4 Special Functions
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SmartAXIS Touch User's Manual
4.17 Watchdog Timer Setting
This section describes watchdog timer setting with monitoring the operation state of the Touch.
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Feature Description
A watchdog error occurs when the processing time for one scan exceeds the allowed time while the ladder program
or FBD program is running.
If a watchdog error occurs, the system is reset with the purpose of returning the system to normal operation.
If the watchdog error occurs frequently, you can assume that there is a hardware problem and that the Touch
requires replacement.
Some of the reasons why a watchdog timer will occur are problems with the Touch hardware and the length of the
processing time in the ladder program. If the processing time for one scan of the ladder program exceeds the time
configured for the watchdog timer on the ladder program, place a NOP (no operation) instruction in the ladder
program. The watchdog timer is reset when the NOP instruction is executed.
For FBD program, the watchdog timer cannot be reset in the program.
Watchdog timer setting time
The watchdog timer setting time can be changed in the function area settings. Decide on the watchdog timer setting
time in either of the following two ways.
• Decide by user system specification
Determine the maximum on time (milliseconds) so the output signals do not stay on if the Touch loses control and
set that value as the watchdog timer setting time. However, if the ladder program processing time takes longer
than the design specification, use an NOP (no operation) instruction in the ladder program. For example, when the
watchdog timer is set to 100 milliseconds and the maximum value for one scan is 120 milliseconds on the ladder
program, insert an NOP instruction in the ladder logic program to ensure that the error does not occur.
• Match the ladder program processing time
Check the maximum value for one scan (D8024) and set the watchdog timer value as a value with a safety margin
added to the maximum value.
Select the watch dog timer setting between 100 milliseconds and 5,000 milliseconds. The default time is 400
milliseconds.
When changing the watchdog timer setting value, select an appropriate value that fully takes into
consideration the safety of the system.
The ladder program or FBD program execution time can be checked with the value of LSD38.
Содержание SmartAXIS Touch FT1A Series
Страница 1: ...FT1A Series FT9Y B1390 4 SmartAXIS Touch User s Manual ...
Страница 22: ...Contents Preface 21 SmartAXIS Touch User s Manual ...
Страница 240: ...6 Using Library Screens 4 36 SmartAXIS Touch User s Manual ...
Страница 416: ...2 Multi State Lamps 8 26 SmartAXIS Touch User s Manual ...
Страница 558: ...9 Calendar 9 142 SmartAXIS Touch User s Manual ...
Страница 668: ...6 Timer 11 52 SmartAXIS Touch User s Manual ...
Страница 754: ...4 Using Data and Detected Alarms 13 34 SmartAXIS Touch User s Manual ...
Страница 792: ...4 Using the Data 14 38 SmartAXIS Touch User s Manual ...
Страница 810: ...4 Using the Data 15 18 SmartAXIS Touch User s Manual ...
Страница 870: ...3 Text Manager 19 16 SmartAXIS Touch User s Manual ...
Страница 924: ...6 Important Notes 20 54 SmartAXIS Touch User s Manual ...
Страница 1036: ...5 User Communication 22 74 SmartAXIS Touch User s Manual ...
Страница 1092: ...2 Monitoring on the Touch 24 26 SmartAXIS Touch User s Manual ...
Страница 1142: ...2 Word Devices 27 18 SmartAXIS Touch User s Manual ...
Страница 1186: ...2 Analog Cartridge 29 34 SmartAXIS Touch User s Manual ...
Страница 1194: ...3 Handling Problems 30 8 SmartAXIS Touch User s Manual ...