[editor : Carl T. Helmers Jr.] [publisher : Virginia Peschke Londner] [art : Wai Chiu Li, Dorothy Shamonsky, Ellen Shamonsky] #Magazine
#Abstract
With good reason, many computers these days have no front panel for low level data entry and display. But sometimes a real time pattern "signature" of an exec uting program can be useful. This month, Steve Ciarcia shows how to build A Penny Pinching Address State Analyzer which can be used with an X-Y oscilloscope to monitor the address bus of your computer in real time. If you build this state ana lyzer, you'll see a unique pattern corresponding to each "steady state" loop of an executing program.
When is a personal computer more than a personal computer? When it is plugged into a network of personal computers for purposes of message transfer via phone lines, sharing of programs, and perhaps even execution of multiple player logical games. In this issue, Mike Wilber begins a three part series of articles on the concept of CIE Net: A Design for a Network of Community Information Exchanges. Page 14
Are you looking for a driver for your model railroad's roundhouse turntable? Perhaps you need some motive power for a robot. For generation of controlled rotary motion, stepper motors as described in Robert E Bober's article Taking the First Step are essential. He provides readers with valuable background information on these fascinating mechanical outputs for personal computers. Page 35
When is a boat like a raft of bottles? When it is conceptually chopped into many individual buoyancy elements for the purpose of simulating its performance on a choppy water surface? In this issue Stephen P Smith continues his series of articles on the simulation of motion in personal computers with a discussion of motion of extended objects in Simulation of Motion, Part 4: Extended Objects, Applications for Boating. Turn to Stephen's article for more details and a BASIC program which simulates rolling or pitching motions of an arbitrary boat hull cross section. Page 42
Interactive editing is enhanced when a light pen can be used to zero in on a text location . See how to Add a $3 Light Pen to Your Video Display using the combination of hardware and software techniques provided by John Webster and John Young in this issue. Page 52
If you own a KIM-1 computer, here's an answer to the perpetual problem of entering and debugging large programs. Dan Fylstra's article SWEETS for KIM shows you how to add a mini text editor and assembler that fits in the KIM's 1 K bytes of programmable memory and still leaves room for your programs. Page 62
In past BYTEs Mike Wilber and Dave Fylstra have suggested the concept of a "Community Information Exchange." Read Jeff's Personal Computers in a Distributed Communications Network for a discussion of some of the technological (and political) aspects of such a concept, which is well within reach of our present personal computing hardware and software. Page 80
Last month, we began Ernest W Kent's series of articles on The Brains of Men and Machines. The discussion continues this month with the next installment, How the Brain Controls Output. Aspiring robotics hackers will find this to be an invaluable background input on the information systems found in nature, which can serve as a source for ideas on new information systems designed by humans. Page 84
The minifloppy has arrived, as many readers probably know, and its popularity is increasing with time. If you'd like to take advantage of its low cost, then read David Allen's Minifloppy Interface and try your hand at adding a minifloppy to your system. Page 114
Entomology is the study of bugs. Gary McGath provides some introductory insight into various species of programming bugs, and some general design guidelines to prevent their occurrence in his background article on Programming Entomology. Page 162
Have you ever needed to experiment with a circuit and ended up rewiring it again and again? Wouldn't it be nice to have a program that simulated the circuit and could be easily modified to change the parameters? Read Robert Grappel's A Simple Digital Filter and find out all about filter simulation on your own computer. Page 168
TABLE OF CONTENTS
[theme : Hardware] [author : Ciarcia] #Electronic #Display
Extract : « Three years ago I got my first home microcomputer, a Scelbi 8H. This was before the advent of widespread interest in personal computers and it was naturally based upon the Intel 8008 processor. Back then I was satisfied with the tedious task of hand toggling a program into the computer and watching the front panel memory address and data buffer lights twinkle, signifying that the program was executing something. After that I bought more memory which consisted of 2102s. That gave me enough space to write only the simplest of monitor programs, again using the front panel as the display medium. At the end of its evolution, my 8008 did have a rudimentary video display and 300 bps cassette interface; but, if there was one major physical characteristic of the first generation home computers, it was the predominance of the front panel display and data entry switches. The concept of the integrated home computer "system" was yet to be seen. A computer required display and data entry switches if it was to be powered up and exercised. Additional IO devices such as video displays and keyboards were luxuries. [...] »
[theme : Hardware] [author : Bober] #Electronic #Interface #Robotics
Extract : « Stepper motors are coming down in cost now to the point where they can be designed into home projects. They are a natural for variable speed or precise angular movement controlled by a microprocessor.
All stepper motors convert electrical pulses into mechanical movements. In this article I will be referring to permanent magnet stepper motors such as those shown in photo 1. This type of motor is classified as either a pulse stepper or a logic stepper. Pulse steppers usually are unidirectional and have one center tapped coil. Logic steppers are multicoil and bidirectional. I will confine my drive controls to the bidirectional logic stepper. [...]
[...] BIBLIOGRAPHY
1. Intel Corporation, 8080 Microcomputer Systems User's Manual, 1975.
2. Bober, Robert E, "Stepperdrive Circuit Simplifies Printer Control," EDN, April 5 1976, page 114.
3. Helfrick, Albert, "8 bit Frequency Source Suited for Microprocessor Control," EDN, September 20 1976, page 116.
4. Webster, John and Simpson, William, Software Design for Microprocessors, Texas Instruments Learning Center, 1976.
5. Baker, Robert, "Put the 'Do Everything' Chip in Your Next Design," BYTE, July 1976, page 40.
6. Shogren, Carl, "The AC/PM Motor: A Drive Whose Time Has Come," Machine Design , June 27 1974, page 83.
7. Hollis, Ralph, "Newt: A Mobile Cognitive Robot," BYTE, June 1977, page 36 (stepper motor discussion).
8. Guilder, J, "Focus on Stepping Motors," Electronic Design, October 25 1977, page 48 (an excellent tutorial). »
[theme : Software] [author : Smith] #Simulation #Listing #BASIC
Extract : « Have you ever wondered why the shapes of boat hulls differ so widely? Boating enthusiasts know that certain designs will be best in lakes and rivers, and certain others in open seas. Some boats are much roomier than others; some are safer in rough water; but what penalties in stability and riding comfort might you pay for the extra room or seaworthiness? The motion of a boat depends on its response to the variety of waves it encounters. These motions can be simulated on your personal computer. You can determine how a given design will respond to any sea condition. The basic equations for stepping speed and position into the future will still apply, as they were discussed in the earlier articles of this series; but you'll also need some new techniques. As you implement this simulation, you'll discover that forces in a linear degree of freedom can also produce moments and their resulting motion in an angular degree of freedom. In this article, I'll show how that interaction is handled. I'll also introduce the concept of distributed forces, and a numerical technique to handle them. Although developed for a boating application, these new ways of calculating forces should find use in updating many of our previous simulations. [...] »
[theme : Hardware] [author : Webster-Young] #Electronic #Interface #LightPen #DataEntry
Extract : « The use of a light pen can greatly facilitate entry of display characters on your video display. The layout of complex game boards, charts and graphs, or character editing can be accomplished more quickly and easily if you have the ability to add or delete characters anywhere on the screen without first having to position the cursor. This article describes the design and construction of a very inexpensive light pen and driver program to accomplish this function with a Processor Technology VDM-1. [...] »
[theme : Software] [author : Fylstra] #Listing #Assembly #Programming
Extract : « If you would like to experiment with microcomputers on a limited budget, the MOS Technology KIM-1 is an excellent choice. For $245, it comes preassembled with, among other things, a 6502 microprocessor, a read only memory monitor, an audio cassette interface, 1 K bytes of programmable memory, and its own special peripheral: a 23 key keyboard plus a 6 digit LED display. The monitor lets you load a machine language program byte by byte from the keyboard, and once loaded the program can be saved on tape via the audio cassette interface. The KIM-1 manual shows how you can "hand-translate" an assembly language program into the absolute hexadecimal form required for keyboard entry.
This is fine for very small programs, but the process of hand translation gets rather tedious after you've assembled a few hundred bytes of code. And, worse, once you've painstakingly worked out all the subroutine call addresses and branch displacements and keyed the whole program in, you invariably find that you've forgotten something. Often, instructions must be inserted or deleted in the middle of the program, which throws everything off by a few bytes.
The obvious solution to this problem is to obtain a text editor and assembler program for the 6502. But, alas, such a program probably needs more than the 1 K bytes of memory provided on the KIM-1, and, more seriously, it requires an alphabetic character terminal device such as a Teletype. What if you can't afford the extra peripherals and memory? Are you doomed to spend most of your microcomputing hours keying in the same program over and over again?
Maybe not. [...] »
[theme : Mass Storage Subsystems] [author : Allen] #Interface #Storage #Electronic
Extract : « Floppy disk drives have been around for some years now; the basic technology of such drives is well proven and the drive designs seem reliable as mass storage for small systems. Having used the standard size floppy for some time, my first reaction to the introduction of the "minifloppy" was to view it as a cute gimmick, since the minifloppy's price had not then dropped in proportion to its performance.
However, after using the minifloppy for a while and having seen the inevitable dropping in price as production expands, I am becoming much more enthusiastic. The reduction in bit rate will make it easier to interface, and the reduction in bit density should make it slightly more reliable in small user environments. Its performance, while reduced, is quite adequate for many applications, especially when its price is taken into account. [One personal computing manufacturer, for instance, markets a dual drive peripheral for their systems at a total of $1000, which is hard to find in a dual drive standard size floppy disk... CH] Its small size and relaxed specifications allow room for more cost cutting than the full-size design. Competitive technologies like bubble memories are perhaps several years away from equivalent costs per bit. It is thus quite appropriate to give serious consideration to the small floppy. [...] »
[theme : Personal Computing Networks] [author : Wilber] #Networks #Initiation
Extract : « Motivation and Background: Why Build a Network?
A good, cheap and practical telecommunication network can be extremely useful to the personal information processing community. It can provide a means by which people exchange programs and files of data. For example, a respectable dictionary can be built by 1000 people who each contribute 20 words. Just as important, a good telecommunication facility can help people talk to one another, for instance, to advertise the presence of a good data file, or to explain just when one technique is superior to another. These considerations and others are explored in more detail in an earlier BYTE article. (See "Homebrewery vs the Software Priesthood," by Wilber and Fylstra, October 1976 BYTE, page 90.)
The need for a personal computer telecommunication network is rapidly becoming inescapable. Now that personal computers are economically feasible, manufacturers are selling cheap reliable systems in astounding quantities to personal users of information processing, each of whom stands to gain from freely shared interactive experience. Already, hobbyist clubs and other, more primitive, information exchanges have sprung up to fill the void. Telecommunication can greatly facilitate the free exchange of ideas and data that currently take place on a limited but increasing scale. [...] »
[theme : Tutorial] [author : Bunce-Schwartz] #Mathematics #Electronic
Extract : « The purpose of this article is to unify the concepts of digital electronics, the graphical representation of set theory and propositional calculus, using Boolean algebra. Our motivation for the background work represented in this article was the design of an encoder for a surplus keyboard. That was as much a problem in set theory and propositional calculus as it was in digital design. [...] »
[theme : Systems] [author : Steinwedel] #Networks #Book
Extract : « Since the first microprocessors became available I have been convinced that their most dramatic applications would be in connection with a large-scale communications network. The economics of a distributed network would suit the individualized structure of personal computing. The combination of many small processors with some way to communicate from one to another clearly has much potential. Already, the processor technology has arrived; but it seems that a simple, inexpensive communications system is not forthcoming. Both the telephone system and cable TV could be technically workable, but require centralized expenditures of large amounts of capital, as well as a political commitment to the application. My argument is that there is an economic and technological short cut to a distributed network through use of the radio spectrum for communications.
This article is speculative, in that new radio spectrum rules would have to come into effect for this network to exist. However, I think the idea is technically feasible, and the political aspects perhaps provide a raison d'etre for a national personal computing organization. Further, the FCC has already validated some of the principles involved. [...] »
[theme : Robotics] [author : Kent] #ArtificialIntelligence #Book
Extract : « With this second article on the brain's output control system, we begin a more detailed look at the mechanisms by which the brain accomplishes some of the functions which robot systems will also be called upon to perform. (A number of the terms which are used in this article were defined and discussed in the first part which began on page 11 last month.) As we reach a more concrete level of description of the brain's operation, we will encounter many points which are not yet entirely resolved, and many questions which are subjects of dispute between competing theories. Since it would seem that the present reader is more likely interested in potential applications of brain architecture than in the exact nature of the debate on fine points of physiology, I will simply present the position which seems to me to be most strongly supported at the present time. I will also make some simplifications where they seem warranted by the intended purpose of these articles. (To atone for these sins, I will also offer a list of references for the reader who is interested in pursuing the subject in greater depth.) [...]
[...] Bibliography
Elementary
Llinas, R, "The Cortex of the Cerebellum," Scientific American , January 1975.
Advanced
Kornhuber, H, "Cerebral Cortex, Cerebellum, and Basal Ganglia: an Introduction to Their Motor Functions," Neurosciences, Third Study Program, Schmitt, F, and Worden, F, eds, MIT Press, Cambridge, 1974. »
[theme : Software] [author : McGath] #Method #Programming
Extract : « An entomologist is a bug expert. When he sees an insect, it isn't just a bug to him (in fact, he will vociferously protest that not all insects are bugs); it has a particular habitat, lifespan, favorite food, and breeding pattern. Nor is his knowledge just academic; he can tell you how to protect yourself from a harmful one by killing it or keeping it away.
The same sort of knowledge is necessary for programming. The skilled programmer knows what kinds of bugs may attack a program, how to track them down, and how to keep them from getting there in the first place. He knows the ways to get at particular bugs, as well as the general treatments which are effective against all of them.
The first thing to realize about bugs is that they don't appear by spontaneous generation. They have a creator, and their creator is the programmer. [...] »
[theme : Hardware] [author : Grappel] #Electronic
Extract : « At first glance, using a computer to build an analog filter seems like the height of overkill. Imagine an analog to digital converter, a microprocessor with memory and peripheral interfaces, a digital to analog converter, and more, just to do the job of a capacitor, a resistor and a coil of wire! People have been building analog filters for years without computers. How can an analog filter be constructed with a digital device like a microcomputer? Digital filtering may be the answer. [...] »
#Association
