This is surely a dumb question, but what is the purpose of the NOP adapter? _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com http://seven.pairlist.net/mailman/listinfo/techtoolslist FTP site is: ftp://ftp.flippers.com/TTL/TestEquipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/
Its basicaly used to exercise the addresss bus on the board...(The cpu constantly runs the nop instruction which is hard wired - so it 'counts' through all memory locations).. By using a signature analyser on various lines on the board, is is possible to produce useful fault finding information.... For instance... if say A15 was faulty down stream from the cpu (maybe due to a driver IC or a short) - it would produce a differnt signature than a working board.... you could also test eproms and such to an extent... Hope this helps.... I'm sure someone can provide a much better explanation.... Cheers, Colin ----- Original Message ----- From: "kevin spears" <micrologix1500@yahoo.com> To: <techtoolslist@flippers.com> Sent: Thursday, February 05, 2009 8:16 PM Subject: [Techtoolslist] Atari 6502A NOP adapter
This is surely a dumb question, but what is the purpose of the NOP adapter?
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_______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com http://seven.pairlist.net/mailman/listinfo/techtoolslist FTP site is: ftp://ftp.flippers.com/TTL/TestEquipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/
Not a dumb question at all. A NOP adapter is simply an adapter that you slap onto a microprocessor to force it to execute nothing but NOP (no-op) instructions. The reason you would want to do this is to force the entire system into a known state, or steady predictable behavior. Then, you can use a signature analyzer to probe points on the PCB to debug and find the source of a problem. Typically what someone will do is use a NOP adapter in a know, correctly working system, and probe a bunch of points on the PCB and record a set of signatures. Then, if the system ever fails, they can repeat the process and look for any signatures that differ from the ones recorded. If the signature on the input to an IC matches but the signature on the output didn't, chances are that IC is the problem. On Thu, Feb 5, 2009 at 3:16 PM, kevin spears <micrologix1500@yahoo.com>wrote:
This is surely a dumb question, but what is the purpose of the NOP adapter?
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-- -Adam "Please don't judge my God by my inability to follow him" - Chris Mollins =============== www.onecircuit.com www.youtube.com/user/ajcrm125 =============== _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com http://seven.pairlist.net/mailman/listinfo/techtoolslist FTP site is: ftp://ftp.flippers.com/TTL/TestEquipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/
participants (3)
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Adam Courchesne -
Colin Davies -
kevin spears