Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 27

Phase and execution order
For the normal/low-speed execution cycle, set the phase.
With the phase setting, a program block can be executed at a timing shifted by a constant interval from the set execution
cycle.
Set the phase on the "Properties" window of the program block.
Ex.
Phase for the normal-speed execution cycle of 800ms
On the "Options" window of the engineering tool, set "200ms" to the high-speed execution cycle and "4" to the setting value of normal-speed execution cycle.
200ms 200ms
High speed
#1
Normal speed
In this case, the execution cycle of 800ms is divided into four sections. The phases #1 to #4 can be set for the normal-speed program block.
Ex.
Fixed period execution of program block with phase
800ms
200ms 200ms 200ms
#1 #2 #3
A
B
The execution cycle of 800ms is divided into four sections (200ms  4). Set the program block A to be executed in the phase #1 and the program block B in the
phase #2.
Consequently, when the execution time of the program block A is 200ms or shorter, the execution cycle of the program block B is always 800ms regardless of
the execution time of the program block A.
200ms 200ms 200ms
#2 #3 #4 #1
800ms
200ms 200ms 200ms
#4 #1 #2
800ms
200ms 200ms 200ms
#2 #3 #4
800ms
800ms
200ms 200ms
#3 #4
1 PROCESS CONTROL FUNCTION BLOCK
1.5 Program Execution Control
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