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

  1. #91
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    Quote Originally Posted by Eudimorphodon View Post
    I've got an order of five DS1315s coming on the slow boat. (It should be pin/API compatible with the older DS1215/1216. I found a source that had them for a comparable price... assuming they're actually good, of course.)
    Or you could use a standard DS12885 with an XO and CR2032 holder and use the 5170 BIOS RTC code to have a driverless clock.

    Quote Originally Posted by Eudimorphodon View Post
    Here's a mickey-mouse idea for enabling D000 without needed another RAM chip, but you'd need two more decoder ICs:

    *** lots of steps and chips with later corrections just in this thread ***
    Quote Originally Posted by Eudimorphodon View Post
    If I thought this out correctly this should work...
    Quote Originally Posted by Eudimorphodon View Post
    Might want to double-check my reasoning...
    Quote Originally Posted by Eudimorphodon View Post
    ...if you actually went with this idea I'd also suggest...
    Quote Originally Posted by Eudimorphodon View Post
    I was *this* close to sending off a PCB order with the memory map hard-set to the wrong locations.
    Quote Originally Posted by Eudimorphodon View Post
    Actually, I just did double-check it, and realized this idea needs...
    Here's a crazy thought... Just put an 22V10 on the first run prototype board in-place of all that speculative logic, work out the solution with a text editor and ROM programmer, and then translate it to discrete 74xx/4xxx logic in run #2.
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

  2. #92
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    Also here are my dimensions for the PLUS cards I've built (XT-IDE, HardMPU, Memory, and NE2000) so you can cross-check your footprint:
    tandy_plus_drawing.jpg

    Edit: Just realized the forum decimates the resolution a great deal.

    Re-hosted here
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

  3. #93
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    Quote Originally Posted by eeguru View Post
    Or you could use a standard DS12885 with an XO and CR2032 holder and use the 5170 BIOS RTC code to have a driverless clock.
    Sure, sounds great, but way beyond my x86 coding ability. Does a version of code to do this already exist in a discrete form to work in an XT? A DS1215 driver sounded like a lot easier problem to handle, I'm reasonably sure I've seen one written in BASIC.

    The first post of this thread also makes it sound like it wouldn't necessarily be easier to interface, either, but maybe he was all wrong about that.

    Here's a crazy thought... Just put an 22V10 on the first run prototype board in-place of all that speculative logic, work out the solution with a text editor and ROM programmer, and then translate it to discrete 74xx/4xxx logic in run #2.
    I'm sorry if my thinking out loud is getting on your nerves. I'm sorry. One glaring problem with that suggestion, alas, is I don't have a 22V10 programmer so I can't just wave my hand and make it happen. First time it came up I did do some digging, and essentially what I found was a bunch no doubt bad information that roughly summarized like so:

    1: Circa 2017 the cheapest options were apparently running around $70 on eBay (in 2017), but some of them were really sketchy. To really do it right you need a proper commercial programmer, not some made in China thing that *may* work if you use one very specific device SKU.

    2: Found a number of rants going on at further length about how getting a programmer that works reliably is non-trivial.

    3: Claims that these chip, while fairly widely available, have been discontinued. Which apparently isn't actually true, probably, but the ones made now have differences...

    In short, it seemed like there's a lot of bootstrapping there if you're starting from zero. But I'm sure you know all about this subject and can tell me how wrong I am about that.

  4. #94
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    Quote Originally Posted by eeguru View Post
    Also here are my dimensions for the PLUS cards I've built (XT-IDE, HardMPU, Memory, and NE2000) so you can cross-check your footprint:
    Since you've built a RAM card for the PLUS slot would you be able to confirm the memory map for add-on RAM starts at 0000h? (or doesn't)

  5. #95
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    If you've got a TL866 programmer, they're "supposed" to be able to program the 20v10 & 22v10 series, though I have no experience with them. Good news is that unlike FPGAs, PLAs are pretty cheap, and Digi-key has the clones available.
    How are these programmed? Just write out a truth table in notepad and plop it into the programmer? Or is there a GUI availible?
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, and some random Pentium in a Hewitt Rand chassis...

    Some people keep a classic car in their garage. Some people keep vintage computers. The latter hobby is cheaper, usually takes less space, and is less likely to lead to a fatal accident.

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    For what little it's worth (obviously I didn't think of it in time) there are some interesting logic simulators out there to let you paint out your problem and test assumptions without burning anything. I just made this:

    https://circuitverse.org/users/6802/projects/18960

    (you can play with the preview, clicking on the input boxes changes their states) The boxes labeled A16-A19 represent the address line inputs. "CHIP A17" is the output address line routed to the RAM chip, "Enable" is the low-active chip enable output, and D000 and E000 are active low enables for the D and E pages respectively. (Derived from the '138 not included) Walking through the truth table I get this for all 16 possible states of the top four address lines: ("chipadd" is the condition of A18-16 as presented to the RAM chip.)

    Page | chipadd | Enable
    --------------------------
    0 | 010 | 0
    1 | 011 | 0
    2 | 000 | 0
    3 | 001 | 0
    4 | 110 | 0
    5 | 111 | 0
    6 | 100 | 1
    7 | 101 | 1
    8 | 010 | 1
    9 | 011 | 1
    A | 000 | 1
    B | 000 | 1
    C | 110 | 1
    D | 101 | 0
    E | 100 | 0
    F | 101 | 1

    Subtract the states where chip enable isn't on and rearrange according to the RAM chip's point of view:

    2 | 000 | 0
    3 | 001 | 0
    0 | 010 | 0
    1 | 011 | 0
    E | 100 | 0
    D | 101 | 0
    4 | 110 | 0
    5 | 111 | 0

    That looks like full utilization of the RAM chip using 4 NANDs ('00), 3 ANDs ('0, and a 74138. But maybe I need coffee.

  7. #97
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    Quote Originally Posted by Eudimorphodon View Post
    Sure, sounds great, but way beyond my x86 coding ability. Does a version of code to do this already exist in a discrete form to work in an XT?
    Of course. Check out: http://retrotronics.org/jride and reference the linked utilities and SVN repo to the left side-bar.

    Quote Originally Posted by Eudimorphodon View Post
    I'm sorry if my thinking out loud is getting on your nerves. I'm sorry. But I'm sure you know all about this subject and can tell me how wrong I am about that.
    Just trying to help.

    Quote Originally Posted by Eudimorphodon View Post
    I don't have a 22V10 programmer...
    A lot of inexpensive ROM programmers will do SPLDs. Atmel still makes clones as ATF22V10 and are available through most part distributors. It's a good tool to have in your toolbox. I've dead-bugged or proto-boarded several just to simulate a combinatorial logic function in-circuit.

    WinCUPL is a horrible program to use. But if you can push through the pain of birth, the baby is worth it.

    Quote Originally Posted by Eudimorphodon View Post
    Since you've built a RAM card for the PLUS slot would you be able to confirm the memory map for add-on RAM starts at 0000h? (or doesn't)
    Yes, you map it at zero. I didn't know that until I built one for a 1000A. I've never tried to map UMBs as I didn't have the upper address lines remap'able.

    If you prototype it, you can always poke around in debug.exe and see which writes stick.


    Quote Originally Posted by Eudimorphodon View Post
    ...there are some interesting logic simulators out there to let you paint out your problem and test assumptions...
    Check out a tool called Logic Friday. You can input a truth table and it will optimize row count or generate an equivalent and optimized 74xx series circuit.
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

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    Quote Originally Posted by eeguru View Post
    Of course. Check out: http://retrotronics.org/jride and reference the linked utilities and SVN repo to the left side-bar.
    Okay. The chip does still look considerably harder to interface than the smartwatch chip, though. (That only needs a chip select to sit on and like three connections to single address and data lines. This one has a multiplexed data/address bus? Which I'm sure is no big deal with a CPLD sitting in front of it.)

    I also already bought the DS1315s and crystals, but if someone else wants to chase this idea...

    Just trying to help.
    Sorry for being prickly about it. It's just not a suggestion I'm in the position to implement. Not that I think that programmable logic is a bad idea, I just have no grounding in it nor the equipment to do it, so going that route for step #1 throws a *giant* mountain of prerequisites into the way of actually making "a thing".

    A lot of inexpensive ROM programmers will do SPLDs. Atmel still makes clones as ATF22V10 and are available through most part distributors. It's a good tool to have in your toolbox. I've dead-bugged or proto-boarded several just to simulate a combinatorial logic function in-circuit.
    Do you have any opinions regarding the aforementioned TL866? (Or specifically the TL866II Plus, since that seems to be the current model actually for sale.) The thing that has me worried is I keep finding these threads that essentially boil down to "with (Device X) I could program the (insert brand here) GALs, but ones from (other brand(s)) won't work even though the software claims it was programmed successfully...".

    If I could lay hands of a programmer I could be confident in I wouldn't mind learning to use it for some other projects I've had on the back burner for a long time. But I can't justify hundreds of dollars if that's what it takes to get a device that won't randomly screw up in inscrutable ways.

    Thank you for once and for all confirming the shape of the T1000's memory map. *Technically* you can derive the right answer from the 1000 EX technical manual but only the original 1000's service manual actually seems to come out and say how it works.

  9. #99
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    I can't speak to most current gen PROM programmers. I used first used a Willem parallel port version when I was a broke college student. 25 years later I have a gaggle of Elnecs and EETOOLS but both are pricey. One could say I'm a bit spoiled.

    As for the other design choices.. there is always a version 2! I just found eventually learning a bit of 5V/PTH programmable logic saved a few bodge-wires and re-spins over the years. Good luck. If I had the time to do this sort of thing still, I'd eagerly contribute.
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

  10. #100
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    Quote Originally Posted by Eudimorphodon View Post
    Do you have any opinions regarding the aforementioned TL866? (Or specifically the TL866II Plus, since that seems to be the current model actually for sale.) The thing that has me worried is I keep finding these threads that essentially boil down to "with (Device X) I could program the (insert brand here) GALs, but ones from (other brand(s)) won't work even though the software claims it was programmed successfully...".

    If I could lay hands of a programmer I could be confident in I wouldn't mind learning to use it for some other projects I've had on the back burner for a long time. But I can't justify hundreds of dollars if that's what it takes to get a device that won't randomly screw up in inscrutable ways.
    I've had good experience with the TL866 Plus that I got from Amazon about a year ago. No idea how it will handle older PROMS, but it works with modern CMOS EEPROMS like the Atmel and SSTs that are popular these days, and even has the ability to test logic ICs (which has aided in troubleshooting/repairing one board already).You'll want to look up the compatibility list, of course. The more expensive "professional" programmers will be capable of more, but for the price, it's not too bad for an introductory programmer. The one I got came with extra adapters for non-DIP packages. I've only needed one of those adapters so far, but it gives other options if a through-hole DIP package is impractical for your project.

    Thank you for once and for all confirming the shape of the T1000's memory map. *Technically* you can derive the right answer from the 1000 EX technical manual but only the original 1000's service manual actually seems to come out and say how it works.
    I'll thank you as well. By the time this is all done, I think we'll both have something we'd be proud to stick in somebody else's machine
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, and some random Pentium in a Hewitt Rand chassis...

    Some people keep a classic car in their garage. Some people keep vintage computers. The latter hobby is cheaper, usually takes less space, and is less likely to lead to a fatal accident.

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