Date   : Thu, 07 Feb 2008 09:30:34 +0000
From   : robert@... (Rob)
Subject: Text screen?

On 07/02/2008, Mark McDougall <msmcdoug@...> wrote:
> Rob wrote:
>
> > Has this not already been done?  I know the topic has been discussed
> > on this list in the past -you might wish to search the archives.
>
> No, the atom has been done, but not the BBC.

Ah,  my mistake.

>
> >> * When *not* running in mode 7, how is the text generated? IIUC non-mode7
> >> displays are basically just bit-mapped displays - yes? Does the BASIC ROM
> >> draw text characters on the bitmap from data embedded in the ROM?
> >
> > The MOS does exactly that.
>
> OK, thanks. Don't s'pose you know off-the-top of your head where the
> character data is stored in the MOS ROM, and/or the format?
>

&C000 - &C2FF on a Model B at least.  8 bytes per character, bit
mapped 8x8 matrix.  This is exactly the same format as used in
monochrome mode screen memory, so (on a B) you could use:
MODE 0 : F.I%=0 TO &2FF : I%?HIMEM = I%&C000 : N.
to see them!

Without looking them up, I think there are probably OSBYTE calls to
get the exact address, or character data perhaps, which would then be
guaranted to work on all models.