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General-purpose timers (TIM2 to TIM5) RM0090

592/1749 RM0090 Rev 18

Figure 135. Counter timing diagram with prescaler division change from 1 to 2

Figure 136. Counter timing diagram with prescaler division change from 1 to 4

18.3.2 Counter modes

Upcounting mode

In upcounting mode, the counter counts from 0 to the auto-reload value (content of the

TIMx_ARR register), then restarts from 0 and generates a counter overflow event.

An Update event can be generated at each counter overflow or by setting the UG bit in the

TIMx_EGR register (by software or by using the slave mode controller).

The UEV event can be disabled by software by setting the UDIS bit in TIMx_CR1 register.

This is to avoid updating the shadow registers while writing new values in the preload

registers. Then no update event occurs until the UDIS bit has been written to 0. However,

the counter restarts from 0, as well as the counter of the prescaler (but the prescale rate

MS35833V1

CK_PSC

CNT_EN

Timerclock = CK_CNT

Counter register

Update event (UEV)

Prescaler control register

Write a new value in TIMx_PSC

Prescaler buffer

Prescaler counter

01010101

01 02 03FA FBF7 F8 F9 FC

MS35834V1

01230123