Emerson PACSystems RSTi-EP - Additional Counter Features

User Manual Section 5
GFK-2958L May 2021
Detailed Description of I/O Modules 242
Periodic Counting/ Primary Direction Down
Figure 133: Periodic Counting, Primary Direction Down
•
Down-counting starts at the load value.
•
If the parameterized end value +1 is reached during counting in the negative direction,
the counter jumps back to the load value at the next count pulse and continues
counting from there. The status bit End value reached is set and a process alarm will be
triggered if it is parameterized.
•
Upon reaching the upper count limit the counter jumps to the lower count limit to
continue counting from there. The status bit Overflow performed is set and a process
alarm will be triggered if it is parameterized. All status bits remain set until they are reset
with the bit Reset status bits in the control word.
Counting Range
Limits
Valid range of values
End value
–2 147 483 647 (–2
31
) to +2 147 483 647 (2
31
–1)
Upper count limit
+2 147 483 647 (–2
31
–1)
5.17.10 Additional Counter Features
You can define the additional features for the counter listed below by parametrizing or via
the process data outputs:
•
Reset: resets the counting value to the load value during counting.
•
Comparator: Upon meeting the comparison condition, the comparison bit is activated,
or a process alarm is triggered.
•
Hysteresis: reduces frequent toggling of the comparison bit and/or excessive triggering
of a process alarm, e.g. when the value of a sensor signal fluctuates around the
comparison value. It is possible to count beyond the lower count limit.