-------- Original-Nachricht --------
> Datum: Thu, 07 May 2009 01:27:43 -0500
> Von: Jim Brain <brain@jbrain.com>
> An: cbm-hackers@ling.gu.se
> Betreff: Re: FLASH ROM replacement
> I'm looking at this schematic:  
> http://zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001/320008-2.gif
> 
> I think you're original idea would work, *assuming* pin 16 does not 
> matter.  If the ROMS need to clear off the bus on PHI2 inactive and the 
> SELECT lines don't handle that, then you'll have issues.


I don't think you need to consider Phi2. If you have a look at this schematic http://zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001/320081-2.gif which is the same as above except the design uses 2316B ROMs, you see that there is no Phi2 used. It might be something special with the 6540, to clock the address inputs or something. Someone might do some measurements on the 6540 if the pin 16 is a clock or enable input.

Nicolas

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