1766-RM001A-EN-P MicroLogix 1400 Programmable Controllers ...

Chapter 8Timer and Counter InstructionsTimers and counters are output instructions that let you control operationsbased on time or a number of events. The following Timer and CounterInstructions are described in this chapter:Instruction Used To: PageTON - Timer, On-Delay Delay turning on an output on a true rung 179TOF - Timer, Off-Delay Delay turning off an output on a false rung 180RTO - Retentive Timer OnDelay turning on an output from a true rung.The accumulator is retentive.181CTU - Count Up Count up 185CTD - Count Down Count down 185RES - ResetReset the RTO and counter’s ACC and statusbits (not used with TOF timers).186For information on using the High-Speed Counter output(s), see Using theHigh-Speed Counter and Programmable Limit Switch on page 99.Timer InstructionsOverviewTimers in a controller reside in a timer file. A timer file can be assigned asany unused data file. When a data file is used as a timer file, each timerelement within the file has three sub-elements. These sub-elements are:• Timer Control and Status• Preset - This is the value that the timer must reach before the timertimes out. When the accumulator reaches this value, the DN statusbit is set (TON and RTO only). The preset data range is from0…32767. The minimum required update interval is 2.55 secondsregardless of the time base.• Accumulator - The accumulator counts the time base intervals. Itrepresents elapsed time. The accumulator data range is from0…32767.Timers can be set to any one of three time bases:175 Publication 1766-RM001A-EN-P - October 2008