Compaq 850 manual INPUT/OUTPUT Interfaces, Enhanced IDE Interface, IDE Programming

Technical Reference Guide

Chapter 5

INPUT/OUTPUT INTERFACES

5. Chapter 5 INPUT/OUTPUT INTERFACES

5.1INTRODUCTION

This chapter describes the standard (i.e., system board) interfaces that provide input and output (I/O) porting of data and specifically discusses interfaces that are controlled through I/O-mapped registers. The following I/O interfaces are covered in this chapter:

♦	Enhanced IDE interface (5.2)	page 5-1
♦	Diskette drive interface (5.3)	page 5-4
♦	Serial interfaces (5.4)	page 5-8
♦	Parallel interface (5.5)	page 5-11
♦	Keyboard/pointing device interface (5.6)	page 5-16
♦	Universal serial bus interface (5.7)	page 5-22
♦	Audio subsystem (5.8)	page 5-26
♦	Network support (5.9)	page 5-33

5.2ENHANCED IDE INTERFACE

The enhanced IDE (EIDE) interface consists of primary and secondary controllers integrated into the 82801 ICH2 component of the chipset. Two 40-pin IDE connectors (one for each controller) are included on the system board. Each controller can be configured independently for the following modes of operation:

♦Programmed I/O (PIO) mode – CPU controls drive transactions through standard I/O mapped registers of the IDE drive.

♦8237 DMA mode – CPU offloads drive transactions using DMA protocol with transfer rates up to 16 MB/s.

♦Ultra ATA/100 mode – Preferred bus mastering source-synchronous protocol providing transfer rates of 100 MB/s.

NOTE: These systems include 80-conductor data cables required for UATA/66 and /100 modes.

5.2.1 IDE PROGRAMMING

The IDE interface is configured as a PCI device during POST and controlled through I/O-mapped registers at runtime.

Compaq Deskpro EXS and Workstation 300 Personal Computers 5-1

Featuring the Intel Pentium 4 Processor

First Edition - December 2000