Time-Based Logic; One Shot Family; One Shot - Crestron SIMPL Windows User Manual

Software

Time-based Logic

One Shot Example: video projector power on
52 • Crestron SIMPL Windows
All of the logic that we have seen up to now is strictly event-driven; when an event
(a positive-edge transition, for example) occurs the symbol drives its output signals
to the appropriate levels. Sometimes this is not sufficient, however, and you need to
control when things will happen. The symbols discussed in this section all allow
some form of control based on time.

One Shot Family

Thus far we have seen how symbols drive their output signals to different values
(high or low), but as a programmer, you do not have any control over the duration of
time that those signals maintain their levels. The One Shot family of symbols allows
this type of control.

One Shot

The most fundamental symbol in this family is simply called One Shot. It responds
to a positive-edge on the 'trigger' input by driving the output signal (connected to
'out') high for the duration specified by the double-precision 'time' parameter. The
output signal will remain high only for this duration, regardless of what is happening
on the 'trigger' input. Once 'out' has gone low, the symbol may be re-triggered by
another positive-edge. The output 'out*' is simply the complement of 'out' just as
we saw with the Set/Reset Latch and Toggle symbols.
One Shot also has a 'trigger*' input, which causes the symbol to trigger on the
negative-edge of a signal. Thus a negative-edge seen on 'trigger*' will have the
identical effect as a positive-edge on 'trigger.' Also notice the 'reset' input. This
input allows you to cancel a one-shot operation that is already in progress. That is,
once a positive-edge is seen by the trigger input, the signal connected to 'out' will go
high for the amount of time specified by the 'pulse_time' parameter. Once this output
pulse has started, the only way to cancel it before the full pulse_time has elapsed is
by driving the reset input high. The trig and trig* inputs are ignored for as long as
reset is held high.
All symbols in the One-Shot family provide a reset input (with the exception of the
Multiple One-Shots symbol) that works in the same manner.
Vproj_Power
pulse_time
Some brands of video projectors require that you hold down the 'power on' button
on their IR remotes for a lengthy period before the projector turns on. This is to
prevent you from switching it on (or off) accidentally while handling the remote. In a
Crestron SIMPL Windows
One Shot
trig
out
trig* out*
reset
5s
IR Driver
POWER
Primer – DOC. 6253