Re: could anyone explain me how does "break" work in USART ? and why is it used ?
A break is a long '0', so long that the receiver will see it as a zero byte regardless of the receiver baudrate.
The stop bit will also be a zero, so the break condition is identified by all data bits set to '0' together with a framing error.
One usage is to tell the other end to change baudrate.
Re: could anyone explain me how does "break" work in USART ? and why is it used ?
A "break" is an illegal sequence on an asynchronous data line (framing error),
Since there is no illegal sequence on a synchronous data line, a "break condition" is not possible.
Re: could anyone explain me how does "break" work in USART ? and why is it used ?
If the UART receiver has extra logic to check for a "break" (checking for a specified length), it can make a better decision.
Without the extra logic, a "break" will only generate a data byte 0x00 with a framing error. In this situation, you can not be sure that is really is a break. It can also be a normal byte with the wrong baud rate.