Thursday, November 01, 2012

The Good Old Days

Polaroid of my past
You're looking at something I'd completely forgotten about, something I built around 1980. It's a custom perf board I built on a slab of aircraft-grade aluminum, on which I wired a complete 6502-based embedded computer. It has 4,096 bytes of static RAM, 16K of EPROM (2716), a combo-peripheral chip that included two serial ports and two eight-bit-wide parallel I/O ports, a fully decoded keypad and a six digit display broken into four digits for an address and two for data, all in hex. I was proud of those displays. They were special HP multi-segmented alphanumeric displays that read ASCII bytes. I had them display hexadecimal and special words, and then got them to scroll text. Although the keypad looks like it will only handle hex digit input, I had added software so that if you held the key down it would give you a display of the function and an alt function. Primary and alt key functionality was toggled by the tiny switch on the top left.

The calculator is a TI Programmer (hexadecimal calculator) for scale.

I used it for 6502 software testing as well as driving external devices. Software development was on an Apple II using a source assembler. The resultant binary file was written to tge 2716 with an EPROM programmer. I was proud of the fact that the 6502 was clocked at 2MHz, twice as fast as the Apple II's 1MHz clock speed. That and the fact its memory was fully static meant the system ran with no wait states. I used it for driving stepper motors at one point, and then built a light tracker and then combined all that into a simple wheeled line tracker. I had big dreams back then. I was going to build Asimov-like robots. I wonder what happened to them all...

The image at the top is a scan of a black and white Polaroid I took of it all and sent off to someone I haven't heard from in 32 years. He scanned it and sent it back to me this evening.

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