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RM Doc error: USART RXNE set not correctly described

flyer31
Senior
Posted on November 28, 2012 at 13:26

In the Ref Manual (DM00031020 Nov 2012), the exact time, when RXNE is set during the receive of a bit is not described exactly:

On page 746 (26.3.3), it says, that RXNE is set if the start bit is confirmed (which should be pure NONSENSE - at this time not even the data byte available).

On page 750 (still 26.3.3), it says that RXNE is set at the the end of the 1.5 stop bit, if USART works with 1.5 stop bits. And RXNE is set at the end of the 1st stop bit, if USART works with 2 stop bits. And for the case of 0.5 stop bits or 1 stop bits, when will RXNE be set then?

We are just programming LIN BUS, where every TX byte is read back - in such a case it is quite crucial at which bit time RXNE is set exactly (and please in the case of 1 stop bit). This definitely should be specified exactly.
1 REPLY 1
frankmeyer9
Associate II
Posted on November 28, 2012 at 14:58

As this is presumably a pure hardware issue of the UART peripheral, you might need to ask ST.

Or you set a really low baudrate, and measure with GPIO pulses ...