Re: BASIC and System ROM replacements

From: Michał Pleban <>
Date: Mon, 27 May 2013 12:52:08 +0200
Message-ID: <>

Baltissen, GJPAA (Ruud) wrote:

> Assume that the main bank contains the main interrupt routines. The interrupt vectors of the other banks point to a small routine. This small routine pushes A, Y and X, and then reads the bank register and pushes that as well. Next it JSRs to a routine in RAM that 1) switches to the main bank and 2) JSRs to the main interrupt routine. The main routine pushes the same value but can skip the RAM routine.

OK, so you have the bank switching routine in RAM somewhere. But RAM can
be overwritten easily by user applications over which you have no control.

That's why I put them in ROM area taken from I/O space - nobody can
overwrite them in that case ;-)


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Received on 2013-05-27 11:01:58

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