CTU — Count Up

CTU

Counter

counter

(CU)

Preset

(DN)

Accum

Increments .ACC by 1 on each rising edge of the rung. Sets .DN when .ACC reaches .PRE; keeps counting past the preset.

Operands

Name	Type
`counter`	`COUNTER`

Event	`.ACC`	`.CU`	`.DN`
Rising edge of rung	`+1`	`1`	`1` when `.ACC` ≥ `.PRE`
Rung stays true	unchanged	`1`	unchanged
Rung false	unchanged	`0`	unchanged
`RES` on the tag	`0`	`0`	`0`

CTU counts on the transition from false to true. Holding the input true does not keep counting.

Count boxes passing a sensor. Signal "full" at 10 boxes.

Tag setup: Boxes is a COUNTER with .PRE = 10.

XIC(BoxSensor)CTU(Boxes);XIC(Boxes.DN)OTE(BinFull);XIC(ResetBtn)RES(Boxes)

Adding ONS before a CTU — unnecessary. CTU already counts on the rising edge.
Expecting .DN to block further counting — it does not. .ACC keeps climbing. Add a RES or an interlock if you need to stop.