When update the reptition counter in STM32 TIM block?

The spec mentioned taht REP_CNT is updated at U_RC (repetition update event). But no more detail about U_RC is found in the spec.

I want to know when the repetition counter is reload the new RCR value after TIM RCR is changed if base counter is enabled.

I guess two kinds of possiblity:

(1) At the first base counter overflow or underflow after RCR is changed

(2) When current receptition downcount to zero after RCR is changed.

Hope your answer. Thanks.

Hi Jeffrey,

Here is some description FYI.  It is updated at the moment when the upate event occurs.
It is the same meaning as mentioned in the " TIMx repetition counter register " which is just change the point of view from REP_CNT.

Considering your possibilities:
1、The first base counter overflow or underflow after changing the RCR: This is correct. The new RCR value will be reloaded into the repetition counter at the first subsequent update event, which happens when the base counter overflows or underflows.

2、When the current repetition count downcounts to zero after changing the RCR: This possibility is not accurate. The repetition counter does not directly affect the update event itself; rather, it determines the number of consecutive overflows or underflows required before triggering an update event.

还是说中文吧。大家方便点。


首先，RCR寄存器只有高级定时器才具备，且带预装功能。


RCR 计数器的重装更新 只能借助更新事件。而更新事件的产生一般可以有三种方式：


第一种方式：对于高级定时器而言，就是每当RCR计数器向下计到零的时候；对于通用或基本定时器而言就是每次发生溢出的时候；
第二种方式：就是工作在复位从模式的定时器接收到复位触发信号的时候；
第三种方式：基于软件方式手动产生更新事件；

STMCU-管管 发表于 2023-9-19 15:26
Considering your possibilities:
1、The first base counter overflow or underflow after changing the R ...

Thanks for your answer. As we all know, if RCR is 5, UEV only occurs when repetition counter reached to 0.

If writing a new value 7 to RCR when REP_CNT is 4，new value (7) should be loaded into REP_CNT when REP_CNT is 3 accourding to you answer. But there is no UEV (update event) occurs at this moment, right?

If yes, it conflicts with the answer aboved: repetition counter is reloaded with new RCR when an update event occurs.

Could you give more advice？Thank you again.

JeffreyChen 发表于 2023-9-19 16:47</p>
<p>Thanks for your answer.  As we all know, if RCR is 5,  UEV only occurs when repetition counter ...

[md]hi, if we prepared a new value 7 to RCR when REP_CNT is 4, the new value will not be reloaded into repeated counter until the REP_CNT downcounts to 0 .

of course, there is another 2 methods to complete the reload like manually generating update event or reset slave mode Timer triggered by signal.