Date   : Wed, 27 Jul 2005 16:07:51 +0200 (BST)
From   : Johan Heuseveldt <johan@...>
Subject: Re: ARM copros, speech cartridges, real timeclocks, etc

Hi Jules,

On Wed 27 Jul, Jules Richardson wrote:
> On Tue, 2005-07-26 at 21:57 +0000, Jules Richardson wrote:

> > You know, for some reason I think that the ACW (and possibly the ABC3xx
> > machines) perhaps did make use of an interrupt mechanism. I just can't
> > remember who told me that and exactly what I was told now though! I've
> > got the ACW schematics; I'll have to have a look and see. Maybe it
> > wasn't through the Tube though and wired in via some other way...  (of
> > course the BBC I/O processor side ran BOS, so it's entirely possible the
> > Tube-handling code was entirely different to a normal BBC)
> 
> Hmm, found the ACW service manual. It says the following TUBE lines are
> used:
> 
>   8x data, A0-A4, R/NW, 2E, NRS, and NIRQ.

Pretty standard.

> 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;

It is to me.

> I assume a copro can interrupt the I/O processor to do stuff,

No need, neither used, as the I/O processor (Beeb) is polling. Writing
by the CoPro sets a status flag, which the Beeb will read during its
polling.

My previous posts has mentioned that interrupting the host (by hardware
interrupt) is not used in the Beeb. That possibility is switched off
in the Beeb, during initialisation.

> it's just that the I/O processor can't interrupt the copro (it's polled
> only)

Is that really you want to write down? The CoPro /is/ interrupted by the
I/O processor (=Host, =Beeb). But the following probably influenced the
above?

> 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 :)

Defenitely. 
For the moments I can't figure out what exactly you are trying to say.


Hm, it seems the extra facility in the Tube ULA isn't used in these
machine either.

greetings,
Johan

-- 
Johan Heuseveldt <johan@...              >
  aka  waarland

  The best place is a Riscy place
 
Speak when you're angry, and you'll make
the best speech you'll ever regret.