Rockwell Automation AutoMax Enhanced Ladder Language Reference Manual - Manual (Page 36)

2Ć2
2.1 Count Up Down (CTUD)
Use this instruction to increment or decrement a counter.
When EN is true, the instruction:
D increments the double integer value stored in Current for every falseĆtrue transition
of the CU input
D decrements the double integer value stored in Current for every falseĆtrue transition
of the CD input
The QD output becomes true when the value stored in Current is less than or equal to
zero. The QU output becomes true when the value stored in Current is greater than or
equal to the value stored in CPreset.