Date   : Mon, 15 Jun 2009 23:49:22 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Definative memory map for DFS

michael.firth wrote:
> Presumably when DFS is the active filesystem it would be allowed to use
> (assuming it claims NMIs):
> &A0-&A7: Current NMI owner
 
No. When DFS is *THE* *NMI* *OWNER* it can use &A0-&A7.
 
> &B0-&BF: Filing system scratch, contents may change between calls
 
Yes. The filing system must be able to cope with the contents of
&B0-&BF changing since the last time the filing system was used.
 
> &C0-&CF: Filing system workspace, contents same between calls
 
Yes. The filing system is allowed to assume that the contents of
&C0-&CF has not changed since the last time the filing system has
been called, as long as no other filing system has been used since.
 
> And if it is processing a command, also
> &A8-&AF: Transient commands
 
No. Filing systems are *NOT* allowed to use that memory, it is for
transient commands, as stated.
 
If a filing system needs to use any other zero-page space it must
stack it before use and restore it afterwards.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
NOBODY expects the MACRO ARGUMENT INQUISITION!  Our chief weapon is
unexpected addressing modes... unexpected addressing modes and local
branches out of range.  Our two weapons are unexpected addressing modes and
local branches out of range and quoted argument lists.  Our *three* weapons
are unexpected addressing modes, local branches out of range, quoted
argument lists, and an almost fanatical devotion to the pope.  *Amongst* our
weapons are such elements as unexpected addressing modes, local branches out
of range... I'll come in again.
The most perfect world is an imperfect world as the imperfections
give people a reason to strive to change it.