Rockwell Automation 1756-LSC8XIB8I ControlLogix Low-speed Counter Module - Manual (Page 14)

14 Rockwell Automation Publication 1756-UM536A-EN-P - April 2012
Chapter 2 Module Operation
Figure 2 compares two On/Off windows by using the Accumulated Count
comparison method. In the first window, the On value is less than the Off value.
In the second window, the On value is greater than the Off value.
Figure 2 - Window States Based on Accumulated Count
The Counter[
x].InWindow0 and Counter[x].InWindow1 input tags can be
consumed by a controller or a 1756-OB16IEF peer output module and used to
affect outputs. For more information about using peer modules, see the
ControlLogix Peer I/O Control Application Technique, publication
1756-AT016 .
Rollover Values
A rollover value determines how many counts accumulate before the count rolls
over to zero. The count rolls over to zero on the rollover value. Each counter can
have one rollover value.
For real-time control, you define a rollover value in the Counter[
x].Rollover
output tag. The following criteria applies to a rollover value:
• The default rollover value is a maximum count of 2 31
.
• A rollover value must be a positive DINT value. If an invalid rollover value
is defined, the module will use a value of 2
31
.
Counter[x].Window0On tag = 2000
Counter[x].Window0Off tag = 5000
Counter[x].InWindow0
turns On at count 2000.
Counter[x].InWindow0
remains On for 3000 counts.
Counter[x].InWindow0
turns Off at count 5000.
On Value < Off Value
Counter[x].Window1On = 5000
Counter[x].Window1Off = 2000
Counter[x].InWindow1
remains Off for 3000 counts.
Counter[x].InWindow1
turns Off at count 2000.
Counter[x].InWindow1
turns On at count 5000.
On Value > Off Value
EXAMPLE A rollover value of 100 produces the following count sequences:
• Increasing count sequence: 98, 99, 0, 1, 2…
• Decreasing count sequence: 2, 1, 0, 99, 98…