Sunday, October 27, 2019

Reading AM2708DC EPROMs on the Scanner Board

On the Nixdorf 620 system owned by the Heinz Nixdorf MuseumsForum in Paderborn, Germany, the Scanner board in slot #5 contains two AM2708DC EPROMs.

Of course, we must read these EPROMs!

According to:

[Translated from Italian to English] To read the EPROM 2708, power it with -5V to the VBB pin (21), +12 V to the VDD pin (19), + 5V to the VCC pin (24) and placing the VSS pin (12) to ground. Then the Not Chip Select pin (20) and the programming pin (18) must be connected to ground. At this point it is sufficient to write the memory address to be read into the indexing bus (A0 ... A9), wait for the output signal to settle (according to the datasheet at most 450 ns) and read in the data bus (Q0… .Q7) the data read.

Everybody else talks about using 2716s in systems that are designed to use 2708s, which is in essence the opposite of what I want to do right now, yet still different.  I just want to accurately and safely read a 2708.

Could it be as simple as building a chip socket adapter, and applying constant +5v, -5v and +12v to the pins 24, 21 and 19 respectively, then setting the MiniPro TL866 to read an AM2716 chip, and click go?

Maybe I should lift/isolate pin 18 as well, so programming can't accidentally happen?

Also reference
Other threads about using 2716s in systems designed for 2708s:
(which is roughly the opposite of what I wish to do...)


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