IAI PSEL, Operation Manual

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3. Program
148
3.6.2 Setting of Multi-tasking and Task Level
[1] Multi-tasking
Controllers come standard with the multi-tasking function that allows multiple programs to be
run simultaneously, such as moving actuators in one program and turning ON/OFF solenoid
valves in another programs.
“Multi-tasking” literally means performing multiple tasks. The main CPU processes each
program step by step. If multiple programs are run that contain actuator commands, timer
commands, input waiting commands, etc., however, the main CPU uses an idle time while
waiting for completion of each commanded task to process different programs.
(If a given program has no idle time, the system forcibly switches to the next program after
1mS based on “task slicing” action.)
XSEL controllers adopt high-speed CPUs, so multi-tasking is also performed at high speed.
Note that this function also supports simulated ladder circuits, which means that as long as
your equipment is small enough you can build it as a sequencer.
[Example of multi-tasking (running multiple programs)]
[2] Task level
If you want to perform a given task (program) preferentially over other tasks (programs), you
can do so with a CHPR command by setting the parameter to “1: HIGH”. If the parameter is
set to “0: NORMAL”, no priority is set.
You can also set task levels for simulated ladder programs. [Refer to Section 3.6.3]
Main
program
Operation
Sub
-program
Solenoid
valve
control
Simulated
ladder
program
Sensor
monitoring
Communication
program
Camera, etc.
Main CPU