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Thread: Here is a dump of the character ROM from the TRS-80 DT-1...

  1. #1

    Default Here is a dump of the character ROM from the TRS-80 DT-1...

    ... in case anyone ever needs it to fix theirs. The sticker over the erase window had fallen off of mine, but fortunately the board was component-side-down so I guess it didn't get enough light over the years to erase it.

    It's a 2716 ROM. Both bin and hex files are in the attached archive.

    Now I have to figure out if there is some way to dump the internal ROM of the 8051. Hrmmm, I doubt that is possible....
    Attached Files Attached Files
    -- Lee
    If you get super-bored, try muh crappy YouTube channel: Old Computer Fun!
    Looking to Buy/Trade For (non-working is fine): TRS-80 Model II,12,16,6000, Mac IIci hard drive sled and one bottom rubber foot, Hercules card + mono monitor (preferably IBM 5151), Multisync VGA CRTs, 040 or 601 card for Mac IIci, Decent NuBus video card, Commodore PC(286+), PC-era Tandy stuff, Aesthetic Old Serial Terminals, Amiga 2000 or 3000UX

  2. #2
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    Some other dumps of the DT-1 ROMs have been made including one set that is in MAME.

    A search for trs80dt1.zip should find it easily enough.

    I did a quick comparison and it looks like your character ROM dump agrees in the bottom 4 bits but the upper 4 bits are mostly zero. I couldn't discern a pattern but I don't think you got a good dump.

    It is possible to dump the internal ROM of the 8051. I recall someone pointing out the procedure in a datasheet. There's some kind of test mode you can trigger that is normally used to verify the ROM contents.

    But I don't think there's much need for you to go to the trouble. The one in MAME agrees with another dump I've seen so chances of your ROM being different seems low.

    Thanks for taking the time to do the dump -- you never know when a differ ROM could turn up.

  3. #3

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    Hmmm, interesting. The characters appear valid on my screen, so I either dumped it wrong (which seem unlikely, but I guess anything is possible; perhaps the sticker over the erase window has been off long enough that the data is getting sketchy and my reader had trouble with it) or something strange is going on.

    Were there two different versions of the DT-1? Mine has a bunch of bodge wires in it, and a 373 that latches data on the parallel printer port has been replaced with a 374. These bodge wires and chip change are identical (well, other than wire color, heh) to the DT-1 owned by the guy on the youtube channel "Tech Tangents by (guy with the hair whose name I can't pronounce)", so I think it must be factory or a TSB modification. It has something to do with the printer enable line, but it's a little too weird for me to suss out. There is also another DT-1 board that I've seen on the web that lacks the bodge wires.

    The reason I mention this is because the modification makes use of an unused output line on a 3-8 decoder, which I presume would also require a software change in the 8051 ROM to make use of it. I assume that the character ROM is used by the video driver chip and never touched by the 8051, so I can't imagine that it would need to be programmed differently, but I suppose anything is possible.
    Last edited by bladamson; May 29th, 2020 at 03:04 PM.
    -- Lee
    If you get super-bored, try muh crappy YouTube channel: Old Computer Fun!
    Looking to Buy/Trade For (non-working is fine): TRS-80 Model II,12,16,6000, Mac IIci hard drive sled and one bottom rubber foot, Hercules card + mono monitor (preferably IBM 5151), Multisync VGA CRTs, 040 or 601 card for Mac IIci, Decent NuBus video card, Commodore PC(286+), PC-era Tandy stuff, Aesthetic Old Serial Terminals, Amiga 2000 or 3000UX

  4. #4

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    There's already dumps at bitsavers, but let's see if you got a different version.

  5. #5

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    I think gp2000 is right and it's probably corrupt.

    Tried dumping it again and got the same thing. I'm gonna burn what I read to another ROM and try it, and then I'll know.

    Edit: Here's some YouTubery about the aforementioned bodge wires. Skip ahead to about 5:43.
    Last edited by bladamson; May 29th, 2020 at 04:44 PM.
    -- Lee
    If you get super-bored, try muh crappy YouTube channel: Old Computer Fun!
    Looking to Buy/Trade For (non-working is fine): TRS-80 Model II,12,16,6000, Mac IIci hard drive sled and one bottom rubber foot, Hercules card + mono monitor (preferably IBM 5151), Multisync VGA CRTs, 040 or 601 card for Mac IIci, Decent NuBus video card, Commodore PC(286+), PC-era Tandy stuff, Aesthetic Old Serial Terminals, Amiga 2000 or 3000UX

  6. #6
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    Quote Originally Posted by bladamson View Post
    I think gp2000 is right and it's probably corrupt.

    Tried dumping it again and got the same thing. I'm gonna burn what I read to another ROM and try it, and then I'll know.

    Edit: Here's some YouTubery about the aforementioned bodge wires. Skip ahead to about 5:43.
    oh man.... the DT-1 part of the video was difficult to watch. actually, you got it pretty close on your "bodge wire" guesses!

    most of these mods were done in the field--your's was and i can tell from the workmanship, which wasn't bad, but the factory or national repair depot mods look much cleaner. for your wire that seems to do nothing, i suspect there was a cut associated with that and it may not have been done... but.... i have the bulletins for the DT-1, and you can now look for yourself.

    these bulletins were written on a 68000 mux box system using SCO Lyrix as the word processor--hence the very odd looking format info inline. i was too lazy to strip it out by hand.

    share and enjoy!
    Attached Files Attached Files

  7. #7

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    Thank you very much!!!

    What made it difficult to watch? I'm always looking for ways to improve my recordings, assuming it doesn't take too much extra time (busy busy busy, lol).

    Edit, after reading the TSBs: So there *are* two different versions of the 8051 ROM. My programmer won't dump the 8051, but maybe I can program an arduino to do it.
    Last edited by bladamson; May 30th, 2020 at 02:22 PM.
    -- Lee
    If you get super-bored, try muh crappy YouTube channel: Old Computer Fun!
    Looking to Buy/Trade For (non-working is fine): TRS-80 Model II,12,16,6000, Mac IIci hard drive sled and one bottom rubber foot, Hercules card + mono monitor (preferably IBM 5151), Multisync VGA CRTs, 040 or 601 card for Mac IIci, Decent NuBus video card, Commodore PC(286+), PC-era Tandy stuff, Aesthetic Old Serial Terminals, Amiga 2000 or 3000UX

  8. #8
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    Quote Originally Posted by bladamson View Post
    Thank you very much!!!

    What made it difficult to watch?
    you're welcome! just difficult watching you tracing wires, conjecturing what they did, etc... i wanted to tell you what was going on!

  9. #9

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    Quote Originally Posted by shank View Post
    you're welcome! just difficult watching you tracing wires, conjecturing what they did, etc... i wanted to tell you what was going on!
    he's a back seat video commentator
    Gaming: i7-8700K, 16GB, 1TB SSD, RTX 2060, Dual 27" LG IPS Monitors.
    Vintage: TRS-80 MODEL 4, 128K RAM, 360K FDD, Gotek USB FDD, FreHD HDD, RS232-WIFI MODEM, DWP-510.
    Programmer: Dell Inspiron 660S i3-3220 with 16GB Ram, running a BK-844USB & EP-2A-88.
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  10. #10
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    Quote Originally Posted by Patrick Bureau View Post
    he's a back seat video commentator
    yeah... like watching sports on tv!

    ...no...NO...itís not a typo!

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