Memory maps, chip documentation

Talk about programming CreatiVision (except games programming). Projects of homebrew hardware are also welcome.
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carlsson
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Location: Västerås, Sweden

Re: Memory maps, chip documentation

Post by carlsson » Tue Aug 27, 2013 2:54 pm

I had a brief look into Barry Klein's BIOS disassembly. It shows that the cartridge ROM pointers at $BFFC at power on are copied to $0200 - $0203. This was actually described already in Wizzdom #1. If either of those RAM bytes are changed, the console will perform a cold start the next time the reset button is pressed. It can be interesting to know, so we have ways both to detect if the reset button was pressed and to cold start on reset.

Other than that, I can't see any obvious references to that memory page. I checked for mirrored locations $0600 and $0A00 too. I suppose it should mean $0204 - $03FF is free RAM for applications, unless someone else has additional information.

When it comes to zeropage, of course Basic uses a fair bit of it, but as our machine code programs don't rely on Basic, we can ignore that part of the Wizzdom.
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Mobsie
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Location: Weinheim, Germany

Re: Memory maps, chip documentation

Post by Mobsie » Sat Dec 28, 2013 4:22 pm

carlsson wrote:I read the manual for the Wizzard parallel I/O interface, and it says that if you've got the memory expansion module, it needs to be connected to the Creativision and then the I/O interface into the memory expansion and any additional cartridge into the I/O interface.
Yes, is because the 74LS138 in the I/O interface use the ROM0 + A11+A12+A13 Lines. If the Address then is NOT $E800 (I/O interface) then send the ROM0 Line to ROMRW to possible read $f800 Bios. So after the I/O interface is not possible to use ROM0 to access $c000.
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