Date   : Tue, 03 Aug 1999 09:43:57 +0100 
From   : Jon Bloomfield <Jon.Bloomfield@...>
Subject: Re: Econet hardware 

       To be honest it would be better to not use the 68B54 at all.  The
Ecolink only 
       works because it has an onboard cpu to handle the low-level tasks.
Assuming 
       you don't want that in a homebrew design you would be better off
using a 
       different chip that's better able to handle latency (and hopefully a
bit 
       easier to interface to a PC as well).

       The best solution would be to put the whole thing into an FPGA if
you have the 
       technology to do so (though I'm guessing the original poster
doesn't).

       p.
       
I was intending to use a PIC to act as the interface between the 68B54 and
the PC. I considered dropping the ADLC completely, but this would mean
emulating its transfer protocol in the PIC, and this would take some time to
do reliably. Why bother when there is a chip to do the hard work for me ?
Using Acorns circuit as the basis for the interface card means that it I
don't need to worry about the low level transfer issues when I'm debugging
the software.

The main benefit to avoiding the ADLC is that it makes the design somewhat
more future proof - Motorola have stopped making the 68B54, so it's only a
metter of time before sources dry up completely. I'm a software engineer, so
I tend to be quite lazy in my approach to hardware designs ;-)

Jon