9.
9 -
2
MAINTENANCE FUNCTION
9.2
Watchdog Timer
(1) Watchdog timer (WDT)
The watchdog timer is an internal timer of PLC that detects PLC CPU hardware
errors and sequence program errors.
200ms is set as the default setting for this timer.
REMARK
The time set for the watchdog timer can be changed using "WDT" in PC RAS setting
in the GPP function parameter mode.
The setting range is 10ms to 2000ms (in 10ms units).
(2) Resetting the watchdog timer
The QnACPU resets the watchdog timer during END processing.
When the QnACPU is normally operating and executing the END instruction within
the setting value of the watchdog timer, the watchdog timer does not give time-out.
WDT times out when the END instruction is not executed within the value set for the
watchdog timer due to a QnACPU hardware error or an excessively long sequence
program scan time.
REMARK
Scan time is the time taken for the execution of the sequence program, starting from
step 0 and ending at step 0.
The scan time is not the same in every scan: it differs according to the execution or
non-execution of the instructions used in the program. (Refer to Section 12.1.)
Fig. 9.1 Resetting the watchdog timer
0
Scan execution
type program A
Scan execution
type program B
Low-speed execution
type program C
END
Scan time
Time measured by watchdog
timer
WDT reset
(Internal processing of a PLC)
Sequence program
Internal processing time
0
Next scan time
WDT reset
(Internal processing
of a PLC)
Содержание Q2ACPU
Страница 1: ......
Страница 2: ......
Страница 221: ...12 12 12 OVERVIEW OF PROCESSING PERFORMED BY THE QnACPU ...
Страница 222: ...12 13 12 OVERVIEW OF PROCESSING PERFORMED BY THE QnACPU ...
Страница 237: ...12 28 12 OVERVIEW OF PROCESSING PERFORMED BY THE QnACPU MEMO ...
Страница 269: ...16 11 16 POWER SUPPLY MODULE 2 Names and description of parts of the A62P A62PEU and A65P module ...
Страница 271: ...16 13 16 POWER SUPPLY MODULE 4 Names and description of parts of the A66P ...
Страница 343: ...21 21 13 MAINTENANCE AND INSPECTION 21 4 2 Replacement of the fuse for an output module ...
Страница 357: ...22 12 22 TROUBLESHOOTING ...
Страница 359: ...22 14 22 TROUBLESHOOTING MEMO ...
Страница 417: ...App 20 APPENDICES 3 Shift instructions Classification Symbol Description n bit shift 1 bit shift 1 word shift ...
Страница 429: ...App 32 APPENDICES Trigonometric function Classification Symbol Description ...
Страница 432: ...App 35 APPENDICES 15 Clock instructions Classification Symbol Description Clock data read write ...
Страница 537: ...App 140 APPENDICES REMARK 1 Message 1 An error code is displayed in 2 Alert 1 3 Alert 2 ...
Страница 538: ...App 141 APPENDICES APPENDIX 6 EXTERNAL DIMENSIONS Appendix 6 1 CPU Module 1 Q3ACPU Q4ACPU modules Unit mm inch ...
Страница 539: ...App 142 APPENDICES 2 Q2ACPU Q2ACPU S1 modules Unit mm inch ...
Страница 541: ...App 144 APPENDICES 2 A66P power supply module Unit mm inch ...
Страница 542: ...App 145 APPENDICES Appendix 6 3 Main Base Unit 1 A32B base unit 2 A32B S1 base unit Unit mm inch Unit mm inch ...
Страница 543: ...App 146 APPENDICES 3 A35B base unit 4 A38B A38HB A38HBEU base unit Unit mm inch Unit mm inch ...
Страница 567: ...MEMO ...
Страница 569: ......
Страница 570: ......