LM3S2965 Luminary Micro, Inc, LM3S2965 Datasheet - Page 35

• Manufacturer Part Number: LM3S2965
• Description: Lm3s2965 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

1.4.2.1
1.4.2.2
1.4.3
1.4.3.1
July 25, 2008
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 LM3S2965, PWM motion control functionality can be achieved through:
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PWM Pins (see page 472)
The LM3S2965 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 219)
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 508)
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. The LM3S2965
microcontroller includes two QEI modules, which enables control of two motors at the same time.
Analog Peripherals
To handle analog signals, the LM3S2965 microcontroller offers an Analog-to-Digital Converter
(ADC).
For support of analog signals, the LM3S2965 microcontroller offers three analog comparators.
ADC (see page 272)
An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a
discrete digital number.
The LM3S2965 ADC module features 10-bit conversion resolution and supports four 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.
Dedicated, flexible motion control hardware using the PWM pins
The motion control features of the general-purpose timers using the CCP pins
Preliminary
LM3S2965 Microcontroller
35