Small Things Come In Big Packages


During December 2015, Digi-Key Electronics have been running a Christmas Draw; by posting to Twitter or Facebook with an appropriate keyword (“#DigiWish”), you can wish for parts from their catalog, and if you are drawn out of the hat, Digi-Key would gift them to you for no charge and with free delivery.

Of course, to prevent abuse, the offer is limited to parts costing less than $100 and also only parts shown as “in-stock” on their website. Perfectly reasonable!

So far so good, but there is a little tale to tell…

Being Fair
I know some people who, when faced with such an offer, would automatically pick the most expensive eligible item they could find, whether they needed it or not. I’m not a fan of such behaviour, it is a form of abuse, so I was of course only #DigiWish-ing for parts that I really needed and could use.

I have been toying with the idea if building my own miniature old-fashioned 8-bit computer using a 68hc11 CPU (I have a few of these), so around the 2nd week of December, I #DigiWish-ed for a (single) memory chip – an MT 23K256-I/P: an asynchronous 32-Kbyte SRAM chip with a serial SPI interface and through-hole mounting. 8-DIP_sml

I wanted to play with the SPI capabilities of the 68hc11 and had some ideas for using SPI-based storage for an editor-buffer and filing-system-index cache, assuming I get as far as building the computer!

Such an SRAM chip is listed on the Digi-Key website at $1.08 each.

Information Requested
For non-USA residents who win one of the draws, Digi-Key require a little information from the winner, to keep the US export authroities happy: (1) what is the item going to be used for, and (2) where is the ultimate destination of the resulting “product”.

I dutifully emailed them with a brief description of my home-brew old-fashioned 8-bit computer project, and asserted that the result would not be travelling any further abroad than my home. ie: this is a one-off construction, for my own enjoyment only.

That’s One Heck of a Big Matchbox
It turns out I won that days’ draw, and had thus been eagerly anticipating a matchbox-sized parcel from the postman.

However, what turned up was a large parcel over 2 feet long! The contents were even more amazing:
chips1_1chips1_2.

Yes indeed – the package contained 90 SRAM chips – $100 worth of chips, in fact!

Crikey!

Even allowing for me breaking a couple whilst soldering, I’m going to have to dream up some other uses for all these! Maybe a multi-drop multi-slave SPI circuit so I can have a dozen or so attached to the single 68hc11 SPI port at the same time?!! Mind you, a 2MHz 68hc11 would take some time to read or write the equivalent of 6 times its’ main-memory address-space across an SPI interface…

So a big thank-you is due to Digi-Key, even though their generosity has overwhelmed me and given me a little headache trying to find a use for the other 2848 Kbytes of serial SRAM I now have to hand…

Merry Christmas!

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