Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!uunet!math.fu-berlin.de!opal!ki
From: ki@opal.cs.tu-berlin.de (Karsten Isakovic)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: How to use the VDI from the Autofolder
Message-ID: <3491@quepasa.cs.tu-berlin.de>
Date: 26 May 91 19:09:45 GMT
References: <1991May24.184249.21414@imada.ou.dk> <1991May25.152208.2925@actrix.gen.nz>
Organization: Technical University of Berlin, Germany
Lines: 33


In article <1991May25.152208.2925@actrix.gen.nz> Roger.Sheppard@actrix.gen.nz
(Roger Sheppard) writes:
>This came from a File that I found some time back on Genie, it could
>be of help to otheres, with the Trap #2 problems.
>
>        btst    #5,(sp)         ; Super or user mode?
>        beq.s   t13_ex          ; If user mode, let's forget the whole thing
>        cmp.l   #$050101,6(sp)  ; Setexec call for critical error vector?

The code does not use the XBRA method, which _is_ standard...

> first_time:
>        tst.l   10(sp)          ; Reading the vector?
>        bmi.s   t13_ex          ; Yes, let the system take care of it
>        cmp.l   #$FC0000,10(sp) ; Is this address below the ROMs?
>        blo.s   t13_ex          ; Yes, bail out

And it does not work with RAM-TOS versions, or even with the new STE or
TT machines...  (Please use the os_start entry in the _sysbase structure
pointed to by the system variable $4f2.)

>  A better method than the magic hockey puck is to issue an OS call with an
>undefined function number, like BIOS #73, or AES #1200, and have your program
>return a pre-defined value somehow, indicating that it's installed.

This method is not good. The 'unused' function call might be used in a 
future TOS version.
You simply have to install a Cookie interface for the TSR. The value of
the cookie points to an internal TSR structure, so that a DA, CPX or PRG
can configure the TSR.

Sincerly, Karsten   (ki@opal.cs.tu-berlin.de)