Date   : Tue, 02 Dec 2003 00:19:07 +0000
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: Puzzling out the OSBYTE 121 and f0cc

BBC Micro <b_b_c_m_i_c_r_o@...> wrote:
> Still puzzling through the code at f0cc. I know the
> OSBYTE 121 will return the negative key value if it is
> currently pressed but I can't tie up the description
> with the code walkthrough.
>   What is at (01DF) as (02DF) is the keyboard hold?
 
&01DF is the base that offset with Y points to some keyboard workspace
locations at &2CB, &2CC and &2CD. &02DF - Typo maybe?
 
>   "X determines the key to be detected and also
> determines the range of keys to be scanned" I'm not
> entirely sure about the "also" part...
 
If X>=&80 -> scan for specified key. If X<&80, scan range starting@...
specified key.
 
> The loop points are f0e3 and f103 but I can't make out
> what they are doing...
 
Does this help at all:
http://www.mdfs.net/Docs/Comp/BBC/OS1-20/os_F0CC
 
Sorry I can't help further, I'm in a bit of rush this week ;)
 
-- 
J.G.Harston (JGH BBC PD Library) 70 Camm Street, Walkley, SHEFFIELD S6 3TR
jgh@...                - Running on BBCs & Masters with SJ MDFS FileServer
Z80+6502/CoPro+Tubes/Econet+SJ - - - - - - - http://www.mdfs.net/User/JGH/