RM0090 Rev 18 527/1749
RM0090 Advanced-control timers (TIM1 and TIM8)
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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 if the update source is a counter overflow, the auto-
reload is updated before the counter is reloaded, so that the next period is the expected
one (the counter is loaded with the new value).
The following figures show some examples of the counter behavior for different clock
frequencies.
Figure 100. Counter timing diagram, internal clock divided by 1, TIMx_ARR = 0x6
1. Here, center-aligned mode 1 is used (for more details refer to Section 17.4: TIM1 and TIM8 registers).
Figure 101. Counter timing diagram, internal clock divided by 2
MS31189V2
CK_PSC
Timerclock = CK_CNT
Counter register
Update event (UEV)
Counter overflow
Update interrupt flag (UIF)
CEN
Counter underflow
00020304 05 0601 02 03 0401 05 0304
MS31190V2
CK_PSC
Timerclock = CK_CNT
Counter register
Update event (UEV)
Update interrupt flag (UIF)
CNT_EN
Counter underflow
0003 0002 0001 0000 0001 0002 0003
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