Rockwell Automation DeviceLogix System User Manual - Manual (Page 101)

Publication RA-UM003B-EN-P - February 2010 101
Navigate the Old Ladder Editor Interface Chapter 4
Down Counter
The down counter can be an independent down counter or it can
work in combination with an up counter as an up down counter. The
down only counter can be consider an up down counter, but without
count up input.
The counter increments the accumulator any time the count up input
changes from false to true and decrements the counter any time the
count down input changes from false to true. When the accumulator is
above or equal to the preset value, the counter sets its output to true.
When the accumulator falls below the preset value, the counter resets
its output to false. As with the up counter, the up down counter resets
when a true level is detected on the reset input. When a reset occurs,
the counter causes the accumulator to be set to zero and sets the
output to false. Refer to the illustration of the counter function for
clarification.The illustration shows an up counter with a preset value
of 3.
Count Down Input
Count Input
Reset
Output
Count Value
3
0
1
2
2
4
3
1
0
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