Denial

Mike wrote: ↑Sat May 10, 2025 1:45 am This happens to be the one by Peter Gerrard and Kevin Bergin?

Yes that 'book'. When I acquired my first C64 it came with that book.. Funny, I never used it.

I got it!

I just needed to tab the *=$C000 over and remove the tabs/spaces between. That fixed that problem - then the assembler complained about '^^' not fitting in 1 byte.. so I changed that to '^' and it has assembled!

Here it is if it's useful to someone else:

Orangeman96 wrote: ↑Thu May 08, 2025 8:00 pm I would PM srowe, as he is identified within the text file, and is a Denial frequenter. Good luck! -OGM

Thanks OGM - I'll see what gives.

I just found this: https://github.com/jdimeglio/6502-Simulator.git I'll have to see if that will assemble the code when I can find a Windows machine. UPDATE: No it won't assemble.. "Unrecognized data--space or label expected. ROW 1275" . That's at the *=$C000 line. I tried .ORG $C000 and I...

This problem sound crazy, but I would like to reassemble this ROM disassembly: vic-20-rom.asm.zip I think this is the most commented version of the ROM disassembly I have seen (please correct me if I'm wrong) but what I'd like to do is assemble it and generate a .lst file so I can see all of the add...

Gotcha, Sparky, I was just trying to ascertain how many half-byte locations were acutally in-play/meaningfully-usable. - OGM If its 4-bit x 1K.. For a default screen size of 22x23, that would be 506 nybbles.. so I guess 1024 - 506 nybbles free? Hehe. This is all quite fun and hacky - I would never ...

So its only two low nybbles then, AndyH: the low nybble of $9400 (four bits) and the low nybble of $9600 (four bits)? - OGM I'm pretty sure the read of $9600 on an unexpanded Vic reads the same physical chip and location as $9400 does with 8K RAM expansion. In other words the address mapping change...

AndyH wrote: ↑Wed May 07, 2025 5:40 pm Depending where your screen is set, either $9400 or $9600 will be free to use (the lower 4 bits).

Oh sorry, I thought you were meaning that the upper 4 bits could be used to store additional 4 bits of data.

Yes, those bits are just not available. It can be used for storing data within these limitations for the range that's spare. On Emu's Massive Hunt I use it to store 4 flags per screen to determine what objects you've collected on that screen. So whereabouts do your 4 bits actually get written to? T...

Wilson wrote: ↑Mon May 05, 2025 4:39 pm The color RAM is only 4-bit. What you read on the upper 4 bits will just be garbage on the bus.
You need to AND your read value with $0f to get the actual contents of the memory between $9400-$9800.

Oh, is it that simple? Hehe. Of course - that makes perfect sense now. Thanks for that

I've noticed that if I try to do a PEEK(38400), I don't always get the actual colour value back - and I see the same thing in VICE (unexpanded Vic). When the kernel scrolls the screen up (as it would during a LIST for example), I assume that the the kernel must read the colour RAM in order to move t...

Orangeman96 wrote: ↑Wed Apr 16, 2025 7:43 pm Good luck, SparkyNZ! -OGM

Thanks - the PCBs arrived today.. Just populated a board.. and it works!

You really should use a 74LS00 and do /OE = /(CR/W & SΦ2) - as I already wrote, CR/W on its own has the wrong timing. My v2 PCBs arrived today. Cartridge/ROM images started straight away. RAM bank switching also working. Happy chappy :-) Now I'll have to get back to the reason I went down this ...

Just an update since I went pretty quiet (and busy). I'm still waiting for my new cartridge PCB arrive but I did manage to get a BASIC program to autostart within Vice using a (raw) .crt image.. so thanks for all the help. I'll should be able to test this out on the real thing in the next few days.

groepaz wrote: ↑Sat Apr 05, 2025 9:00 am I'll add a warning to cartconv for this case NOW. i can see how its a stumbling block

Excellent, thank you - and noted. It doesn't take much to make me stumble