
Rev. 2.0, 09/02, page 274 of 732
the T2 period, compare-match
c
that turns off the positive phase has the highest priority, and
compare-matches occurring prior to
c
are ignored.
In normal cases, compare-matches occur in the order
a
→
b
→
c
→
d
(or
c
→
d
→
a'
→
b'
), as
shown in figure 11.40.
If compare-matches deviate from the
a
→
b
→
c
→
d
order, since the time for which the negative
phase is off is less than twice the dead time, the figure shows the positive phase is not being turned
on. If compare-matches deviate from the
c
→
d
→
a'
→
b'
order, since the time for which the
positive phase is off is less than twice the dead time, the figure shows the negative phase is not
being turned on.
If compare-match
c
occurs first following compare-match
a
, as shown in figure 11.41, compare-
match
b
is ignored, and the negative phase is turned off by compare-match
d
. This is because
turning off of the positive phase has priority due to the occurrence of compare-match
c
(positive
phase off timing) before compare-match
b
(positive phase on timing) (consequently, the waveform
does not change since the positive phase goes from off to off).
Similarly, in the example in figure 11.42, compare-match
a'
with the new data in the temporary
register occurs before compare-match
c
, but other compare-matches occurring up to
c
, which turns
off the positive phase, are ignored. As a result, the positive phase is not turned on.
Thus, in complementary PWM mode, compare-matches at turn-off timings take precedence, and
turn-on timing compare-matches that occur before a turn-off timing compare-match are ignored.
T2 period
T1 period
T1 period
a
b
c
a'
b'
d
TGR3A_3
TCDR
TDDR
H'0000
Positive phase
Negative phase
Figure 11.40 Example of Complementary PWM Mode Waveform Output (1)