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I wish to create a new DMA/RAM expansion card for the Tandy 1000 line.

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  • rkrenicki
    replied
    Huh, I had forgotten about the clock chip.. my HX already has one installed. I could go back and implement it into my next prototype, but honestly, it has very limited use for games of the era.

    I decided to go the Monotech XT-CF route on my next prototype, and use an IDE to CF adapter mounted "upside down" to get the CF interface. Those are cheaper than buying the sockets themselves new, and are less of a headache than surface mounting them with their 0.635mm pitch. I do not have any problems drag soldering 0.635 surface mount chips, but the CF sockets are always a pain for some reason.. It will require some modification of the backplate, but I still think it kills two birds with one stone by providing a backplate at the same time as fixing my CF socket issues.

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by blackepyon View Post
    By the way, what are you guys using for UART controllers? I've got an ISA multi-I/O card that I'm using for now, but I should probably work the RS232 into another card at some point to get rid of that annoying PLUS to ISA cable arrangement.
    I'm using the PC16552DV, which is the equivalent of two 16550s Siamese-twinned into the same PLCC-44 space as the standard 16550. (It manages this by getting rid of a bunch of connections that aren't used in standard PC applications and using the freed-up lines to drive the second SN75185N transciever.) I really like having the second serial port (the latest thing I've done with it is configured it to drive an Apple Imagewriter II printer), but I don't suppose it's really a must have if all you want is a mouse for games. The 16552 is pricey from sources like Digikey, but it seems to be pretty easy to get surplus.

    (FWIW, if you don't mind the connectors being just recessed enough to be annoying I'd be happy to send you one of my PCBs for the "just serial" card for the price of shipping. I didn't include a buffer on it but it seems to work fine.)

    According to the tracker my next gen boards should arrive today; If everything works the set will provide:

    * 384k base RAM
    * 0k-128k UMB RAM (128k max for an EX, 96k for an HX)
    * 32k of Flash (Located at either C0000 or C8000)
    * DS1215/1315 clock/calendar
    * 44 pin IDE connector
    * Dual serial ports
    * 1x ISA slot

    I guess that makes it the "Cadillac Option".

    Need to hit the local shop soon and pick up some parts so I can build up the tester. (In small quantities I can actually get 74HCT cheaper locally than Digikey; I really hope the march of progress doesn't put an end to that.)

    Leave a comment:


  • rkrenicki
    replied
    Originally posted by blackepyon View Post
    Looks nice, but you've got the external connectors on the wrong side of the board. :P This only matters if you intend to have anything on top of it.

    By the way, what are you guys using for UART controllers? I've got an ISA multi-I/O card that I'm using for now, but I should probably work the RS232 into another card at some point to get rid of that annoying PLUS to ISA cable arrangement.
    It is intended to be a single-board solution, so there would be no need of anything on top of it. I made no provisions for the bus passthrough either.. but I suppose the connector could be replaced with a stackable header.. but what would one realistically install into an EX/HX that isn't already on this?

    For the UART, I am using a PLCC packaged 16C550 and GD75232 transceiver combo, with some '138s for address logic.

    Leave a comment:


  • mojorific
    replied
    Originally posted by rkrenicki View Post
    [ATTACH=CONFIG]57177[/ATTACH]

    My first prototype of my 3-in-1 board arrived yesterday, and I quickly assembled one. It turns out that the footprint for my CF card slot was completely wrong for the part, so I did not assemble the XT-IDE portion of the board. I also apparently put the PLUS connector 2mm too far to the left, shifting the whole board to the right, so I needed to trim the board slightly to make it fit... but hey, that is what prototypes are for.

    But, in the meantime, the SRAM and RS232 portions of the board seem to work well, and I am currently working on optimizing the layout to be a little less of a jumble.
    Great work!

    Leave a comment:


  • blackepyon
    replied
    Originally posted by rkrenicki View Post
    [ATTACH=CONFIG]57177[/ATTACH]

    My first prototype of my 3-in-1 board arrived yesterday, and I quickly assembled one. It turns out that the footprint for my CF card slot was completely wrong for the part, so I did not assemble the XT-IDE portion of the board. I also apparently put the PLUS connector 2mm too far to the left, shifting the whole board to the right, so I needed to trim the board slightly to make it fit... but hey, that is what prototypes are for.

    But, in the meantime, the SRAM and RS232 portions of the board seem to work well, and I am currently working on optimizing the layout to be a little less of a jumble.
    Looks nice, but you've got the external connectors on the wrong side of the board. :P This only matters if you intend to have anything on top of it.

    By the way, what are you guys using for UART controllers? I've got an ISA multi-I/O card that I'm using for now, but I should probably work the RS232 into another card at some point to get rid of that annoying PLUS to ISA cable arrangement.

    Leave a comment:


  • blackepyon
    replied
    So, regarding the original intent of this post, I have a T512CLK-A1 here that I still intend to finish reverse engineering for it's DMA logic, which is entirely TTL.
    IMG_20191107_063039644.jpg

    I think we're all satisfied with the 00/32 RAM logic at this point, and people are building their own cards based on that, but once I finish up my current project, is there interest in having DMA function as well for "insane" EX/HX builds or is DMA just a curiosity for you guys? The RAM portion of the T512CLK is inconsequential at this point, and we've no need for DMA-0 since we're using static RAM, so it's basically down to whether or not you want the extra floppy performance and to run a sound card, scanner card, or something-whatever that can actually take advantage of DMA.

    And then with the other DMA schematics (Sergey's 8088, the IBM 5150 technical reference manual, etc), we should be able to come up with a useful DMA circuit in case somebody wants to populate that section of the board.

    Leave a comment:


  • rkrenicki
    replied
    20191106_223443016_iOS.jpg

    My first prototype of my 3-in-1 board arrived yesterday, and I quickly assembled one. It turns out that the footprint for my CF card slot was completely wrong for the part, so I did not assemble the XT-IDE portion of the board. I also apparently put the PLUS connector 2mm too far to the left, shifting the whole board to the right, so I needed to trim the board slightly to make it fit... but hey, that is what prototypes are for.

    But, in the meantime, the SRAM and RS232 portions of the board seem to work well, and I am currently working on optimizing the layout to be a little less of a jumble.

    Leave a comment:


  • bladamson
    replied
    Positive pressure on the inside of the enclosure.

    Keeps the magic blue smoke in the chips. :3

    Leave a comment:


  • dJOS
    replied
    Originally posted by blackepyon View Post
    I'm surprised you didn't fry the buffer on your card, with the +12v and -12v pins sitting opposite D0 and D2. The 5v pins won't kill anything immediately, but poking around with my multimeter the one time, my probe slipped and I accidentally fried the bus buffer on the motherboard in this manner. Fortunately, replacing that buffer chip fixed everything, but having that chip buggered prevented anything else on the data bus from working.
    I was surprised too, but my CF-IDE card lived ... somehow. I saw the black screen plus no beep and powered off immediately.

    Leave a comment:


  • blackepyon
    replied
    Originally posted by dJOS View Post
    Yep, that's the one that got me. Luckilly no damage was done - my EX just refused to boot.
    I'm surprised you didn't fry the buffer on your card, with the +12v and -12v pins sitting opposite D0 and D2. The 5v pins won't kill anything immediately, but poking around with my multimeter the one time, my probe slipped and I accidentally fried the bus buffer on the motherboard in this manner. Fortunately, replacing that buffer chip fixed everything, but having that chip buggered prevented anything else on the data bus from working.

    Leave a comment:


  • dJOS
    replied
    Originally posted by Eudimorphodon View Post
    I almost did manage to swap them when I was making my first card; the EX tech manual has diagrams on page 6 and page 9, and the two sides are swapped on the latter one, which I was referencing a lot because it's the one that translates any differences between standard ISA signal names and Tandy's names. (I can only assume the page 9 one was lifted straight from the conventionally-slotted 1000's tech reference.) I growled a lot when I realized my mistake and had to reconnect all the PCB routes, but I guess I at least caught *that* before I sent it off to the board mill.
    Yep, that's the one that got me. Luckilly no damage was done - my EX just refused to boot.

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by blackepyon View Post
    Yeah, the PLUS expansion bus is more or less compatible with the XT (ISA) bus, but if you miss the fact that the A and B sides are flipped... You're gonna have a bad time!
    I almost did manage to swap them when I was making my first card; the EX tech manual has diagrams on page 6 and page 9, and the two sides are swapped on the latter one, which I was referencing a lot because it's the one that translates any differences between standard ISA signal names and Tandy's names. (I can only assume the page 9 one was lifted straight from the conventionally-slotted 1000's tech reference.) I growled a lot when I realized my mistake and had to reconnect all the PCB routes, but I guess I at least caught *that* before I sent it off to the board mill.

    Leave a comment:


  • blackepyon
    replied
    Yeah, the PLUS expansion bus is more or less compatible with the XT (ISA) bus, but if you miss the fact that the A and B sides are flipped... You're gonna have a bad time!

    Leave a comment:


  • dJOS
    replied
    Originally posted by rkrenicki View Post
    Hey, putting a 245 with the A side and B side flipped is nothing compared to the time I designed a board with the entire IO bus flipped side to side.. >.>
    lol my first ISA adapter design was mirrored because I read the wrong diagram in the technical reference manual while designing it.

    Leave a comment:


  • rkrenicki
    replied
    Hey, putting a 245 with the A side and B side flipped is nothing compared to the time I designed a board with the entire IO bus flipped side to side.. >.>

    Leave a comment:

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