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Crestron SIMPL+
Understanding Processing Order
Programming Guide – DOC. 5789A
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This example introduces two new system functions, which are extremely useful for
string manipulation, the Find and Mid functions. To search for the existence of a
substring inside of another string, use Find. If it is located, the return value of the
function is the character position where this string was found. If the substring was
not found, then Find returns zero. Notice that towards the top of the example the
program checked to see if the substring "Artist=" is found in the string. If it is not,
then assume that the incoming data was of another format and there is no need to
bother looking for the other search strings ("Track=" and "Album=").
How SIMPL+ and SIMPL Interact
Advanced SIMPL programmers should be familiar with how logic is processed in
SIMPL programs. This guide does not attempt to explain this concept here, but it
does detail how SIMPL+ programs fit into the picture. However, a couple of
definitions may be helpful.
Logic Wave - The act of propagating signals from the input to the output of a logic
symbol. In a typical program, a single logic wave may include the processing of
many symbols.
Logic Solution - An arbitrary number of logic waves, processed until the state of all
signals in the program have settled to a stable (i.e. unchanging) state.
In general, when a SIMPL+ event function is triggered, it is processed to conclusion
in a single logic wave. That is, if this event caused a change to one of the output
signals, that signal would be valid one logic wave after the event was triggered. In
this simple case, a SIMPL+ program acts identically to a SIMPL logic symbol from
a timing standpoint. In addition, for multiple SIMPL+ events triggered on the same
logic wave (whether or not they are in the same module), these events multi-task (run
at the same time) and complete before the next wave.
As SIMPL+ programs become more complex and processor intensive however, this
general rule may no longer apply. Instead, the operating system may determine that
too much time has elapsed and temporarily suspend the SIMPL+ program while it
continues to process the SIMPL logic (which may also include other SIMPL+
programs). For example, if an event function must run through a loop 2000 times
before completing, the processor may decide to perform a task switch and process
other logic before completing the loop.
This task-switching ability has the benefit of not freezing up the rest of the program
while a particularly intensive calculation is proceeding. After the completion of the
current logic solution, the SIMPL+ program that was exited continues from where it
left off.
Forcing a Task Switch
There may be times in programming when it is necessary to force a task switch to
occur. For example, when a digital_output is set high, it normally is not propagated
to the SIMPL program until the SIMPL+ completes. To guarantee that the digital
signal is asserted, force the system to switch from the SIMPL+ module back into the
SIMPL program.
Software
• 49
SIMPL+
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