LM3S6952 Datasheet, PDF (40/626 Pages) Texas Instruments – Stellaris LM3S6952 Microcontroller

Architectural Overview
1.4.2
1.4.2.1
1.4.2.2
1.4.3
Motor Control Peripherals
To enhance motor control, the LM3S6952 controller features Pulse Width Modulation (PWM) outputs
and the Quadrature Encoder Interface (QEI).
PWM
Pulse width modulation (PWM) is a powerful technique for digitally encoding analog signal levels.
High-resolution counters are used to generate a square wave, and the duty cycle of the square
wave is modulated to encode an analog signal. Typical applications include switching power supplies
and motor control.
On the LM3S6952, PWM motion control functionality can be achieved through:
■ Dedicated, flexible motion control hardware using the PWM pins
■ The motion control features of the general-purpose timers using the CCP pins
PWM Pins (see page 492)
The LM3S6952 PWM module consists of two PWM generator blocks and a control block. Each
PWM generator block contains one timer (16-bit down or up/down counter), two comparators, a
PWM signal generator, a dead-band generator, and an interrupt/ADC-trigger selector. The control
block determines the polarity of the PWM signals, and which signals are passed through to the pins.
Each PWM generator block produces two PWM signals that can either be independent signals or
a single pair of complementary signals with dead-band delays inserted. The output of the PWM
generation blocks are managed by the output control block before being passed to the device pins.
CCP Pins (see page 228)
The General-Purpose Timer Module's CCP (Capture Compare PWM) pins are software programmable
to support a simple PWM mode with a software-programmable output inversion of the PWM signal.
Fault Pin (see page 497)
The LM3S6952 PWM module includes one fault-condition handling input to quickly provide low-latency
shutdown and prevent damage to the motor being controlled.
QEI (see page 530)
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 with index (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.
Analog Peripherals
To handle analog signals, the LM3S6952 microcontroller offers an Analog-to-Digital Converter
(ADC).
For support of analog signals, the LM3S6952 microcontroller offers three analog comparators.
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April 05, 2010
Texas Instruments-Production Data