It’s important to note that the “Time Base” of our timer is set to 0.001. In the example above, this value is set to 10000. The timer will begin counting at from 0 until it reaches the value specified by the “Preset” integer. The RTO instruction will begin counting as soon as the B3:0/10 XIC is energized. IF the B3:0/10 bit is set to LOW while the timer is counting, the Accum is set retained at the current value.As the timer is initialized by the B3:0/10 XIC which energizes it starts to count.The “Accum” of T4:3 is set to 0 which translates to the timer starting to count from 0.The “Preset” of T4:3 is set to 10000 which translates to the timer counting up to 10 seconds.The Time Base of T4:3 is set to 0.001 which translates to the timer counting in milliseconds.The RTO instruction specifies a Timer in the PLC: T4:3.The bit above is tied to an XIC instruction which enables the RTO instruction.An “Ingredient Pump RUNNING” is indicated by an internal bit B3:0/10.A Micrologix 1100 Allen Bradley PLC is used to control a process.Here’s a real-world scenario of an RTO instruction: Keep in mind that most programmers would achieve the same effect through the use of a TON or TOF instruction paired with a way to store the value such as a MOV Instruction. The RTO is not a frequently utilized instruction but may come in handy in certain instances. For example, you can easily create a timer which would allow a certain valve to only open for a certain duration even though it is stopped in between. Due to this capability, it’s an excellent tool for a process which may be interrupted but needs to keep track of a continuous event. In other words, the timer will retain the value it currently has until it is energized again or forced to reset. The RTO will simply “pause” the accumulated value during this transition. The TON instruction will automatically reset the accumulated time upon a transition from HIGH to LOW.
However, there is a key difference between the two. The RTO, also know as Retentive Timer, an instruction is used to keep track of time just like the TON Instruction.
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