Date   : Thu, 28 Jul 2005 18:25:15 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: ARM copros, speech cartridges, real timeclocks, etc

Jules Richardson <julesrichardsonuk@...> wrote:
> Hmm, found the ACW service manual. It says the following TUBE lines are
> used:
> 
>   8x data, A0-A4, R/NW, 2E, NRS, and NIRQ.
> 
> It says that an interrupt scheme is used on the copro side of the Tube
> and polling on the I/O processor (bbc B+) side of the Tube. That sounds
> normal; I assume a copro can interrupt the I/O processor to do stuff,
> it's just that the I/O processor can't interrupt the copro (it's polled
> only)
> 
> But then further on it says of the copro that "the only source of
> interrupts is the Tube", implying that the B+ board *can* interrupt the
> copro. Hence I'm confused :)
 
You've got the previous paragraph the wrong way around.
 
The host polls the client to see if the client wants anything to
tell it anything, ie to request the host do something. The host
interupts the client to inform it of Escape state changes, errors
and events.
 
The client sends commands to the host, which the host poll for.
The client never interupts the host.
 
If you have access to the New Advanced User Guide or one of the
other books I mentioned in an earlier post[1] there's explanations
of the Tube protocol there. I'll have to try and get around to
typing up a better explanation than the brief notes currently on
my site.
 
[1]Search the mailing list archive for "Subject: Tube protocol"
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
HADFS System Resources - http://mdfs.net/Software/HADFS