Chapter 9—C445 Logic Engine and Expansion I/O
Power Xpert C445 Global Motor Management Relay
MN042003EN—January 2019
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RTOF—Retentive Off-Delay Timer
The RTOF function block is a retentive off-delay timer that delays a TRUE to FALSE
transition of IN to OUT by a time defined by PT. Once the timer reaches the PT, the timer
stops running and sets the OUT to FALSE. This behavior is the same as that of the TOF
function block, but compared to TOF, the RTOF function block can retain the state of the
timer when IN transitions from FALSE to TRUE before the timer could complete (ET = PT),
essentially “pausing” the timer. When the IN transitions back to FALSE while the timer is
in the paused state, the timer resumes from its retained state instead of starting from
zero. The timer can be reset by providing a rising edge trigger to the RESET input. In
addition to being retentive, the timer is also persistent through power cycle, meaning that
the timer will retain its state in the event of a power loss to the device.
Parameter
Data type
Description
IN
BOOL
Input trigger to start timer—falling edge
PT
UINT
Preset time (x1ms, x10ms, 100ms, x1s)
RESET
BOOL
Reset timer—rising edge
OUT
BOOL
Timer expired flag—active low
ET
UINT
Elapsed time (x1ms, x10ms, 100ms, x1s)
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