Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual page 533

Desired baud
USARTn_CLKDIV/256
rate [baud/s]
(to 32nd position)
38400 5.5
57600 3.34375
76800 2.25
115200 1.15625
230400 0.09375
18.3.2.4 Auto Baud Detection
Setting AUTOBAUDEN in USARTn_CLKDIV uses the first frame received to automatically set the baud rate provided that it contains
0x55 (IrDA uses 0x00). AUTOBAUDEN can be used in a simple LIN configuration to auto detect the SYNC byte. The receiver will
measure the number of local clock cycles between the beginning of the START bit and the beginning of the 8th data bit. The DIV field in
USARTn_CLKDIV will be overwritten with the new value. The OVS in USARTn_CTRL and the +1 count of the Baud Rate equation are
already factored into the result that gets written into the DIV field. To restart autobaud detection, clear AUTOBAUDEN and set it high
again. Since the auto baud detection is done over 8 baud times, only the upper 3 bits of the fractional part of the clock divider are
populated.
18.3.2.5 Data Transmission
Asynchronous data transmission is initiated by writing data to the transmit buffer using one of the methods described in
mit Buffer Operation. When the transmission shift register is empty and ready for new data, a frame from the transmit buffer is loaded
into the shift register, and if the transmitter is enabled, transmission begins. When the frame has been transmitted, a new frame is loa-
ded into the shift register if available, and transmission continues. If the transmit buffer is empty, the transmitter goes to an idle state,
waiting for a new frame to become available.
Transmission is enabled through the command register USARTn_CMD by setting TXEN, and disabled by setting TXDIS in the same
command register. When the transmitter is disabled using TXDIS, any ongoing transmission is aborted, and any frame currently being
transmitted is discarded. When disabled, the TX output goes to an idle state, which by default is a high value. Whether or not the trans-
mitter is enabled at a given time can be read from TXENS in USARTn_STATUS.
When the USART transmitter is enabled and there is no data in the transmit shift register or transmit buffer, the TXC flag in
USARTn_STATUS and the TXC interrupt flag in USARTn_IF are set, signaling that the transmission is complete. The TXC status flag is
cleared when a new frame becomes available for transmission, but the TXC interrupt flag must be cleared by software.
silabs.com | Building a more connected world.
USART - Universal Synchronous Asynchronous Receiver/Transmitter
USARTn_OVS =00
Actual baud rate
Error %
[baud/s]
38461.54 0.160
57553.96 -0.080
76923.08 0.160
115942 0.644
228571.4 -0.794
USARTn_OVS =01
USARTn_CLKDIV/256 Actual baud rate
(to 32nd position) [baud/s]
12.03125 38369.3
7.6875 57553.96
5.5 76923.08
3.34375 115107.9
1.15625 231884.1
Reference Manual
Error %
-0.080
-0.080
0.160
-0.080
0.644
18.3.2.6 Trans-
Rev. 1.1 | 533