On 06/28/2014 11:54 PM, David Shoemaker wrote:
Have a space invaders deluxe board.
Rom tests based on quarterarcade fluke crc's are fine on loop. Game does not run correctly.
Ram short fails all over the place.
So trying to narrow it down a touch I do a write 0x2000 = 0xff then a read 0x2000.
Comes back with 0xFF. Hit loop and it starts to wander all over creation.
Thinking I have a bad bit I do some testing.
Write 0x01, read & loop is stable=0x01.
Same with 0x02, 04, 08, 10, 20, etc etc. In fact everything I tried came back with a good read loop EXCEPT 0xFF. With that value I get random garbage.
WTF?????
Any ideas on why ram would fail this way?
Thanks,
David
Hi David, How about the 'ol AA/55h test? This is similar to my problem with my 8080 pod having trouble resolving FF on a number of ROM locations - read them as other characters - alternating. Do you get the same read value if you loop the read (typo fixed for clarity) for that memory address? John :-#)# -- How to subscribe or unsubscribe from TTL http://seven.pairlist.net/mailman/listinfo/techtoolslist _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com http://seven.pairlist.net/mailman/listinfo/techtoolslist FTP site is: ftp://ttl.arcadetech.org/TTL/Test_Equipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/