vic20 part 4

Sometimes it’s like two steps forward and one step backwards but I already learned a lot of the vic20 inner workings.
The roms with the additional two bytes I mentioned in the previous post are simply autostart cartridge roms “converted” to the .prg format which contains the in memory starting address in the first two bytes.
To upload those roms with the MiST interface would require a continuous block of ram instead of the multi blocks I use currently. But using one big block requires multiplexing of the different signals to the ram (ram and block select).
After I did this the vic20 didn’t work anymore. The screen went mad or – the best case – just blinks with the ready. I didn’t figured out why it behaved like that but using again single blocks for the basic working ram, the screen ram and the screen color ram helped to make it stable again. But cartridge uploads to the big block still won’t work.
I can make an own block for the blk5 memory block again but something is wrong with the multiplexing and it would be nice if I could find and fix it.

Leave a Reply

Your email address will not be published. Required fields are marked *