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cdoty

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Posts posted by cdoty

  1. Posted · Edited by cdoty

    On 12/6/2020 at 6:08 PM, Falonn said:
     

    I'm having trouble finding my notes on it--I've never seen any of the 91xx's in the wild--but from memory I thought the only difference was an extra video mode and a slightly different palette (with better gamma correction) in the PAL version.  It was more of a revision to the 9928A/29A than a whole new chip.

    My guess is that it should work just fine.  Out of curiosity what do you have that uses the 9128?

    I think the major difference is support for 4416 SRAM chips.

     

    Several MSX machines use it, but I'm interested in using it on the BBC Bridge Companion, which I'm working on developing for.

  5. Posted · Edited by cdoty

    1 hour ago, ChildOfCv said:

    ..... that's weird.  The 4416s should be exclusive to the 9129.  The CPU has to use the VDC's memory read/write commands to access it.

     

    The data sheet for the 4416 says it uses A0-A7 for 8 bits of the address space, then only A1-A6 for the additional 6 bits.  It is not specific about which are intended to be the high or low half of the address (and indeed, it is completely up to the designer to choose).  But the A0-A7 pins of each 4416 should be connected to each other, and they should be connected to one of pins 3-10 of the 9129, and nothing else.  At least, that's what the 9129 expects.

     

    If they are doing something different, then programming it will be far different than expected for normal 9x2x-based systems.

    Problem solved.. Thank you.

     

    That's all it needed was A6 and A7 split out and A7 connected.

     

    And, the pins, from the VDP to the SRAM were wired backwards, AD7 goes to A0, etc, as was the Z80 PIO.

    So, I wonder if the diagram uses AD0 as the MSB, like the documentation does for the registers?

     

    Edit: it is shown that way on the TMS9918 document. AD0 (MSB)..

     

     

  6. Posted

    19 hours ago, ChildOfCv said:

    Yep, especially check AD0 and AD7.  I don't know which is which because TI has a tendency to count bits in reverse order.  But one of those is probably not connected fully between the VDC and its memory.  Looks like pin 10 from 9128 should go to pin 14 of each 4416, and pin 3 from 9128 should go to pin 10 of each 4416.

     

     

    Yeah that was it. I convinced myself that it needed all address lines to set both the low and high values of the address. But, yesterday I read the sc3000.txt document which indicates it would only need 6 address lines to access 8k.

     

    The A7 pins are connected to Pin 10 (A4) on the Z80 PIO chip.

  7. Posted · Edited by cdoty

    On 11/20/2020 at 6:13 AM, Tony Cruise said:

    The TMS chips can be configured with either 16k or 4k of video ram.  When in 4k mode the addresses get mirrored, that sort of sounds like the behavior you are seeing.

    It wasn't the TMS9129, I replaced it with no change.

     

    I did some testing and found out the chip is only seeing 8k, instead of 16k. It's using two 4416s, so that doesn't make a lot of sense.

    But, I was able to move the sprite stuff to either $3800 to $1800, etc. and it works the same regardless of the setting. Moving it to $800 overwrites the screen, so it is definitely seeing 8k.

     

    There is something about 8k or 16k memory mapping, but I can't find anything in the documentation dealing with that.

  8. Posted · Edited by cdoty

    8 hours ago, Tony Cruise said:

    The TMS chips can be configured with either 16k or 4k of video ram.  When in 4k mode the addresses get mirrored, that sort of sounds like the behavior you are seeing.

    I set register 1 to $82 initially, and then $E2 to turn on the screen.

     

    The sprite patterns are at $1800 and the attribute table is at $3B00, and those do work. I can also write to $800, and $1000 and see the effects on the different areas of the screen.

     

  9. Posted

    3 hours ago, ChildOfCv said:

    What do you mean by the above?  How does order of operation affect verifying where bytes went?  It seems to me that a better verification would be to write 00-3F into memory at 256-byte intervals, then read them back to see what ends up at each location.

     

    Anyway, the TMS chips allow you to specify where in memory colors, patterns, sprites, and the name table all go.  So programming the mode registers isn't enough.  Do you also program the buffer location registers?  Different systems may set them up with different values, so to ensure that it works across the board, you should program those values yourself.

    It's writing to $0000, so the last write to that location is the final value.

     

    Yes, they are all set:

        ld        b, 02h        ; Disable external VDP, set M3 for Graphics mode 2
        ld        c, 0
        call    writeVDPReg

        ld        b, 82h        ; Enable 16K VRAM, NMI interrupt, and 16x16 sprites. Disable screen.
        ld        c, 1
        call    writeVDPReg

        ld        b, NameTable / 400h    ; Set Name Table location.
        ld        c, 2
        call    writeVDPReg

        ld        b, (ColorTable / 40h) | 7Fh    ; Set Color Table location.
        ld        c, 3
        call    writeVDPReg

        ld        b, (PatternTable / 800h) | 3    ; Set Pattern Table location.
        ld        c, 4
        call    writeVDPReg

        ld        b, SpriteAttributes / 80h    ; Set Sprite Attribute Table location.
        ld        c, 5
        call    writeVDPReg

        ld        b, SpritePattern / 800h    ; Set Sprite Pattern Table location.
        ld        c, 6
        call    writeVDPReg

        ld        b, 00h        ; Set background color to black
        ld        c, 7
        call    writeVDPReg

     

    writeVDPReg ors the c value with $80.

     

  10. Posted

    I recently picked up a BBC Bridge Companion to see if I could get my code running on it. But, I'm having some issues with the TMS 9129.

     

    I am using Mode 2, and the code runs on all known TMS 99x8 based systems, but doesn't run correctly on the TMS 9129, or this particular system.

     

    The problem I am seeing is that writes to $2000-$3800 range go to $0000-$1800, but writes to $3800 work fine.

    I've been able to verify this by writing the color data first and then writing the pattern data. The sprites work fine, so writes to $1800 and $3800-$3C00 work fine.

    I've tried the exact delay they use when writing to the registers and VRAM.

    I've also changed the black color, as I've seen that cause problem on one system. The external VDP bit also doesn't make a difference.

    The code does run fine under Mame, and I've double and triple checked all of my register settings, and they are correct.

     

    The system itself only uses Mode 1 for it's software.

    I've tried piggybacking RAM on top of the two 4416 chips and that didn't work. I ordered a replacement TMS 9129. The existing one looks like it might have overheated at some point, and does get fairly warm in a particular spot. The system has no power switch, so it could have been left running for an extended period of time.

     

    Is there anything I'm missing, or does this sound like a damaged chip?

  11. Posted

    On 5/29/2020 at 12:27 PM, DavidC said:

    No tape counter though.  I bought one at my local walmart last year. I didn't notice the lack of a tape counter until I got home. I returned it.  Since then I have been buying any tape recorder I find at flea-markets and thrift stores.  I have a nice collection now! 🙂

    I've been doing the same. I picked up a boxed Radio Shack one in almost new condition a few months ago. It's my go to tape player now.

  12. Posted

    On 5/29/2020 at 10:45 AM, Omega-TI said:

    It would be interesting to know what the output level on the audio out jack is.

     

    I have tested it on a TRS-80 CoCo 2, and it's not loud enough to work on that. But, it does seem to work well enough on ZX spectrums.

  14. Posted

    On 9/5/2020 at 11:27 PM, matthew180 said:

    Life and job due to the pandemic have caused me to not have as much time as I planned the last few months, so the MK2 is not where I anticipated it would be by now.  I hate to keep apologizing, but that's all I can do for now, and I suppose I'll keep doing so until I get the MK2 done.

     

    I'm waiting on one to build an AppleTI card.. no pressure though. 😄

     

    I'm kidding of course, looking forward to a release. I would be happy with a VGA only release.

    • Like 1

  16. Posted · Edited by cdoty

    7 hours ago, Ikrananka said:

    The eBay auction cdoty linked to above (https://ebay.us/ASnj1W) illustrates quite nicely how problematic this can be as the photos show that Smurf, in this example, has 3 PROMS and yet the total ROM size of this game is 16KB.  The PROMS are stamped with proprietary codes specific to the game rom and not the PROM type.

    The board linked removes all of the complexities of a multi rom board. You don't need 3 roms for the Smurfs to work, you only need a 16k chunk of data, which can be accomplished with a single EPROM. This applies to all roms 32k or less.

    All of the wiring between chips is invisible to the Colecovision.

  17. Posted

    6 hours ago, Ikrananka said:

    It's not for me but for someone who is helping me with a project.  I actually have a bunch of the Pixels Past boards and offered to send one his way but unfortunately where he lives it isn't reliable at the moment sending anything there.  So, he'd much rather try and re-purpose one of his existing carts.

    Your best bet may be a 3rd party cart that had lower sales numbers. I've seen Sord M5 and Casio PV-2000 carts that contain EPROMs.

    There was probably a minimum purchase required for masked roms, which a smaller publisher wouldn't be comfortable with.

     

  18. Posted · Edited by cdoty

    On 8/31/2020 at 7:32 PM, Ikrananka said:

    But does it matter what size EPROM I put in the socket?  Does it have to match the size of the PROM removed? What about Coleco carts that contain 2 or more PROMs?

    Probably not, but I haven't tested it. As long as it is the same type of eprom and has the same number of pins, you can duplicate the data, and it will probably work.

    I was able to use a 27c256 in the place of a 27c64 when I was messing around with the Coleco BIOS.

     

    The available cartridge boards will only support up to 32k.

     

    I would suggest getting 28c256s. They are EEPROMs and work decently well.

     

    The 2 PROM boards should also support larger EPROMS, but you will still have to split the ROM into the original size.

     

    Another issue you could run into is the cartridge not being set up to accept 27 series EPROMS. The 3 chip Donkey Kong would be a good example of this.

     

  20. Posted

    These are EBay inflated prices. Super Cassette Vision systems and software can still be found pretty cheap through Sendico, or similar services.

    You can often see where someone has taken the pictures from a Mercari listing and placed them on EBay at an inflated price.

    I'm pretty sure that's where mine came from. I saw a few listing with the same picture, and assumed it was from Super Potato or somewhere similar,

    but having spent a decent amount of time on Sendico, I see this all too often.

    • Like 1

  21. Posted · Edited by cdoty

    On 8/27/2020 at 12:04 AM, Steven Pendleton said:

    The Marty is pretty expensive, I think. BEEP has a small collection of X68000 games for sale, but I don't think I've ever seen any games for the FM Towns or the Marty, now that I think about it. Maybe I just overlooked it since I was looking specifically for X68000 stuff, but I'll definitely check for FM Towns (Marty) next time I go to BEEP. I heard they are making a MiSTer core for the Marty (and X68000, for that matter), but I'm not sure of the details.

    They come up pretty consistently through Sendico, so it seems there is still a market for them. There's more under FM Towns, but there's certain software the Marty can't run because of it's limited memory.

    https://www.sendico.com/browse?category=&query=fm+towns+marty

  23. Posted · Edited by cdoty

    On 7/7/2020 at 10:24 AM, 0078265317 said:

    What do you think?  Only Japan for now.  Hope it comes here.

     

    https://www.polygon.com/2020/7/7/21315855/sega-astro-city-mini-release-price

     

    You can pre-order on Amazon Japan, but the shipping will be expensive. When I purchased a PC Engine mini, the shipping was almost offset by the exchange rate.

     

    On 7/8/2020 at 7:58 AM, NE146 said:

    As someone who saw the transition of Japan arcades from cocktails w/ uprights.. to eventually as the years progressed becoming samey looking long rows of clean white sit-down cabinets like the Sega City, I will tell you what games were normally on them. MAHJONG :lol: 

    I remember a lot of them having Neo Geo games on them in the early to mid 90s.

  24. Posted

    16 hours ago, Steven Pendleton said:

    I'm guessing I'm probably the only person here who has actually seen a real X68000, and yes, it is absolutely beautiful.

    I saw the x68000 and FM Towns Marty in Japan, in the 90's. I also bought one, and developed a game for it about 15 years ago.

     

    I've considered getting another one, but the repair horror stories have me reconsidering that decision.

  25. Posted · Edited by cdoty

    35 minutes ago, ApolloBoy said:

    The SG-1000 II with the custom Sega chip can be easily modded for RGB by using an amplifier circuit or even a Genesis Triple Bypass board.

    Yep, the RGB and CSync points are labeled on the board.

    I was just after a composite signal, and audio, I found those also.

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