How To Execute Process Control Instructions - Mitsubishi Electric MELSEC iQ-R Series Programming Manual

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.
Execution method
Timer
Interrupt program
Fixed scan execution type program
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.
0 1
Execution cycle
1s 1s
Control cycle
(Execution cycle)×5
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.
11 PROCESS CONTROL INSTRUCTIONS
1192
11.1 Overview
Description
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 programs I28 to I31 are each executed every execution cycle.
Fixed scan execution type programs are each executed every execution cycle.
2 3 4 5 6 7
1s 1s 1s
5s
8 9 10 11 12 13 14
5s
15 16 17 18 (s)
5s