@head: Max’s Chips and Dips: Excitement Mounts!

@deck: New book features virtual computer-calculator

@text: Way back in those mists of time we used to call the 1970s, when I was a bright-eyed college student, I used to avidly read the UK electronics hobbyist magazine Practical Electronics. Ah, how well I remember drooling over the adverts for one of the early home computers called the NASCOM1 with its whopping 1K of ROM and 1K of RAM. Sad to relate, it was way outside my budget at the time, so I was only able to dream of playing with the little scamp.

Now, of course, we have access to machines whose capabilities would have made our eyes water in those days of yore. While I love the processing power and graphics capabilities of today’s computers, however, I miss the relative simplicity and the fun associated with the simple 8-bit microprocessors of yesteryear.

Quite apart from anything else, I sometimes wonder how newcomers to the industry learn how computers actually work. By this, I don’t mean how to use computers (even today’s kids think nothing of creating a school report in Word or throwing a PowerPoint presentation together), but rather how they are actually performing their magic.

It was for this reason that I and my mate Alvin recently finished a book called “How Computers Do Math” (so recently, in fact, that it’s poised to roll off the printing presses as I pen these words. As part of this project we designed a really simple 8-bit microprocessor featuring a very rudimentary instruction set (add, subtract, shift, rotate, AND, OR, XOR, etc). Next, we designed a simple microcomputer system that combines our microprocessor with some ROM, RAM, and input/output (I/O) ports. Finally, we connected this little rascal to a calculator front panel containing buttons and an alphanumeric display (the buttons are connected to one of the microcomputer’s input ports and the display is driven by one of its output ports).

But the really cool thing about all of this is that we actually implemented our computer-calculator as a virtual machine that comes on the CD-ROM accompanying the book. This little rapscallion – which we call the DIY Calculator (where “DIY” stands for “Do It Yourself,” of course) – comes equipped with a complete development environment including an assembler, CPU register display, and so forth. Once you’ve created a program in our assembly language, you can assemble it, load the ensuing machine code into the DIY Calculator, single-step and run your program, set breakpoints, and so forth. The idea is that the book walks readers through a series of interactive laboratories until we end up with the program (in our assembly language) for a simple four-function calculator.

Strange as it may seem, creating assembly-level programs for the DIY Calculator is way more fun than you might expect. Apart from anything else, it’s great to absolutely understand everything that the (virtual) computer is doing. And it’s really cool when you perform the first “2 + 2” type calculation using a calculator program you’ve written yourself and you actually get “4” (or thereabouts).

But we digress … I very much hope you enjoy this issue of iDESIGN. Please feel free to email me with your thoughts and comments on the material in this issue, and also let me know if you have any ideas for technical articles or viewpoints for future issues of iDESIGN (you can drop me a line at ). Until next time, have a good one!

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<P<B>By Clive (Max) Maxfield.</B> Author of "Bebop to the Boolean Boogie (An Unconventional Guide to Electronics)" and "The Design Warrior's Guide to FPGAs (Devices, Tools, and Flows)", Max is also the co-author of <a href="http://service.bfast.com/bfast/click?bfmid=37920629&siteid=41516738&bfpage=product_discount&isbn=0471732788" target="_blank">How Computers Do Math</a> (ISBN: 0471732788) featuring the pedagogical and phantasmagorical virtual <a href="http://www.DIYCalculator.com" target="_blank">DIY Calculator</a>. In addition to being a hero, trendsetter, and leader of fashion, Max is widely regarded as being an expert in all aspects of computing and electronics (at least by his mother). Max was once referred to as "an industry notable" and a "semiconductor design expert" by someone famous who wasn't prompted, coerced, or remunerated in any way.