csmstr - Omega Engineering

ADVANCED TOPICS
CRIMSON USER MANUAL - MODULAR CONTROLLER
DATA AVAILABILITY
Crimson’s communications infrastructure reads only those data items that are required for the
current page. This means that when a page is first selected, certain data items may not be
available. For a display primitive, this is no problem, as the primitive simply displays an
undefined state (typically a number of dashes) until the data becomes available. For actions,
though, things can get more complex.
For example, suppose a local action increases the speed of a motor by 50 rpm. If the motor
speed is not referenced on the previously displayed page, then, when the page is first
displayed, Crimson will not know the current speed, and will thus be unable to write the new
value. To handle this, if the operator attempts to perform an action for which the required data
is not available, the Master module will display a “NOT READY” message until the key in
question is released. The operator must then wait a short while, and try the operation again. In
practice, communications updates normally take place quickly enough that even the most
nimble-fingered operator will be hard pressed to get the message to appear, but since it may
on occasions be seen, it is worth explaining.
A slightly more complex issue comes about if the action defined by a page’s On Select
property is unable to proceed because it also finds that required data is not available. Here,
Crimson will wait up to thirty seconds for the data to arrive. If it does not, the action will not
be performed, and a “TIMEOUT” message will be displayed for the operator. This timeout
mechanism is required to avoid problems should a communications link become severed.
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