GD32VF103 User Manual
338
Figure 16-9. Break frame occurs during idle state
frame0
frame1
frame2
1 frame time
USART_DATA
data0
data1
0000000
0
data2
FERR
RX pin
LBDF
As shown in
Figure 16-10. 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 16-10. Break frame occurs during a frame
frame0
frame2
USART_DATA
data0
data1
data2
FERR
RX pin
LBDF
1 frame time
frame1
16.3.9.
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 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.