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From: "Tauno Voipio"
References: <email@example.com> <firstname.lastname@example.org>
Subject: Re: ISA IRQ signal active how long?
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Fri, 11 Oct 2002 17:39:54 GMT
NNTP-Posting-Date: Fri, 11 Oct 2002 20:39:54 EET DST
Organization: Sonera corp Internet services
"Meindert Sprang" wrote in message
> "Norm Dresner" wrote in message
> > Regardless of what the Intel bus spec says, the Intel data sheet for
> > the 8259 PIC clearly says that it can be either edge (default) or level
> > triggered.
> You are right. But if you design a piece of hardware that should run in
> windows, how hard would it be to reprogram the PIC?
The Microsoft systems leave the PIC in edge-triggered mode due to the
hardware design of the timer interrupts (IBM originally saved a latch and
created endless woes requiring the PIC to stay in edge mode). The whole chip
follows the command, so it is not possible to select individually which
inputs are level-triggered and which edge-triggered.
The APIC used in multi-processor motherboards may be a different beast.
If you're running under Windows (and not using a PCI board) you'll be on the
safe side if the board interrupt comes active when something happens and
resets only when the software driver reads/writes/accesses a suitable port
on the board.
Please note that if you're handling hardware interrupts in a 32 bit Windows
system, you'll need the DDK (Driver Development Kit) to create a driver for
your hardware - it is not directly accessible from the application running
tauno voipio @ iki fi
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