GD32F20x User Manual
496
RTS flow control
The USART receiver outputs the nRTS, which reflects the status of the receive buffer. When
data frame is received, the nRTS signal goes high to prevent the transmitter from sending
next frame. The nRTS signal keeps high when the receive buffer is full, and can be cleared
by reading the USART_DATA register.
CTS flow control
The USART transmitter monitors the nCTS input pin to decide if a data frame can be
transmitted.
If the TBE bit in USART_STAT0 is ‘0’ and the nCTS signal is low, the transmitter
transmits the data frame. When the nCTS signal goes high during a transmission, the
transmitter stops after the current transmission is accomplished.
Figure 19-8. Hardware flow control
nCTS
RX
nRTS
RTS follow control
CTS follow control
TX
start
data 2
start
data 3
stop
stop
data 1
stop
start
data 1
start
data 2
stop
stop
USART_DATA
data 2
empty
empty
data 3
empty
idle
idle
idle
idle
If the CTS flow control is enabled, the CTSF bit in USART_STAT0 is set when the nCTS pin
toggles. An interrupt is generated if the CTSIE bit in USART_CTL2 is set.
19.3.7.
Multi-processor communication
In multiprocessor communication, several USARTs are connected as a network. It will be a
big burden for a device to monitor all of the messages on the RX pin. To reduce the burden
of a device, software can put an USART module into a mute mode by setting the RWU bit in
USART_CTL0 register.
If a USART is in mute mode, all of the receive status bits cannot be set. Software can wake
up the USART by resetting the RWU bit.
The USART can also be wake up by hardware in one of the two methods: idle frame method
and address match method.
The idle frame wake up method is selected by default. When an idle frame is detected on the
RX pin, the hardware clears the RWU bit and exits the mute mode. When wake up at an idle
frame, the IDLEF bit in USART_STAT0 is not set.
When the WM bit in USART_CTL0 register is set, the MSB bit of a frame is detected as the
address flag. If the address flag is high, the frame is treated as an address frame. If the
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...