Logix5000 Controllers General Instructions - SLAC Confluence

Timer and Counter Instructions (TON, TOF, RTO, TONR, TOFR, RTOR, CTU, CTD, CTUD, RES) 125Execution:Conditionprescanrung-condition-in is falseRelay Ladder ActionThe .CU bit is set to prevent invalid increments during the first program scan.The rung-condition-out is set to false.The .CU bit is cleared.The rung-condition-out is set to false.rung-condition-in is trueexamine .CU bit.CU bit = 0.CU bit is set.ACC = .ACC + 1.ACC valuerolls overyes.CU bit = 1no.UN bit is cleared.DN bit is cleared.UN bit = 1examine .UN bit.UN bit = 0examine .UN bit.UN bit = 0examine .OV bit.OV bit = 0.UN bit = 1.OV bit = 1.OV bit is setexamine .ACC.ACC ≥ .PRE.ACC < .PRE.DN bit is cleared.DN bit is setrung-condition-out is set totrueendpostscanThe rung-condition-out is set to false.Publication 1756-RM003I-EN-P - January 2007