Level and Edge-triggerred IRQ on NT4 and W2K

NTDEV
1

I have a NT4 driver (kernel mode) that works fine (written by someone else
but I have the source code). I tried it on W2K and it didn’t work (hangs at
startup) even when recompiled with the W2K DDK. After several trials and
errors, I realized that the IRQ I was using was configured as
Level-sensitive (when calling IoConnectInterrupt()) while the hardware this
driver is for does not support level-sensitive interrupt (since it
generates a pulse of fixed duration on the IRQ line). After setting it to
Latched, everything is working fine. I even used the NT4 (binary) driver on
W2K and it also works without any problems.
However, this puzzles me quite a bit. In the level-sensitive mode, why did
it work on NT4 but not on W2K?
Also, since the PIC can be programmed in only one mode (at least the 8259
or alike), what happens when two drivers try to use different mode for
different IRQ on the same controller?

Thanks,

Francois Gallichand

2

> Also, since the PIC can be programmed in only one mode (at least the 8259

or alike), what happens when two drivers try to use different mode for
different IRQ on the same controller?

PCI interrupts are level-sensitive, while ISA ones are latched - no problems
with the PIC.

Max

3

On 11/13/00, ““Maxim S. Shatskih” ” wrote:
>
> PCI interrupts are level-sensitive, while ISA ones are latched - no problems
> with the PIC.
>
> Max
But what happens if one tries to set the latched mode for a PCI card, or
the level mode for an ISA card?

Francois

4

> But what happens if one tries to set the latched mode for a PCI card, or

the level mode for an ISA card?

IMHO this will lead to mismatch between PIC hardware logic and ISR
prolog/epilog code logic and will surely cause problems.

Max

5

I personally have never understood why this is even an option. Isn’t the
interrupt mode a characteristic of the bus, not of a device on the bus?

Mark Roddy
xxxxx@hollistech.com
www.hollistech.com
WindowsNT Windows 2000 Consulting Services

-----Original Message-----
From: Maxim S. Shatskih [mailto:xxxxx@storagecraft.com]
Sent: Tuesday, November 14, 2000 11:38 AM
To: NT Developers Interest List
Subject: [ntdev] Re: Level and Edge-triggerred IRQ on NT4 and W2K

> But what happens if one tries to set the latched mode for a
PCI card, or
> the level mode for an ISA card?

IMHO this will lead to mismatch between PIC hardware logic and ISR
prolog/epilog code logic and will surely cause problems.

Max

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