Operation Modes
7-18 ADSP-214xx SHARC Processor Hardware Reference
4. Emergency Dead Time Insertion
5. Output Polarity
Operation Modes
The following sections provide information on the operating modes of the
PWM module.
Waveform Modes
The PWM module can operate in both edge- and center-aligned modes.
These modes are described in the following sections.
Edge-Aligned Mode
In edge-aligned mode, shown in Figure 7-5, the PWM waveform is
left-justified in the period window. A duty value of zero, programmed
through the PWMAx registers, produces a PWM waveform with 50% duty
cycle. For even values of period, the PWM pulse width is exactly period/2,
whereas for odd values of period, it is equal to period/2 (rounded up).
Therefore for a duty value programmed in two’s-complement, the PWM
pulse width is given by:
To generate constant logic high on PWM output, program the duty regis-
ter with the value ≥ + period/2.
To generate constant logic low on PWM output, program the duty regis-
ter with the value ≥ – period/2.
For example, using an odd period of p = 2n + 1, the counter within the
PWM generator counts as (–n...0...+n). If the period is even (p = 2n) then
the counter counts as (–n+1...0...n).
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