Publication 1763-RM001C-EN-P - October 2009
Timer and Counter Instructions
173
RTO - Retentive Timer,
On-Delay
Instruction Type: output
Use the RTO instruction to delay turning “on” an output. The RTO begins
to count time base intervals when the rung conditions become true. As
long as the rung conditions remain true, the timer increments its
accumulator until the preset value is reached.
The RTO retains the accumulated value when the following occur:
•
rung conditions become false
•
you change the controller mode from run or test to program
•
the processor loses power
•
a fault occurs
When you return the controller to the RUN or TEST mode, and/or the
rung conditions go true, timing continues from the retained accumulated
value. RTO timers are retained through power cycles and mode changes.
Timer instructions use the following control and status bits:
To reset the accumulator of a retentive timer, use an RES instruction. See
RES - Reset on page 178.
EN
DN
RTO
Retentive Timer On
Timer
T4:0
Time Base
1.0
Preset
0<
Accum
0<
RTO
Execution Time for the RTO Instructions
Controller
When Rung Is:
True
False
MicroLogix 1100
2.74 (DN=1),
4.06 (DN=0)
μ
s
2.52
μ
s
Counter Control and Status Bits, Timer Word 0 (Data File 4 is configured as a timer file for this example.)
Bit
Is Set When:
And Remains Set Until One of the
Following Occurs:
bit 13 - T4:0/DN
DN - timer done
accumulated value
≥
preset value
the appropriate RES instruction is enabled
bit 14 - T4:0/TT
TT - timer timing
rung state is true and accumulated
value < preset value
•
rung state goes false, or
•
DN bit is set
bit15 - T4:0/EN
EN - timer enable
rung state is true
rung state goes false
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