Hello, * On Sat, May 29, 2021 at 12:45:32PM -0500 tokafondo wrote: > I've been studying the VIC-II datasheet and how the C64 initializes it when > booting. > > The only thing I've seen while booting is > > LDX $#FF > [...] > STX $D016 Well, that's not completely correct. The JSR $FD02 in-between modifies the X-register. In most cases, without a cartridge, it will end with X=5. > that I think is a kind of "enable 40 columns text mode". This STX $D016 is the reason why the left/right border of the C64 goes smaller when doing a RESET. But: Have a look at the routine at $E5A0-$E5B3 (especially the loop starting at $E5A8, and its data area at $ECB9). It writes the data array at $ECB9 into $D000, thus initializing all 47 registers of the VIC at boot time. This routine is called as part of the RESET ($FCFB -> $FF5B -> $E518 -> $E5A0). Additionally, $FDCB-$FDD4 set the VIC-II bank to $0000-$1FFF. Although it initialized the CIA, it is still part of the initialization for the VIC-II. But other than that, you are right, the C64 does not do much with the VIC-II. Regards, Spiro. -- Spiro R. Trikaliotis https://spiro.trikaliotis.net/Received on 2021-05-29 22:00:23
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