Logix5000 Controllers General Instructions - SLAC Confluence

132 Timer and Counter Instructions (TON, TOF, RTO, TONR, TOFR, RTOR, CTU, CTD, CTUD, RES)Input Parameter Data Type DescriptionCDEnable BOOL Enable down count. When input toggles from clear to set, accumulator counts down by one.Default is cleared.PRE DINT Counter preset value. This is the value the accumulated value must reach before DN is set.Valid = any integerDefault is 0.Reset BOOL Request to reset the timer. When set, the counter resets.Default is cleared.Output Parameter Data Type DescriptionEnableOut BOOL The instruction produced a valid result.ACC DINT Accumulated value.CU BOOL Count up enabled.CD BOOL Count down enabled.DN BOOL Counting done. Set when accumulated value is greater than or equal to preset.OV BOOL 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.UN BOOL 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.DescriptionWhen enabled and CUEnable is set, the CTUD instructions incrementsthe counter by one. When enabled and CDEnable is set, the CTUDinstruction decrements the counter by one.Both the CUEnable and CDEnable input parameters can both betoggled during the same scan. The instruction executes the count upprior to the count down.Publication 1756-RM003I-EN-P - January 2007