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Thread: Question about 3270 Coax Protocols

  1. #11

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    Quote Originally Posted by MossyRock View Post
    Unless I'm misunderstanding something here, just emulating a MFM drive from a 3174 is only a fraction of what is required as you have none of the required infrastructure hardware for a 327x terminal to work.
    I should have been more clear. I'm not interested in getting a 3174 but I very well might if its the only solution. Emulating the mfm drive is just a way of getting that setup working.

    From what I was able to find on the type A coax protocol (http://bitsavers.org/pdf/dca/82C570_Data_Sheet.pdf), the protocol doesn't appear to be too complex. The complex bit is the connection between the 3174 and the host. I reckon a board (perhaps ISA) could be made quite simply with a DP8340 and DP8341 which do most of the electrical work.

  2. #12
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    Quote Originally Posted by cfsimmons View Post
    The complex bit is the connection between the 3174 and the host.
    Yes, that's where the transport protocol transformations from synchronous line, ethernet, or token ring to the polled bisync protocol of the 3270 happen.
    As far as I know, there is no open-sourced code around that does that, which is why the people I know who have it working with a real terminal just buy
    a 3174-23L with ethernet or token ring.

    The reason I brought up the Telex was that was an alternative to the 3174 which has options for modem, ethernet or token-ring connectivity,
    but there is even less known about them. At least they have off the self parts in them like 68000's and DP834x.

  3. #13

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    You can think of the IBM coax protocol as a layer 1/2 transport using a bi-phase protocol and . In 1987 Capstone Technology did an ISA development board for National Semiconductor's then new DP8344 BCP (biphase communications processor). Here is one of their boards with a Engineering Sample of the chip from my collection:

    BCP.jpg



    As other pointed out earlier in the thread the actual display on the screen was carried by the 3270 data stream (think layer 3) which is well documented.

    This paper suggests that the layer 1/2 is not well documented (I don't have the actual journal paper):

    https://www.sciencedirect.com/scienc...4193319591861W

    but you can find the National BCP datasheet here:

    http://www.bitsavers.org/components/...work_Mar88.pdf

  4. #14

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    Quote Originally Posted by Kiwi View Post
    You can think of the IBM coax protocol as a layer 1/2 transport using a bi-phase protocol and . In 1987 Capstone Technology did an ISA development board for National Semiconductor's then new DP8344 BCP (biphase communications processor).
    That looks nicer than the old DP8340/8341 chips (separate chips for transmit and receive). As I recall, those were pretty much glorified serial/parallel converters. The TAC / DCA IRMA boards used an 8X305 CPU to do the actual protocol work. The ISA IRMA board had an 8X305 CPU to handle the coax side of things. The IRMAprint / IRMAlink added an 8085 CPU for the user side, since there was no PC to handle that. I have the 8085-side source code around here somewhere, and probably still have the listings for the 8X305 side. [I did NOT want to deal with that CPU, but needed the listings to see what was going on, from the 8085's point of view.]

    NS's reasoning for separate TX/RX chips was that mainframe-side controllers might need many more receivers than transmitters. I don't know if they ever got any substantial design wins on the mainframe side, though.

    Later IRMA boards ditched the code ROMs for the 8X305 in favor of RAM, and used a DCA-labeled part instead of the 8340/8341 set. The DCA-labeled part may well have been an 8344.

  5. #15
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    Quote Originally Posted by Kiwi View Post
    You can think of the IBM coax protocol as a layer 1/2 transport using a bi-phase protocol and . In 1987 Capstone Technology did an ISA development board for National Semiconductor's then new DP8344 BCP (biphase communications processor). Here is one of their boards with a Engineering Sample of the chip from my collection:
    Do you have any of the BCP development tools (pretty much just the assembler) or their sample code?

    They show up in a couple of companies terminals. Telex used a later DP83445 which appears to have integrated the CRT controller as well.
    Information on that part doesn't seem to exist.

    National sold an MPA ISA card. I just bought this one and am planning on dumping the code from it and the code in the Telex terminal.

    ns_mpa.jpg

  6. #16
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    Quote Originally Posted by Kiwi View Post
    This paper suggests that the layer 1/2 is not well documented (I don't have the actual journal paper):

    https://www.sciencedirect.com/scienc...4193319591861W
    I spent the $35 for a pdf (all 5 pages of it). Pretty much an echo of the data sheet, other than them saying they used
    a coax packet sniffer to build a printer interface. They didn't describe anything in detail.

    The best source outside of IBM is the National 1990 IBM Data Communcations Handbook, which is under
    http://bitsavers.org/components/national/_dataBooks
    Last edited by Al Kossow; September 17th, 2018 at 07:00 PM.

  7. #17
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    Quote Originally Posted by Terry Kennedy View Post
    The DCA-labeled part may well have been an 8344.
    It would have been obvious if there were two high speed proms or rams attached to it for the 8344 code.

    I'd be interested in the code you might have. I'd like to try turning some IRMAprints into IRMAlinks (which are MUCH more rare)
    Apple actually sold the IRMAlink for Lisa. THOSE are really rare. I have the manual here: http://bitsavers.org/pdf/apple/commu...uide_Jul84.pdf

  8. #18

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    Quote Originally Posted by Al Kossow View Post
    It would have been obvious if there were two high speed proms or rams attached to it for the 8344 code.
    No, it just appears to be a re-spin of the older designs, since it still has the 8X305 and 3 2KB RAM chips. I'll attach 3 pictures (none taken by me) of what appear to be 3 generations of the card design.

    I'd be interested in the code you might have. I'd like to try turning some IRMAprints into IRMAlinks (which are MUCH more rare)
    I think the standalone converter was the IRMAline and IRMAlink was the name of the file transfer software that ran on the PC-based IRMA boards. That part of my memory does not have parity protection, though.

    The IRMAprint came in serial and parallel versions (PC/3287-S and -P, respectively) with a different logic board inside. -S used a Signetics 2651 USART and the -P used a 7406 and 2 7407s. A universal board would have been nice.

    I modified both the IRMAprints (to speak Dataproducts protocol instead of Centronics) and IRMAlines (in conjunction with local mods to MS-DOS Kermit, to have a full additional line for the status display instead of bouncing the image up and down the screen by one line). The binaries at least should be on my old "ROM-burner PC", if it still works after 25+ years. It should also have the last version of the 8X305 PROMs - the earlier versions had a nasty problem where a 43xx CPU with integrated 3278 controller would fail to IMPL if the IRMAline was powered on and connected to the coax at the time. Arguably IBM's problem, but given the relative sizes of IBM and DCA, DCA fixed it on their side. I also remember that the power supplies for the IRMAline tended to fail if there were brief hits on the 120VAC line.

    IRMA-1983.jpg

    IRMA-1986.jpg

    IRMA-1987.jpg

  9. #19
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    Ok, so I happen to have a small quantity (EDIT: 9) of some generic C&T 82C570 cards that have an EPROM on them; would a dump of that EPROM be of any help to anyone? I don't have one in front of me right now, but I'll take a pic when I get a chance later today.

    Pic:

    1537478339379-2010646007.jpg

    EDIT: I have dumped the ROM. Here's edited output of 'strings' on the binary:
    Code:
    J1 Coax Version 1.25
    Copyright (c) 1989,91 J1 Systems, Inc.
    Version 1.25-J1
    ICOT ShortCUT Terminal Emulation  ROM 
    Qrom E
    Quadram MainLink II   ROM 
    ...
    J1 Coax Version 1.25
    Unable to load micro code.
    $QMIC3.02
    ...
    That 'Unable to load micro code.' string leads me to believe that this ROM has uploadable microcode for the 82C570 embedded.
    Last edited by lowen; September 21st, 2018 at 12:09 PM. Reason: Added quantity
    --
    Bughlt: Sckmud
    Shut her down Scotty, she's sucking mud again!

  10. #20
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    I spotted a National MainLink (same C&T chipset as your boards) on ebid, and picked it up
    National bought Quadram, so I'm guessing the firmware will be the same, given the Qrom
    reference in the prom

    The C&T chip isn't as well documented as the National DP8344, particularly the instruction
    set of the embedded processor.

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