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STM32G474 USART: Confusing reference manual: How to clear Auto Baud Rate Error

TwelveSquared
Senior

The reference manual (RM0440 Rev4, page 1667 and page 1672), regarding the USART_ISR register, bit ABRE "Auto Baud Rate Error" says the following:

Bit 14 ABRE:Auto baud rate error

This bit is set by hardware if the baud rate measurement failed (baud rate out of range or character comparison failed)

It is cleared by software, by writing 1 to the ABRRQ bit in the USART_CR3 register.

However the USART_CR3 register does not contain a bit ABRRQ.

Only bit called ABRRQ is in USART_RQR register. However this is for requesting a Auto Baud Rate function. Is this how to clear the error? Or is mistake in manual?

Thanks

3 REPLIES 3
TDK
Guru

Sounds like it both clears the flag and requests a baud rate measurement. So no clearing the flag without requesting a new measurement. Still an error that's it's in RQR and not CR3.

Bit 0 ABRRQ: Auto baud rate request

Writing 1 to this bit resets the ABRF flag in the USART_ISR and request an automatic baud

rate measurement on the next received data frame.

If you feel a post has answered your question, please click "Accept as Solution".

So the error in the reference manual should be reported to ST somehow. I don't know where/how to report that.

Imen GH
ST Employee

Hello,

Both ABRF and ABRE are cleared by writing ABRRQ to 1 in USART_RQR register.

I have raised the error internally for correction.

Thank you