[ntp:questions] Kernel PPS programs.
g8kbv at uko2.co.uk
Wed Feb 8 17:45:56 UTC 2012
In article <VUBSq.3384$%x7.3294 at newsfe10.iad>, unruh at invalid.ca says...
> > 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.
> I have looked carefully, and can onlyfind a bit for turning off
> interrupts (which of course does not turn on again). That would be fine
> if it were edge triggered, but not for level triggered.
When you program that I/O bit to "turn off" interupts on that port, it
probably clears a latch too, so that it is ready for the next change in
input level to trigger another IRQ.
See if you can find some original IBM PC schematics and bios listings on
t'interweb somewhere. We all learnt a lot back in the day from them.
Just about all the plugin cards and adapters since then, were designed
to behave in much the same way, if not using the same circuitry, just
integrated all into one small bit of plastic.
PS: Anyone remember Data General's "Busy" and "Done" flags?
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