RM0312 datasheet(114/275 Pages) STMICROELECTRONICS

114 / 275 page

16-bit general purpose timer (TIM2/TIM3)

RM0312

114/275

DocID022352 Rev 3

Figure 29. Counter timing diagram, CK_PSC divided by 1, TIMx_ARR=06h, ARPE=1

Hints on using center-aligned mode:

•

When starting in center-aligned mode, the current up-down configuration is used. It

means that the counter will start counting up or down depending on the value written in

the DIR bit in the TIMx_CR1 register. Moreover, the DIR and CMS bits must not be

changed at the same time by the software.

•

Writing to the counter while running in center-aligned mode is not recommended as it

can lead to unexpected results. In particular:

–

The direction is not updated if you write a value in the counter that is greater than

the auto-reload value (TIMx_CNT>TIMx_ARR). For example, if the counter was

counting up, it will continue to count up.

–

The direction is updated if you write 0 or write the TIMx_ARR value in the counter

but no Update Event UEV is generated.

•

The safest way to use center-aligned mode is to generate an update by software

(setting the UG bit in the TIMx_EGR register) just before starting the counter and not to

write the counter while it is running.

CK_PSC

CNT_EN

TIMER CLOCK = CK_CNT

COUNTER REGISTER

UPDATE INTERRUPT FLAG (UIF)

COUNTER UNDERFLOW

UPDATE EVENT (UEV)

03 04 05 06 05 04 03

03 02 01 00 01

COUNTER OVERFLOW

AUTO-RELOAD PRELOAD REGISTER

AUTO-RELOAD SHADOW REGISTER

Write a new value in TIMx_ARR

New value transferred in shadow register

on update event

RM0312 Datasheet(PDF) 114 Page - STMicroelectronics