Special Signals '0' And '1; Logic Waves And Logic Solutions - Crestron SIMPL Windows User Manual

Crestron SIMPL Windows
Example Signal Colors
Primer – DOC. 6253
Some signals are ambiguous, meaning that the signal type is determined by the
driving source. For example, the inputs and outputs of a Serial Buffer symbol can be
either serial or analog. The ambiguous signal is resolved when the signal is
connected to an analog or serial symbol. Ambiguous signals should be resolved
before the program is finalized; otherwise a compiler error will be generated.
In SIMPL Windows, ambiguous signals are represented by a green line. Once they
are resolved, the line color changes to blue (digital), red (analog) or black (serial).

Special Signals '0' and '1'

The special signals '0' and '1' are used to force a value on a signal. '1' is a digital-
only signal whose value is always logic high. A digital signal named '0' will always
be logic low. A '0' on an analog signal forces the signal to a constant value of zero.
On a serial signal, a '0' will result in no string being transmitted.

Logic Waves and Logic Solutions

A logic wave is a processor unit of measurement defined as the elapsed time
between the moment a signal's state changes and the moment that all symbols
connected to that signal have been evaluated. This is analogous to the term
"propagation delay" used when describing digital hardware. Although logic waves
are not expressed in real-world time units (i.e., milliseconds) due to the fact that the
actual time is indeterminate at compile time, SIMPL guarantees that all symbols
have a propagation delay of exactly one logic wave.
Note that some symbols do not always conform to this rule. Examples are time-based
symbols such as Delay and One-Shot. While the propagation delay of the Delay
symbol is determined solely by its parameter values, a One-Shot will propagate in a
single logic wave when its trigger input goes high. However, the falling edge of the
input has no effect, and the symbol's output will go low only after the specified time
has expired.
One or more logic waves make up a logic solution.
A logic solution is defined as the time it takes, starting with an external impetus, for
the SIMPL logic processor to evaluate all symbols to the point at which all signals in
the program have reached a "steady state" that is, the time required for all signals to
settle to stable, unchanging states. The length of a logic solution can vary at runtime,
and can be expressed in logic waves, i.e., "when this button is pressed, the
subsequent logic solution should take 6 logic waves".
It is important to realize that time-based (scheduled) events do not occur during a
logic solution, except to serve as the impetus to initiate one. Thus using an Oscillator
symbol would not cause an endless logic solution. Instead, each time the output
signal of the Oscillator changes, it triggers a new logic solution that runs until all
affected signals arrive at their final states. On the other hand, endless logic solutions
can be created by connecting logic incorrectly (i.e., routing the output of a NOR
symbol back into its input). This situation should obviously be avoided.
Software
Crestron SIMPL Windows • 19