Re: Switchless ROMs

Date: Tue, 27 Dec 2016 08:33:11 +0100
Message-Id: <>
> On 2016-12-26, at 23:51, Michał Pleban <> wrote:
> Hello!
> smf wrote:
>> Another method you can use is magic read sequences. i.e. come up with a
>> sequence of rom reads that wouldn't happen in normal circumstances, long
>> enough to make accidental activation so unlikely that it's practically
>> impossible for there to be a collision. Then have the next read after
>> this sequence use the address bits as data lines for writing the new bank.
> In this scenario, you don't have the RESET line, so once you select a
> KERNAL, you are stuck with it until the computer is switched off. Unless
> you can somehow detect the actual reset sequence of the 6510 just by
> looking at KERNAL accesses, but I am not sure if it is ever possible.
> If you accept this limitation, then you actually don't need any magic
> sequence at all. You just boot into the menu, the user selects the
> KERNAL from the menu, then a single read from e.g. $E0xx selects the
> KERNAL and disables further selections.

That's almost exactly what I bugged you to finish some time ago :-P remember? And also what I now have on my bench as half of my next-gen ROM replacement.


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Received on 2016-12-27 08:00:02

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