Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 112)

Preface MicroLogix 1000 Programmable Controllers User Manual
6–14
Retentive Timer (RTO)
Use the RTO instruction to turn an output on or off after its timer has been on for a
preset time interval. The RTO instruction is a retentive instruction that lets the timer
stop and start without resetting the accumulated value (ACC).
The RTO instruction retains its accumulated value when any of the following
occurs:
•
Rung conditions become false.
•
You change controller operation from the REM Run or REM Test mode to the
REM Program mode.
•
The controller loses power.
•
A fault occurs.
Using Status Bits
This Bit Is Set When
And Remains Set Until One
of the Following
Timer Done Bit DN (bit 13)
accumulated value is equal
to or greater than the preset
value
the appropriate RES
instruction is enabled
Timer Timing Bit TT (bit 14)
rung conditions are true and
the accumulated value is less
than the preset value
rung conditions go false or
when the done bit is set
Timer Enable Bit EN (bit 15) rung conditions are true rung conditions go false
Note To reset the retentive timer’s accumulated value and status bits after the RTO rung
goes false, you must program a reset (RES) instruction with the same address in
another rung.
When the controller changes from the REM Run or REM Test mode to the
REM Program or REM Fault mode, or user power is lost while the timer is timing
but not yet at the preset value, the following occurs:
•
Timer Enable (EN) bit remains set.
•
Timer Timing (TT) bit remains set.
•
Accumulated value (ACC) remains the same.
Execution Times
(
µ
sec) when:
True False
38.34 27.49
(EN)
(DN)
RTO
RETENTIVE TIMER ON
Timer
Time Base
Preset
Accum