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

On Sunday 26 February 2012, you wrote:
> 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.

for CIA you even have to be faster (and still timing exakt), because the 
sampling period doesnt exactly fall in between two cycles but is delayed 
somewhat.


-- 

http://www.hitmen-console.org    http://magicdisk.untergrund.net
http://www.pokefinder.org        http://ftp.pokefinder.org

Ach, lass mich doch mit deinen Argumenten in Ruhe. Ich habe schon eine 
Meinung!


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