Hardware Flow Control; Figure 243. Reception Using Dma; Figure 244. Hardware Flow Control Between 2 Usarts - ST STM32F205 series Reference Manual

Advanced arm-based 32-bit mcus
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RM0033
TX line
RXNE flag
DMA request
USART_DR
DMA reads USART_DR
DMA TCIF flag
(Transfer complete)
software configures the
DMA to receive 3 data
blocks and enables
the USART
Error flagging and interrupt generation in multibuffer communication
In case of multibuffer communication if any error occurs during the transaction the error flag
will be asserted after the current byte. An interrupt will be generated if the interrupt enable
flag is set. For framing error, overrun error and noise flag which are asserted with RXNE in
case of single byte reception, there will be separate error flag interrupt enable bit (EIE bit in
the USART_CR3 register), which if set will issue an interrupt after the current byte with
either of these errors.
24.3.14

Hardware flow control

It is possible to control the serial data flow between 2 devices by using the CTS input and
the RTS output. The
RTS and CTS flow control can be enabled independently by writing respectively RTSE and
CTSE bits to 1 (in the USART_CR3 register).
Universal synchronous asynchronous receiver transmitter (USART)

Figure 243. Reception using DMA

Frame 1
set by hardware
cleared by DMA read
F1
DMA reads F1
from
USART_DR
Figure 244
shows how to connect 2 devices in this mode:

Figure 244. Hardware flow control between 2 USARTs

USART 1
TX
TX circuit
CTS
RX
RX circuit
RTS
RM0033 Rev 8
Frame 2
F2
DMA reads F2
from
USART_DR
RTS
CTS
Frame 3
F3
set by hardware
DMA reads F3
The DMA transfer
from
is complete
USART_DR
(TCIF=1 in
DMA_ISR)
USART 2
RX
RX circuit
TX
TX circuit
cleared
by software
ai17193b
MSv31169V2
667/1378
682

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