Mitsubishi Electric MELSEC iQ-R Series, Programming Manual

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11 PROCESS CONTROL INSTRUCTIONS
11.1 Overview
How to execute process control instructions
Execution cycle and control cycle
■
Execution cycle
The execution cycle is an interval at which process control instructions are executed.
The following methods can be used to execute process control instructions in each execution cycle.
Specify the execution cycle value used by process control instructions in SD816 and SD817 in a single-
precision real number.
■ Control cycle
The control cycle is a cycle in which PID control is performed by instructions such as S.2PID. For the control cycle, specify an
integral multiple of the execution cycle. Execution cycles are counted during execution, and PID operation is performed when
the specified control cycle is reached.
Specify the control cycle used in the loop tag memory. Instructions such as S.2PID perform PID control based on the control
cycle value specified in the loop tag memory.
Ex.
The S.2PID instruction performs monitoring every second and implements PID control every 5 seconds.
Setting the control cycle to an integral multiple of the execution cycle enables monitoring such as for checking
the process value range every execution cycle.
Execution method Description
Timer A timer is used to measure the execution cycle and a process control instruction is executed when the
time of the timer is up.
Interrupt program Interrupt programs I28 to I31 are each executed every execution cycle.
Fixed scan execution type program Fixed scan execution type programs are each executed every execution cycle.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1s 1s 1s 1s 1s
5s 5s 5s
(s)
Execution cycle
Control cycle
(Execution cycle)×5