Chapter 6 Ras Functions; Scan Monitoring Function; Scan Time Monitoring Time Setting; Watchdog Timer Reset - Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual

6
RAS FUNCTIONS
6.1

Scan Monitoring Function

RnPCPU RnPCPU
RnCPU RnENCPU
(Process) (Redundant)
• When using the Process CPU (redundant mode), refer to the following as well.
Page 435 FUNCTIONS
• When using the SIL2 Process CPU, refer to the following as well.
Page 605 FUNCTIONS
This function detects hardware and program errors of the CPU module by monitoring the scan time. The watchdog timer, an
internal timer of the CPU module, is used to monitor the following scan.
• Initial scan (first scan)
• Second and later scans

Scan time monitoring time setting

Set the scan time monitoring time.
[CPU Parameter]  [RAS Setting]  [Scan Time Monitoring Time (WDT) Setting]
Window
Displayed items
Item Description
Initial Scan Sets the scan-time monitoring time (WDT) for the initial scan (first
scan).
After 2nd Scan Sets the scan-time monitoring time (WDT) for the second and later
scans.

Watchdog timer reset

The watchdog timer is reset when the END/FEND instruction is executed. While the CPU module is running correctly, if the
END/FEND instruction is executed within the set time of the watchdog timer, the watchdog timer does not count up. If the
END/FEND instruction cannot be executed within the set time of the watchdog timer due to a hardware error of the CPU
module or increase in program execution time due to an interrupt or other causes, the watchdog timer counts up.
RnPSFCPU RnPSFCPU RnSFCPU RnSFCPU
(Standard) (Safety) (Standard) (Safety)
Setting range
10 to 2000ms (in units of 10ms)
10 to 2000ms (in units of 10ms)
6 RAS FUNCTIONS
6.1 Scan Monitoring Function
6
Default
2000ms
200ms
125