Advanced-control timers (TIM1&TIM8)
RM0090
524/1731
DocID018909 Rev 11
Figure 104. Counter timing diagram, update event with ARPE=1 (counter underflow)
Figure 105. Counter timing diagram, Update event with ARPE=1 (counter overflow)
17.3.3 Repetition
counter
Section 17.3.1: Time-base unit
describes how the update event (UEV) is generated with
respect to the counter overflows/underflows. It is actually generated only when the repetition
counter has reached zero. This can be useful when generating PWM signals.
This means that data are transferred from the preload registers to the shadow registers
(TIMx_ARR auto-reload register, TIMx_PSC prescaler register, but also TIMx_CCRx
capture/compare registers in compare mode) every N+1 counter overflows or underflows,
where N is the value in the TIMx_RCR repetition counter register.
CK_PSC
00
CEN
Timer clock = CK_CNT
Counter register
Update interrupt flag (UIF)
Counter underflow
Update event (UEV)
01 02 03 04 05 06 07
05 04 03 02 01
06
Auto-reload preload register
FD
36
Write a new value in TIMx_ARR
Auto-reload active register
FD
36
CK_PSC
36
CEN
Timer clock = CK_CNT
Counter register
Update interrupt flag (UIF)
Counter overflow
Update event (UEV)
35 34 33 32 31 30 2F
F8 F9 FA FB FC
F7
Auto-reload preload register
FD
36
Write a new value in TIMx_ARR
Auto-reload active register
FD
36