Block Execution Sequence - Mitsubishi Q series Programming Manual

5 SFC PROGRAM PROCESSING SEQUENCE

5.3.2 Block execution sequence

(1) In the SFC program, the step in the active block is executed every scan.
(2) When there are multiple blocks, the blocks are processed in order of lower to higher block
numbers.
(a) In the active block, the active step in that block is executed.
(b) The inactive block is checked for a START request, and if there is a START request, the
block is activated and the step in that block is executed.
The SFC program is executed in order of 1) to 6).
1): Whether block 0 is active or inactive is checked.
2): Since block 0 is active, the active step (S2) is executed.
3): Whether block 1 is active or inactive is checked.
4): Since block 1 is active, the active step (S0) is executed.
5): Whether block 2 is active or inactive is checked.
6): Since block 2 is inactive, whether the next block is active or inactive is checked.
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1) Block0 3)
S0
t0
S1
BLT1 BLT2
t1
S2
2)
t2
Block1 5)
S0 S0
4)
t0 t0
S1
S1
t1 t1
S2 S2
t2 t2
: Active step, : Inactive step
MELSEC-Q
Block2
6)
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