somehow... but i need a gigahertz processor, because i want to able measuring nanoseconds delay interval. wondering if theres a way to use nowaday mobo that using gighz processor, so that i can build something and put it on the slot (PCI/whatever), is this realistic/possible?

Posted on 2003-08-16 02:50:46 by dion
Why not use a counter with the clock gated by the delay.

Suppose you what to see how long a signal is high. Connect that signal along with the clock through an AND gate to the clock pin of a counter.

When the signal is high, the counter will be counting. Divide the count by the frequency and you'll have the time the the signal was high.
Posted on 2003-08-16 05:20:31 by eet_1024
Any processor cannot measure nanoseconds by itself because the time to execute one instruction is much longer than that. eet has the right idea but you may need ecl or such logic to accomplish it.
Posted on 2003-08-16 12:42:11 by drhowarddrfine
Regarding the use of a processor for timing, the bottleneck (slowest part) will be data bus speed. Even if you managed to put your critical timing loop completely in the cache, the sampling I/O will still run at the speed of the external data bus.

In a lot of cases, the simplest way is to simply use a (triggered & digital) storage oscilloscope.

The storage scope can "freeze" a wave sample on display, at the end of a capture interval. You set the triggering conditions to capture the sample you want. You can measure visually using the graticule (grid), or use the builtin cursor features to measure a time interval.
Posted on 2003-08-18 22:31:15 by tenkey
eet, can u explain it more further? with a pic is better :)

tenkey, how big the freq capability, i just saw the highest 'd be 100MHz.
Posted on 2003-08-20 05:56:20 by dion
The card will have it's own crystal. Are you familiar with stripline PCB design?
Posted on 2003-08-25 22:51:44 by mrgone
Here's a pict. Change the 1 GHz oscillator to something that will give you enough resolution. You could use the counter as just a divider, and feed the divided count into a PIC.

You'll have to figure out how to count only one pulse; this circuit will increment the counter every time the pulse is high.
Posted on 2003-08-27 01:49:18 by eet_1024
hi eet, maybe i can stand with the theory, but what in my mind is, what component do i have to use, because afaik theres no device / gate that can accomodate GHz freq. please correct me if wrong :)
Posted on 2003-08-27 06:19:27 by dion
eet is correct when he says counters but he was not specific enough. The counters are known as Pre-scalers and they use ECL (Emitter Coupled Logic). Xsistors operate much faster in emitter follower or common collector configurations. In fact this is what Cray uses for all their buss drivers and data latches in their super computers. Motorola has a superior line of ECL. There are several others and can't think of right of hand. If you have ever seen a Frequency counter that reads into the GHz (SHF) spectrum, than you are looking at a device that has an RF front end followed by a prescaler that scales down the frequency to something say high speed CMOS can deal with and can be displayed digitally.
Posted on 2003-08-27 09:36:01 by mrgone