Logix5000 Controllers General Instructions - SLAC Confluence

Timer and Counter Instructions (TON, TOF, RTO, TONR, TOFR, RTOR, CTU, CTD, CTUD, RES) 115Input Parameter Data Type DescriptionTT BOOL Timer timing output. When set, a timing operation is in progress.DN BOOL Timing done output. Indicates when accumulated time is greater than or equal to preset.Status DINT Status of the function block.InstructFault (Status.0) BOOL The instruction detected one of the following execution errors. This is not a minor or majorcontroller error. Check the remaining status bits to determine what occurred.PresetInv (Status.1) BOOL The preset value is invalid.Description:The TOFR instruction accumulates time until the:• TOFR instruction is disabled• ACC ≥ PREThe time base is always 1 msec. For example, for a 2-second timer,enter 2000 for the PRE value.TimerEnableenable bit (EN)timer timing bit (TT)timer done bit (DN)OFF delaypresettimer accumulated value (ACC)016650Set the Reset input parameter to reset the instruction. If TimerEnable iscleared when Reset is set, the TOFR instruction does not begin timingagain when Reset is cleared.How a Timer Runstimer did not reach PRE valueA timer runs by subtracting the time of its last scan from the time now:ACC = ACC + (current_time - last_time_scanned)Publication 1756-RM003I-EN-P - January 2007