Search found 21 matches

by Richardc64
Fri May 06, 2016 9:27 pm
Forum: Programming
Topic: Writting to $9010-$901F
Replies: 5
Views: 750

Re: Writting to $9010-$901F

Thanks for the mention. I got a little carried away decoding that area. It could've been done much simpler, but I was planning ahead, in case I might think of other items to put in that area. (I have, but that discussion would be more suited to the Hardware subforum.) Anyway, it seemed a waste to ha...
by Richardc64
Sat Jan 09, 2016 7:10 am
Forum: Hardware and Tech
Topic: Thinking of a SuperCPU VIC
Replies: 115
Views: 8923

Re: Thinking of a SuperCPU VIC

To very briefly thread-jack... I have an MD65SC22 (Mitel) salvaged from something years ago. Can I safely use it in a VIC-20, or is it likely to have the IRQ problem mentioned? Also years ago, someone told me tried a CMOS '22 in his VIC and it worked in one VIA socket but not in the other, but I've ...
by Richardc64
Tue Nov 03, 2015 9:14 am
Forum: Hardware and Tech
Topic: UltiMem
Replies: 200
Views: 11657

Re: UltiMem

Cool! I blame my eyesight for missing that. (That and me looking for it among the BLK registers.)
by Richardc64
Tue Nov 03, 2015 6:27 am
Forum: Hardware and Tech
Topic: UltiMem
Replies: 200
Views: 11657

Re: UltiMem

brain wrote:registers have moved a bit:


Awesome work.
I don't see any mention of 3K. Have you eliminated that feature?
by Richardc64
Tue Sep 22, 2015 3:43 pm
Forum: Hardware and Tech
Topic: UltiMem
Replies: 200
Views: 11657

Re: UltiMem

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...
by Richardc64
Sat Aug 01, 2015 10:00 am
Forum: Hardware and Tech
Topic: usefulness of partial inhibition (and not all) of the writing on the RAM expansion
Replies: 12
Views: 658

Re: usefulness of partial inhibition (and not all) of the writing on the RAM expansion

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...
by Richardc64
Fri Apr 24, 2015 4:20 pm
Forum: Hardware and Tech
Topic: Purpose of the vrw pin on the expansion port
Replies: 20
Views: 1600

Re: Purpose of the vrw pin on the expansion port

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...
by Richardc64
Fri Apr 24, 2015 4:38 am
Forum: Hardware and Tech
Topic: Purpose of the vrw pin on the expansion port
Replies: 20
Views: 1600

Re: Purpose of the vrw pin on the expansion port

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...
by Richardc64
Wed Apr 22, 2015 4:37 pm
Forum: Hardware and Tech
Topic: Purpose of the vrw pin on the expansion port
Replies: 20
Views: 1600

Re: Purpose of the vrw pin on the expansion port

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...
by Richardc64
Wed Apr 08, 2015 1:10 pm
Forum: Hardware and Tech
Topic: vic-1110 8k ram cart upgrade (and other solutions)
Replies: 59
Views: 6907

Re: Re:

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...
by Richardc64
Sat Dec 06, 2014 5:12 pm
Forum: Hardware and Tech
Topic: Purpose of the vrw pin on the expansion port
Replies: 20
Views: 1600

Re: Purpose of the vrw pin on the expansion port

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 -- ...
by Richardc64
Thu Dec 04, 2014 8:56 am
Forum: Hardware and Tech
Topic: Purpose of the vrw pin on the expansion port
Replies: 20
Views: 1600

Re: Purpose of the vrw pin on the expansion port

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 ...
by Richardc64
Sun Jul 13, 2014 9:25 am
Forum: Hardware and Tech
Topic: My mod from yesteryear
Replies: 13
Views: 2268

Re: My mod from yesteryear

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...
by Richardc64
Sun Jul 06, 2014 10:35 am
Forum: Hardware and Tech
Topic: My mod from yesteryear
Replies: 13
Views: 2268

Re: My mod from yesteryear

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 ...
by Richardc64
Thu Jul 03, 2014 12:53 pm
Forum: Hardware and Tech
Topic: My mod from yesteryear
Replies: 13
Views: 2268

Re: My mod from yesteryear

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...

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