8MB FLASH ROM 1MB SRAM The memory is organized in 5 "windows": RAM1/2/3, BLK1, BLK2, BLK3, and BLK5. Each "window" can be configured to show any 8kB RAM or FLASH ROM page in the memory space Well, this certainly blows away my plan to upgrade my internal memory expansion. Too bad...
The possibility of buss contention still exists in the simple design, Yogi. VR/W goes low -- if it's going to go low -- near the end of SO2. (PH2) /CS will go low at the start of SO2, and so will the SRAM /OE, putting data on the buss at the same time as the 6502. The duration of this contention wil...
According to Sam's CompFacts, /IO2 and /IO3 as well as the VIA chips CSs are generated by decoder UC6 which is enabled by the CA 15:13 bit pattern. So these signals would go active as soon as the address pattern matches; regardless of the clock phase. OTOH the UC5 address decoder, for the /BLK sele...
Oh, this is a bit confusing to me. I guess I had misunderstood the need for the 65245 xceivers, I thought they provided bus isolation when the 6502 was in RDY state to accommodate the VIC-1. RDY is pulled up and unused in the VIC-20 and irrelevant to this discussion. The rest of your summation seem...
I am also considering banking with the option to WP selected BLKs. I see two ways to do it: By preventing the RAMs' /WE from going low, or by preventing /CS going low and thus not enabling the RAM at all. I'm leaning toward the 2nd method as it avoids buss contention -- a possibily that the VIC's de...
Hi , new here but have been reading for a bit and for VIC this IS the place to be! I had to jump in here. Last week decided to dig my VIC out of storage and get VIC Tracker running on it. So looking for a RAM Expansions, found Ruud's pages, http://www.baltissen.org/newhtm/memv20.htm also linked her...
I see your point about the use of these signals internally to the Vic20 but this still doesn't explain to me why put it on the expansion port. What is possible with this pin that otherwise would not be possible? Versatility? Convenience? If one were building some I/O device using discrete logic -- ...
A better question might be why did Commodore call it "V"r/w, since the VIC IC only reads, and does not write. VR/W is narrower than CR/W, because it is "qualified" with Phase2, and is best used for accessing expansion bus RAM. CR/W would be used with external I/O chips that have ...
Would that mean it would be possible to boot the Vic, copy the character rom to ram, load and overwrite with a custom character set, flick a switch and use the Vic with a custom character set? In my modification mechanical switches were used only to configure the normally expandable areas; RAM1,2,3...
Cool, would you care to share your schematic? The schematics of Richardc64s internal expansion are found on his site . As ambitious as this mod is, it would have been helpful if Richardc64 also had provided some software at least to demonstrate the advantages of doing those mods. That is something ...
I did something similar around the same time. I used an 8kx8 with 3k of it as RAM1,2,3 and 4k "under" the Character ROM so I could have custom characters without using any "main" memory. I've since thought of a way to have both VID accessible internal 3K OR normal external 3k not...
Jeff, for what reason would you want to delete, add, or possibly also modify lines from within a program, How about after filling a largish array with initial values from DATA statements, deleting the DATA lines and the FOR-READ-NEXT so there'd be more memory available for other variables. Could be...
Now how cool is this? I had no idea you had registered here on Denial! :D End of last year, I posted a link to your site in the thread ' What is happening here? '. My mothballed VIC has 76.5K inside. I missed that. I had to reactivate my account. I first registered when I saw that wimoos had incorp...
If you have a VIC-20cr, you can actually have the 32k x 8 installed inside your VIC by piggybacking it on top of one of the 2 2k x 8 SRAM chips and add the 74LS08 somewhere on top of the glue logic chips. You'll get a VIC-20 with internal 32k ram expansion. My mothballed VIC has 76.5K inside. http:...