Modes Of Operation; Asynchronous Operation - Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual

18.3.1 Modes of Operation

The USART operates in either asynchronous or synchronous mode.
In synchronous mode, a separate clock signal is transmitted with the data. This clock signal is generated by the bus master, and both
the master and slave sample and transmit data according to this clock. Both master and slave modes are supported by the USART. The
synchronous communication mode is compatible with the Serial Peripheral Interface Bus (SPI) standard.
In asynchronous mode, no separate clock signal is transmitted with the data on the bus. The USART receiver thus has to determine
where to sample the data on the bus from the actual data. To make this possible, additional synchronization bits are added to the data
when operating in asynchronous mode, resulting in a slight overhead.
Asynchronous or synchronous mode can be selected by configuring SYNC in USARTn_CTRL. The options are listed with supported
protocols in Table 18.1 USART Asynchronous Vs. Synchronous Mode on page
supported in both asynchronous and synchronous mode.
SYNC Communication Mode
0 Asynchronous
1 Synchronous
Table 18.2 USART Pin Usage on page 529
ent modes. Pin functionality enclosed in square brackets is optional, and depends on additional configuration parameters. LOOPBK and
MASTER are discussed in 18.3.2.14 Local Loopback
SYNC LOOPBK
0 0
0 1
1 0
1 0
1 1
1 1

18.3.2 Asynchronous Operation

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USART - Universal Synchronous Asynchronous Receiver/Transmitter
Table 18.1. USART Asynchronous Vs. Synchronous Mode
Supported Protocols
RS-232, RS-485 (w/external driver), IrDA, ISO 7816
SPI, MicroWire, 3-wire
explains the functionality of the different USART pins when the USART operates in differ-
and 18.3.3.3 Master Mode
Table 18.2. USART Pin Usage
MASTER
U(S)n_TX (MOSI)
x Data out
x Data out/in
0 Data in
1 Data out
0 Data out/in
1 Data out/in
529. Full duplex and half duplex communication is
respectively.
Pin functionality
U(S)n_RX (MISO) USn_CLK
Data in -
- -
Data out Clock in
Data in Clock out
- Clock in
- Clock out
Reference Manual
USn_CS
[Driver enable]
[Driver enable]
Slave select
[Auto slave select]
Slave select
[Auto slave select]
Rev. 1.1 | 529