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C128: Writing to $FF03 and $FF04? [message #211821]

Tue, 17 December 2013 11:54

Harry Potter
Messages: 1304
Registered: March 2012

Karma:

Senior Member

I am working on programming the Commodore 128 and am wondering: writing to $FF01 switches the MMU to Bank 0 and $FF02 Bank 1. My documentation says that writing to $FF03 switches to Bank 14 and $FF04 Bank 14 with RAM from Bank 1. This makes no sense, because, when I disassembled the Bank 0/1-specific access routines in the first 1k of RAM, they write to $FF01 or $FF02, perform the access, writes to $FF03 or $FF04 then exits. What do these writes *really* do?

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[Message index]

		C128: Writing to $FF03 and $FF04? By: Harry Potter on Tue, 17 December 2013 11:54
		Re: Writing to $FF03 and $FF04? By: Anton Treuenfels on Wed, 18 December 2013 01:25
		Re: Writing to $FF03 and $FF04? By: epc8 on Wed, 18 December 2013 15:50
		Re: Writing to $FF03 and $FF04? By: Harry Potter on Thu, 19 December 2013 09:12

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