Nations Technologies Inc.
Tel
:
+86-755-86309900
:
Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
457
/
631
Figure 22-3 Word length = 9 setting
Transmitter
After the transmitter is enabled, the data entered into the transmit shift register is sent out through the TX pin.
Idle frame
Setting USART_CTRL1.TXEN will cause the USART to transmit an idle frame before the first data frame.
Character send
Idle frames are followed by characters sent. Each character is preceded by a low start bit. The transmitter sends 8-bit
or 9-bit data according to the configuration of the data bit length, with the least significant bit first. If
USART_CTRL1.TXEN is reset during a data transfer, it will cause the baud rate counter to stop counting and the
data being transferred will be corrupted.
Stop bit
The characters are followed by stop bits, the number of which can be configured by setting USART_CTRL2.
STPB[1:0].
Table 22-1 Stop bit configuration
USART_CTRL2.STPB[1:0]
Stop bit length (bits)
functional description
00
1
default
01
0.5
Receiving in Smartcard mode
10
2
General USART mode, single-wire mode and modem mode.
11
1.5
Transmitting and receiving in Smartcard mode
9-bit word length , 1 stop bit
Data frame
Clock
Stat
bit
bit0
bit1
bit2
bit3
bit4
bit5
bit6
bit7
bit8
Stop
bit
**
Data frame
Idle frame
Break frame
Start
bit
Start
bit
bit8 can be the parity bit
Start
bit
Stop
bit