Re: Hardware emulation of 6509 using 6502?

Den Tue, 6 Mar 2018 23:28:07 +0000 skrev smf <smf@null.net>:
> 
> On 05/03/2018 20:51, Mia Magnusson wrote:
> >
> > Well, the limit is that you can only access 1k in bank F, but there
> > seems to be no special limit on the usage of that 1k. Usually it's
> > probably best to use it for screen ram but in theory you could store
> > sprite data there instead, or whatever you want to have there.
> 
> My understanding is that:
> 
> vicdotsel contols whether font & sprite fetches come from the
> character rom or dram bank 0, these fetches cannot come from static
> ram.
> 
> statvid selects whether the video matix comes from static ram or dram 
> bank 0, when fetching from static ram it ignores the vic2 bank and
> the screen address & you are locked into that 1k page.
> 
> The motherboard has complicated logic to coordinate this.

Which signals from the VIC tell which of this it reads?

Is it just as simple as screen + color ram is read in the "CPU"
phase of the clock cycle ("bad line" in C64 lingo), and char data /
bitmap data and sprite data is read during the "VIC" phase of the clock
cycle?

I really don't understand why there is a need to split theese cycles
though.

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