Newsgroups: comp.sys.transputer
From: jdd@aiki.demon.co.uk (Jim Dixon)
Subject: Re: Error -> Event
Organization: AIKI Parallel Systems Ltd
Date: Sat, 27 Aug 1994 20:54:14 +0000
Message-ID: <778020854snz@aiki.demon.co.uk>

In article <33jou6$7om@goanna.cs.rmit.oz.au>
           aaron@arcadia.cs.rmit.EDU.AU "aaron mcdonough" writes:

> I wish to apply the Error pin of a slave T805 to the EventReq of a master
> T805 but I am unsure as to how to go about it. 
> 
> The hardware consists of a Quintex Fast 9 board for PC x86's. The
> Transputer Databook (2nd ed.1989) states that it is possible to
> determine when an errant transputer has stopped. The manual states that
> this can be done by daisy-chaining the ErrorIn and Error pins of a number
> of slave processors and applying the final error pin to the EventReq of
> "a suitably programmed master transputer".  The master transputer can then
> take appropriate action when a slave processor halts. There is no mention
> of exactly how I can apply the Error pin to the EventReq channel. On the
> Fast9 board there is a DownNotError pin, from what I can gather,
> corresponds to the error pin of the last slave processor. I am unsure as
> to which pin (if it is done this way) the EventReq channel corresponds.

Assuming that the Fast 9 handles its subsystem pins conventionally, the
value of the subsystem pin can be read at location #00000000 in the
root transputer's memory map.  You could just poll on this, scheduling
a process to examine it every so often.  I assume that this is not
satisfactory.

To cause an event, you run the subsystem error pin into a PAL, invert it,
and tie the output to the EventReq pin.  You then run the EventAck pin
into the PAL as well.  Then the EventReq signal is registered, asserted
when SubsystemNotError falls, and deasserted when EventAck rises.  The
PAL logic will have to be a bit more complicated, because you want
EventReq cleared when reset is asserted.  And your software will have
to allow for the possibility of the subsystem powering up with the
error flag set.

You can use any other programmable logic device or even do the logic in
ICs if you like.  Enjoy.
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