AXIOMTEK AX10445 Series, Руководство пользователя

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AX10445 Module Series User
’
s Manual
Technical Reference
13
C h a p t e r 3
Technical Reference
3.1 UART Register Description
This section contains a brief description of the programmable
registers based on the settings of the DIP switches.
In data transmissions from one device to another, an
asynchronous serial communication is preferred. Serial
communication is cheaper than parallel as it requires fewer
data lines. Also, the asynchronous mode of transmission
makes much less demand on hardware because there is no
need for special hardware to maintain synchronism between
the transmitter and the receiver. In asynchronous
communication, data, usually referred to as character, are
transmitted independently. Each byte of data transmitted by
the serial port uses the following sequence of signals:
1. One start bit (the start bit signals the beginning of the
transmission of a new byte by driving the line low for
one cycle).
2. Eight data bits (seven in some situations).
3. Parity bit (if supplied, checks for errors in transmission).
4. One or two stop bits (it does not matter if 1 or 2 stop
bits are used, so long as both the transmitting port and
the receiving port use the same number).
An example of single byte asynchronous transmission format
is shown in Figure 3.
Parity
bit
Data bits
Start
bit
LSB MSB
Stop
bits
Start Start Start Start Stop Stop Stop Stop