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ATmega16M1/32M1/64M1 [DATASHEET]
8209E–AVR–11/2012
The PSC is based on the use of a free-running 12-bit counter (PSC counter). This counter is able to count up to a
top value determined by the contents of POCR_RB register and then according to the selected running mode,
count down or reset to zero for another cycle.
Each of the three PSC modules can be seen as two symetrical entities. One entity named part A which generates
the output PSCOUTnA and the second one named part B which generates the PSCOUTnB output.
Each module has its own PSC Input circuitry which manages the corresponding input.
17.5
Functional description
17.5.1
Generating control waveforms
In general, the drive of a 3-phase motor requires generating six PWM signals. The duty cycle of these signals must
be independently controlled to adjust the speed or torque of the motor or to produce the wanted waveform on the
three voltage lines (trapezoidal, sinusoidal, and so on).
In case of cross conduction or overtemperature, having inputs which can immediately disable the waveform gener-
ator’s outputs is desirable.
These considerations are common for many systems which require PWM signals to drive power systems such as
lighting, DC/DC converters, and so on.
17.5.2
Waveform cycles
Each of the three modules has two waveform generators which jointly compose the output signal.
The first part of the waveform is relative to part A or PSCOUTnA output. This waveform corresponds to sub-cycle A
in the following figure.
The second part of the waveform is relative to part B or PSCOUTnB output. This waveform corresponds to sub-
cycle B in the following figure.
The complete waveform is terminated at the end of the sub-cycle B, whereupon any changes to the settings of the
waveform generator registers will be implemented, for the next cycle.
The PSC can be configured in one of two modes (1Ramp Mode or Centered Mode). This configuration will affect
the operation of all the waveform generators.
Figure 17-2. Cycle presentation in One Ramp mode.
Sub-cycle A
Sub-cycle B
One PSC cycle
UPDATE
PSC counter value