What is the maximum possible baud rate of synchronous USART mode?

[Reinhard Panhuber]

Posted on April 22, 2018 at 20:00

Hey guys,

I am new to STM32 MCUs and i am looking for the maximum possible baud rate in synchronous USART mode for the STM32F031F4. For asynchronous mode this is clearly noted in the manual. For the synchronous mode, however, not. It is only mentioned, that the setup and hold time should be respected, which is 1/16 Bit time.. which i don't really get what that is. Can somebody explain to me what this means?

The manual is

http://www.st.com/content/ccc/resource/technical/document/reference_manual/c2/f8/8a/f2/18/e6/43/96/DM00031936.pdf/files/DM00031936.pdf/jcr:content/translations/en.DM00031936.pdf

 

and the 1/16 Bit time is mentioned on page 715.

Thanks in advance!

[waclawek.jan]

Posted on April 22, 2018 at 23:27

The maximum baudrate is the same as for the asynchronous mode. In fact, the synchronous mode *is the same* as asynchronous, except that clock is output and that the Rx'd bit is clocked in by that same clock.

Setup and hold times are important only for Rx and they mean, that the Rx signal should not change during the period of 1/16 of bit time before to 1/16 of bit time after the active clock edge.

https://community.st.com/community/stm32-community/blog/2018/03/03/using-usart-instead-of-spi

is a writeup which may or may not be interesting for you.

JW

[Reinhard Panhuber]

Posted on April 23, 2018 at 09:02

Thanks for the quick reply!

A pitty, i was hoping that for the syncronous mode, the maximum possible baud rate is higher than in asynchronous mode. This is at least the case for Atmel MCUs and also would make sense since a sampling of the data line is not necessary with a seperate clock line given...

Anyway, thank you very much!