Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbvax.BERKELEY.EDU
Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!PAVEPAWS.BERKELEY.EDU!dillon
From: dillon@PAVEPAWS.BERKELEY.EDU (Matt Dillon)
Newsgroups: net.micro.amiga
Subject: Re: I need an UltraFast Clock
Message-ID: <8605260640.AA13890@pavepaws>
Date: Mon, 26-May-86 02:40:11 EDT
Article-I.D.: pavepaws.8605260640.AA13890
Posted: Mon May 26 02:40:11 1986
Date-Received: Tue, 27-May-86 06:50:05 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: University of California at Berkeley
Lines: 37


	I think we need a bit more information.  I would like to pose the
following questions:

	(1) Is this real-time, or can you do the timing operation and 
	process the results later (i.e. not immediately)

	(2) Are these long timing periods (you need +/-1 uS accuracy over
	several seconds)?  or short (Your only clocking intervals of a
	couple of milliseconds)?

	(3) Are you going to be timing continuously, or will there be times
	during which you will not be timing.

Idle question: What in the world do you need +/- 1 uS accuracy for?

---------------------------------------------------------------------

In anycase, to get the resolution you need will CAN be done in C, but will
require disabling interrupts and probably a busy wait of some sort (not 
necessarily over the entire timing period).

To get such accuracy, you will have to go directly to the hardware (as you
seemed to have tried already).  I believe the Amiga has a micro-second
timer, which is normally used by the timer device.  You could confiscate
that, I suppose (it may be a bit tricky), and handle it manually.

* For short time intervals, you would have to use a busy wait.

* For longer time intervals, you can make it interrupt driven, but cause
the interrupts to go off a couple of milliseconds before the actual timeout,
then busy wait the rest of the time.

The interrupt interfacing will have to be done in assembly.


					-Matt