Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 340)

Programming .01ĆSecond Timers
Appendix C
CĆ9
Figure C.3
Typical 0.01ĆSecond Timer Programming
(ą)
01405
|ą| (ą)
03015 01410
|ą| (ą)
03015 01404
( IOT )
014
2
3
4 |ą|
11002
| I |
110
| I |
113
|ą|
11005
|ą|
11006
|ą|
11014
| / |
11300
( TON )
030
0.01
PR 025
AC 000
|ą|
03017
3 5
2 1
1 Rung No.
Legend:
1 Repeat these 5 rungs (typical) 3 or more places in the program.
2 For rung No. 1, when used near the beginning of the program, [ I ] Instructions may be omitted.
3 For rung No. 5, when used near the end of the program, ( IOT ) Instruction may be omitted.
In Rungs 2, 3, and 4, Output Energize instructions conditioned by timer
bits should also be repeated in the program. When used near the beginning
or middle of the program, the Immediate Output instruction addressed to
output image table word 014 will help to assure that the output modules
respond quickly to timer cycling.
By repeating the timer instructions and related rungs, you can assure that
the processor will update timer accumulated values more frequently than
the rate at which the timing pulses change state. As shown in Figure C.2,
repetition within 8 or 9 msec will be adequate for this purpose.
In order to evaluate programming needs, you may wish to calculate
approximate scan time. An exact computation is not practical, but a
reasonable approximation can be obtained using the approximate execution
times listed in table C.1. Enter the 10-msec timer rungs 3 times per 1K
(1,024) words of program, then compute the scan time. A sample
computation follows:
C.6
Program ScanĆTime
Computation