Re: PDP11 configurator/website idea - VMS

This is a discussion on Re: PDP11 configurator/website idea - VMS ; On Wed, 22 Dec 2004, Tom Ivar Helbekkmo wrote: > ian@beathoven.com (paramucho) writes: > >> I do have one question though, why isn't the line: >> >> csrbase = roundup(csrbase + devtab[i].csralign, >> devtab[i].csralign); >> >> included in the closing ...

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Thread: Re: PDP11 configurator/website idea

  1. Re: PDP11 configurator/website idea

    On Wed, 22 Dec 2004, Tom Ivar Helbekkmo wrote:

    > ian@beathoven.com (paramucho) writes:
    >
    >> I do have one question though, why isn't the line:
    >>
    >> csrbase = roundup(csrbase + devtab[i].csralign,
    >> devtab[i].csralign);
    >>
    >> included in the closing section of the routine below [...]

    >
    > Because I never noticed that bug? :-)
    >
    > Actually, the code in question won't even be reached. There is no
    > device that is in floating CSR space, but with a fixed interrupt
    > vector. If there were, my existing code would expect multiple devices
    > of that type to have individual vectors, but to share a CSR address.
    > That can't be right -- it would just be silly. So, in effect, the
    > whole "if (devtab[i].csr == FLOAT) {" group can be removed, and the
    > loop can be simplified to:


    A small additional nitpick.
    If I read the code correctly, you might skip vector addresses between
    devices. That's wrong, even though it's usually okay. Most systems
    automatically detect the vector anyhow. And some hardware use a software
    settable vector as well.

    Anyhow, it's only for the CSRs that one must skip addresses, in order to
    generate non-existant memory errors when one device type is finished.

    Johnny

    Johnny Billquist || "I'm on a bus
    || on a psychedelic trip
    email: bqt@update.uu.se || Reading murder books
    pdp is alive! || tryin' to stay hip" - B. Idol
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  2. Re: PDP11 configurator/website idea

    Johnny Billquist writes:

    > If I read the code correctly, you might skip vector addresses
    > between devices. That's wrong, even though it's usually okay.


    No, I don't do that. It's just that some devices need their vectors
    allocated starting at an address that's zero modulo 8 or 16.

    -tih
    --
    Tom Ivar Helbekkmo, Senior System Administrator, EUnet Norway Hosting
    www.eunet.no T +47-22092958 M +47-93013940 F +47-22092901 FWD 484145

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