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MELSEC-Q
3 SPECIFICATIONS
3.12 Running a BASIC Program by Multitask Processing
Here, the method of running a QD51 (-R24) BASIC program, etc. is explained.
3.12.1 Multitask processing
The QD51 (-R24) us a unit which operates by BASIC programs created by the user.
The QD51 (-R24) has one main CPU (central processing unit).
Multitasking accomplishes parallel operations by successively switching the execution
between multiple BASIC programs (up to 2 tasks).
1) 2)
3)
4)
5) 6)
Shows the order of
main CPU processing.
[Processing in the case of two tasks]
Example
Task 1 Task 2
In QD51 (-R24) multitask processing, switching of BASIC program execution is done
when the conditions shown below occur.
• When "Task schedule time (50 ms)" has passed.
• When a data input/output (data send/receive) command is run with respect to a
screen, keyboard, disk, peripheral device or external device.
• When a command is run which carries out control of (interrupts, stops, ends) BASIC
program execution.
• When a command is run which carries out multitask control (synchronizes execution,
starts or changes the priority, etc.).
• When a program execution interrupt state is canceled (input/output is completed, the
specified time has passed, etc.)
REMARK
Refer to the Programming Manual (Commands) concerning details of multitask
processing and commands which switch the execution of programs.
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