1. This forum section is a read-only archive which contains old newsgroup posts. If you wish to post a query, please do so in one of our main forum sections (here). This way you will get a faster, better response from the members on Motherboard Point.

old (1985) 68HC11 EVB schematics needed

Discussion in 'Embedded' started by edick, Jun 11, 2005.

  1. edick

    edick Guest

    In '98 I posted the following:

    Richard Erlacher Sep 8 1998, 3:00 am
    Newsgroups: comp.arch.embedded
    Date: 1998/09/08
    Subject: 68HC11 EVB Schematics, etc.

    I have, after 10+ years, found that I've misplaced or lost my
    schematics for the ORIGINAL (1985) 68HC11 EVB . . . you know . . . the
    one they once sold for $68.11 to those willing to experiment with it.
    My main interest is in obtaining the pinout for the 60-pin (?)
    connector at one end, since that's where all the useable signals are

    If someone has this information and is willing to share it, I'd be very

    The schematic is also of interest, even if I am able to get the
    connector pin definitions, though.



    Well, because I was never able to find a copy of the "original"
    schematic, I'm still at a loss ... particularly with respect to that
    original connector, which, seemingly, was changed in later revisions.

    The way to recognize this board version is by counting the 28-pin DIP
    sockets. My old board has two of them, at U3 and U4. Since I'll
    probably need to fiddle with the board some in order to modify its
    resources, and since I'll want to use the signals on the 60-pin P1, a
    scan of the schematic would be really helpful, just in case someone
    happens to have it. Back in '98, I got a number of pointers to later
    versions, but, alas, those were not useable.

    I'd be thankful to have this information.


    edick, Jun 11, 2005
    1. Advertisements

  2. edick

    Brian Dean Guest

    I have a M68HC11EVB from around 1987 or so. It's probably not the
    original, though. The users manual says: "Information contained in
    this document applies to revision (B) M68HC11EVB evaluation modules,
    serial numbers 1000 and up."

    Checking the 28 pin DIP sockets, looks like this one has 3 at U3, U4,
    and U5.

    While I don't think it's the one you are looking for, let me know if
    you think this will be useful and I'll pass the pinouts along.

    Brian Dean, Jun 11, 2005
    1. Advertisements

  3. edick

    Correlious Guest


    I know this sounds tedious but if you want to check the connections you
    could just use a contiuity tester to find the pin to socket
    connections. I'd start by eliminating ground and power first as there
    maybe a few sprinkled in that connector.

    Correlious, Jun 13, 2005
  4. edick

    edick Guest

    I'd be happy to have a look at the connector pinout, if only to check
    against what I have "beeped out" so far, but my goal is to fool with
    the decoding logic in order to put a 32KB battery-backed RAM in place
    of the EPROM at U3 and a similarly sized SRAM at U4 with physically
    present I/O carefully mapped out of the SRAM region. While this is
    readily achievable with a fully documented board, the common practice
    of ambiguously decoding I/O on SBC's makes it risky to rely on such
    decoding for information in this case.

    If you have a connector pinout that you'd like to share, I'd be happy
    to check it out. I'll have to search further for documentation for the
    original, 3Q85 board. Sadly, that board has no identifying features
    visible with the components installed, that would make it uniquely
    identifiable. It simply has "M68HC11EVB" silkscreened in its lower
    left corner.


    edick, Jun 13, 2005
  5. edick

    edick Guest

    Yes, such an effort is tedious. Its result is also ambiguous. As time
    allows, I suppose I'll end up with enough information to make this
    thing useful again. There are a very few power connections. There are
    also some differences between the original and subsequent versions, I'm
    told, though the pinout was maintained after the rev B boards were
    released, and corresponding changes in the monitor firmware made as
    well. I got this information from a fellow at MOT back in '98 when I
    first started pursuing this matter.

    Thanks for your input.

    edick, Jun 13, 2005
  6. edick

    Correlious Guest

    If you have a logic analyzer, you can have the M68 write to mem
    addresses in a counter like fashion. Looking at the screen you should
    be able to decode the address lines at least. Once you have that you
    can force it to write the counter value to a fixed address and from
    that decode the data lines. In both cases, as you get closer to the MSB
    the switching frequency halves.

    Correlious, Jun 14, 2005
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.