Re: [stella] FE Bankswitching

Subject: Re: [stella] FE Bankswitching
From: Adam Wozniak <adam@xxxxxxxxxxxxxxxx>
Date: Fri, 28 Feb 2003 16:51:47 -0800 (PST)
On Fri, 28 Feb 2003, Eckhard Stolberg wrote:
> So to handle FE bankswitching, you only need to wait
> for two consecutive accesses to the stack area ($0100-
> $01FF). During the next cycle the high byte of the
> destination address will be read (from stack for RTS
> and from ROM for JSR), so that you can take data bit
> D5 from there and put it on A12 on your ROM chip.
> You must invert D5, because the emulator ROM images
> have the bank compiled for $F000-$FFFF before the
> bank compiled for $D000-$DFFF.

Almost, but not quite.

Wait for two consecutive accesses to the stack ($0100-$01FF).

IF the first access was at an EVEN address (A0 == 0) then use D5 of the
second access.

IF the first acces was at an ODD address (A0 == 1) then use D5 of the
access AFTER the second access (i.e. the THIRD access).

Will code for food.

Hey, and if you hire me to write a multi-protocol internet capable
program before midnight tonight, you'll get the amazing toast-a-matic!
Be the first on your block!


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