ADSP-21368 SHARC Processor Hardware Reference 8-1
8 PULSE WIDTH MODULATION
Pulse width modulation (PWM) is a technique for controlling analog cir-
cuits with a microprocessor’s digital outputs. PWM is employed in a wide
variety of applications, ranging from measurement to communications to
power control and conversion.
One of the advantages of PWM is that the signal remains digital all the
way from the processor to the controlled system; no digital-to-analog con-
version is necessary. By maintaining a digital signal throughout a system,
noise effects are minimized.
PWM Implementation
The PWM modules in the ADSP-21367/8/9 and ADSP-2137x SHARC
processors are flexible, programmable, PWM waveform generators that
produces switching patterns for various purposes related to motor control,
electronic valve control, or audio power control. The PWM module is
comprised of four identical groups that contain four PWM outputs each,
allowing 16 PWM outputs in total. Figure 8-1 shows a single group. The
PWM generator can produce either center-aligned or edge-aligned PWM
waveforms. In addition, it can generate complementary signals on two
outputs in paired mode or independent signals in non-paired mode.
PWM Waveforms
The PWM module can generate waveforms that are either edge-aligned
(left-justified) or center-aligned. Each waveform is described in detail in
the following sections.
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