NAiS FP2, Technical Manual

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9-9
9.2 Appendix
9.2.1
Detailed Time Chart of Data Transmission and Reception
Explanation of operation
MCU detects the completion of data reception.
The reception done flag X0(X2) is taken in the CPU by the I/O refresh operation.
Makes the reception done flag X0(X2) be the execution condition, and the received data is copied in
the operation memory using F161 (MRCV).
Once copying data completes, the PLC data reception done flag X1(X3) turns on.
After completing the execution of the MRCV instruction, the MCU reception done flag turns off.
As the MCU reception done flag is taken in by the I/O refresh operation of the CPU, X0(X2) turns off.
Also the PLC data reception done flag X1(X3) turns off by the I/O refresh operation.
Precautions
The MCU reception done flag (above-mentioned ) turns off within a maximu of 100 µs after the MRCV
instruction is executed, so that it may not turn off in the next scan after the execution of the MRCV
instruction depending on PLC scan time and the timing to execute the MRCV instruction. In that case,
the received data has been copied from the MCU to the CPU, however, note that the reception done flag
X0(X2) has been left to be on even in the next scan.
It is recommended to execute the MRCV instruction as soon as the reception done flag X0(X2) turned on
as mentioned below.
If the moment that the reception done flag X0(X2) turns on is not used as the execution condition, the
PLC data reception done flag X1(X3) after the execution of the MRCV instruction can be used to tell
whether there are any received data or not.