Figure 137. Counter Timing Diagram, Internal Clock Divided By 1; Figure 138. Counter Timing Diagram, Internal Clock Divided By 2 - ST STM32F405 Reference Manual

RM0090
does not change). In addition, if the URS bit (update request selection) in TIMx_CR1
register is set, setting the UG bit generates an update event UEV but without setting the UIF
flag (thus no interrupt or DMA request is sent). This is to avoid generating both update and
capture interrupts when clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):
•
The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register)
•
The auto-reload shadow register is updated with the preload value (TIMx_ARR)
The following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.
Update interrupt flag (UIF)

Figure 137. Counter timing diagram, internal clock divided by 1

CK_INT
CNT_EN
Timerclock = CK_CNT
Counter register
Counter overflow
Update event (UEV)

Figure 138. Counter timing diagram, internal clock divided by 2

CK_INT
CNT_EN
Timerclock = CK_CNT
Counter register
Counter overflow
Update event (UEV)
Update interrupt flag (UIF)
General-purpose timers (TIM2 to TIM5)
31 32 33 34 35 36 00
0034 0035 0036
RM0090 Rev 18
01 02 03 04 05 06 07
0000 0001 0002 0003
MS35836V1
MS35835V1
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