LM3S3749 Datasheet, PDF (51/898 Pages) Texas Instruments – Stellaris® LM3S3749 Microcontroller

Stellaris® LM3S3749 Microcontroller
1.4.1.5
1.4.1.6
1.4.1.7
1.4.2
1.4.2.1
System Control Block (SCB) (see page 102)
The SCB provides system implementation information and system control, including configuration,
control, and reporting of system exceptions.
Memory Protection Unit (MPU) (see page 102)
The MPU supports the standard ARMv7 Protected Memory System Architecture (PMSA) model.
The MPU provides full support for protection regions, overlapping protection regions, access
permissions, and exporting memory attributes to the system.
Direct Memory Access (see page 300)
The LM3S3749 microcontroller includes a Direct Memory Access (DMA) controller, known as
micro-DMA (μDMA). The μDMA controller provides a way to offload data transfer tasks from the
Cortex-M3 processor, allowing for more efficient use of the processor and the expanded available
bus bandwidth. The μDMA controller can perform transfers between memory and peripherals. It
has dedicated channels for each supported peripheral and can be programmed to automatically
perform transfers between peripherals and memory as the peripheral is ready to transfer more data.
The μDMA controller also supports sophisticated transfer modes such as ping-pong and
scatter-gather, which allows the processor to set up a list of transfer tasks for the controller.
Motor Control Peripherals
To enhance motor control, the LM3S3749 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 LM3S3749, 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 735)
The LM3S3749 PWM module consists of four 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 419)
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.
November 17, 2011
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