Table of Contents
Advertisement
(4) Precautions
(a) Execution interval of a fixed scan execution type program
Execution interval of a fixed scan execution type program may increase from the preset interval
depending on the time set for disabling interrupts by the DI instruction (interrupt disabled time).
If the interrupt disabled time by the DI instruction becomes too long, use an interrupt program by
fixed scan interrupt (I28 to I31) instead of a fixed scan execution type program.
Highest common factor of fixed scan execution interval
This is the highest common factor of execution interval set to multiple fixed scan execution type programs
*1:
When the condition 1) is satisfied, the actual execution interval of a fixed scan execution type
program may increase from the preset interval by the time shown in the expression below.
Interrupt disabled time
Highst common factor of scan
execution interval
The following shows an example of the increase in execution time of a fixed scan execution type
program.
Example
With the settings above, the condition 1) will be 0.5ms < 5ms.
Program execution
operation
Interrupt enabled/
disabled status
Figure 2.32 Program execution and interrupt enabled/disabled status
The execution time of a fixed scan execution type program whose execution interval is set to 10ms
increases 100ms (5
Fixed scan execution interval set to
the corresponding program
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)
n scan
EI
DI
Disabled
Enabled
Less than 0.5ms
Interrupt disabled time = 5ms
0.5
10 = 100) at the most.
CHAPTER2 SEQUENCE PROGRAMS
*1
Interrupt disabled time ••• Condition 1)
<
n+1 scan
DI
END
Disabled
Less than 0.5ms
Interrupt disabled time = 5ms
EI
END
Disabled
Enabled
2 - 29
1
2
3
4
5
6
7
8
Advertisement
Table of Contents
