Filter
Top Products
CHAPTER2 SEQUENCE PROGRAMS
1
2
3
4
5
6
7
8
2.3 Settings When Program is Divided
2.3.4 Fixed scan execution type program
2 - 29
(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.
*1: This is the highest common factor of execution interval set to multiple fixed scan execution type programs
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.
The following shows an example of the increase in execution time of a fixed scan execution type
program.
With the settings above, the condition 1) will be 0.5ms < 5ms.
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
*1
< Interrupt disabled time ••• Condition 1)
• 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 2.32 Program execution and interrupt enabled/disabled status
Interrupt disabled time
Highst common factor of scan
execution interval
Fixed scan execution interval set to
the corresponding program
Example
Program execution
operation
Interrupt enabled/
disabled status
Disabled Disabled Disabled
Enabled
Enabled
Interrupt disabled time = 5ms Interrupt disabled time = 5ms
n scan
n+1 scan
EI
EI
END END
DI
DI
Less than 0.5ms Less than 0.5ms