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FINE–TUNING AN EMBEDDED IDEA

Part 3: Armed and Ready
by Fred Eady

Start ı Retro Rabbit ı Preflight Checklist ı Firmware Developmentı Left Turn, Clyde• Successı Sources and PDF

This is the final installment in this series of articles describing Rabbit Semiconductor and Z-World computing modules. Instead of writing from the familiar confines of the Florida room, this installment is being brought to you from a Gulf shore beach bungalow in the Florida Panhandle. Right now, itıs raining sideways and has been since I arrived. Consequently, Iıve done some TV time that was originally reserved for listening to the surf and watching the gulls and pelicans do some aerial beak fishing.

With rain pounding the ocean-side sliding glass doors, the only "surfing" I can do is with the television remote. I happened upon a History Channel episode featuring the guns of Sam Colt. My Dad is a retired Army Command Sergeant Major, and as a result, over the years I developed an interest in military history. If youıre interested in the ways of the military, youıre also intrigued with a major part of any military operationıguns.

I donıt recall any Westerns where the shoot-out stalled for a major reload session. In fact, some cowboys seemed to have self-loading pistols, as they never seemed to run out of bullets. To my amazement, the TV documentary pointed out that all of Samıs early five-shooters (there were no six-shooters in the beginning) came with a set of specialized tools. The well-built early Colt revolvers had to be partially disassembled to load powder and ball, and the tools included with the guns were a necessary evil for the, at that time, much-sought-after multi-shot capability that the Colt pistols provided.

As a young man, Sam took a job as a common laborer on a cargo vessel. The idea of a multi-shot handgun came to Sam as he watched the helmsman turn and lock down the wheel. He applied the turn and lock method to bullets and barrels, and the rest is history.

As Samıs first series of revolvers found homes in the hands of lawmen and soldiers, the "tool set" disappeared as improvements suggested by the gunsı users were rolled into later production models. Ultimately, the 30-something parts of the first Colt-Patterson guns were reduced to seven. The most famous Colt six-shooter, the Peace Maker, is still in production today alongside the military M-16 automatic rifle, which is also a Colt product.

The success of Samıs revolvers came with the combination of a reduced parts count and prefabricated metal-jacketed ammunition. A minimum of moving parts coupled with a drastically shortened reload time made Sam Coltıs guns must-have items for lawmen, native Americans, soldiers, and bandits.

This is hardly the forum for discussing weapons of war, but watching the piece on Samıs Colt revolvers put a relative thought in my mind about embedded computing. In the beginning, prior to the introduction of the 8047 and 8051 and even through the Z80 days, the smallest of embedded computing platforms consisted of the microprocessor, a clock generator IC with associated crystal, buffers and latches for the address and data busses, one or more ROMs, one or more RAM devices, and a UART IC. If the embedded device required interrupts or analog input, a few more specialty ICs could be added to the mix I just mentioned. Although you had to thoroughly understand the hardware and firmware aspects of such an embedded system to get anything out of it, this conglomeration of discrete ICs could be successfully brought together as a working embedded unit outside the lab by computer hackers of the day.

My first throw at embedded computing was the breadboarding of an Intel 8088 machine, complete with 2716 EPROM, 2 KB of static RAM, a keypad with associated circuitry, and a 4-digit 7-segment LED display array with support circuitry. That was a mouthful, and the 8088 system I assembled was a mass of wire wrap wire crafted on a 0.100ı-center perfboard and wire wrap sockets I purchased at Radio Shack. At the time, I didnıt even own an EPROM programmer. I entered the assembled machine code into the 2716 EPROM by hand using a crude lash-up of latches and toggle switches.

Itıs still raining at the windows here, and Iım just as hard-code embedded now as I was then. I still like to assemble microprocessor- and microcontroller-based embedded systems piece by piece, but sometimes itıs easier (and faster) to use an off-the-shelf embedded component. And, like Samıs Peace Maker, the less complicated the better.

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