User`s manual

3
SEQUENCE PROGRAM EXECUTION
3.2 Concept of Scan Time
3 - 6
1
Overview
2
Performance Specification
3
Sequence Program Configuration and Execution Conditions
4
I/O Nunber Assignment
5
Memories and Files Handled by CPU Module
6
Functions
7
Communication with Intelligent Function Module
8
Parameters
(2) WDT (Watchdog timer)
The watchdog timer (hereafter abbreviated to the WDT) watches the scan time.
The default value is 200ms.
(a) WDT error
A WDT error is 10ms.
When the WDT (t) is set to 10ms, a "WDT ERROR" occurs within a scan time
range of 10ms<t<20ms.
(b) WDT Setting
The WDT setting can be changed within a range of 10ms to 2000ms in the PLC
RAS of the PLC parameter dialog box. (Setting unit: 10ms)
(3) Function that repeats program at fixed intervals
The constant scan function ( Section 6.9) allows a program to be executed
repeatedly at fixed intervals.
When the constant scan is set, a program is executed at intervals of the preset
constant scan time.
Diagram 3.7 PLC RAS (WDT Setting)