
Rev. 1.00
441 of 486
July 31, 2018
32-Bit Arm
®
Cortex
®
-M0+ MCU
HT32F50231/HT32F50241
21 Universal Synchronous
Asynchronous Receiver T
ransmitter (USART)
Features
▄
Supports both asynchronous and clocked synchronous serial communication modes
▄
Full Duplex Communication Capability
▄
Programming baud rate clock frequency up to (f
PCLK
/16) MHz for asynchronous mode and
(f
PCLK
/8) MHz for synchronous mode
▄
IrDA SIR encoder and decoder
●
Support of normal 3/16 bit duration and low-power (1.41 ~ 2.23 μ
s) durations
▄
Supports RS485 mode with output enable
▄
Auto hardware flow control mode – RTS, CTS
▄
Fully programmable serial communication functions including:
●
Word length: 7, 8 or 9-bit character
●
Parity: Even, odd or no-parity bit generation and detection
●
Stop bit: 1 or 2 stop bits generation
●
Bit order: LSB-first or MSB-first transfer
▄
Error detection: Parity, overrun and frame error
▄
FIFO:
●
Receive FIFO: 8 × 9 bits (max. 9 data bits)
●
Transmit FIFO: 8 × 9 bits (max. 9 data bits)
Functional Descriptions
Serial Data Format
The USART module performs a parallel-to-serial conversion on data that is written to the transmit
FIFO registers and then sends the data with the following format: Start bit, 7 ~ 9 LSB/MSB first
data bits, optional Parity bit and finally 1 ~ 2 Stop bits. The Start bit has the opposite polarity of the
data line idle state. The Stop bit is the same as the data line idle state and provides a delay before
the next start situation. Both the Start and Stop bits are used for data synchronization during the
asynchronous data transmission.
The USART module also performs a serial-to-parallel conversion on the data that is read from the
receive FIFO registers. It will first check the Parity bit and will then look for a Stop bit. If the Stop
bit is not found, the USART module will consider the entire word transmission to have failed and
respond with a Framing Error.