Omron NT15S, Руководство по эксплуатации

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84
Standard Mode
Section 4-6
Counter
When writing to a counter variable, any scaling that may have been performed is
first reversed. The BCD-coded value is then computed and transferred to the PLC.
Avoid writing to a counter word in the PLC, as this has uncontrolled results
on the control bits.
Formula for Scaling Input Values
Input values transferred by the PLC are processed according to
formula 1 before
being displayed. After the values have been edited, they are processed in accord-
ance with the inverse function (
formula 2) before being transferred back to the PLC.
The inverse function will automatically be generated in the terminal. Operands
must be defined by the user on the basis of the values in the PLC including the input
value.
Input value × Summand
PLC value = × Divisor
Factor
Fig. 8: Formula 2
During conversion, the last digit is automatically rounded. This must be kept in mind
when defining the upper limit.
(Input value × Factor)
,
(Pos. Upper Limit - Divisor / 2)
Fig. 9: Formula 3
Plausibility Check
A plausibility check is performed on all input variables. As a part of this check, the
entered value is validated against the upper and lower limits specified in the vari-
able definition. System messages are generated if the entered value is outside
these limits. In this case, the invalid value will not be transferred to the controller
and the previous (valid) value will be retained.
If the system message texts ‘Value too large’ and ‘Value too small’ are deleted, the
following applies:
-
if the value drops below the limit, the value corresponding to the lower limit is
used
- if the value exceeds the upper limit, the value corresponding to the upper limit is
used.
A system message is not output during this process.
Help Text for Input Variables
A screen-sized help text can be created for each input variable. This help text can
be displayed in the Editor by pressing the Help key. Important information to be
inserted in a help text may include the upper and lower limits, the impact of vari-
ables on the process to be carried out, or any interactions with other variables.
If a variable-specific help text is not defined, the default help text will be displayed
instead. This is also a screen-sized text which can be edited in the programming
software. If a default help text is not defined, a blank mask will be displayed.