Specifications

Crestron SIMPL Windows Software
considered “level triggered” in that the current input values always determine the
states of the outputs.
Set/Reset Latch symbol
This symbol implements the most basic memory element, also known as a set/reset
flip-flop. The symbol has two possible states, referred to (oddly enough) as set and
reset. When set, the signal connected to the ‘out’ terminal will be high. When reset,
‘out’ will be low. The ‘out*’ output provides the complement of ‘out,’ that is,
whenever ‘out’ is high, ‘out*’ is low and vice-versa. At startup (when the program
resets) the value of ‘out’ will be low (and thus ‘out*’ will be high).
A positive edge on the ‘set’ input will cause ‘out’ to go high. Once this transition is
seen on the ‘set’ input, the output will not change even after ‘set’ goes low. We say
that the output has ‘latched.’ In order for ‘out’ to go low again (and thus ‘out*’ go
high), there must be a positive edge seen on the ‘reset’ input.
Set/Reset Latch Example: System Power Relay
Suppose you are using an AC power controller to switch power on and off to the
equipment rack. Often such a power controller will have a low-voltage contact
closure interface: close the contact and the power switches on, open the contact and
it switches off. Clearly in this case we need a latching signal that we can connect to a
low-voltage relay in the Cresnet system (on a CNRY-8/16 for example).
A Set/Reset Latch symbol will work perfectly for this application. Simply connect
the signal from the ‘power on’ to the ‘set’ input, and the signal for ‘power off’ to the
reset input. Lastly, connect the output marked ‘out’ from the SR Latch to the relay
itself. When the SR Latch is set, the signal connected to ‘out’ will be high, thus
closing the relay and turning on the power. Remember that this output signal will
remain high until the symbol is reset.
Set/Rest Latch Example: system power relay
Power_Off
Power_On A1
A2
A3
A4
A5
A6
A7
A8
Relay Card
set
reset
out
out*
Set/Reset
press87
press88
press89
press90
fb87
fb88
fb89
fb90
Touchpanel
Power_relay
Toggle Symbol
The Toggle symbol has a lot in common with the Set/Reset Latch. In fact, the Toggle
actually is an SR Latch with an additional input added on. This input is labeled
‘clock,’ and each positive edge on this input will cause the symbol’s state to alternate
between set and reset. The ‘set’ and ‘reset’ inputs are still provided to serve as
overrides to force the symbol to a specific state.
Primer – DOC. 6253 Crestron SIMPL Windows • 47