GD32F20x User Manual
498
during a frame on the RX pin, the FERR status will be asserted for the current frame.
Figure 19-10. Break frame occurs during a frame
frame0
frame2
USART_DATA
data0
data1
data2
FERR
RX pin
LBDF
1 frame time
frame1
19.3.9.
Synchronous mode
The USART can be used for full-duplex synchronous serial communications only in master
mode, by setting the CKEN bit in USART_CTL1. The LMEN bit in USART_CTL1 and SCEN,
HDEN, IREN bits in USART_CTL2 should be reset in synchronous mode. The CK pin is the
synchronous USART transmitter clock output, and can be only activated when the TEN bit is
enabled. No clock pulse will be sent through the CK pin during the start bit and stop bit
transmission. The CLEN bit in USART_CTL1 can be used to determine whether the clock is
output or not during the last (address flag) bit transmission. The CPH bit in USART_CTL1 can
be used to determine whether data is captured on the first or the second clock edge. The CPL
bit in USART_CTL1 can be used to configure the clock polarity in the USART synchronous
idle state.
The CPL, CPH and CLEN bits in USART_CTL1 determine the waveform on the CK pin.
Software can only change them when the USART is disabled (UEN=0).
If the REN bit in USART_CTL0 is set, the receiver works differently from the normal USART
reception method. The receiver samples the data on the capture edge of the CK pin without
any oversampling.
Figure 19-11. Example of USART in synchronous mode
USART
(master mode)
RX
TX
CK
Device
(slave mode)
Clock input
Data input
Data output
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 ...