Renesas RX100 Series User Manual page 437

RX13T Group
(j) Method for Generating PWM Output in Complementary PWM Mode
In complementary PWM mode, six phases (three positive and three negative) PWM waveforms can be output. Dead time
can be set for PWM waveforms to be output.
A PWM waveform is generated by output of the level selected in the timer output control register in the event of a
compare match between a counter and a compare register. While TCNTSA is counting, the compare register and
temporary register values are simultaneously compared to create consecutive PWM output from 0 to 100% duty ratio.
The relative timing of turn-on and turn-off compare match occurrence may vary, but the compare match that turns off
each phase takes precedence to secure the dead time and ensure that the positive-phase and negative-phase turn-on times
do not overlap. Figure 19.53 to Figure 19.55 show examples of waveform generation in complementary PWM mode.
The positive-phase and negative-phase turn-off timing is generated by a compare match with the counter indicated by a
solid line, and the turn-on timing is generated by a compare match with the counter indicated by a dotted line, which
operates with a delay equal to the dead time behind the counter indicated by a solid line. In the T1 period, compare match
a that turns off the negative phase has the highest priority, and compare matches before a are ignored. In the T2 period,
compare match c that turns off the positive phase has the highest priority, and compare matches before c are ignored.
In most cases, compare matches occur in the order a → b → c → d (or c → d → a' → b') as shown in Figure 19.53 .
If compare matches deviate from the a → b → c → d order, since the time for which the negative phase is off is shorter
than twice the dead time, the positive phase is not turned on. If compare matches deviate from the c → d → a' → b' order,
since the time for which the positive phase is off is shorter than twice the dead time, the negative phase is not turned on.
As shown in Figure 19.54 , if compare match c follows compare match a before compare match b, compare match b is
ignored and the negative phase is turned on by compare match d. This is because turning off 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 because the positive phase goes from off to off).
Similarly, in the example in Figure 19.55 , turning off the negative phase has priority due to the occurrence of compare
match a' (negative-phase off timing) before compare match d (negative-phase on timing). As a result, the negative 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.
MTU3.TGRA
TCDRA
MTU4.TGRA
TDDRA
0000h
Positive-phase
output
Negative-phase
output
Figure 19.53 Example of Waveform Output in Complementary PWM Mode (MTU3 and MTU4) (1)
R01UH0822EJ0100 Rev.1.00
Jul 31, 2019
T1 interval
c d
TEMP2
a b
ON OFF
OFF ON
19. Multi-Function Timer Pulse Unit 3 (MTU3c)
T2 interval T1 interval
a'
ON
OFF
Output waveform is active-low.
Buffer operation is set for transfer at the crest and trough.
Counter for generating
a turn-off timing
Counter for generating
a turn-on timing
b'
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