28 Rockwell Automation Publication 2080-UM004C-EN-E - March 2015
Appendix 4 High Speed Counter – 2080-MOT-HSC
Counter with External Direction
Pulses on A cause the counter to increment when B is low and decrement when B
is high. When B is open or undriven, the counter will increment. See Pulse
External Direction Counting on page 28.
Pulse External Direction Counting
Two input counter (Up/Down Pulses)
Pulses on A causes the counter to increment. Pulses on B causes the counter to
decrement. Pulses may occur at any time. Note that pulses can occur very closely
(that is, much faster than plug-in scan time) that the plug-in never notices the
change in count. In such cases, both counts may be ignored (the net change being
zero anyway). In no case shall a pulse be lost. See the following diagram.
INPUT A
INPUT B
INPUT Z
Direction control
Count pulse
Incrementing Encoder or Sensor
Sensor or Switch
Count Pulse
(Input A)
Direction Control
(Input B)
Present Count
1
2
3
2
1
0
1
2
A B Change in Count Value
0 (Open or No Connection) +1
1-1
1 X (don’t care) 0
0 X (don’t care) 0
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