Date   : Sun, 13 Jun 1999 14:26:32 +0000
From   : Michael Foot <mikef@...>
Subject: Re: BBC 8271 commands

Thanks for the reply.
The reason I asked the question is because I've been trying to get DDFSE00
(DFS with PAGE=&E00) to work under my emulator. By tracing the calls it does
to the 8271 I've noticed it writing to &FE82,&FE83 and &FE86 and reading
from &FE82.
Does this DFS work under PCBBC for you? I can send you a copy if ou don't
have it.

Mike.


In message <88MjdGA6rhY3EwQn@...>
          Stuart William McConnachie <stuart@...> wrote:

> In message <3.0.5.32.19990611164707.0092e510@...>, Michael
> Foot <mikef@...> writes
> >I'm wanting to know exactly how the BBC controlled the disc via the 8271
> >chip so I can emulate it properly. Can anyone fill in or correct the
> >locations in the memory map below?
> 
> >FE80 read status register, write command
> >FE81 read result register, write parameter
> >FE82
> >FE83
> >FE84 read/write data register
> >FE85
> >FE86
> 
> AFAIAA the missing locations do nothing at all.  I've certainly never
> seen any BBC DFS access them, and pcBBC simply returns &FF as a read of
> these locations and totally ignores writes.  I seem to recall the 8271
> may have been capable of some type of DMA access to memory?  Of course
> the BBC hardware does not support this, so it would be fairly pointless
> emulating it anyway.
> 
> Regards,

-- 
Michael Foot <mikef@...          >
http://www.voyager.co.nz/~mikef