Re: Microsecond resolution timers - final word

Robert Norris (box@box.halls.monash.edu.au)
Tue, 27 Jul 1999 17:36:53 +1000

On Tue, Jul 27, 1999 at 08:24:06AM +0100, Tim Waugh wrote:
> Is that 20-40 usecs response to an interrupt on the port? I'm finding
> that the interrupt latency is around about that, at least by the time you
> respond to the interrupt. Perhaps I'm doing something wrong though.

No. It's not parallel port based (hell, it's not even pc based). Its a custom
bit of hardware that uses three lines on the parallel port, and communicates
using a simple serial-esque protocol. It transfers bytes bit-by-bit, using
an ACK and DATA line.

Here's an example. I send a bit on the data line, and the device responds
by bringing the ACK line high .. I then have to bring ACK low and send the
next data bit within 20-40 usecs.

Is gettimeofday accurate enough for this?

Thanks,
Rob.

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