RE: has anybody tried to replace a vic or vic II chip with a board containing a propeller ?

Beside the 3v to 5v problem perhaps that an arm would to the trick (for
eprom/cia, not for the vic)
I guess it would be possible to read  address + data + cs + rw in one
instruction



-----Message d'origine-----
De : owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] De la part de Gerrit Heitsch
Envoyé : dimanche 26 février 2012 21:03
À : cbm-hackers@musoftware.de
Objet : Re: has anybody tried to replace a vic or vic II chip with a board
containing a propeller ?

On 02/26/2012 08:42 PM, Didier Derny wrote:
> I just forgot the sprites....
>
> I checked the swinSID only the write are supported, R/W is not even
> connected.
> (I tried to emulate an eprom with an avr but I failed, even the "tightest"
> assembler was
> Too slow. Perhaps that it could work with an xmega but the we have the 3v
to
> 5v problem.)

Well, with a 1 MHz 6502, you have less than 500ns from _CS low to 
deliver the data. That's less than 10 cycles on a 20MHz AVR.

I think one would need a CPLD or the like to emulate a CIA or VIC and 
with both you'd have to be cycle-exact since even the one cycle 
difference between the 6526 and 6526A tripped up some software.

  Gerrit



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