Sfc Program Processing Sequence - Mitsubishi Electric MELSEC iQ-F Series Programming Manual

SFC program processing sequence

Block execution sequence
While the SFC program is running, the actions of each step are executed sequentially starting from the initial step of an active
block.
An SFC program containing multiple blocks checks the state (active/inactive) of the blocks in ascending order of block
numbers (block 0 → block 1 → block 2).
An active block executes the actions of active steps in the block.
An inactive block checks for existence of a start request. If a start request exists, the block is activated and the active steps in
the block are executed.
(1)
BL0
BS BL1
(2)
Block 0 can be started automatically when "Auto-start block 0" is specified in "Start Conditions Setting" of the SFC setting.
With this setting, even if block 0 reaches the end step and becomes inactive, it will be restarted in the next scan. (Page 98
Start Conditions Setting)
8 SFC PROGRAM
102
8.5 SFC Program Execution Order
(3)
BL1
(4)
BS BL2
Processing is performed in the following order.
(1) Processing of block 0 (BL0)
(5)
(2) Execution of the step in block 0 (BL0)
(3) Processing of block 1 (BL1)
(4) Execution of the initial step of block 1 (BL1)
(5) Processing of the next block