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From: bammi@cwruecmp.UUCP (Jwahar R. Bammi)
Newsgroups: net.micro.atari
Subject: Re: ST timer tick?
Message-ID: <1368@cwruecmp.UUCP>
Date: Sat, 11-Jan-86 22:53:10 EST
Article-I.D.: cwruecmp.1368
Posted: Sat Jan 11 22:53:10 1986
Date-Received: Tue, 14-Jan-86 04:19:23 EST
References: <1241@gitpyr.UUCP>
Organization: CWRU Dept. Computer Eng., Cleveland, OH
Lines: 49

> Can anyone tell me how I can get a simple timer tick on my ST?  I need a
> high resolution timer so that I can record keystrokes off of MIDI for a 
> simple sequencer I'm writing.  However, I've looked through all the
> developer documentation and can't figure out how to do it...  Do I have to
> write an interupt handler to count timer interupts? (ugh...) I can't believe
> it's as hard as that...
> 
>     Steve Tynor
>     Georgia Instutute of Technology
	The simplest way is to read the value of the 200 Hz system
timer contained in location 4BA -- The hitch Hikers guide says 4BC but
that is a misprint. It has to be done in super mode otherwise you get
mushrooms. Here is a example

long ticks;
long *_hz200 = 0x000004ba;

read_ticks()
{
	ticks = *_hz200;
}

main()
{
......
	/* Call read_ticks in super mode - this def if missing  in
	osbind.h */
	xbios(38,read_ticks);
	/* ticks now has the value of the 200 Hz timer */
}

You could also use the Xbtimer() xbios call with timer a, but I
have'nt gotten it to work correctly as yet ( I had posted a query a
couple of days back, but still have no answer ).

Some people over here have been hacking midi code too. One of their
experiences was that incresing the size of the midi receive buffer
helps a lot too in keeping up with some of the Yahama equipment that
send status bytes every 200 ms (I think). this can be done by using
the Iorec() xbios call. Hope this helps.



-- 
					Jwahar R. Bammi
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