Nations Technologies Inc.
Tel
:
+86-755-86309900
:
info@nationstech.com
Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
456
/
631
device through its own TX interface, and the bus is in an idle state before sending or receiving. Frame format is: 1
start bit + 8 or 9 data bits (least significant bit first) + 1 parity bit (optional) + 0.5,1,1.5 or 2 stop bit.
Use the fractional baud rate generator to configure transmit and receive baud rates.
According to the block diagram, when using the hardware flow control mode, the nRTS output and nCTS input pins
are required. When the USART receiver is ready to receive new data, nRTS becomes low level. If nCTS is valid
(pulled to a low level), the next data is sent, otherwise the next frame of data is not sent.
When using synchronous mode, the CK pin is required. The CK pin is used for clock output for synchronous transfers.
Clock phase and polarity are software programmable. During the start and stop bits, the CK pin does not output clock
pulses.The CK pin is also used when using smart card mode.
USART frame format
The start bit of the data frame is low.
The word length can be selected as 8 or 9 bits by programming the USART_CTRL1.WL bits, least significant bit
first.
The stop bit of the data frame is high.
An idle frame is a complete data frame consisting of '1's, including the start bit. followed by the start bit of a data
frame containing the data .
A break frame is a complete data frame consisting of '0's, including the stop bit. at the end of the break frame, the
transmitter inserts 1 or 2 more stop bits ('1') to acknowledge the start bit.
Figure 22-2 Word length = 8 setting
8-bit word length ,1 stop bit
Data frame
Stat
bit
Start
bit
Start
bit
Stop
bit
Stop
bit
bit7 can be the parity bit
Start
bit
**
Clock
bit0
bit1
bit2
bit3
bit5
bit4
bit6
bit7
Data frame
Idle frame
Break frame