Emerson PACSystems RSTi-EP - Page 255

User Manual Section 5
GFK-2958L May 2021
Detailed Description of I/O Modules 241
•
Upon reaching a count limit, the counter jumps back to the load value and starts
counting again from there. The status bit Overflow performed, or Underflow 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.
Periodic Counting/ Primary Direction Up
Figure 132: Periodic Counting, Primary Direction Up
•
Up-counting starts at the load value.
•
If the parameterized end value -1 is reached during counting in the positive direction,
the counter jumps back to the load value at the next positive 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 lower count limit the counter jumps to the upper count limit to
continue counting from there. The status bit "Underflow 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
+ 1) to +2 147 483 647 (2
31
–1)
Lower count limit
+2 147 483 648 (–2
31
)