Xref: utzoo comp.sys.ibm.pc:39251 comp.lang.pascal:2778
Path: utzoo!attcan!uunet!cs.utexas.edu!rutgers!ucsd!ucbvax!bloom-beacon!eru!luth!sunic!tut!hydra!hylka!kulokari
From: KULOKARI@cc.helsinki.fi (Hannu Kulokari)
Newsgroups: comp.sys.ibm.pc,comp.lang.pascal
Subject: Re: chaining interrupts
Message-ID: <1463@cc.helsinki.fi>
Date: 4 Dec 89 02:31:12 GMT
References: <4543@solo5.cs.vu.nl>
Organization: University of Helsinki
Lines: 20

In article <4543@solo5.cs.vu.nl>, cjveenm@cs.vu.nl writes:
> 	I have written several own interrupt handlers for the ibm pc,
> and I wonder if it's possible to use the old interrupt routines by
> chaining from the new one. One way to do this is by setting the old
> vector on the address of an other interrupt number. A disadvantage
> of this method is that you don't always know which interrupt is free
> and you can run out of all possible interrupts.
> 	So is there an other way, from TP4 for instance:
> 		jmp oldvector (with inline code) 
> doesn't succeed.
> 
> 		thanks in advance, Cor

You should CALL (not JMP to) the old interrupt routine, with a FAR
call. You should also push the flags (PUSHF) before the call. This is what
INT does (besides looking up the address of the routine from the interrupt
table).

Hannu Kulokari
CC, U of Helsinki, Finland