Digital Signals; Analog Signals; Serial Signals - Crestron SIMPL Windows User Manual

Software
18 • Crestron SIMPL Windows
has an analog output, then the signal connected there will by definition become an
analog signal. The three signal types are defined in more detail below:

Digital Signals

Digital signals are the most common in the SIMPL language, and a typical program
will be comprised of between 95% and 100% digital signals. This type of signal can
have only two states, often referred to as on/off. Other common descriptors are
high/low, active/inactive, or 1/0. This transition is called the rising edge, or positive
edge. Generally speaking, actions in SIMPL program are triggered by a digital signal
going from the low to the high state. Although most actions are edge-triggered,
others can be level-triggered (based upon current state, not just last transition). For
example, a Toggle symbol is edge-triggered; it drives its digital output high and low
with each rising edge of its input. In contrast, the Buffer symbol is level-triggered; its
'enable' digital input signal must remain high for signals to flow.
When looking through the symbol library reference, take note as to which symbols
are edge-triggered, and which are level-triggered. You can find this information by
selecting the symbol and pressing F1, which will open the context-sensitive help
window for the symbol.
As stated previously, the type of signal is determined by its driving source. In many
applications there are signals that have multiple driving sources. Such signals are
said to be jammed. As a general rule, digital signals should not be jammed; that is,
they should have only one driving source. But there are two important and common
exceptions: system inputs (such as button presses), and the outputs of Buffer
symbols. These exceptions can be very useful in applications where functionality
must be shared across several user interfaces. For example, a DVD player can be
controlled by a touchpanel as well as by a remote control transmitter.
In SIMPL Windows, digital signals are represented by a blue line.

Analog Signals

Analog signals are represented with 16-bit numbers, and thus can have values
16
between 0 and 65535 (2 - 1). This means that unlike digital signals, analog signals
can vary continuously in value, in the same manner as a parameter such as volume or
temperature. This property makes analog signals useful for controlling devices that
do not have discrete on/off settings, such as volume controllers, pan/tilt head
controllers, and lighting dimmers.
Unlike digital signals, analog signals by their very nature may have multiple driving
sources. Thus analog signals are said to be jammable. In practice, whenever more
than one symbol is driving the same analog signal, the symbol that lasts changes the
signal's value takes precedence. Typical applications for analog signals are volume,
lighting, and temperature levels, as well as advanced string manipulation.
In SIMPL Windows, analog signals are represented by a red line.

Serial Signals

Serial signals facilitate the transmission of serial data (i.e. strings of characters).
These signals can be generated by incoming data on a COM port or by a symbol that
has a serial output. Similar to analog signals, serial signals are jammable; thus
multiple symbols can be used to generate strings on a single signal. By default, serial
signals are transient, meaning that the data on a serial signal is only valid for the
logic wave in which it was created (logic waves are described below). Symbols such
as the Make String Permanent symbol allow serial strings to be retained in memory.
In SIMPL Windows, serial signals are represented by a black line.
Crestron SIMPL Windows
Primer – DOC. 6253