USART in 9 bit mode with 2 stopbits?

[hans5]

Posted on November 26, 2007 at 09:27

USART in 9 bit mode with 2 stopbits?

[hans5]

Posted on May 17, 2011 at 12:18

Hi,

Tried it on an evaluation board and 9 databits in combination with 2 stopbits seems to work fine.

So I assume it's a typo in the reference manual?

regards, Hans

[hans5]

Posted on May 17, 2011 at 12:18

Hi,

For a specific application I want to use the USART in 9 databits mode in combination with 2 stopbits.

The reference manual description of Control register 1 (USART_CR1) states that this combination is not possible:

''Bit 12 M: word length.

 

This bit determines the word length. It is set or cleared by software.

 

0: 1 Start bit, 8 Data bits, n Stop bit

 

1: 1 Start bit, 9 Data bits, 1 Stop bit''

In smartcard mode however, a setting is described with M=1 in combination with 1.5 stopbits:

''8 bits plus parity: where M=1 and PCE=1 in the USART_CR1 register and either:

 

– 0.5 stop bits when receiving: where STOP=’01’ in the USART_CR2 register

 

– 1.5 stop bits when transmitting: where STOP=’11’ in the USART_CR2 register.''

Question:

Is the number of stopbits in 9 bit datamode indeed limited to one?

Thanks in advance for your answer!

Hans Rosenbrand