Spectrum Controls 1746sc-CTR4 - Manual (Page 44)

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SLC 500 ™ 50 KHz Counter / Flowmeter Module
0 Count 10,000
Roll Over
Note: If we change Configuration Bit 9 to 1 the counter will reach the
limit and then hold its value until the Limit Flag is cleared. Then it
will roll to 0, and continue counting to 10,000. Each time the limit is
reached the flag must be reset before proceeding.
Note: If we toggle Configuration Bit 12 the counter counts in a
downward direction. It will start at 0 and count to -32,768. It will
then Roll Under to +32,767. If Configuration Bit 14 is set the
counter will Roll Under to this Preset Value.
Ring Counter
Sample
The figure below demonstrates a ring counter operation. In a ring counter
operation, the count value changes between zero and maximum. If, when
counting up, the counter reaches the maximum value, it rolls over to zero.
If, when counting down, the counter reaches zero, it rolls under to the
maximum value.
Rollover
Ring Counter
Maximum Value Zero
Count Down
Count Up