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Thread: A new G888 manchester read/write module

  1. #51
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    Quote Originally Posted by anders_bzn View Post
    If there ever will be a TU-USB it will be a TD8E-USB thing...
    Please no. The TD8E is the most stupid interface in the universe.
    But then again, maybe that makes sense. USB comes in as a worthy second-worst.

  2. #52

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    Well, TD8E is indeed stupid. What I meant was to build something that has a connector that is similar to the one that sits on the TD8E so you could plug in the cable from the drive either in TD8E or the "thing".

  3. #53
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    Quote Originally Posted by anders_bzn View Post
    Well, TD8E is indeed stupid. What I meant was to build something that has a connector that is similar to the one that sits on the TD8E so you could plug in the cable from the drive either in TD8E or the "thing".
    Oh, well if you just meant the electrical interface, then sure, that would make sense. But I expect that one is the same for all other DECnet controllers as well, since the drive is the same independent of controller.
    But the logical interface, and how you control is it pretty bad. Almost impossible to use in a timeshared or interrupt driven system.
    (I say "almost", since MULTOS proved me wrong if I had said "absolutely impossible"... But it's quite a hack to make it sortof usable...)

  4. #54

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    Electrical and physical to ease interconnecting both TU55 and TU56 to a TD8E. The TU55 have the G888 or G882 in the controller while the TU56 can have them in the drive or in the controller. When using Anders new set of cards both type of drives can be used with TD8E.

    For USB interfacing I then thought it could be useful to do a small device the integrate a small CPLD that deals with the realtime stuff equivalent of what the TD8E is doing and a STM32 blue pill for USB interfacing. This board would then have a TD8E compatible interface for ease of integration with Anders boards or a TU56 with G888s in it.

    Done some preliminary stuff in VHDL. But not finished yet:https://github.com/MattisLind/td8e_usb

  5. #55

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    Quote Originally Posted by MattisLind View Post
    Electrical and physical to ease interconnecting both TU55 and TU56 to a TD8E. The TU55 have the G888 or G882 in the controller while the TU56 can have them in the drive or in the controller. When using Anders new set of cards both type of drives can be used with TD8E.

    For USB interfacing I then thought it could be useful to do a small device the integrate a small CPLD that deals with the realtime stuff equivalent of what the TD8E is doing and a STM32 blue pill for USB interfacing. This board would then have a TD8E compatible interface for ease of integration with Anders boards or a TU56 with G888s in it.

    Done some preliminary stuff in VHDL. But not finished yet:https://github.com/MattisLind/td8e_usb
    No you mixed up TTU55 and TU56, it's only the TU56 that can hold G888 (haven't seen G882 in the drive). What I know about all TC's have the G88x cards in them. The G888's goes in the drive only when TD8E is used (as far as I know).

  6. #56
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    Quote Originally Posted by anders_bzn View Post
    The G888's goes in the drive only when TD8E is used (as far as I know).
    Correct. TC08 and TC11 (TC15?) have the G888s in the controller.
    You would think that the more common TD8E would mean there would be more TU56s with G888s out there, but it doesn't seem to be the case.
    The unique cable between the TU56 and TD8E are pretty rare as well (same for the RK05 to RK8E cable)

    All of my TU56s came out of PDP-11 configurations, so I ended up taking them out of my TC11 to do the stand-alone reading that I
    did at CHM in the mid 00's

  7. #57

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    Roland Huisman solved the problem with the RK05 to RK8E cable, which is great (which is the one I use, thanks Roland). I'm trying to do the same for TD8E to TU56 (and even TU55) cable.

    I have drawn replacement boards for M961 and M960.

    The "M961" board also includes the five G888's. The electrical design is almost 5xG888-Mk2 (have not put in 5x all voltage regulators).
    data-board-image.jpg

    The "M960" board will be in two versions, one for TU55 and one for TU56. This should make it possible to use a TU55 with TD8E!
    DSC_2765_00001.jpg
    Last edited by anders_bzn; January 27th, 2020 at 07:54 AM.

  8. #58
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    Quote Originally Posted by MattisLind View Post
    Electrical and physical to ease interconnecting both TU55 and TU56 to a TD8E. The TU55 have the G888 or G882 in the controller while the TU56 can have them in the drive or in the controller. When using Anders new set of cards both type of drives can be used with TD8E.

    For USB interfacing I then thought it could be useful to do a small device the integrate a small CPLD that deals with the realtime stuff equivalent of what the TD8E is doing and a STM32 blue pill for USB interfacing. This board would then have a TD8E compatible interface for ease of integration with Anders boards or a TU56 with G888s in it.

    Done some preliminary stuff in VHDL. But not finished yet:https://github.com/MattisLind/td8e_usb
    Ah. Good point. I had forgotten that that card might be in the controller for other controllers.

    But you know that the TD8E don't deal with any realtime stuff. It really just feeds pretty much the raw data to the CPU, who have to do everything. And it's not even interrupt driven, so you have to poll the thing all the time. Read out each bit of the control track, and figure out what you are seeing, reading in, combining data, control the motors... Everything is in software.

  9. #59
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    Quote Originally Posted by bqt View Post
    Everything is in software.
    And that it what makes it really useful. Reading and writing DECtapes that didn't come from a PDP-8 is easy.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  10. #60

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    Quote Originally Posted by bqt View Post
    Ah. Good point. I had forgotten that that card might be in the controller for other controllers.

    But you know that the TD8E don't deal with any realtime stuff. It really just feeds pretty much the raw data to the CPU, who have to do everything. And it's not even interrupt driven, so you have to poll the thing all the time. Read out each bit of the control track, and figure out what you are seeing, reading in, combining data, control the motors... Everything is in software.
    Well it does a bit since it has a couple of mono stables that filters out spurious pulses. That part (except for using counters instead of monostables) and latching the data on the clock track signal is done in the CPLD in my implementation. The STM32 code would do basically exactly what the pdp8 does. Non interrupt driven. Just forwarding the raw data to the host over USB for further processing.

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