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Examples of Complementary PWM Mode: Figure 8-35 shows an example of operation in
complementary PWM mode. TCNT3 and TCNT4 operate as up/down-counters, counting down
from compare match between TCNT3 and GRA3 and counting up from the point at which TCNT4
underflows. During each up-and-down counting cycle, PWM waveforms are generated by
compare match with general registers GRB3, GRA4, and GRB4. Since TCNT3 is initially set to a
higher value than TCNT4, compare match events occur in the sequence TCNT3, TCNT4, TCNT4,
TCNT3.
TCNT3 and
TCNT4 values
GRA3
GRB3
GRA4
GRB4
H'0000
TIOCA
3
TIOCB
3
TIOCA
4
TOCXA
4
TIOCB
4
TOCXB
4
Figure 8-35 Operation in Complementary PWM Mode (Example 1)
244
Down-counting starts at compare
match between TCNT3 and GRA3
TCNT3
TCNT4
Up-counting starts when
TCNT4 underflows
(when OLS3 = OLS4 = 1)
Time
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