[Techtoolslist] Data I/O Series 22 problem

[vector]

Following up on my own post....

I'm going to take a logic probe to it to check activity on the address 
lines during a chip read.

Hopefully looking at the schematics that the 4099 connected to that 
socket pin is the culprit.

I'm gathering that one bit at a time the address lines are latched, and 
then the device would read or program.

I just hope it is the 4099 and not one of the 'pin driver' modules.  
Doubt those can be found anymore.

Ebay seller says this works (it passes self test)... so far is not 
willing to work with me on the issue.  His listing does indicate no 
refunds, but then why list something as working ?  sigh.... I hope it is 
that 4099.

-- Curt

On 2016-04-29 16:39, vector wrote:
> I purchased a Series 22.... and now that I've ruined 6 Harris 7641
> equivalent PROMs (minimum value about $15)... I've determined what 
> the
> symptoms are I am seeing.
>
> This is a 512 byte PROM.
>
> I'm thinking A6 line to the PROM during read is either high or
> floating, as if you break the 512 byte range into 8 blocks of 64 
> bytes
> you should have
>
> ABCDEFGH
>
> When I read a good source rom in, I use edit and compare it against a
> known good hex dump, and I'm seeing
>
> BBDDFFHH
>
> with blocks A, C, E, and G missing.
>
> This would seem to idnicate that the A6 line is high during read.
>
> Unfortunately my MOD-EMUP which should handle these PROMs 49 times
> out of 50 (or so it seems) will read any 7641 or compatible as all 
> FFs
> (which it probably ins't reading anything... and the FFs were part of
> the EMUP's software clear).
>
> I think I read you can read these as a 2732 and the 512 bytes ends up
> repeated I think in specific positions in the read.... I have to
> google that again to see if during the writes, the A,C,E,and G blocks
> are all 0 still like on a blank PROM.
>
> I'm going to strip it down to look at the boards... and check first
> at the socket.
>
> If that line is floating will I get this behavior, or only if it is
> driven high ?
>
> Thanks,
>
> -- Curt
>
> _______________________________________________
> Techtoolslist mailing list
> Techtoolslist at flippers.com
> https://pairlist7.pair.net/mailman/listinfo/techtoolslist
> FTP site is: ftp://ttl.arcadetech.org/TTL/Test_Equipment
> Archive site: http://seven.pairlist.net/pipermail/techtoolslist/