I think I narrowed down my rather broken non-cr VIC's problem to either bad ram, or a bad trace. I can't get any cartridges to boot, nor can I get anything more than just garbled characters on screen when no cartridges are inserted. I've been following the document from Ray Carlson, and not really finding the issue.
I'm fairly certain I'm in over my head. I'm not really sure I get the theory of how the VIC works in regard to the address swapping it does. I'm looking at this schematic (pdf warning) http://www.zimmers.net/anonftp/pub/cbm/ ... ematic.pdf the more I read the schematic, the more confused I get. I'm not sure exactly how the 6502 and the VIC actually toggle what set of ram chips are being used at any given point.
Hardware probe in-situ
Moderator: Moderators
-
kaluce
- Vic 20 Newbie
- Posts: 2
- Joined: Wed Dec 30, 2020 5:35 pm
- Website: http://www.google.com
- Location: US
Re: Hardware probe in-situ
The general principle is that UB1 decodes the 8K blocks, UC1 then decodes each 1K block of block zero. The complications arise because the two chips work on opposing phases of the clock and use a different base address. There was a good summary diagram, I'll see if I can find it.