Messages in this thread | | | Date | Tue, 27 Jul 1999 17:36:53 +1000 | From | Robert Norris <> | Subject | Re: Microsecond resolution timers - final word |
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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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