Date   : Mon, 27 Feb 2006 20:43:55 +0100
From   : Eelco Huininga <eelco@...>
Subject: Re: SHELIA and the VIA's

Since the VIA's have 16 registers, and there were 32 addresses reserved for
the user VIA, &FE70-&FE7F maps to the same addresses as &FE60-&FE6F. &FE69
maps to the 'T2C-H' register, the T2 high order counter. Try searching for
&FE69 or T2C-H.

Cheers,
Eelco


BBC Micro schreef:
> Hi again, I've been looking at the AUG and getting
> confused...Page 397 tells us that the VIA's are
> &FE40-&FE7F. The next chapter tells us that VIA-B is
> &FE60-&FE6F.
> 
> I'm having trouble tying up the memory locations with
> the registers/ports on the VIA can anyone give a list
> from &FE40-&FE7F? I only found the Electron one on the
> internet search.
> 
> I've dissasembled Castle Quest (with 6502dis) and
> looking at the VIA calls. &FE79? Joystick/Timer?
> 
> This was the one of the pieces of code:-
> 
> $2cfc: a5 32            LDA $32
> $2cfe: 38               SEC
> $2cff: ed 79 fe         SBC $fe79
> $2d02: c9 3b            CMP #$3b
> $2d04: 30 01            BMI .M5s2
> $2d06: 60               RTS
> 
> .M5s2: 4a               Yada, yada...
> 
> 
>   
>   
>           
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