Date   : Sun, 14 Mar 2010 16:41:09 +0000
From   : samwise@... (samwise)
Subject: Master 128: Hiding a routine from memory clear

Hi,

I may be way out of my depth (my assembler skills are pretty ropey),
but I've been trying to catch a Break or Ctrl+Break (once only) and
basically CHAIN a BASIC program.  Once it has been captured once, the
routine should be deactivated so that a double break / ctrl-break will
reset the machine.

The problem is the program (Chuckie Egg) I'm then running sets flag
&258 which results in a memory clear on Break, clearing out my custom
routine.

By hiding my routine at &140, I appear to be able to get round this on
a Model B or Electron.  Unfortunately, a B+ and Master 128 still wipes
the routine out.

Further discussion of the evolution of this issue is here, along with
some SSD with sample code I've been trying out:

http://www.retrosoftware.co.uk/forum/viewtopic.php?f=11&t=455

Can anyone suggest a (preferably simple) approach which will work on
Electron/B/B+/Master ?

Peter.