Date   : Thu, 07 Feb 2008 07:39:40 +0000
From   : robert@... (Rob)
Subject: Text screen?

On 07/02/2008, Mark McDougall <msmcdoug@...> wrote:
> Hi,
>
> I'm a complete newbie to the BBC-micro. I'm looking at emulating the BBC in
> an FPGA,

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.

>
> * When the BASIC ROM boots, what mode is the machine running in? Mode 7? I
> suspect this is the case because the screen text appears at $3C00...

When the *MOS* fires up, it does usually start in Mode 7, unless the
default has been changed by means of the keyboard links or *config. on
a Master.  (And mode 7 starts at  &7C00 on a Model B - it would only
be &3C00 on a Model A.)

BASIC is started much later one, and doesn't change or assume any
particular screen mode, being merely one of  range of possible
ROM-based applications.


>
> * 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.


Rob.