Complementing the motor control PWMs is the Quadrature Encoder Interface (QEI) block. The QEI module decodes the digital pulses from a quadrature encoder wheel to integrate position over time and determine direction of rotation. The digital pulses from an external quadrature encoder wheel can be decoded to integrate position over time and determine direction of rotation. By monitoring both the number of pulses and the relative phase of the two signals, the position, direction of rotation, and velocity can be tracked. The Index signal (3rd signal) can be used to reset the position counter. In addition, it can capture the velocity of the encoder wheel. The QEI tracks encoder position and increments/ decrements depending on direction with three position compare registers with interrupts and is programmable for 2X or 4X position counting. By using 32-bit registers for position and velocity, the QEI can be used for velocity capture using a built-in timer with a compare function and interrupt. The QEI first received three input signals: phase A (PHA), phase B (PHB), and index. By monitoring the phase of the first two signals, the QEI can detect if the encoder wheel is moving in a forward or backwards direction. The index signal provides the absolute position of the wheel.