Date   : Sat, 11 Aug 2007 01:01:19 +0200 (BST)
From   : johan@... (Johan Heuseveldt)
Subject: Emulating Econet hardware?

Hi Jules,

On Fri 10 Aug, Jules Richardson wrote:
> Jonathan Graham Harston wrote:
> > Johan Heuseveldt <johan@...> wrote:

> >> OTOH there is the SJ Research design - in its MDFS - with only a
> >> Z80 SIO, and lots need to be done in software. I'm not familiar with
> >> that serial device, so don't know how much it can do in hardware, and
> >> what's left to be done in software.
> >  
> > The Z80 SIO does more or less everything the 6854 does. It is
> > interfaced 8-style (IORQ, WR, RD), rather than 6-style (CS, R/W).
> >  
> > A useful extra the Z80 SIO has is that it can match the first byte
> > in the packet itself and reject the frame if it's not destined for
> > me. With the 6854 the CPU has to do that.
> 
> Interesting - I'd always assumed that the SIO was more concerned with 
> RS-232/423 comms and wasn't flexible enough to do much else.

I had the same thoughts about these more 'normal' serial applications. 
That's why I'm impressed.

> The chips still seem pretty common. Farnell still sell them, although it's
> not clear what the  difference is between a SIO/0 and a SIO/2 (without
> downloading both PDF files  and comparing, and I can't be bothered ;)

I suppose the difficult part would be the interrupt structure used. Most
likely presenting a byte on the databus?

> Maybe it's a better solution to attach one of those to a PC parallel
> port  rather than a 68B54 though? Better performance and still
> commercially available...

Seen it in a Dutch catalogue. The full set in 'B' version.
I had thought about bying, but only as spares for the MDFS.
(not building something myself!)


Johan

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

  The best place is a Riscy place
 
If the facts do not conform to the
theory, they must be disposed of.