Programming Concepts; Programs And Tasks - Omron CP - PROGRAMMING MANUAL 05-2007 Programming Manual

Programming Concepts

1-1 Programming Concepts
1-1-1

Programs and Tasks

1,2,3...
2
Tasks specify the sequence and interrupt conditions under which individual
programs will be executed. They are broadly grouped into the following types:
1. Tasks executed sequentially that are called cyclic tasks.
2. Tasks executed by interrupt conditions that are called interrupt tasks.
Note Interrupt tasks can be executed cyclically in the same way as cyclic tasks.
These are called "extra cyclic tasks."
Programs allocated to cyclic tasks will be executed sequentially by task num-
ber and I/O will be refreshed once per cycle after all tasks (more precisely
tasks that are in executable status) are executed. If an interrupt condition
goes into effect during processing of the cyclic tasks, the cyclic task will be
interrupted and the program allocated to the interrupt task will be executed.
Cyclic
task 0
Interrupt condition
goes into effect
Cyclic
task 1
Cyclic
task n
I/O refreshing
In the above example, programming would be executed in the following order:
start of A, B, remainder of A, C, and then D. This assumes that the interrupt
condition for interrupt task 100 was established during execution of program
A. When execution of program B is completed, the rest of program A would be
executed from the place where execution was interrupted.
With earlier OMRON PLCs, one continuous program is formed from several
continuous parts. The programs allocated to each task are single programs
that terminate with an END instruction, just like the single program in earlier
PLCs.
Program A
Allocation
Interrupt
task 100
Allocation
Program C
Allocation
Program D
Allocation
Section 1-1
Program B