[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Level / edge interrupts

Steve,

Part of the reasons was clarified somewhere in PCI spec. or somewhere else. 
A few PCI devices share interrupt signal lines(#INTA, #INTAB, #INTC or #INTD) using wire_AND logic. After sharing, one composite interrupt signal goes to the programmable interrupt controller. This requires all #INTx has to be driven as level, so the 
interrupt request lasts for a while until the interrupt controller sense its happen. On the contrary, the edge was driven by device, and then released, as a result the shared interrupt line become back to high very fast, the interupt controller cannot 
sense device's interrupt request reliably.

Paul Yang C.M.
Philips Semiconductors





steve.turner@motion-media.com on 08/06/2000 20:14:34
To:	pci-sig@znyx.com@SMTP
cc:	 
Subject:	Level / edge interrupts
Classification:	Restricted
Dear PCI-SIG members,

I believe this is the correct forum for the following Question
My company produces a PCI plug in card that works on 99% of PC's (Uses
Philips SAA7146 PCI interface)

On one machine we get some extraordinary behaviour. A card plugged into one
particular slot causes the PC to reboot during normal operation in Windows
98. (Black screen - BIOS boot) In other slots applications running on our
card are unreliable. Its is all very bizarre.

(a) Via Chipset
(b) Intel P2
(c) Award Bios 1.0a

The award bios gives incredible flexibility not normal with a BIOS.
Experimentation has revealed the following (not normally possible to change
this with AMI BIOS)

PCI IRQ = level sensitive, perfect
PCI IRQ = edge sensitive, system failure

It would however be nice to know why?
Can anybody shed any light on this?

Thanks in advance

-------------------------------------------------------
Stephen Turner  : steve.turner@motion-media.com
Motion Media Technology Ltd, Horton Hall, Horton,
Sth Glos BS37 6QN
URL:    http://www.motion-media.com
DIRECT: +44(0)1454 338504
SWB:    +44(0)1454 313444           FAX: +44(0)1454 313678
-------------------------------------------------------