GD32W51x User Manual
600
As shown in
Figure 18-10. Break frame occurs during a frame
, if a break frame occurs
during a frame on the RX pin, the FERR status will be asserted for the current frame.
Figure 18-10.
Break frame occurs during a frame
frame0
frame2
USART_RDATA
data0
data1
data2
FERR
RX pin
LBDF
1 frame time
frame1
18.3.9.
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 cleared in synchronous mode. The CK pin is
the clock output of the synchronous USART transmitter, and can be only activated when the
TEN bit is enabled. No clock pulse will be sent through the CK pin during the transmission of
the start bit and stop bit. The CLEN bit in USART_CTL1 can be used to determ ine whether
the clock is output or not during the last (address flag) bit transmission. The clock output is
also not activated during idle and break frame sending. 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).
The clock is synchronized with the data transmitted. The receiver in synchronous mode
samples the data on the transmitter clock without any oversampling.
Figure 18-11. Example of USART in synchronous mode
USART
(master mode)
RX
TX
CK
Device
(slave mode)
Clock input
Data input
Data output