Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!cs.utexas.edu!wuarchive!psuvax1!rutgers!mcdchg!michael
From: michael@mcdchg.chg.mcd.mot.com (Michael Bodine)
Newsgroups: comp.sys.m88k
Subject: Re: Request for help: Location Monitors on the Motorola MVME188 board
Message-ID: <54437@mcdchg.chg.mcd.mot.com>
Date: 14 Jan 91 20:48:52 GMT
References: <14423@june.cs.washington.edu>
Reply-To: michael@chg.mcd.mot.com (Michael Bodine)
Organization: Motorola Computer Group, Schaumburg, IL
Lines: 29

Robert Bedichek (robertb@june.cs.washington.edu) writes:
> The documentation from Motorola mentions these things, but doesn't say
> how to use them or exactly what they do.  I guess they are some sort of
> memory breakpoint facility built outside of the MC88100/88200 chips.
> But the documentation also suggests that this facility only works with
> VME accesses.
> Could someone tell me more about this?  Has anyone used this hardware
> facility?
The location monitor implements the "Address-only" cycle on the VMEbus.  It's
a quick way to communicate an event or an interrupt when no resource is 
available, say, on a peripheral board to do so.  A quick functional description:
a device wants to notify the 188 of some sort of event -- usually the exact
message would be stored in some location per the software design of the 
application.  The device would access the address of one of the location 
monitors on the 188;  this address is determined by the setting of the Global
Control and Status Register per table 3-12 in the 188 manual (MVME188/D1).
This access would invoke the Location Monitor Interrupt (LMI) the state of
which is reflected in the Interrupt Status Register detailed in table 4-3.
An interrupt is generated and the actual location monitor that was accessed
would be shown as a bit in the "GLOBAL0" GCSR, table 4-11.  The interrupt
handler would then reset the interrupt bit and go grab the message or otherwise
take note of the occurence of this event.  Also, the location monitors can
be set up to reside at the same locations on groups of 188 boards so that
events can be quickly broadcast to more than one cpu without having to access
multiple registers, ie. for purposes of synchronization.  I'm sure there are 
other uses you could make up.
-- 
[  Michael Bodine, michael@chg.mcd.mot.com, Dial: (708) 576-7840, FAX: x8875  ]
[  Motorola TSD; Loc IL38; 1100 Woodfield; Suite 334;  Schaumburg, Il  60173  ]