MCBSTM32EXL Keil, MCBSTM32EXL Datasheet - Page 323

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

Specifications of MCBSTM32EXL

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

RM0008
14.3.2
Figure 101. Counter timing diagram with prescaler division change from 1 to 4
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
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 following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.
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)
Prescaler control register
Timer clock = CK_CNT
Update event (UEV)
Prescaler counter
Prescaler buffer
Counter register
Write a new value in TIMx_PSC
Doc ID 13902 Rev 9
CK_PSC
CNT_EN
F7
0
0
0
F8
F9 FA FB FC
0
General-purpose timer (TIMx)
1
00
2 3
3
3
0 1
01
2 3
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