MCBSTM32EXL Keil, MCBSTM32EXL Datasheet - Page 260

• Manufacturer Part Number: MCBSTM32EXL
• Description: BOARD EVALUATION FOR STM32F103ZE
• Manufacturer: Keil

Specifications of MCBSTM32EXL

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Advanced-control timers (TIM1&TIM8)
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Figure 59. Counter timing diagram, update event when ARPE=1 (TIMx_ARR
Downcounting mode
In downcounting mode, the counter counts from the auto-reload value (content of the
TIMx_ARR register) down to 0, then restarts from the auto-reload value and generates a
counter underflow event.
If the repetition counter is used, the update event (UEV) is generated after downcounting is
repeated for the number of times programmed in the repetition counter register
(TIMx_RCR). Else the update event is generated at each counter underflow.
Setting the UG bit in the TIMx_EGR register (by software or by using the slave mode
controller) also generates an update event.
The UEV update 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 UDIS bit has been written to 0.
However, the counter restarts from the current auto-reload value, whereas the counter of the
prescaler restarts from 0 (but the prescale rate doesn’t 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 repetition counter is reloaded with the content of TIMx_RCR register
The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register)
The auto-reload active register is updated with the preload value (content of the
TIMx_ARR register). Note that the auto-reload is updated before the counter is
reloaded, so that the next period is the expected one
preloaded)
Auto-reload shadow register
Auto-reload preload register
Update interrupt flag (UIF)
Timer clock = CK_CNT
Update event (UEV)
Counter overflow
Counter register
Write a new value in TIMx_ARR
Doc ID 13902 Rev 9
CK_PSC
CEN
F5
F5
F0
F1 F2 F3 F4 F5
00
01 02 03 04 05 06 07
36
36
RM0008