[editor : Carl T. Helmers Jr.] [publisher : Virginia Peschke, Manfred Peschke] [art : Mary Jane Frohlich, Bill Morello] #Magazine

#Abstract

Have you ever looked through the surplus catalogs and wondered whether those memory core planes and stacks advertised could be used for anything other than tea strainers? For theory and practical information on Coincident Current Ferrite Core Memories turn to James R Jones' article.

Bruce A Anderson describes his experiences Assembling a Sphere in his review of what rolled out of the production facilities in Bountiful UT last fall.

One of the most important questions people ask is "how do I learn about what a computer does? " One way to help out friends who are trying to get into the swing of things with programming is to implement a version of Charles Howerton's Educator-8080 program so that they can interactively Explore an 8080 with Educator-8080.

A thorough explanation of the instruction set should accompany any product intended for wide distribution. An example of such an explanation is provided by Nat Wadsworth's Machine Language Programming for the "8008" and Similar Microcomputers, a manual which is sold by Scelbi Computer Consulting Inc. In this issue is the first of three direct reprints from that manual: Chapter 1 which describes the 8008 instruction set.

One of the problems of interfacing unknown electronics is figuring out how to accomplish the match. Ken Barbier built a character generator, went out and bought a TV set, then faced the problem of building a driver for the TV. The result was The "Ignorance is Bliss" Television Drive Circuit.

While not really promising the entire big blue sky, when you Put the "Do Everything" Chip in your Next Design you'll end up with a computer that has five separate programmable real time clocks, standard serial communications data rates from 110 baud to 9600 baud, automatic generation of an 8080's RST n interrupt vectors, an 8 bit parallel output and an 8 bit parallel input port. Turn to Robert Baker's latest article to find out about this nifty chip.

Robert Suding asks "Why Wait?" in a rhetorical fashion, and proceeds to demonstrate his schematic of a fast cassette interface which uses software and a one bit 10 port to implement an audio cassette system.

What's it like to be isolated from bountiful US surplus markets? In a sense, it means a relative isolation from modern LSI products, as Dr Michael N Hayes reports on his experiences in Tokyo and Manila in December 1975. Read his report on Surplus Electronics in Tokyo and Manila in this issue.

There are many ways to wire a circuit. The most common manufacturing method is printed wiring. But you can also Make Your Own Printed Circuits at home, using techniques described by James Hogenson in his article.

One of the most interesting applications of computers is in the area of graphic outputs. Using a vector CRT or a plotter, drawing pictures of mathematically generated abstractions or simple cartoons can be the beginning of hours of fun. But A Plot Is Incomplete Without Characters so Richard J Lerseth concocted some software described in his article on the generation of an ASCII character set (or special characters) for a plotter or vector display device.

[author : Carl Helmers] #Edito

Extract : «  One item which backyard entrepeneurs tend to overlook is the fact that the hardware and software engineering of computer systems which are both manufacturable and marketable is a complex process. I had a taste of the problems of working out the details of a system about the time BYTE became a much more compelling personal project in mid 1975. I quickly dropped any illusions of converting the designs I was working upon at that time into a manufactured product when BYTE with its own intricate and unique challenges came into being. But the period of time spent thinking about the problem of engineering a salable combination of hardware and software leaves an impression. [...]  »

TABLE OF CONTENTS

[theme : Recycling] [author : Jones] #HowItWorks #Electronic #Memory #Storage

Extract : «  Have you ever looked through the surplus catalogs and wondered whether those memory core planes and stacks advertised could be used for anything other than tea strainers? How are they supposed to work, and what kind of circuitry is required? Could you troubleshoot and repair that surplus core memory and drive electronics? What good is a core stack without data? Is it a worthwhile project to build a memory system around a core stack? [...]  »

[theme : Software] [author : Howerton] #Listing #Assembly #Education #Programming

Extract : «  What Is an Educator?

Educator-8080 was designed as a classroom instruction aid for a microprocessor programming course. The principal design goals were to develop a system which would illustrate the architecture of the machine and the effect of the execution of various instructions. For example, the reader might ask to what use the logical EXCLUSIVE OR function may be put in an 8080. This function, which operates on each bit, has a value of 1 if either of the two operands or arguments, but not both, has a value of 1; otherwise it has a value of 0. The Educator-8080 can simply illustrate this function. [...]  »

[theme : Hardware] [author : Barbier] #Electronic #Display

Extract : «  I had not yet heard of BYTE magazine, or hams building such hardware, when I built my CRT terminal (a computerhead's term for "TV typewriter") in the fall of 1975. I didn't even own a TV set! Two situations resulted: I had to buy a new all solid state TV, and I didn't have any idea how to interface with it. I knew approximately what it took to create horizontal and vertical sync, but had no idea whether levels, pulse widths, and frequencies would be noncritical. I was delighted, therefore, when my sync generator worked just fine the first time I patched its output across the video driver base resistor using the circuit as shown in figure 1. My big fat TTL level pulses swamp the AGC circuity so effectively that normal signals and noise from the TV IF just disappeared and I had nothing to switch off! [...]  »

[theme : Hardware] [author : Suding] #Electronic #Interface #Storage

Extract : «  This cassette interface does not have a ±30% speed tolerance. The design requires ±12V and +5 V to run. A good quality recorder must be used, along with excellent quality tapes. Careful adjustments are required.

So why use it? Well, it works! It's dependable. And it's fast. In contrast, the proposed BYTE standard cassette interface runs at 300 Baud. A Teletype paper tape reads @ 110 Baud. I have 24 K on my system. How long would it take me to completely load my system (not including any Bootstrap Loader operations)? [...]  »

[theme : Review] [author : Anderson] #ComputerKit #Build

Extract : «  Sometime in July an advertisement was being run in several magazines which offered a complete computer system for only $650. Up until this time I had been interested in microprocessors but had not even remotely considered buying one. I sent off for the brochure anyway. After reading the claims about the system, I quickly convinced myself that I could justify the expense as an educational expense; so I sent off a check to Bountiful UT where resides Sphere Corporation, the company making these claims. [...]  »

[theme : Software] [author : Wadsworth] #HowItWorks #Microprocessor #Method #Assembly

Extract : «  The '8008' microprocessor has quite a comprehensive instruction set that consists of 48 basic instructions, which, when the possible permutations are considered, result in a total set of about 170 instructions. [...]  »

[theme : Hardware] [author : Baker] #HowItWorks #Microprocessor #Interface

Extract : «  The TMS-5501 is a multifunction, IO controller available from Texas Instruments in a 40 pin dual in line package. It provides an asynchronous communications interface with programmable data rate, a parallel data IO buffer, interrupt control logic, and five programmable interval timers in a single chip. Although designed specifically for use with a TMS-8080 central processor, it may be used with almost any other microprocessor as described in this article. Figure 1 shows a functional block diagram of the TMS-5501 and table 1 lists the pin assignments along with a brief description of each pin. [...]  »

[theme : Travelogue] [author : Hayes] #Experience #TradeAndLaws

Extract : «  This article is a brief summary of some of my experiences, opinions, and observations while searching for and buying surplus electronic components in Tokyo, Japan, during October 1975; and in Manila, Republic of the Philippines, during November 1975. Perhaps this information will be of interest to US buyers and hobbyists for comparison purposes or in case they have the opportunity to visit these places. [...]  »

[theme : Hardware] [author : Hogenson] #Electronic

Extract : «  The widespread commercial use of printed circuits in electronic equipment began a few decades back when engineers started looking for more efficient wiring techniques to replace laborious hand-wiring methods. One of the first methods tried was to deposit (in other words, to print) a conductive ink pattern on a base of insulating material. The original method, printing, gave its name to all subsequent methods. Today, the term printed circuit refers to any electrical circuit in which individual wire lead connections have been replaced by a two dimensional conductive pattern bonded to an insulating base material. [...]  »

[theme : Software] [author : Lerseth] #Printer #Algorithm #Glossary

Extract : «  As computer hobbyists, a number of us will sooner or later play around with graphics using vector CRTs or XY pen plotters; but very few of us will be willing to pay the high price of a number of copyrighted plotting packages available today through computer graphics houses. Besides, most of us will not want to miss the opportunity of creating our own packages. [...]  »

#Graphics

#Association

#Book

Extract : «  Microprocessors and Microcomputers by Branko Soucek. Published by John Wiley and Sons, New York. [...]  »