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Various Evaluation Module and Prototype Design Photos

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I thought it might be fun to put together an "album" of photos of original development boards and prototype designs in my collection. This is by no means complete, but I have to start somewhere and I'll add to it as I organize my stuff.

First is a Digital Equipment Corporation DCT11 Evaluation Module Kit.

I came to really love the PDP-11 before ever considering a design based on it. A huge amount of my early work was on DEC systems and when the possibility of adapting one to the 8-bit bus architecture I'd been working on a couple years became evident, I couldn't resist.

The design went easily, although it was a bit complex to weed out features that were compatible with the existing bus. The prototype worked immediately, but then I had to develop software to really verify it. This would present challenges.

I obtained a copy of Paper Tape ODTX [with some pain to my boss who I conned into helping me fix a 1200bps paper tape reader one evening making him late for a dinner party] Then I had to translate the source code to run on the T11 [originally for a UNIBUS machine], and figure out how to compile and link it in a mode that would execute on the hardware. [almost a bootable image] Then a procedure had to be written to extract the executable code from assembled output and burn it to an 8-bit wide eprom. All in all, not a trivial exercise.

Eventually it all worked. That version of ODTX would find it's way into other T11 projects, including KXT11-AB and KXT11-CA based systems and would be enhanced to work with a TRACE-11 QBUS logic analyzer board.

[Can you tell yet, how much I miss this work??]

Next is an original Motorola 68000 Development Board Kit. I didn't use this knowledge immediately. Eventually I designed a board to replace a 6809 based module, about 10 years later. [I wonder if I kept one?]

Next up is a 68HC11 Development Board Kit I rescued from oblivion. I'd already done several designs based on this CPU by this time, so this never helped me. Still, it is pretty, isn't it? It's one of the most thorough development boards I've seen for it's day.

Ok, now we transition to Prototypes or simply examples of boards I've done.

First - Wire-wrap prototypes and their respective PCB versions. For those who don't know, Wire-Wrap used to be a respectable means of manufacturing even "production level" products. Eventually, this gave way to a PCB based world, and Wrap was only used in prototypes which were to be added to, or in a highly uncertain state, and subject to heavy revision as an interim stage before committing to a PC layout.

When a working, finalized design had been achieved, a PCB layout was undertaken to reduce the cost of manufacturing, and improve reliability.

What follows then is a series of boards for a proprietary 8-bit bus architecture. The upper row is the Wire-Wrap version, and the lower row is the same design in PCB form.

From Left to Right we have:

  • An RCA 1805 CPU with 2k ROM and 2K RAM
  • An 1854 Enhanced mode Serial Interface [that was intended only for an I/O bus, but we memory mapped it anyway]
  • The DCT11 CPU with 2K RAM and 2K ROM I referred to earlier

I would do many other prototypes for this bus. All would work, but after a while it became apparent that the process of wire-wraping itself was less reliable than the new computer verified PCB layouts we were doing by then.
It all came to a head one day, when I'd spent almost a week trying to figure out the error in "my latest prototype" which had been wire-wrapped by a contractor because I didn't have time. I found the problem was actually a Wire-Wrap error. I then realized, it would have been cheaper, faster and saved me a huge headache if I'd simply gone directly from design to PCB. From then on, this would be the rule more than the exception for product destined devices.
For a while, my career took a detour, and I was away from hardware design for a couple years. In this time I worked at applications level in Networking systems which were evolving during that period. With the Internet coming on strong, and PC networks exploding everywhere, I was consumed by this work.

I returned to hardware design as a consultant to the company I'd done this design work for previously. At first the work was all Software and Firmware. Eventually I was doing hardware again. New highly integrated chips were common and it was a great time in the world.

This brings us to an 80386EX design. This was a Protocol Converter used to translate communications traffic in realtime between two completely incompatible systems. To accomplish this really should have required a full blown computer, but it needed to be highly reliable, low power and totally solid state.

I used a previous product's hardware enclosure and cabinetry to speed up the process and minimize costs. [It was not forecast to be a high volume item at first] The translation required a database and had to be programmable after delivery. I chose a PC compatible CPU and ROM DOS in order to use Borland's Turbo C and Turbo Remote Debugger to write the software. The database and firmware would be stored in FLASH [pretty novel for the day] and be online updateable.

The architectural communications requirements mimicked a 16:1 "data concentrator" made of serial ports. I decided on a modular approach to again simplify, and constrain design costs and my time.

Based on the experience of a friend, I used NEC 72002 SCCs, equivalent to the Zilog 8530 SCC with which I was familiar. These are CMOS and actually functionally superior to the Zilog counterpart. I chose this approach because we had to leave the possibility open to interface to both Async and Sync DTE and DCE devices for future applications.

I was really amazed at how well this eventually worked. By the end of the project, I could understand and explain every odd behavior the device had ever exhibited during development. It was a completely reliable platform, and great fun to do.

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Updated May 4th, 2011 at 10:34 PM by RSX11M+ (Spelling corrections)

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