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Post by eslapion on Jul 24, 2016 20:23:20 GMT
Cant really help with your PLA query or the serial transfer speed as Ive never had an external burst mode drive to tinker about with. The 8568 is the 'improved' version of the 8563 VDC. It was standard on the C128 DCR and some plastic case 128D's. It eliminated some glue logic, came fully populated with 64kb ram and included some little improvements like a reverse polarity setting for the sync for an EGA compatible output. Its also not pin compatible with the '63. The PLA checker AFAIK is something that should be relatively simple to do. The only aspect of it I can't do myself is really the programming. The hardware is very simple. A PLA has 16 inputs and 8 outputs, all purely digital. On the Commodore 64, the IO1 and IO2 lines show up at $DE00-$DEFF and $DF00-$DFFF. You can either connect a 6522 at one of these two addresses or connect a 74LS273 at each IO range and you'll get the ability to output and signal 16bits, what you want to feed the tested PLA. You can then read the resulting 8 bit output on the PB0-7 of the user port. Now this gives you 65536 combinations to check against something and here's why you can't do it on a VIC-20 or C64, you need to store these 64k combinations to check in RAM. Also, because the C128 runs at 2MHz, it can do the job twice as fast. What I am lacking is a correct knowledge of the C128 memory map; I am quite sure I could do a program in BASIC to do the job and then compile it. Where do you read the value of the user port PB lines ? Where is the available RAM ? Where do I access the IO1-IO2 areas ? Do you read the PB lines on the C128 the same way as on a C64? Same address? Where can I find a block of 64k RAM in the C128 to store the values to check against? Concerning the VDC, I think increasing the RAM to 64k is plenty enough for what I want to do.
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Post by Pyrofer on Jul 25, 2016 11:29:12 GMT
If you want the best output from the VDC (80 col) then use a GAL as I have. A bit of programmed logic and you get a 6bit RRGGBB output, some resistors in a standard video DAC config and it's a near perfect picture. I also did the H+V sync to composite sync in the same GAL. There is a standard RGB to S-Video chip. It's got standard and perfectly working circuits published, I bought one with the intention of making a dual RGB+S-Video board but haven't as yet made the PCB.
I desoldered the VRAM on my 128 when the plug-in board didn't work. It was a pain, as mentioned, bent pins etc. I suspected the ram was dead anyway so I just cut the chips out and then slowly pulled each pin one by one for a good clean pull. As per "always" sockets went in in their place.
If you want real fun, investigate the genlock ability of the VDC. There is a pin input that resets the timings so you can sync it with the VIC, I don't think it's connected at the moment. If you get that hooked up right you can then genlock one over the other for some amazing effects.
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Post by Zippy Zapp on Jul 25, 2016 14:58:37 GMT
Yeah but... as I said above... Well I was merely stating a fact, not directly replying to you but I do get what you are saying. The ZoomFloppy is a good piece of kit. I keep old computers around just in case I need something that requires an old OS version or an actual parallel or serial port. Do you have an old system lying around that maybe has Windows XP english on it? If you lived near by I would give you one as I can usually find them at one or more of my clients offices laying around in stacks waiting for recycle or asset expiration or whatever. A c128 program that could read/write D64/D71/G64 disks would be awesome. You could easily put them on a 1581 disk and write them out at burst speeds. Of course there isn't a program like that at least for burst and G64. Have you had a look at CBM Command? CBM Command It doesn't write G64s but perhaps it could be a start...
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Post by eslapion on Jul 25, 2016 15:22:33 GMT
A c128 program that could read/write D64/D71/G64 disks would be awesome. You could easily put them on a 1581 disk and write them out at burst speeds. Of course there isn't a program like that at least for burst and G64. Have you had a look at CBM Command? CBM Command It doesn't write G64s but perhaps it could be a start... The native burst mode of the C128/1571 is not nearly as fast as the transfer speed of NIBWrite. The same hardware in the drive is used (the CIAs SP line) but the code using it is completely different. When I asked Peter Rittwage if it would be possible for a 2MHz C128 to take the place of Zoomfloppy to do the same thing he said it's impossible but I find that quite difficult to believe; the 1571 itself receives data at that rate AND it has the time to write it to a floppy in real time. The hardware for my PLA tester is almost complete... worked on it last night.
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Post by molebrain on Aug 16, 2016 13:23:11 GMT
I use my c128 to telnet to bbs through tcp/serv on raspbery pi. It is my original that I got for Christmas in 1985 I really would like to get more than monochrome 80 columns on my screen though I would like to buy an interface. I came across this: www.ebay.com/itm/161919633436Not sure if this is completely what I need though. Any suggestions?
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Post by eslapion on Aug 16, 2016 14:43:15 GMT
... I really would like to get more than monochrome 80 columns on my screen though I would like to buy an interface. I came across this: www.ebay.com/itm/161919633436Not sure if this is completely what I need though. Any suggestions? The information I have regarding the GBS-82xx series of converter is that they require converting the digital RGBi signal from the VDC to be converted into analog RGB first. The Ambery AV-1 I have also says CGA compatible in their specs but they have the same requirement.
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Post by molebrain on Aug 16, 2016 15:03:06 GMT
ah yes! you are correct. I remember Robert mentioning a blog post here someplace.
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Post by robertb on Aug 17, 2016 7:33:29 GMT
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Post by molebrain on Aug 17, 2016 12:50:35 GMT
Thank you Robert! You da man!
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