[ntp:questions] Kernel PPS programs.

unruh unruh at invalid.ca
Wed Feb 8 17:45:53 UTC 2012

On 2012-01-21, Uwe Klein <uwe at klein-habertwedt.de> wrote:
> unruh wrote:
>> On 2012-01-21, Uwe Klein <uwe at klein-habertwedt.de> wrote:
>>>The interrupt controller works differently.
>>>you switch from edge triggered to level triggered.
>> Not sure what you mean by this.
> http://kernel.org/doc/htmldocs/genericirq.html
> http://www.google.com/search?q=linux+shared+interrupts+level+edge

I am sure that your two sentences did not mean a 40 page article or
12 million  web addresses. If you are saying that in going from
exclusive intrupts, which can be edge triggered, to shared interrupts
you need to go to level triggered interrupts-- that was what I thought I
said. The problem at least with the cheap parallel cards I had supplied
with my machine, NM9735 Rev C, is that the parallel interrupt has no way
of signalling that it has been handled. Ie, each time that I service the
interrupt, and return, it interrupts again, until finally ( many
milliseconds later and many thousands of interrupts later) the ack line
changes state again. I at least have not found any  way of informing the
card that this interrupt has been serviced and not to interrupt again
until the device makes its next low to high transition. 
I suppose I could turn of the interrupts on the card for 500ms then turn
them on again to catch the next PPS, but that is a real kludge.

> uwe

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