Mitsubishi Q00JCPU User Manual page 488

9
DEVICE EXPLANATION
(5) Precautions
Basic
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9.2 Internal User Devices
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9.2.11 Counter (C)
(a) Execution of interrupt counter and interrupt program
One interrupt pointer is insufficient to execute interrupt counter and interrupt
program operation.
Moreover, an interrupt program cannot be executed by an interrupt counter setting
designated at the "PLC system" tab screen in the "(PLC) Parameter" dialog box.
(b) Processing that delays count processing
If the processing items shown below are in progress when an interruption occurs,
the counting operation will be delayed until processing of these items is
completed.
The count processing starts after the execution of programs is completed.
Even if the same interruption occurs again while processing of these items is in
process, only one interruption will be counted.
• During execution of sequence program instructions
• During interrupt program execution
• During execution of a fixed scan execution type program
(c) Maximum counting speed of interrupt counter
The maximum counting speed of the interrupt timer is determined by the longest
processing time of the items shown below.
• Instruction with the longest processing time among the instructions used in
the program
• Interrupt program processing time
• The processing time of a fixed scan execution type program
(d) When many interrupt counters are used
The use of too many interrupt counters will increase the sequence program
processing time, and may cause a "WDT ERROR".
If this occurs, reduce the number of interrupt counters or the counting speed for
the input pulse signal.
(e) Resetting the interrupt counter
The interrupt counter's count value can be reset by using the RST C
in the sequence program prior to the FEND instruction.
(f) Reading the count value
The interrupt counter's count value can be read out by using the sequence
program MOV instruction.
The Basic model QCPU cannot execute fixed scan execution type programs.
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