Block - Mitsubishi Electric MELSEC iQ-F Series Programming Manual

Block

A block is a unit showing a series of operation consisting of steps and transitions.
Block0
For the maximum number of blocks that can be created in an SFC program, refer to the following.
Page 73 Specifications
A block begins with an initial step, a step and a transition are connected alternately, and ends with an end step or jump
sequence.
A block is in the active or inactive state.
• Active: The block has an active step.
• Inactive: All steps in the block are inactive.
When the block state changes from inactive to active, the initial step becomes active to start sequential processing. (Page
102 Block execution sequence)
• Depending on the CPU parameter setting, only the block 0 can be started automatically when the SFC
program starts. In this case, when the end step is activated and the block 0 is finished, the block 0 will be
automatically restarted and executed again from the initial step. (Page 98 Start Conditions Setting)
• If a start request is issued to a step in an inactive block by using the SFC control instruction (activating a
step), the block is activated to execute processing from the specified step.
Block1 Block2
8 SFC PROGRAM
75
8.2 Structure
8