Allen-Bradley MicroLogix 1200 - Page 90

Publication 1762-RM001C-EN-P
5-20 Using the High-Speed Counter
Using the 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.
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.
HSC Mode 6 - Quadrature Counter (phased inputs A and B)
Quadrature Encoder
Input 0
Input 1
Input 2
A
B
Z
(Reset input)
Reverse Rotation
Forward Rotation
B
A
1
2
3
2
1
Count
Table 5.10 HSC Mode 6 Examples
(1)
Input Terminals I1:0.0/0 (HSC0)
I1:0.0/4 (HSC1)
I1:0.0/1 (HSC0)
I1:0.0/5 (HSC1)
I1:0.0/2 (HSC0)
I1:0.0/6 (HSC1)
I1:0.0/3 (HSC0)
I1:0.0/7 (HSC1)
CE Bit Comments
Function Count A Count B Not Used Not Used
Example 1
(2)
⇑
off (0) on (1) HSC Accumulator + 1 count
Example 2
(3)
⇓
off (0) on (1) HSC Accumulator - 1 count
Example3 off (0) Hold accumulator value
Example 4 on (1) Hold accumulator value
Example 5 on (1) Hold accumulator value
Example 6 off (0) Hold accumulator value
(1) HSC1 only applies to the MicroLogix 1500.
(2) Count input A leads count input B.
(3) Count input B leads count input A.
Blank cells = don’t care,
⇑
= rising edge,
⇓
= falling edge
NOTE
Inputs I1:0.0/0 through I1:0.0/7 are available for use as
inputs to other functions regardless of the HSC being used.