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MELSEC-Q
8 COMMUNICATION WITH INTELLIGENT FUNCTION MODULE/SPECIAL
FUNCTION MODULE
8.1.3 Communication using FROM/TO instruction
(1) FROM/TO instruction
At the execution of the FROM/TO instruction, the data stored in the buffer
memory of the intelligent function module can be read, or data can be written to
the buffer memory of the intelligent function module.
The FROM instruction stores the data read from the buffer memory of the
intelligent function module to the designated device.
The TO instruction writes the data of the designated device to the buffer memory
of the intelligent function module.
REMARK
1) For the details of the FROM/TO instruction, refer to the following manuals.
• QCPU (Q mode)/QnACPU Programming Manual (Common Instructions)
2) For the details of the buffer memory of the intelligent function module, refer to the
manual of the intelligent function module being used.
8.1.4 Communication using the intelligent function module device
(1) Intelligent function module device
The intelligent function module device is the buffer memory of the intelligent
function module represented as a device of High Performance model QCPU in
High Performance model QCPU programs.
It enables reading data stored in the buffer memory of the intelligent function
module, or enables writing data to the buffer memory of the intelligent function
module.
(2) Difference from the FROM/TO instruction
The intelligent function module device can be handled as a device of High
Performance model QCPU, enabling the processing of data read from the
intelligent function module with one instruction.
This saves the number of steps in the entire program.
The processing speed is the total of the instruction execution time and the access
time to/from the intelligent function modules.
POINT
When reading and processing the data of the intelligent function module frequently
in the program, use the FROM instruction to read the data at one point in the
program and store and process it in a data register, instead of using the intelligent
function module device every time.
Otherwise, the intelligent function module device accesses the intelligent function
module every time the instruction is executed, resulting in longer scan time for the
program.
REMARK
For the intelligent function module device, see Section 10.5.
