Date   : Fri, 30 Apr 2010 13:39:09 +0100
From   : robert@... (Rob)
Subject: 68B54 memory locations and ANFS puzzle

On 30 April 2010 13:10, paul aslin <station240@...> wrote:
> Referring to the memory map at:
> http://mdfs.net/Docs/Comp/BBC/AllMem
>
> It shows the B/B+ to have the 68B54 in one memory location, and a different
location in the Master.
> &FEA0-&FEBF 6854 ADLC Econet controller (B/B+)
> &FEC0-&FEDF 6854 ADLC Econet controller (Master)
>
> But decompiling ANFS 4.25 shows it only uses &FEA0 to &FEA3

I've never got into poking about in the hardware on a real Master, but
when I initially added Econet support to BeebEm I just specified
FEA0-BF  for all computer types - just checked the 4.11 source and
it's still the same, and it seems to work fine ...

It does seem wasteful to give it 32 possible addresses for just 4
registers, but it simplified the address decoding.  Similarly the
address jumpers/NMI toggle at FE18-FE1F (on the B) get 8 addresses,
when they only need one.

Rob