GD32W51x User Manual
591
18.3.
Function overview
The interface is externally connected to another device by the main pins listed in
Description of USART important pins
.
Table 18-1. Description of USART important pins
Pin
Type
Description
RX
Input
Receive Data
TX
Output I/O (single-
w ire/smartcard mode)
Transmit Data. High level When enabled but
nothing to be transmitted
CK
Output
Serial clock for synchronous communication
nCTS
Input
Clear to send in Hardw are flow control mode
nRTS
Output
Request to send in Hardw are flow control mode
Figure 18-1. USART module block diagram
CPU/DMA
R
W
IrDA
Block
TX
SW_RX
RX
CK Controler
Transmit
Shift
Register
Receive
Shift
Register
USART Control
Registers
CK
Transimit
Controler
Hardware
Flow
Controler
nRTS
nCTS
Receiver
Controler
USART
Address
Wakeup Unit
USART Guard Time
and Prescaler Register
USART Status Register
USART Interrupt
Controler
/USARTDIV
/8*(2-
OVSMOD)
USART Baud
Rate Register
UCLK
Transmitter
clock
Receiver
clock
Write
Buffer
Read
Buffer
Read FiFO
18.3.1.
USART frame format
The USART frame starts with a start bit and ends up with a number of stop bits. The length
of the data frame is configured by the WL bit in the USART_CTL0 register. The last data bit
can be used as parity check bit by setting the PCEN bit of in USART_CTL0 register. When
the WL bit is reset, the parity bit is the 7th bit. When the WL bit is set, the parity bit is the 8th
bit. The method of calculating the parity bit is selected by the PM bit in USART_CTL0 register.