LM3S8971 Luminary Micro, Inc, LM3S8971 Datasheet - Page 35

• Manufacturer Part Number: LM3S8971
• Description: Lm3s8971 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

1.4.2.2
1.4.3
1.4.3.1
1.4.3.2
July 26, 2008
wave is modulated to encode an analog signal. Typical applications include switching power supplies
and motor control.
On the LM3S8971, PWM motion control functionality can be achieved through:
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PWM Pins (see page 476)
The LM3S8971 PWM module consists of three 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 216)
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.
QEI (see page 512)
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 LM3S8971 microcontroller offers an Analog-to-Digital Converter
(ADC).
For support of analog signals, the LM3S8971 microcontroller offers one analog comparator.
ADC (see page 269)
An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a
discrete digital number.
The LM3S8971 ADC module features 10-bit conversion resolution and supports eight input channels,
plus an internal temperature sensor. Four buffered sample sequences allow rapid sampling of up
to eight analog input sources without controller intervention. Each sample sequence provides flexible
programming with fully configurable input source, trigger events, interrupt generation, and sequence
priority.
Analog Comparators (see page 465)
An analog comparator is a peripheral that compares two analog voltages, and provides a logical
output that signals the comparison result.
Dedicated, flexible motion control hardware using the PWM pins
The motion control features of the general-purpose timers using the CCP pins
Preliminary
LM3S8971 Microcontroller
35