Universal synchronous asynchronous receiver transmitter (USART) RM0008
786/1096 Doc ID 13902 Rev 12
Figure 293. IrDA SIR ENDEC- block diagram
Figure 294. IrDA data modulation (3/16) -normal mode
27.3.13 Continuous communication using DMA
The USART is capable of continuing communication using the DMA. The DMA requests for
Rx buffer and Tx buffer are generated independently.
Note: You should refer to product specs for availability of the DMA controller. If DMA is not
available in the product, you should use the USART as explained in Section 27.3.2 or
27.3.3. In the USART_SR register, you can clear the TXE/ RXNE flags to achieve
continuous communication.
Transmission using DMA
DMA mode can be enabled for transmission by setting DMAT bit in the USART_CR3
register. Data is loaded from a SRAM area configured using the DMA peripheral (refer to the
DMA specification) to the USART_DR register whenever the TXE bit is set. To map a DMA
channel for USART transmission, use the following procedure (x denotes the channel
number):
USART
SIR
Transmit
Encoder
SIR
Receive
Decoder
OR
USART_TX
IrDA_OUT
IrDA_IN
USART_RX
TX
RX
SIREN
TX
IrDA_OUT
IrDA_IN
RX
Start
bit
0
1
0
1
0
0
1
1
0
1
3/16
stop bit
bit period
0
1
0
1
0
0
1
1
01
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