DTACK failed?

tcdev

NEST Puppet
Joined
Aug 22, 2002
Posts
168
Hi All,

I've got an MVF-1A (from memory) which displayed garbled graphics on power-up and continually reset. Traced it to a bad DTACK to the 68K - pulled it active and my one-and-only game runs fine!

Any ideas on the cause? Anyone with schematics that can tell me what generates this signal? or give me a copy of the schematics???

TIA
Regards,
 

Nightmare Tony

*Account control passed, on to Tony's family.Ex Ro
Joined
Sep 19, 2001
Posts
1,029
The DTACK signal (I forget the DT, but DT Ackknowledge) is set up so after every single CPU instruction is performed, the circuit answers back with a low pulse that it was executed and done. basically (I'm doing doing my biz, give me another instruction!) sort of thing...
 
Top