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From: glenn@sdcrdcf.UUCP (Glenn C. Scott)
Newsgroups: net.micro.atari16
Subject: Calling BIOS from interrupt handlers
Message-ID: <3032@sdcrdcf.UUCP>
Date: Mon, 22-Sep-86 16:40:41 EDT
Article-I.D.: sdcrdcf.3032
Posted: Mon Sep 22 16:40:41 1986
Date-Received: Wed, 24-Sep-86 23:39:50 EDT
Reply-To: glenn@sdcrdcf.UUCP (Glenn C. Scott)
Distribution: world
Organization: System Development Corporation R&D, Santa Monica
Lines: 22


  Has anyone been able to successfully call BIOS/XBIOS functions from interrupt
handlers ?  There was some discussion on this couple of months ago in the BIX
section of BYTE and the final message said you should subtract 46 from "savptr"
before calling the BIOS function and restoring the previous value of savptr
before returning.  The interrupt handler is supposed to ensure its own
atomicity.  Unfortunatly this doesn't work.

  I've also tried assigning savptr to my own buffer and making BIOS calls which
doesn't work either.

  My application for this is to have Xbtimer() set up an interrupt handler
which, at certain times, sends a byte (or two) out the MIDI port.  But the
usefulness of calling BIOS from interrupt routines is, I'm sure, pretty wide.

Please help !!

Glenn
--------------------------------------------------------------------------------
Glenn C. Scott
System Development Corporation, 2525 Colorado Ave, Santa Monica, CA. 90406 
213-820-4111 X5653	UUCP: glenn@sdcrdcf.UUCP   ARPA: Scott@DOCKMASTER.ARPA