RM0090: Reference manual - STMicroelectronics

Advanced-control timers (TIM1&TIM8) RM0090
14.3.14 6-step PWM generation
When complementary outputs are used on a channel, preload bits are available on the
OCxM, CCxE and CCxNE bits. The preload bits are transferred to the shadow bits at the
COM commutation event. Thus you can program in advance the configuration for the next
step and change the configuration of all the channels at the same time. COM can be
generated by software by setting the COM bit in the TIMx_EGR register or by hardware (on
TRGI rising edge).
A flag is set when the COM event occurs (COMIF bit in the TIMx_SR register), which can
generate an interrupt (if the COMIE bit is set in the TIMx_DIER register) or a DMA request
(if the COMDE bit is set in the TIMx_DIER register).
Figure 110 describes the behavior of the OCx and OCxN outputs when a COM event
occurs, in 3 different examples of programmed configurations.
Figure 110. 6-step generation, COM example (OSSR=1)
counter (CNT)
OCxREF
Example 1
Example 2
Example 3
COM event
OCx
OCxN
OCx
OCxN
OCx
OCxN
(CCRx)
CCxE=1
write OCxM to 100
CCxNE=0
OCxM=100 (forced inactive)
Write CCxNE to 1
and OCxM to 101
CCxE=1
CCxNE=0
OCxM=100 (forced inactive)
write CCxNE to 0
CCxE=1
and OCxM to 100
CCxNE=0
OCxM=100 (forced inactive)
379/1416 Doc ID 018909 Rev 3
Write COM to 1
CCxE=1
CCxNE=0
OCxM=100
CCxE=0
CCxNE=1
OCxM=101
CCxE=1
CCxNE=0
OCxM=100
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