Duh! Of course; I should have thought to look at the 2316 schematic.
Well, then I don't see why your 6540 CG adapter would not work in the 
ROM areas as well with one or two jumper mods; do you have one or
two of those little boards (bare) available by any chance?

mike
**********************************************************************************
----------
From: 	Nicolas Welte[SMTP:no_spam@x1541.de]
Sent: 	Thursday, May 07, 2009 12:14 PM
To: 	cbm-hackers@ling.gu.se
Subject: 	Re: FLASH ROM replacement

-------- 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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