CHAPTER 7

SERIAL I/O (SIO) PORT

A serial input/output (SIO) port provides a means for the system to communicate with external devices. The 8XC196MH device has a two-channel serial I/O port that shares pins with ports 1 and 2. (The 8XC196MC and 8XC196MD devices do not have serial I/O ports.) This chapter de- scribes the SIO port and explains how to configure it. Chapter 6, “I/O Ports,” explains how to con- figure the port pins for their special functions. Refer to Appendix B for details about the signals discussed in this chapter.

7.1SERIAL I/O (SIO) PORT FUNCTIONAL OVERVIEW

The serial I/O port (Figure 7-1) is an asynchronous/synchronous port that includes a universal asynchronous receiver and transmitter (UART). The UART has two synchronous modes (modes 0 and 4) and three asynchronous modes (modes 1, 2, and 3) for both transmission and reception.

TI

Interrupts

RI

Internal

Data

Bus

SBUFx_RX

SBUFx_TX

Control Logic

Receive Shift Register

Transmit Shift Register

BCLKx

0

XTAL1

1

RXDx

TXDx

Baud Rate

Generator

SPx_STATUS SPx_CON

MSB

SPx_BAUD

A2774-01

Figure 7-1. SIO Block Diagram

The serial port receives data into the receive buffer (SBUFx_RX) and transmits data from the port through the transmit buffer (SBUFx_RX). The transmit and receive buffers are separate registers, permitting simultaneous reads and writes to both. These buffers support continuous transmissions and allow reception of a second byte before the first byte has been read.

7-1

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Intel 8XC196MC, 8XC196MD, 8XC196MH manual Serial I/O SIO Port Functional Overview, SIO Block Diagram