Intel 210200-002 manual Chapter Introduction

CHAPTER 1

INTRODUCTION

WHAT ISTHE 8088?

An iAPX 88* Microcomputer system has the three main elements typical to most compu- ter systems: The central processor (8088 CPU), the input/ output ports, and memory (Fig. 1-1).

The iAPX 88 is unique in many ways, how- ever, and the remainder of this chapter describes the basics of the 8088 CPU and' iAPX 88 Microcomputer systems.

One of the most unique aspects of the 8088 is shown in the simple block diagram (Fig. 1-2). The 8088 combines the powerful resour- ces of a l6-bit microprocessor internal architecture with an easy-to-use 8-bit bus interface. The bus interface is easy for hard- ware designers because it is similar to other 8-bit microprocessors. In particular, most of the bus lines are identical in function to the popular 8085A. Those designers who have interfaced memories and I/O devices to 8085

*iAPX refers to the entire microsystem built around the 8088 CPU.

microprocessors will find it easy to incorpo- rate the 8088 into new systems.

16-BIT POWER ON AN 8-BIT BUS

The 16-bit internal architecture provides 16- bit wide registers, data paths, a l6-bit ALU, and a set of powerful16-bit instructions iden- tical to the ones found in the popular l6-bit 8086 microprocessor.

With this new internal architecture, the 8088 has features that were never before available with an 8-bi~microprocessor. Among these features is a 20-bit memory address range and a l6-bit input/ output port address range for I/O cycles. This gives the 8088 a full megabyte (l,OOO,OOO-plus bytes) of memory

16-BIT ~

INTERNAL8085A ARCHITECTURE ~ BUS INTERFACE

BRINGS 16-BIT CAPABILITY TO 8-BIT

ENVIRONMENTS

Figure 1-2. 8088 CPU

MEMORYI/O

CPU

MODULE

CONTROL BUS

Figure 1-1. Microcomputer Block Diagram

1-1