3
SEQUENCE PROGRAM CONFIGURATION AND
EXECUTION CONDITIONS
3.3 Settings for Creation and Execution of Multiple Sequence Programs
3.3.5 Fixed scan execution type program
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(f) Execution interval of a fixed scan execution type program
Note that the execution interval of a fixed scan execution type program may
increase from the set interval depending on the time set for disabling interrupts by
the DI instruction (interrupt disabled time).
When the interrupt disabled time by the DI instruction is set to longer, use an
interrupt program by fixed scan interrupt (I28 to I31) instead of a fixed scan
execution type program.
* Means the highest common factor of fixed scan execution interval set to several fixed scan execution
type programs.
When the expression 1) is satisfied, the actual execution interval of a fixed scan
execution type program may increase from the set interval by the time shown in
the expression below.
The following shows an example of the increase in execution time of a fixed scan
execution type program.
With the settings above, the expression 1) is 0.5ms < 5ms.
Therefore, the execution time of a fixed scan execution type program whose
execution interval is set to 10ms increases 100ms (5 0.5 10 = 100) at the
most.
Highest common factor of fixed scan execution interval* < Interrupt disabled time ••• Expression 1)
Example
• Fixed scan execution interval •••10ms, 5ms, 1ms, 0.5ms
• Highest common factor of fixed scan execution interval ••• 0.5ms
• Interrupt disabled time (DI) •••5ms
• (Interrupt enabled time (EI) •••less than 0.5ms)
Figure 3.49 Program execution operation and interrupt enabled status
Interrupt disabled time
Highst common factor of scan execution interval
Fixed scan execution interval set to the corresponding program
EI
EI
END
END
DI
DI
Program execution
operation
Interrupt enabled/disabled
status
n scan
n+1 scan
Ena-
bled
Ena-
bled
Disabled
Disabled
Disabled
Less than
0.5ms
Less than
0.5ms
Interrupt disabled time = 5ms
Interrupt disabled time = 5ms