A compact programmer for 1702A EPROMs

It’s no secret that EPROMs have great nostalgic value to me, and even today I include them in my projects where ever I can.

For many years now I’ve had a set of the worlds’ first ever commercially available EPROM – the 1702A, sitting in a piece of anti-static foam, waiting to be used once again.

As I’ve long been aware this would be a tall order, because this is a particularly difficult EPROM to program. There are no commercially available programmers and second hand programmers are practically unobtainable. Even if you could obtain one, you may find that is quite large, heavy and difficult to use, perhaps having to program each byte by hand.

This has turned out to be a very tempting idea for a project – a small, compact, easy to use 1702A programmer which interfaces with modern computers.

Fortunately availability of 1702A type devices is actually quite good. I was able to obtain a number of them from eBay for fairly reasonable sums.

A variety of 1702A type EPROMs. All tested successfully in this programmer

Design Details

I’m not going to go into the detail of programming these devices. This has been done at length on this page. Instead let’s focus on how my design differs from other two-socket designs of which there are a few already on the internet.

Single power supply

Because reading and writing the 1702A requires a cornucopia of different voltages, D.I.Y. programmers are often found to have perhaps three or four different power supplies hanging off them. This is of course a little inconvenient and certainly something I wanted to avoid. My design achieves this with three on-board switching (step-up + inverting) regulators.

Single socket operation

The reason for using two sockets is that the voltages used for reading and writing are so completely different that it becomes difficult to do both on the same socket.

Clearly it is possible because the original design from Intel did do this, as did others of the day. Mine does not share much in common with that design, except for the drivers for the data pins, a less than perfect, but tricky bit of circuitry which I was not able to improve upon.

SMD or through-hole?

I did consider building this as a through-hole design however with 204 components this was going to end up quite large and difficult to lay out. In fact it would likely end up with more than 220 components in a through-hole design due to some of the dual transistor parts I’ve used not being available in through-hole packages.

Here is an example of a dual socket programmer in through-hole. My single socket design would have been considerably larger.

Physical form factor

I decided to build it as an Arduino mega shield, mainly so I could use it on my previously constructed 8086 Arduino contraption (The reason it has a DE-9 RS-232 connector fitted, this board does not have USB to serial like the Arduino)

Another reason for this form is because if attached to an Arduino, this reduces the overall size even further.

Building one yourself

If you have a sound understanding of how these devices are programmed, are well equipped and have very good soldering and troubleshooting skills – everything you need to build one is provided below.

Update: I was rather surprised to find that people are actually building these things. There are now two others that I am aware of:

By Gary Kaufman
By Wolfgang Robel

If you go to the trouble of building one, let me know about it. I enjoy seeing them ๐Ÿ˜‰

Host software / firmware

Please see the main project page for more information.

Schematic

  • Can be downloaded from here.
  • You can also see the schematic for the reader board seen in the YouTube video here.

Gerbers

There are two version of gerbers for this board.

  • “Long” version – which has the exact dimensions of the Arduino mega PCB. It’s 101.5mm x 53.5mm in size, which is over the 100×100 limit of seeedstudio’s $4 PCB service. Use this gerber if using a PCB house that doesn’t charge a lot more for exceeding 100mm (image).
  • Short” version – which has the tab at the end of the board cropped a little. It’s 99.95mm x 53.5mm in size (image).

Neither version includes any signatures or graphics seen in my photos. Those are for my boards only ๐Ÿ˜‰

BOM

A complete BOM can be downloaded here. Exact part numbers for special components are specified, however generic stuff such as resistors and capacitors are not. Up to you to choose those.

10 thoughts on “A compact programmer for 1702A EPROMs

  1. Hello

    This is Hassan from Pakistan. I am an electronics engineer and came across a vintahe eprom Part#: AM1702 OR MM1702. I see that you have its programmer. Can you please share price and details of this programmer

    BR
    Hassan

    1. Hassan,

      Please note that the programming algorithm for 1702 EPROMs is different than the algorithm for 1702A EPROMs, so this programmer probably will not work with your AM1702 and MM1702 EPROMs.

  2. I like this idea, but that is a lot of tiny SMC components to mount. Have you considered splitting the circuit into two boards that can stack on top of each other? That is, a lower and upper board that stack on top of the Arduino Mega, that way you can use through hole components (especially those transistors and caps). If you keep each one under a 100×100 mm^2 the cost is a lot cheaper than making a larger board.

    1. You would probably need to stack it 5 or 6 high to get everything on there. 4 layer PCBs would probably also be required because the routing between components and interconnects would be so complicated. It would be a very expensive and zany contraption indeed.

      I have pondered a through-hole version of it. I worked out that it would be quite large, so large that basing it on an Arduino wouldn’t make sense.

  3. Hi Charles,
    I must apologise Matt for being “off topic” here, I have a query relating to the PCB board shown on your web pages that is a Mega2560 shield EPROM Programmer and a link to your eBay site to purchase a blank board. That link does not go to your board, nor can I find it any where else.
    Are you still selling these multi-eprom boards? If yes, how can I purchase one?
    Apologies for hijacking your conversation.
    I used an Intel EPROM programmer in 1973 to program a 1702A in Melbourne, Australia. I used it to generate a monitor program for my SCMP prototyping board (256bytes exactly). Dead bug wired it into the system. 16 Hex+Fn keys, and 6 character bubble 7 Seg display. Intel had an outlet in Swanston St Carlton, just up from Melbourne Uni where I was studying. I had to hand enter and program the code in their waiting room, as I was not allowed to borrow their programmer. I am impressed with your endeavours here. I still have my only 1702A and SCMP CPU, both ceramic+gold pins!. I am wanting to program 2764A EPROMs for a SYM-1.

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