LM3S8933 Luminary Micro, Inc, LM3S8933 Datasheet - Page 33

• Manufacturer Part Number: LM3S8933
• Description: Lm3s8933 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

1.4.2.1
1.4.3
1.4.3.1
1.4.3.2
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 LM3S8933, PWM motion control functionality can be achieved through:
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CCP Pins (see page 217)
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.
Analog Peripherals
To handle analog signals, the LM3S8933 microcontroller offers an Analog-to-Digital Converter
(ADC).
For support of analog signals, the LM3S8933 microcontroller offers three analog comparators.
ADC (see page 270)
An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a
discrete digital number.
The LM3S8933 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.
Analog Comparators (see page 502)
An analog comparator is a peripheral that compares two analog voltages, and provides a logical
output that signals the comparison result.
The LM3S8933 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:
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■
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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.
The motion control features of the general-purpose timers using the CCP pins
An individual external reference voltage
A shared single external reference voltage
A shared internal reference voltage
Preliminary
LM3S8933 Microcontroller
33