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1745D–ATARM–04-Nov-05
AT91M55800A
The standard break transmission sequence is:
1. Wait for the transmitter ready
(US_CSR.TXRDY = 1)
2. Send the STTBRK command
(write 0x0200 to US_CR)
3. Wait for the transmitter ready
(bit TXRDY = 1 in US_CSR)
4. Send the STPBRK command
(write 0x0400 to US_CR)
The next byte can then be sent:
5. Wait for the transmitter ready
(bit TXRDY = 1 in US_CSR)
6. Send the next byte
(write byte to US_THR)
Each of these steps can be scheduled by using the interrupt if the bit TXRDY in US_IMR is
set.
For character transmission, the USART channel must be enabled before sending a break.
18.6.2 Receive Break
The receiver detects a break condition when all data, parity and stop bits are low. When the
low stop bit is detected, the receiver asserts the RXBRK bit in US_CSR. An end of receive
break is detected by a high level for at least 1-bit + 1/16 of a bit period in asynchronous oper-
ating mode or at least one sample in synchronous operating mode. RXBRK is also asserted
when an end of break is detected.
Both the beginning and the end of a break can be detected by interrupt if the bit
US_IMR.RXBRK is set.