Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 108)

Timer and Counter Instructions
Chapter 5
5Ć10
timer, the CTU instruction continues to increment its accumulated value
after the preset value has been reached. If the accumulated value goes
above 999, bit 14 is set on to indicate an overflow condition and the CTU
continues up-counting from 000. Bit 14 can be examined to cascade
counters for counts greater than 999 (Section 5.3).
Figure 5.7
UpĆCounter Diagram and Programming for Preset = 9
ON
OFF
ЙЙЙЙ
ЙЙЙЙ
1 2 3 4 5 6 7 8 9 10 11
Overflow Bit Comes On at 1000th Event. The Counter Does Not Reset.
Event to be
Counted, 111/11
AC = PR
997 998 999 1 2 0 Accumulated Value
ON
OFF
Enable Bit
053/17
ON
OFF
Count Complete
Bit 053/15
ЙЙЙЙЙЙЙЙ
ЙЙЙЙЙЙЙЙ
ЙЙЙЙ
ЙЙЙЙ
ЙЙЙЙ
ON
OFF
Output Lamp
013/06
ЙЙЙЙЙЙЙЙ
ЙЙЙЙЙЙЙЙ
ЙЙЙЙЙЙЙЙ ON
OFF
Overflow Bit
0137/07
ЙЙЙЙ
ЙЙЙЙ
ON
OFF
Overflow Output
013/07
Rung 1 - CTU Instruction
Preset to 9.
Rung 2 - Counter Tuns On
Bit 013/06 at Count
Complete.
|ą|
11
( CTU )
111 053
|ą|
15
(ą)
06
053 013
PR 009
AC 009
Count Switch
Count Complete Bit Output Lamp
Rung 3 - Counter Turns On
Bit 013/07 at Overflow.
|ą|
14
(ą)
053 013
Overflow Bit
07
Overflow Lamp
ЙЙЙЙ
ЙЙЙЙ