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MK48Z02 Non-Volatile RAM for the Boyd Calculator

December 11, 2018

My last effort with the Boyd used the onboard 64 byte ram memory with a 2732 eprom in an adapter.  I wasn’t hitting the ram limit but i thought using a non-volatile ram chip as primary memory would give me more flexibility.  I got an old signetics part from eBay to try out and today i got around to comparing the pinouts to the 2532 that’s original to the Boyd.

As usual the data and address lines are more-or-less ok.  The 4K 2532 has one extra address line A11 which would hit /CE on the nvram but that’s ok because it would just deselect the nvram for addresses above 2K.  The PD/PGM on the 2532 seems ominous but it really just acts as a low-going chip enable and connects to /G which is /output enable on the nvram.  again VPP sounds ominous but i bet it’s tied to +V in the Boyd – it connects to /write on the nvram.

So to use the nvram fully, I would need to connect /mwrite to pin 21 and /mread to pin 20.  I don’t think either of those would interfere with the normal 2532 chip.

I currently have a 2732 adapter in the boyd.  I should look hard at the 2732 pinout but it looks like i would have to remove A11 from pin 21 and supply /mwrite instead.  this is a bit simpler but the adapter is already high and putting the tall nvram on top of it would probably break the camel’s back.

18-12-11 TMS2732

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