Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 48)

Fundamental Instruction Set
Chapter 5
5Ć11
Retentive Timer Instruction
Symbol: -(RTO)-
Purpose: Similar to the TON instruction. The AC value is retained through
false rung conditions.
Syntax: Programmed as an output instruction.
Function: When the rung condition becomes:
True
Timer begins counting time-base intervals.
Bit 15 is set when AC=PR and the timer stops timing.
Bit 17 is set.
False
Accumulated value is retained.
Bit 15 - no action is taken.
Bit 17 is reset.
NOTE: The RTO instruction retains its AC value when the:
Rung condition turns false.
Mode select switch is changed to the PROG position.
Power outage occurs and memory backup is maintained.
Retentive Timer Reset Instruction
Symbol: -(RTR)-
Purpose: Resets the accumulated value and timed bit of the retentive timer.
NOTE: Give this instruction the same word address as its corresponding RTO
instruction.
Function: When the rung condition becomes:
True
RTR instruction resets the accumulated value of the RTO instruction.
Bits 15 and 17 and reset.
False
No action is taken.
Introduction
A counter counts the number of events that occur and stores this count in its
accumulated value word. An event is defined as a false-to-true transition.
Counter instructions have no time base.
Counter Instructions