LM3S2939 Datasheet, PDF (48/749 Pages) Texas Instruments – Stellaris® LM3S2939 Microcontroller

Architectural Overview
1.4.3
1.4.3.1
1.4.3.2
1.4.4
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 LM3S2939 microcontroller offers an Analog-to-Digital Converter
(ADC).
For support of analog signals, the LM3S2939 microcontroller offers three analog comparators.
ADC (see page 394)
An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a
discrete digital number.
The LM3S2939 ADC module features 10-bit conversion resolution and supports three 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 596)
An analog comparator is a peripheral that compares two analog voltages, and provides a logical
output that signals the comparison result.
The LM3S2939 microcontroller provides three independent integrated analog comparators that can
be configured to drive an output or generate an interrupt or ADC event.
A comparator can compare a test voltage against any one of these voltages:
■ An individual external reference voltage
■ A shared single external reference voltage
■ A shared internal reference voltage
The comparator can provide its output to a device pin, acting as a replacement for an analog
comparator on the board, or it can be used to signal the application via interrupts or triggers to the
ADC to cause it to start capturing a sample sequence. The interrupt generation and ADC triggering
logic is separate. This means, for example, that an interrupt can be generated on a rising edge and
the ADC triggered on a falling edge.
Serial Communications Peripherals
The LM3S2939 controller supports both asynchronous and synchronous serial communications
with:
■ Three fully programmable 16C550-type UARTs
■ One SSI module
■ One I²C module
■ One CAN unit
48
June 18, 2012
Texas Instruments-Production Data