Path: utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!mcsun!hp4nl!inducom!meindert
From: meindert@inducom.UUCP (Meindert Kuipers)
Newsgroups: comp.sys.m88k
Subject: Re: Request for help: Location Monitors on the Motorola MVME188 board
Message-ID: <2026@inducom.UUCP>
Date: 15 Jan 91 09:03:13 GMT
References: <54451@mcdchg.chg.mcd.mot.com>
Organization: Inducom Systems BV, Oss Netherlands
Lines: 27

From article <54451@mcdchg.chg.mcd.mot.com>, by heiby@mcdchg.chg.mcd.mot.com (Ron Heiby):
> I think Michael didn't mention one thing that some of my 68K customers
> have run into when using location monitors.  That is that the board
> that is the target of the LM access, the one that is about to enter an
> interrupt routine, does *NOT* respond to the VMEbus cycle.  The board
> that makes the access to trigger the LM must be prepared for a bus
> error (BERR) on that cycle.

That would be very bad practice. It might take a LOT of microseconds before
the bus timer generates BERR*. Thus, it does not make these boards very
useful in a real-time environment. very difficult writing the software.
Also, a lot of CPU-boards are not capable of doing address-only cycles.
A true address-only cycle does not lead to a BERR*, because the cycle is
terminated after a certain period.

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