Mitsubishi Electric MELSEC iQ-R Series - Page 107

8 RUNNING A PROGRAM
8.5 Program Execution Type
105
8
Fixed scan execution mode
For fixed scan interrupts (I28 to I31, I48, I49) triggered by the fixed scan execution type program or the internal timer of the
CPU module, this mode specifies the program execution operation that is performed when more than one interrupt occurs
( Page 116 Operation upon occurrence of an interrupt factor) However, an execution cause which occurs while the
interrupt is disabled by the DI instruction is excluded from the fixed scan execution mode target.
■Operation in the fixed scan execution mode
This section describes the operation which can be performed in the fixed scan execution mode.
• Execution Count Takes Priority
The program is executed for all the pending number of executions so that it can be executed the same number of times as
execution causes.
• Precede Fixed Scan
When a pending execution exists, it is performed within the delay limit value behind a cycle. ( Page 106 Delay limit value
behind a cycle) Note that, even if more than one pending execution exists, only one execution is performed.
■Fixed scan execution mode setting
Use the fixed scan execution mode setting.
[CPU Parameter]  [Interrupt Settings]  [Fixed Scan Execution Mode Setting]
Window
Displayed items
(1) The program is executed just three times, which is the pending number of executions, as soon as interrupt becomes available.
Item Description Setting range Default
Fixed Scan Execution
Mode
When fixed scan characteristics are prioritized, an execution is performed
within the delay limit value behind a cycle. When the number of executions
is prioritized, all the pending executions are performed.
• Precede Fixed Scan
• Execution Count Takes
Priority
Precede Fixed Scan
(1)
Section where interrupts
are disabled
Section where interrupts
are disabled
"MAIN"
(Fixed scan execution type program)
Cycle interval of MAIN
Execution cause:
6 times
Number of
executions: 6 times
Section where interrupts
are disabled
Cycle interval of MAIN
"MAIN"
(Fixed scan execution type program)
Number of
executions: 4 times
Execution cause:
6 times
Delay behind the cycle