Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) User Manual
Page 262
Chapter 14
Using High-Speed Counter Instructions
14–12
When up and down input pulses occur simultaneously, the high-speed
counter counts up, then down.
Using the Bidirectional Counter with Reset and Hold with a Quadrature
Encoder
The Quadrature Encoder is used for determining direction of rotation and
position for rotating, such as a lathe. The Bidirectional Counter counts the
rotation of the Quadrature Encoder.
Bidirectional Counters operate in the –32,768 to
+
32,767 range inclusive and
can be reset to zero using the reset (RES) instruction. The figure below
shows a quadrature encoder connected to inputs 0, 1, and 2. The count
direction is determined by the phase angle between A and B. If A leads B,
the counter increments. If B leads A, the counter decrements.
The counter can be reset using the Z input. The Z outputs from the encoders
typically provide one pulse per revolution.
Input 0
A
B
Z
(Reset input)
Quadrature Encoder
1
2
3
2
1
Forward Rotation
Reverse Rotation
A
B
Count
Input 1
Input 2