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MELSEC-Q
7 PROGRAMMING WHEN EXECUTING THE MASTER FUNCTION
7
7 PROGRAMMING WHEN EXECUTING THE MASTER FUNCTION
This chapter explains programming when the master function is executed.
7.1 Precautions on Programming
This section explains the precautions when creating a program.
(1) Observe the following to perform input/output communication with a slave node.
• Place the I/O communication read processing program at the beginning of a
sequence program.
• Place the I/O communication write processing program at the end of a sequence
program.
Refresh processing request, I/O communication read processing
I/O communication write processing
•
•
•
•
•
•
(2) Perform the reading of reception data and the writing of transmission data only
when there is no error in the module and the module is in the ready status.
Program for communication
X0FX0
Module error Module ready
(3) Create a program that detects the communication status of each node and
performs interlock. Also, create a program that handles errors when they occur.
M0
Node No. 0 error handling program
X0FX0
Module error Module ready
FROM H0 H1BC K4K4MO
Slave station communication status
M1
Node No. 1 error handling program
M0
Node No. 0 normal processing program
M1
Node No. 1 normal processing program