[ntp:questions] Kernel PPS programs.

unruh unruh at invalid.ca
Wed Feb 8 17:45:49 UTC 2012

On 2012-01-21, Uwe Klein <uwe at klein-habertwedt.de> wrote:
> Hal Murray wrote:
>> In article <X5nSq.1459$kp5.81 at newsfe18.iad>,
>>  unruh <unruh at invalid.ca> writes:
>>>Further to my kernel pps problems. I have now managed to get pps-ldisc
>>>which is supposed to timestamp the serial port DCD transition interrupt,
>>>and the pps_parport. In the case of the latter I was wondering if anyone
>>>has any idea of how it works. The on board parallel port interface on
>>>old motherboards used the edge transition to signal the interrupt. This
>>>would mean that once the routine had serviced the interrupt, no other
>>>one would occur until that next edge. However, for the add in parallal
>>>cards, they use shareable, level triggered interrupts. Since the input pulse is
>>>many ms long, this means that the interrupt keeps triggering about once
>>>every usec as long as the ack line is up. 
>>>Does anyone know if the pps_parport module treats such shareable
>>>interrupts correctly?
>> Usually, that sort of hardware has a way to turn off the interrupt.
>> It's something like you write a bit in a register to "ACK" that
>> interrupt.  When the external signal turns off, it clears that bit.
>> The info should be in the fine print if you can get a good data sheet.
> The interrupt controller works differently.
> you switch from edge triggered to level triggered.

Not sure what you mean by this.

> uwe

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