Allen-Bradley Logix5000 Reference Manual page 150

Chapter 3 Timer and Counter Instructions (TON, TOF, RTO, TONR, TOFR, RTOR, CTU, CTD, CTUD, RES)
Output Parameter Data Type
EnableOut BOOL
ACC DINT
CU BOOL
CD BOOL
DN BOOL
OV BOOL
UN BOOL
Description
Count-up Enable Bit (CU)
Count-up Done Bit (DN)
Counter Accumulated Value (ACC)
150
Description
The instruction produced a valid result.
Accumulated value.
Count up enabled.
Count down enabled.
Counting done. Set when accumulated value is greater than or equal to preset.
Counter overflow. Indicates the counter exceeded the upper limit of 2,147,483,647.
The counter then rolls over to −2,147,483,648 and begins counting down again.
Counter underflow. Indicates the counter exceeded the lower limit of −2,147,483,648.
The counter then rolls over to 2,147,483,647 and begins counting down again.
When enabled and CUEnable is set, the CTUD instructions increments the
counter by one. When enabled and CDEnable is set, the CTUD instruction
decrements the counter by one. Both the CUEnable and CDEnable input
parameters can both be toggled during the same scan. The instruction executes
the count up prior to the count down.
Figure 1 - Counting Up
CUEnable
Preset
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
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