Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet
Product codes
ATSAM4E-XPRO
907
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
Figure 38-26. Break Transmission
38.7.3.14 Receive Break
The receiver detects a break condition when all data, parity and stop bits are low. This corresponds to detecting a
framing error with data to 0x00, but FRAME remains low.
framing error with data to 0x00, but FRAME remains low.
When the low stop bit is detected, the receiver asserts the RXBRK bit in US_CSR. This bit may be cleared by
writing US_CR with the bit RSTSTA to 1.
writing US_CR with the bit RSTSTA to 1.
An end of receive break is detected by a high level for at least 2/16 of a bit period in asynchronous operating mode
or one sample at high level in synchronous operating mode. The end of break detection also asserts the RXBRK
bit.
or one sample at high level in synchronous operating mode. The end of break detection also asserts the RXBRK
bit.
38.7.3.15 Hardware Handshaking
The USART features a hardware handshaking out-of-band flow control. The RTS and CTS pins are used to
connect with the remote device, as shown in
connect with the remote device, as shown in
.
Figure 38-27. Connection with a Remote Device for Hardware Handshaking
Setting the USART to operate with hardware handshaking is performed by writing the USART_MODE field in
US_MR to the value 0x2.
US_MR to the value 0x2.
The USART behavior when hardware handshaking is enabled is the same as the behavior in standard
synchronous or asynchronous mode, except that the receiver drives the RTS pin as described below and the level
on the CTS pin modifies the behavior of the transmitter as described below. Using this mode requires using the
PDC or DMAC channel for reception. The transmitter can handle hardware handshaking in any case.
synchronous or asynchronous mode, except that the receiver drives the RTS pin as described below and the level
on the CTS pin modifies the behavior of the transmitter as described below. Using this mode requires using the
PDC or DMAC channel for reception. The transmitter can handle hardware handshaking in any case.
shows how the receiver operates if hardware handshaking is enabled. The RTS pin is driven high if
the receiver is disabled and if the status RXBUFF (Receive Buffer Full) coming from the PDC channel is high.
Normally, the remote device does not start transmitting while its CTS pin (driven by RTS) is high. As soon as the
receiver is enabled, the RTS falls, indicating to the remote device that it can start transmitting. Defining a new
buffer to the PDC clears the status bit RXBUFF and, as a result, asserts the pin RTS low.
Normally, the remote device does not start transmitting while its CTS pin (driven by RTS) is high. As soon as the
receiver is enabled, the RTS falls, indicating to the remote device that it can start transmitting. Defining a new
buffer to the PDC clears the status bit RXBUFF and, as a result, asserts the pin RTS low.
D0
D1
D2
D3
D4
D5
D6
D7
TXD
Start
Bit
Parity
Bit
Stop
Bit
Baud Rate
Clock
Write
US_CR
TXRDY
TXEMPTY
STPBRK = 1
STTBRK = 1
Break Transmission
End of Break
USART
TXD
CTS
Remote
Device
RXD
TXD
RXD
RTS
RTS
CTS