LM3S6950 Datasheet, PDF (451/524 Pages) List of Unclassifed Manufacturers – Microcontroller

LM3S6950 Microcontroller
18
18.1
Quadrature Encoder Interface (QEI)
QEI
A quadrature encoder, also known as a 2-channel incremental encoder, converts linear displacement
into a pulse signal. By monitoring both the number of pulses and the relative phase of the two signals,
you can track the position, direction of rotation, and speed. In addition, a third channel, or index
signal, can be used to reset the position counter.
The Stellaris^® quadrature encoder interface (QEI) module interprets the code produced by a
quadrature encoder wheel to integrate position over time and determine direction of rotation. In
addition, it can capture a running estimate of the velocity of the encoder wheel.
The Stellaris^® quadrature encoder has the following features:
■ Position integrator that tracks the encoder position
■ Velocity capture using built-in timer
■ Interrupt generation on:
– Index pulse
– Velocity-timer expiration
– Direction change
– Quadrature error detection
Block Diagram
Figure 18-1 on page 452 provides a block diagram of a Stellaris^® QEI module.
June 14, 2007
451
Luminary Micro Confidential-Advance Product Information