Date:	Wed, 5 Apr 1995 09:56:39 +0500
From:	hvb AT netrix DOT com
To:	sarda_jea AT lsi DOT supelec DOT fr
Cc:	djgpp AT sun DOT soe DOT clarkson DOT edu
Subject:	Re: Re : Interrupt programming (keyboard)
References:	<95040420202402 AT lsi DOT supelec DOT fr>

If this is the real mode interrupt code, then you do not save any
registers here.  I guess it crashed because from time to time, the
interrupt occurs in real mode.

Hope this helps.


==============================================================
Hung Bui                            Internet: h DOT bui AT ieee DOT org
Netrix Corporation                    Phone: +1 703 793 1016
13595 Dulles Technology Drive           Fax: +1 703 713 3805
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==============================================================

sarda jea writes:
 > Hello everybody,
 > 
 > Carsten Benecke wrote :
 > 
 > >I programmed an interrupt service function for a hardware interrupt (IRQ 9). I 
 > >used the source code from David Baggett`s Sound Blaster Sample (9-Nov-93) and 
 > >did some small changes for the IRQ 9:
 > >+ use slave PIC at base 0xa0 to enable and acknowledge the IRQ
 > >+ install a new real mode interrupt vector for interrupt 0x71 (IRQ 9)
 > >+ chain a new protected mode interrupt vector for interrupt 0x71
 > 
 > >The service function is called only for the first two hardware interrupts!
 > >No more hardware interrupts can be served by my function!
 > 
 > I had EXACTLY the same problem as you and I think I have nearly solved it but 
 > there is still some problems(by the way thanks to Tim Hesketh, Long Doan, Carl 
 > Burke for their helpful answers).
 > 
 > I have included my keyboard handler code in this article. It works (at least for 
 > more than the first two hardware interrupts) but the problem is that at random 
 > times (4,5 or 20 minutes after the execution begining) ,it makes a segmentation 
 > fault, or a unknow instruction code or even a SYSTEM RESET !!
 > I need your comments and help.
 > 
 > this the code :
 > 
 > /*
 >  * Interrupt handler
 >  *
 >  * This is called in both protected mode and in real mode -- this means
 >  * we don't have to switch modes when we service the interrupt.
 >  */
 > static unsigned char scan1,scan2;
 > 
 > void intr(_go32_dpmi_registers *reg)
 > {
 > 
 > 
 > 
 >   scan1=inportb(0x60);
 >   scan2=scan1;
 > /*********************** scan2 contain the useful scan code **************/
 > 
 > /********************** this is what i added to the soundblaster exemple
 > *********************** but in fact ,I dont know why it works with it
 > *********************** since I have taken this from another keyboard handler
 > ******************************************************************************/
 >   scan1=inportb(0x61);
 >   scan1=scan1 | 0x82;
 >   outportb(0x61,scan1);
 >   outportb(outportb(0x61,scan1 & 0x7f);
 > 
 > /******************* _pressed is just a flag to know if a key was pressed or 
 > *******************   realesed **********************************************/
 > 
 >   _pressed=1;
 > 
 > 
 >   outportb (0x20, 0x20);
 >   outportb (0xa0, 0x20);
 > 
 > 
 > 
 > }
 > 
 > 
 > (I install this handler like it is done in the soundblaster demonstration 
 > programm.)
 > 
 > 
 > 
 > Jean-Philippe.
 > 
 > 

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