Xref:	news2.mv.net comp.os.msdos.djgpp:815
Newsgroups:	comp.os.msdos.djgpp
From:	rhk AT farpoint DOT newimage DOT com (Ray Kelm)
Subject:	Re: Timer interrupts
Organization:	New Image Software, Inc.
Message-ID:	<DMC480.HAq@farpoint.newimage.com>
References:	<DM41sD DOT GLL AT granite DOT mv DOT net> <4f2rto$dbp AT krel DOT iea DOT com>
Date:	Tue, 6 Feb 1996 03:26:23 GMT
Lines:	41
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Larry Blanchard (larryb AT comtch DOT iea DOT com) wrote:
: James T. Sweeten Jr. (sweeten AT belgarath DOT nwscc DOT sea06 DOT navy DOT mil) wrote:
: : 	I have a question concerning the timer interrupt 8.
: : What is the difference between the protected mode int8 and the real mode
: : int 8?
: : 	I need to output a value on a d/a board at specific intervals.  I
: : originally did this with borland by installing my own timer interrupt routine.
: : I was able to get down to 100 micro second (10khz) resolution.  I am trying to
: : do the same thing using djgpp.  I have read the faq and have also gotten
: : pctime13.zip (This has milisecond resolution for djgpp).  I modified the
: : interrupt routines in pctime13.zip, (gccint8.c), to output the data to the
: : d/a board ok but I can't get down to 100 micro second resolution.  With an
: : input value of 3000 hz I get a nice 1500 hz square wave.  With a value of 
: : 4000 hz it works for a while but then locks the machine up.  Any help would
: : be appreciated.
: : 	I am using 1.12m4 on a 486/66.

: I recently had exactly the same need, tried just what you did (also on a
: 2/66), and got almost the same results.  Mine sometimes even hung at 3000.
: Apparently, the overhead of the DPMI stuff is just too great for high
: frequencies.  I gave up on djgpp and did it in real mode.  I can do 20Khz
: with no problems.

Try DJGPP 2.0, it works much better for interrupts. 

I have used 8Khz interrupts just fine on a DX4/100.

The code in the interrupt does the following: 
	reading and converting 6 10-bit absolute encoders
	controlling 6 stepper motors using step/dir bits complete with 
		speed control and acceleration
	reading 12 16-bit force measurements from a DSP-based card
	reading 56 bits of digital I/O (sensors) from a PIO card

All of this is in C, and is using approximately 50% of the CPU time. (The
foreground task is using GRX to display all of this info, and control it)
-- 
===========================================================================
Raymond H Kelm II                                   New Image Software, Inc
rhk AT farpoint DOT newimage DOT com                               Makers of Image BBS
===========================================================================

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