Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 341)

Programming .01ĆSecond Timers
Appendix C
CĆ10
Assume the processor is using a 128-word data table and has 1,024 words
of memory. If all memory words are used, the program will contain 896
instructions. A program of this size might typically have the following
distribution:
546 instructions x 18
µ
sec = 9.8 ms
306 instructions x 28
µ
sec = 8.6 ms
44 instructions x 83
µ
sec = 3.7 ms
Total (rounded) 22.0 ms
The I/O scan time adds (approx.) 1.0 ms
The program panel interaction requires about 3.0 ms
Grand Total 26.0 ms
Table C.A
Instruction Execution Times (Approximate) 1
Instructions Time
-|ą|-
-| / |-
RTR
GET BYTE
ă18 µ s
-(ą)-
-( L )-
-( U )-
CTR
GET
MCR
ă28 µ s
PUT
EQU
LES
LIMIT TEST
ă28 µ s
+ ă60 µ s
TOF
TON
RTO
CU
CTD
-
ă83 µ s
IMMEDIATE I/O 105 µ s
ZCL 130 µ s
1 These execution times are approximate, but are sufficient for the purpose of programming one or more 0.01Ćsecond timers.
To repeat: if a 10-msec timer is used in a program of this duration, the rung
used to initialize the timer must occur at least 3 times in the program at
evenly spaced intervals. For longer programs, it may be necessary to repeat
the timer instruction and related rungs several more times to assure that
timing is accurate.