2 Visual Components Manuals

The following describes how VC 2.2 Runtime performs with scaling and the possibilities available to the user. In
addition, how user settings are processed internally is shown to give the user and developer a better idea of this.
4.13.2.4 Internal Performance
Without having to go too much into detail, two principle VC 2.2 Runtime procedures are described:
− Scaling Output
− Scaling Input
For the most part, code excerpts have been avoided when describing internal processes. Instead, we will try to
explain things using graphics and text alone.
4.13.2.5 Decimal Places
A potentially configured decimal place exerts an exceptional influence on the display value range limits. There is
basically one rule to keep in mind:
The decimal place does not have any effect on the actual calculation. It only has an effect on the format
of the output string which is formed as display output after the values are calculated.
When decimal positions are referred to in the following, it always means the sum from fixed and dynamic
decimal places using PVs.
The decimal place only exerts this aforementioned influence when fixed limit values are scaled. This influence
works in such a way that the maximum display value is greater internally by the number of "zeroes", as decimal
places are present. An example shows this more clearly:
Ex. a)
Field length: 5 Decimal places: 2 Configured maximum display value: 100.33
Internal maximum display value: 10033
Ex. b)
Field length: 5 Decimal places: 2 Configured maximum display value: 100
Internal maximum display value: 10000
Ex. c)
Field length: 5 Decimal places: 2 Configured maximum display value: 1000
When this configuration is attempted, the editor changes this value to 999.99.
This is because it is necessary that the entire maximum value plus the decimal places may not exceed the
maximum field length. From 1000 comes 1000.00 which corresponds to a field length of 6 places à can't be
displayed.
This problem should be taken into account when using dynamic decimal point shifts. Each increase in the
decimal position increases the maximum display value limit by a factor of 10. In turn, this leads to an increase of
places in the display string when entering the configured maximum value.
Ex. a)
Field length: 5 Decimal places: 1 Configured maximum display value: 100
Dynamic decimal point shift: 0
Internal maximum display value: 1000
Input: 100 à 100.0 (4 numeric places) à OK
Introduction to Visual Components 2.3
440 4.13.2.4 Internal Performance