PixArt Imaging Inc.

PAC107

All rights strictly reserved any portion in this paper shall not be reproduced, copied or transformed to any other forms without permission.

36

PixArt Imaging Inc.

V1.4, Aug, 2005

4.3 SERIAL I/O PORT

Both synchronous and asynchronous communication modes are provided in the serial I/O

port. It operates as UART in three full-duplex modes (modes 1, 2, and 3). Asynchronous

transmission and reception can occur simultaneously and at different baud rates. The serial

port also operates in a single synchronous mode (mode 0).

Mode 0 – Synchronous mode: operates at a single baud rate.

Mode 1 - operate over a wide range of baud rate generated by timer 1 and timer 2.

Mode 2 - operates at two baud rates.

Mode 3 - operate over a wide range of baud rates generated by timer 1 and timer 2.

Asynchronous modes, Pin-TXD: transmits. Pin-RXD: receives.

Synchronous mode (mode 0), Pin-TXD: clock output. Pin-RXD: sends and receives data.

SBUF holds received data byte and data to be transmitted, actually consists of two buffers.

The receive shift register allows reception of a second byte before the byte be read from

SBUF. And the 1

sets interrupt bits TI and RI for transmission and reception, respectively. Both of these two

bits share a same interrupt vector.

Watchdog Timer 1

Reset

RWT

EWT

XTAL 1

overflow

Counter

WD1-1 WD1-0

Counting

00

0

0

1

1

11

17

2

20

2

23

2

26

2

WDTRSTFg

0000000h