chapter explains how the A1FXCPU reads data from the special module/special
block and write data to the special module/special block.
(1) Special module/special block
The special module/special block is a module designed for the A1FXCPU to
handle analog values, high-speed pulses, etc. which cannot be handled by the
extension module/extension block.
The special module has memory (buffer memory) which stores data imported
from external equipment and data to be output to the external equipment.
(2) Read/write of data from/to A1FXCPU
The FROM/TO instruction is used by the A1FXCPU to read/write data from/to the
special module/special block.
• Execution of the FROM instruction allows reading of the data stored in the
buffer memory of the special module/special block.
• Execution of the TO instruction allows writing of data to the buffer memory of
the special module/special block.
Special module/special block
Write by TO instruction
Buffer memory
A1FXCPU
External
equipment
Read by FROM
instruction
POINT
Note that a frequent execution of FROM/TO instructions on the target special
module/special block may not be processed normally. When executing the
FROM/TO instructions on the special module/special block, set the special
module/special block timer or a constant scan with the FROM/TO instruction
timings.
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