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7. Designing Guidelines
7.1. Variables
The number of variables in a project for Movicon CE should be proportioned to the device's
performances. Generally, you need to consider the number of variables the project has "In use" and
the type of driver being used.
Technically speaking there are no set limits in the programming phase due to the many different
factors which determine device performances.
Therefore the programmer will have to decide whether the number of variables to be allocated and
managed are adequate according to device's capacity.
It is important how retentive variables are managed as their values, which change constantly, are
recorded on the Compact Flash and therefore should be kept to a minimum using only those thought
to be indispensable.
Slow Compact Flash access in read/write is quite commonly used in CE devices. Therefore the less it
is accessed, the better the device's performances will be. This also goes for the Variable Trace
function which should be used only when necessary.
Tips:
1.
The number of variables in a project must to proportioned to the panel’s capacity. The
Movicon CE fixed limit on “Lite” licenses is 1024 bytes and 4096 bytes for standard licenses.
However, the designer’s own limit must be determined on the panel’s potentiality and the
communication drivers to be used. It is best not exceed the limit of 512 bytes in use in a 400
Mhx (approx.) panel with PLC communications via serial.
2.
Variable retentivity should not be used unless really needed. As values are recorded on the
Compact Flash, a good rule of thumb would be to keep a minimum number of necessary
variables retentive especially when these change quite frequently. Compact Flash read/write
access is quite slow in CE devices and therefore the less the compact flash is accessed the
better the device performances will be.
3.
3. The variable Trace function should only be used when really necessary. Each variable value
variation traced is recorded on disk with the same concept as that for the retentive variables.
4.
The use of dynamic variable via OPC or Networking is onerous for WinCE system resources.
Therefore, it would be best to create variables and link them statically using the OPC Client
resource or the Tag’s Client properties.
5.
A good thumb of the rule to stick to would be to map data exchanged in the Word type
variables and in the adjoining areas to optimize communications and thus performances. The
bit variables can then be addressed to graphic objects or alarms using the name of the word
followed by the bit: <name_tag>.<bit>
7.2. The Graphics
Operator panel screen pages should contain simple graphics. Don’t get too carried away with the
powerful functionalities provided by Movicon without knowing the capabilities of your Touch Panel
hardware first. Make sure that the project’s platform properties are set to WinCE and go through the
Windows CE graphics restrictions indicated in the manual to get a clear picture of the situation
beforehand.
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