: Re: MSI 6800 EPROM Software

Brent Hilpert bhilpert at shaw.ca
Tue Feb 23 17:17:30 CST 2021

On 2021-Feb-23, at 1:45 PM, Frank Tuccio via cctech wrote:
> On 02/22/2021 01:31 PM, Brad H via cctalk wrote:
>> A longshot I'm sure - but I am wondering if anyone familiar with MSI
> (Midwest Scentific - SS50 bus system) would happen to have a copy of the
> software for their 1702A EPROM burner, I think the model is PR-1.  I just
> picked one up and am eager to see if I can use it to read/burn 1702As,
> something that has been an issue for me for a while now.
> Reading them is pretty easy.  BURNING them is crazy.  They 
> need an 80 V power supply, and I think you XOR the address 
> or something as you apply the programming voltage.
> Jon
> Actually,  programming a 1702 only requires a  -48 volt pulse for each
> address.  Here's the datasheet:
> https://www.jmargolin.com/patents/1702a.pdf

Ya, but that's with a Vbb of +12V, so the differential required from the power supplies is 60V.
(Per the datasheet, it was ~ 55V in the 1702 programmer I once had.)

But that's the easy part.
And the semi-complex timing and switched-complementing of the address can be done in software.

The hassle is that the data lines, address lines and several of the supply and control lines all have to be switched independently with these high voltages. So it's a small mess of specialised discrete drivers and hardware.
It's not just pulse a high voltage to one PGM pin like it was for 2716s and later eproms.

I don't know what the 2708 (after the 1702, before the 2716) requirements were.

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