Atmel SAM4S Series, Preliminary Data Sheet

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915
11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
37.6.2.3 2-bit Gray Up/Down Counter for Stepper Motor
It is possible to configure a couple of channels to provide a 2-bit gray count waveform on 2 out-
puts. Dead-Time Generator and other downstream logic can be configured on these channels.
Up or down count mode can be configured on-the-fly by means of PWM_SMMR configuration
registers.
When GCEN0 is set to 1, channels 0 and 1 outputs are driven with gray counter.
Figure 37-6. 2-bit Gray Up/Down Counter
37.6.2.4 Dead-Time Generator
The dead-time generator uses the comparator output OCx to provide the two complementary
outputs DTOHx and DTOLx, which allows the PWM macrocell to drive external power control
switches safely. When the dead-time generator is enabled by setting the bit DTE to 1 or 0 in the
“PWM Channel Mode Register” (PWM_CMRx), dead-times (also called dead-bands or non-
overlapping times) are inserted between the edges of the two complementary outputs DTOHx
and DTOLx. Note that enabling or disabling the dead-time generator is allowed only if the chan-
nel is disabled.
The dead-time is adjustable by the “PWM Channel Dead Time Register” (PWM_DTx). Both out-
puts of the dead-time generator can be adjusted separately by DTH and DTL. The dead-time
values can be updated synchronously to the PWM period by using the
“PWM Channel Dead
Time Update Register” (PWM_DTUPDx).
The dead-time is based on a specific counter which uses the same selected clock that feeds the
channel counter of the comparator. Depending on the edge and the configuration of the dead-
time, DTOHx and DTOLx are delayed until the counter has reached the value defined by DTH or
DTL. An inverted configuration bit (DTHI and DTLI bit in the PWM_CMRx register) is provided
for each output to invert the dead-time outputs. The following figure shows the waveform of the
dead-time generator.
PWMH0
DOWNx
GCEN0 = 1
PWMH1
PWML0
PWML1