Allen-Bradley MicroLogix 1400 Instruction Manual page 124

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122 Using the High-Speed Counter and Programmable Limit Switch
Count
HSC Mode 6 Examples
Input Terminals I1:0.0/0 (HSC0)
Function Count A
⇑
(1)
Example 1
(2)
Example 2
Example3
Example 4 on (1)
Example 5
Example 6
(1) Count input A leads count input B.
(2) Count input B leads count input A.
⇑
Blank cells = don't care, = rising edge,
Publication 1766-RM001A-EN-P - October 2008
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.
Quadrature Encoder
Forward Rotation
A
B
1 2
HSC Mode 6 - Quadrature Counter (phased inputs A and B)
I1:0.0/1 (HSC0)
Count B
off (0)
⇓
off (0)
off (0)
on (1)
⇓
= falling edge
Input 0
A
Input 1
B
Input 2
Z
(Reset input)
3
I1:0.0/2 (HSC0) I1:0.0/3 (HSC0)
Not Used Not Used
Reverse Rotation
2 1
CE Bit Comments
on (1) HSC Accumulator + 1 count
on (1) HSC Accumulator - 1 count
Hold accumulator value
Hold accumulator value
Hold accumulator value
off (0) Hold accumulator value