PROMs and EPROMs, specifically 2332/2532/2732

[John Robertson]

On 10/24/2015 5:56 PM, Adrian Graham wrote:
>
>
> On 24/10/2015 19:18, "John Robertson" <jrr at flippers.com> wrote:
>
>> On 10/24/2015 5:43 AM, Adrian Graham wrote:
>>> Hi folks,
>>>
>>> PET4032 repair continues with all ROMs, video RAM and dodgy sockets removed
>>> thanks to a hot air gun. Holes cleaned and I have new turned pin sockets for
>>> everything I've removed which I'll be fitting this afternoon.
>>>
>>> Since the ROMs came out OK I'm trying to dump them using my Pinmaster48
>>> programmer, being from the 90s it doesn't read 2332/2532 PROMs but it WILL
>>> read a lot of variants of 2732 so I've made an adapter as found thanks to
>>> google and USENET:
>>>
>>> 2332 pin 18 to 2732 pin 21 (A11)
>>> 2332 pin 20 to 2732 pin 18 (Chip enable/Power Down)
>>> 2332 pin 21 to 2732 pins 20 and 24 via diodes with banding at the 2332 end
>>> (2332 Vpp)
>>>
>>> Wiring checks out and the diodes are aligned correctly so pins 20 and 24
>>> don't interfere with each other, however the pinmaster continually gives me
>>> "continuity error on pin 20"
>>>
>>> Have I goofed somewhere?
>>>
>>> Cheers,
>>>
>> You just tie pin 21 of the 2332 to Vcc (+5) - Pin 24 of the 2732 - to read.
>>
>> There are only two modifications needed normally for reading a 2532/2332
>> in a 2732 socket.
>>
>> 2332
>>
>> Pin 21 - Vcc (2732 Pin 24)
>> Pin 18 - A11 (2732 Pin 21)
>>
>> If your reader coughs up a /OE error then use diodes:
>>
>> 2332
>>
>> Pin 20 - 2 Diodes, one to 2732 pin 20, the other to 2732 pin 18. Banded
>> end to these pins, and you will also need a pullup resistor on the
>> 2532/2332 socket pin 20 so /CE (2332/2532) goes high when not selected.
>> 2K2 would do fine. Anything from your junk box between 1K and 4K7 should
>> work though.
>>
>> I don't think you will need the diodes though.
>>
>> John :-#)#
> Hi John and others,
>
> Thanks for that. I removed the diodes and wired 2332 (21) to 2372 (24)
> leaving the A11 swap in place, the programmer complained about pin 18
> missing. The adapter in front of me is now wired like this:
>
> 2332 (18) to 2372 (21)
> 2332 (20) 2x diodes to 2372 18 (band) and 20 (band)
> 2332 (20) 2k2 resistor to 2332 (24)
> 2332 (21) to 2372 (24)
>
> Now I get "reverse insertion" hinting I've wired something upside-down which
> isn't the case. I can read 27256 and 2764's no problem so I'm mounting
> things the correct way.
>
> Further digging into available eproms that the programmer can read reveals
> it CAN read 2532s, specifically the MCM2532 which the datasheet tells me has
> the same pinout as the 2332. I still get "reverse insertion error" so I'm
> guessing my PROMs are toast.
>
> Cheers,
>

Reverse insertion may just mean you are drawing more current on the /OE 
and /CS than expected.

How about this - go back to my original suggestion (no diodes) and this 
time add a small resistor to the 2732 pin 18 and Vcc to act as a load. 
Try larger resistors if the reader still complains - and try reading 
with NO 2332 in the reader (all FFs). Once you can trick the reader into 
reading air as highs then try your 2332 again with the working resistor 
values for the unused select.

Oh, and what reader are you using? Did you check with the manufacturer 
(or archives somewhere - archive.org?) to see if they have a trick for 
reading 2532/2332s?

John :-#)#

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