at32uc3b0512-z2ues ATMEL Corporation, at32uc3b0512-z2ues Datasheet - Page 325

• Manufacturer Part Number: at32uc3b0512-z2ues
• Description: 32-bit Avr Microcontroller
• Manufacturer: ATMEL Corporation

Figure 21-27. Receiver Behavior when Operating with Hardware Handshaking
32059J–12/2010
RXBUFF
Write
RXD
RTS
CR
RXEN = 1
Figure 21-26. Connection with a Remote Device for Hardware Handshaking
Setting the USART to operate with hardware handshaking is performed by writing the MODE
field in the Mode Register (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 Peripheral DMA Controller channel for
reception. The transmitter can handle hardware handshaking in any case.
Figure 21-27
pin is driven high if the receiver is disabled and if the status RXBUFF (Receive Buffer Full) com-
ing from the Peripheral DMA Controller 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 Peripheral DMA Controller clears the status bit RXBUFF and, as a result, asserts the pin
RTS low.
Figure 21-28
pin disables the transmitter. If a character is being processing, the transmitter is disabled only
after the completion of the current character and transmission of the next character happens as
soon as the pin CTS falls.
Figure 21-28. Transmitter Behavior when Operating with Hardware Handshaking
shows how the transmitter operates if hardware handshaking is enabled. The CTS
shows how the receiver operates if hardware handshaking is enabled. The RTS
CTS
TXD
USART
TXD
RXD
CTS
RTS
RXD
TXD
RTS
CTS
Remote
Device
RXDIS = 1
AT32UC3B
325