Emerson PACSystems RSTi-EP - Page 233

User Manual Section 5
GFK-2958L May 2021
Detailed Description of I/O Modules 219
gate is automatically closed, the status bit End value reached is set and a process alarm
will be triggered if it is parameterized.
•
To restart counting, the internal gate must be reopened. Counting starts again at the
load value.
•
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)
Upper count limit
+2 147 483 648 (2
31
)
One-time Counting/ Primary Direction Down
Figure 113: 1-time 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. The internal gate is
automatically closed, the status bit End value reached is set and a process alarm will be
triggered if it is parameterized.
•
To restart counting, the internal gate must be reopened. Counting starts again at the
load value.
•
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.