Old MOS Mask-Programmed ROM forgetfulness?

It is interesting, I have 1702As that were programmed in 1973 sometime and they still have their data ( used on my SIM4-01 ). And yes, I have them backed up. It is interesting that Data I/O has added supply current checks. I've used many home made pin adapters over the years to read old ROMs, as John probably knows, as some were from pin ball machines. Some of the earlier ROM also had address latches built in, making reading tough. Anyway, making pin adapters is not that hard. I usually stack a three solder pin, machine pin sockets. In place I don't want any connection, like Vpp, I pop the pin out. In other places where I need to rewire, I break the solder pin off and file it down a little so it won't short. I do connections and sometimes vector side boards with soldered wire wrap wire. Often I need switches or sometimes logic off to the side. It only takes 15 or so minute to put a typical adapter together. Dwight ________________________________________ From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Brent Hilpert <hilpert at cs.ubc.ca> Sent: Tuesday, February 16, 2016 11:06 AM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: Old MOS Mask-Programmed ROM forgetfulness? On 2016-Feb-15, at 11:25 PM, Eric Smith wrote: Apparently there actually is an equivalent EPROM, according to this datasheet for the MM4203/MM5203 EPROM: http://www.datasheetarchive.com/dl/Scans-006/Scans-00137265.pdf It states they are pin-compatible to the MM5213/MM5231 mask ROMs. The EPROM even has the selectable configuration mentioned by Rick. (This is the only mention I've found of the 5231, I haven't come across this Nat Semi ROM series before.) Similar pinout to the 1702 (quite different than the industry standard of the 2708,2716,2732,etc.) I expect they're too early and too uncommon to be covered by anything other than a specifically-targeted programmer from the period. It shouldn't be difficult to read them either way - adapter for an EPROM reader or microcontroller, with additional power supplies as necessary, might have to consider power-sequencing issues though. Rick, what calculator are they in?, I'd be interested in looking it up on your site.