Intel 80C196NU ユーザーズマニュアル

8-1

A serial input/output (SIO) port provides a means for the system to communicate with external
devices. This device has a serial I/O (SIO) port that shares pins with port 2. This chapter describes
the SIO port and explains how to configure it. Chapter 7, “I/O Ports,” explains how to configure
the port pins for their special functions. Refer to Appendix B for details about the signals dis-
cussed in this chapter.

The serial I/O port (Figure 8-1) is an asynchronous/synchronous port that includes a universal
asynchronous receiver and transmitter (UART). The UART has one synchronous mode (mode 0)
and three asynchronous modes (modes 1, 2, and 3) for both transmission and reception.

The serial port receives data into the receive buffer; it transmits data from the port through the
transmit buffer. The transmit and receive buffers are separate registers, permitting simultaneous
reads and writes to both. The transmitter and receiver are buffered to support continuous trans-
missions and to allow reception of a second byte before the first byte has been read.

SP_CON

SP_STATUS

SBUF_TX

SBUF_RX

Receive Shift Register

Transmit Shift Register

RXD

TXD

Control Logic

Baud Rate

Generator

TI

RI

Interrupts

T1CLK

MSB

1

0

Internal

Data

Bus

SP_BAUD

A3070-02

Internal

Clock

Signal

Prescale

(

÷

2

)

SP_CON.6

Note: The prescale circuitry is unique to the 80C196NU.