AT32F425
Series Reference Manual
2022.03.30
Page 156
Ver 2.01
12.11
I/O pin control
The following five interfaces are used for USART communication.
RX: Serial data input.
TX: Serial data output. In single-wire half-duplex and Smartcard mode, the TX pin is used as an I/O for
data transmission and reception.
CK: Transmitter clock output. The output CLK phase, polarity and frequency can be programmable.
CTS: Transmitter input. Send enable signal in hardware flow control mode.
RTS: Receiver output. Send request signal in hardware flow control mode.
12.12
USART registers
These peripheral registers must be accessed by words (32 bits).
Table 12-5 USART register map and reset value
Register
Offset
Reset value
USART_STS
0x00
0x0000 00C0
USART_DT
0x04
0x0000
USART_BAUDR
0x08
0x0000
USART_CTRL1
0x0C
0x0000
USART_CTRL2
0x10
0x0000
USART_CTRL3
0x14
0x0000
USART_GDIV
0x18
0x0000
12.12.1 Status register (USART_STS)
Bit
Register
Reset value
Type
Description
Bit 31: 10 Reserved
0x000000
resd
Forced 0 by hardware.
Bit 9
CTSCF
0
rw0c
CTS change flag
This bit is set by hardware when the CTS status line
changes. It is cleared by software.
0: No change on the CTS status line
1: A change occurs on the CTS status line.
Bit 8
BFF
0
rw0c
Break frame flag
This bit is set by hardware when a break frame is detected.
It is cleared by software.
0: Break frame is not detected.
1: Break frame is detected.
Bit 7
TDBE
1
ro
Transmit data buffer empty
This bit is set by hardware when the transmit data buffer is
empty. It is cleared by a USART_DT register write
operation.
0: Data is not transferred to the shift register.
1: Data is transferred to the shift register.
Bit 6
TDC
1
rw0c
Transmit data complete
This bit is set by hardware at the end of transmission. It is
cleared by software. (Option 1: read access to
USART_STS register followed by a USART_DT write
operation; Option 2: Write “0” to this bit )
0: Transmission is not completed.
1: Transmission is completed.
Bit 5
RDBF
0
rw0c
Receive data buffer full
This bit is set by hardware when the data is transferred
from the shift register to the USART_DT register. It is
cleared by software. (Option 1: read USART_DT register;
Option 2: write “0” to this bit)
0: Data is not received.
1: Data is received.