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

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Sun, 26 Feb 2012 21:02:36 +0100 Message-ID: <4F4A8FDC.8090601@laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

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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