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SYSTEM CONTROL MODULE
How the quadrature decoder/counter works
146 Hardware Reference NS9215
A quadrature decoder/counter module performs these tasks at real time speed and
interrupts the CPU at the predetermined conditions.
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How the quadrature decoder/counter works
Provides input
signals
A quadrature encoder provides a pair of signals (in-phase and quad-phase) with
opposite polarities and a 90-degree phase shift. Decode these signals to create an
algorithm to determine the direction, speed, and position of a motion wheel.
Input signals
Quadrature
encoding truth
table
Legend:
NC — No change
CW — Clockwise
CCW — Counter clockwise
Err — Error
00 01 101100 01 1011 00 00 1001 01 0011
Clockwise
Counter
Clockwise
I:Q 00 01 10 11
00 NC CW CCW Err
01 CCW NC Err CW
10 CW Err NC CCW
11 Err CCW CW NC