From: Jim Brain (brain_at_jbrain.com)
Date: 2005-01-15 05:41:50
I am trying to design a 32 kB ROM cart for the VIC-20. I've found some
RAM expansions that come close to the design I am looking for, but
here's the rub:
On a RAM cart, you cna just feed the BLK signals to a encoder and get
the 2 high address bits. RAM is contiguous. No issues.
In a ROM/EPROM, there are lots of options:
8kB ROM mapped into BLK1, or BLK2, or BLK3, or BLK5
16kB ROM mapped into BLK1, BLK2, BLK3
32kB ROM mapped into BLK1
32kB ROM mapped in as two separate 16kB images
32kB ROM mapped in as 4 separate 8kB images
16kB ROM mapped in as 2 separate 8kB images
Does anyone have ideas on how to enable such configurations? If I
didn;t have to worry about swapping address lines, I could simply put
switches on the 4 lines. ON would enable that 8kB segment. Since
address line swapping is needed to implement the above, I thought about
some jumper blocks.
Anyone have better ideas or know of projects already doing this?
Jim
--
Jim Brain, Brain Innovations
brain@jbrain.com http://www.jbrain.com
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times!
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