Publication 1762-RM001C-EN-P
8-6 Timer and Counter Instructions
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 8-10.
EN
DN
RTO
Retentive Timer On
Timer T4:0
Time Base 1.0
Preset 0<
Accum 0<
RTO
Table 8.9 Execution Time for the RTO Instructions
Controller When Rung Is:
True False
MicroLogix 1200 18.0
µ
s2.4
µ
s
MicroLogix 1500 15.8
µ
s2.2
µ
s
Table 8.10 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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