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Lesson 1: Introduction

by David G. Larsen, Peter R. Rony, and Jonathan A. Titus

An Introduction to Microprocessors

WE INDICATED last month that you can readily interface , using asynchronous serial techniques, any laboratory instrument with moderate data rates to anyone of a variety of different devices, including a teletypewriter, a minicomputer, a programmable calculator, a microprocessor, a time share terminal, a cathode ray tube terminal, or even a large computer. In this column, we would like to discuss microprocessors, probably the most exciting recent development in the entire field of electronics, and to briefly compare them to programmable calculators for typical laboratory applications.

The best description of what a microprocessor is, and isn't, has been given by Laurence Altman in a recent issue of Electronics 1: "A microprocessor is not a computer but only part of one. To make a computer out of a microprocessor requires the addition of memory for its control program, plus input and output circuits to operate peripheral equipment ... What a microprocessor is, then, is the control and processing portion of a small computer or microcomputer. Moreover, it has come to mean the kind of processor that can be built with LSI MOS, or more recently, Bipolar, circuitry, usually on one chip. Like all computer processors, microprocessors can handle both arithmetic and logic data in bitparallel fashion under control of a program. But they are distinguished both from a minicomputer processor by their use of LSI with its lower power and costs, and from other LSI devices (except calculator chips) by their programmable behavior."
Read More: Adobe Acrobat PDF FileAn Introduction To Microprocessors.pdf [32.6KB]

What's Next? Microprocessors
WITH THIS twelfth column in the "Computer Interfacing" series, we would like briefly to list the topics covered in previous columns and to describe the direction that this series will take in subsequent issues.

Beginning with the April 1974 issue of American Laboratory, we have discussed:
The advantages of asynchronous serial data transmission
The precision of digital data transmission
Digital codes-binary, BCD, and ASCII
Real-time data acquisition, control, and logging
Interfacing with asynchronous serial
How one gets started in digital electronics
The universal asynchronous receiver/ transmitter (UART)
First-in first-out (FIFO) memories
Serial data exchange modules
Half and full duplex current loops
An introduction to microprocessors
With the exception of the EIA RS-232C interface standard, which we will cover in a future column, the above topics summarize the most important aspects of interfacing via the use of asynchronous serial techniques.
Read More: Adobe Acrobat PDF FileWhats Next.pdf [53.6KB]

Microprocessors: where do they fit?
IN THIS COLUMN, we would like to discuss what a microprocessor is and how it fits into the general scheme of controllers and computers that exists today. Eadie! has defined the term data processor as "A digital device that processes data. It may be a computer, but in a larger sense it may gather, distribute, digest, analyze, and perform other organization or smoothing operations on data. These operations, then, are not necessarily computational. Data processor is a more inclusive term than computer." A microprocessor is a single integrated circuit chip that contains at least 75% of the power of a computer. It usually cannot do anything without' the aid of support chips and memory and therefore can be distinguished from a microcomputer, which is a full operational system based upon a microprocessor chip. The microcomputer contains memory, latches, counters, input/output devices, buffers, and a power supply, in addition to the microprocessor chip. A microcomputer may be a "black box" with only a single switch: OPERATE/RESET. The 8080 microprocessor chip, a 4o-pin LSI chip, is shown in Figure 1. A typical system based upon this chip is shown in Figure 2; the 8080 chip is located on the CPU board on the left.
Read More: Adobe Acrobat PDF FileMicroprocessors.pdf [101KB]

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