Mitsubishi MELSEC-A series, Programming Manual

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6. BASIC INSTRUCTIONS
6
−
72
MELSEC-A
(2) When the A3N, A73, A3V and A3N board are used, the CHG instruction is only
executed on the leading edge of its input condition. Since M9050 is not
provided, execution contents of the CHG instruction are always same.
Ladder example
The following program is written before END or FEND of the main and subsequence programs.
Timing chart
OFF No switching between the main and subsequence programs. (4), 5), 11))
ON
The main sequence program is only switched to the subsequence program, then back to the main sequence
program on the first leading edge of the CHG instruction execution command (X0). (2))
Operation
depending
on ON/OFF
of X0
OFF
↓
ON
Switched between the main and subsequence programs ( 1), 6), 12))
Remarks
When the CHG instruction is executed, END processing (e.g. timer timing, counter counting, WDT reset) is
performed for the current program and operation is started from step 0 of the other program.
(3) When the A3H, A3M, AnA, A3U, A4U and Q06H are used, the CHG instruction
is executed repeatedly while its input condition is on.
Ladder example
The following program is written before END or FEND of the main and subsequence programs.
Timing chart
OFF No switching between the main and subsequence programs. (4), 5), 11))
ON
CHG instruction is executed every scan and switches between the main and subsequence programs. (2), 3),
7), 8), 9), 10))
Operation
depending
on ON/OFF
of X0
OFF
ON
Switched between the main and subsequence programs (1), 6), 12))
Remarks
When the CHG instruction is executed, END processing (e.g. timer timing, counter counting, WDT reset) is
performed for the current program and operation is started from step 0 of the other program.
X000
Interlock
CHG
Input condition
X0
CHG instruction execution
in main sequence program
Main sequence program
Subsequence program
CHG instruction execution
in subsequence program
1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12)
X000
Inter lock
CHG
↓
X0
CHG instruction
execution in main
sequence program
Main sequence
program
Subsequence program
CHG instruction
execution in
subsequence program
1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12)