12 -
8
12. OVERVIEW OF PROCESSING PERFORMED BY THE QnACPU
(5) Scan time
• The scan time is a total of the scan execution type program execution time, the
END processing time, and either the low-speed program execution time or the
constant scan waiting time.
*1
When more than one scan execution type program is executed, "the execution
time of the scan execution type program" is the time required for completing
execution of all these programs.
*1
Refer to Section 12.1.3.
• The QnACPU measures the present, minimum, and maximum values for the scan
time and stores them in special registers SD520, SD521, and SD524 to SD527.
*2
The scan time can be checked by monitoring these special registers.
*2
The accuracy of each scan time stored in the special registers is 0.1ms. Note that, even if
the watchdog timer (WDT) reset instruction is executed in the sequence program,
measurement of each scan time is continued.
(6) WDT (watchdog timer)
This is a timer that monitors the scan time; and 200ms is set as a default value.
WDT is set within the range of 10ms to 2000ms in "PLC RAS" in the parameter
mode. (Unit: 10ms).
When using a low-speed execution type program(s), make sure that the specified
WDT value is greater than the sum of the scan time and the low-speed execution
type program execution time.
If the scan time (total of execution times for scan execution type programs and low-
speed execution type programs, END processing time, and low-speed END
processing time) exceeds the time set for WDT, a "WDT ERROR" occurs and the
QnACPU stops its operation.
Example:If "3" and "400" are stored in SD520 and SD521 respectively, the scan
time is 3.4ms.
POINT
The WDT measurement error is 0 to 10ms.
Because of this, when WDT (t) is set to 10ms, a WDT ERROR may not occur
even if the scan time exceeds the limit within the range of 10ms t 20ms.
Summary of Contents for Q2ACPU
Page 1: ......
Page 2: ......
Page 221: ...12 12 12 OVERVIEW OF PROCESSING PERFORMED BY THE QnACPU ...
Page 222: ...12 13 12 OVERVIEW OF PROCESSING PERFORMED BY THE QnACPU ...
Page 237: ...12 28 12 OVERVIEW OF PROCESSING PERFORMED BY THE QnACPU MEMO ...
Page 271: ...16 13 16 POWER SUPPLY MODULE 4 Names and description of parts of the A66P ...
Page 343: ...21 21 13 MAINTENANCE AND INSPECTION 21 4 2 Replacement of the fuse for an output module ...
Page 357: ...22 12 22 TROUBLESHOOTING ...
Page 359: ...22 14 22 TROUBLESHOOTING MEMO ...
Page 429: ...App 32 APPENDICES Trigonometric function Classification Symbol Description ...
Page 537: ...App 140 APPENDICES REMARK 1 Message 1 An error code is displayed in 2 Alert 1 3 Alert 2 ...
Page 539: ...App 142 APPENDICES 2 Q2ACPU Q2ACPU S1 modules Unit mm inch ...
Page 541: ...App 144 APPENDICES 2 A66P power supply module Unit mm inch ...
Page 543: ...App 146 APPENDICES 3 A35B base unit 4 A38B A38HB A38HBEU base unit Unit mm inch Unit mm inch ...
Page 567: ...MEMO ...
Page 569: ......
Page 570: ......