From: jih-shin ho <u7711501 AT bicmos DOT ee DOT nctu DOT edu DOT tw>
Subject: Timer subroutine
To: djgpp AT sun DOT soe DOT clarkson DOT edu (djgpp)
Date: Wed, 14 Jul 93 10:29:18 EAT

Hi:
  Here is the timer subroutines I use. The original subroutines are for
Turbo-C. I modify them to make them work with djgpp.
  You can find the original version in M_SEC12.ZIP at SIMTEL20 mirror sites.
  These subroutines DO NOT affect system timing.

  The time between start and stop must be less than one hour.
  Allow multiple read_timer() calls between timer_on() and timer_off().

Usage:

  #include "timer.h"

  .....

  timer_on(); /* Start timer */ 

  .....
  start = read_timer();

  .....

  stop = read_timer();
  timer_off();
  time_passed = elapsed_time(start,stop); /* unit = msec  */
  count_passed = elapsed_count(start,stop); /* unit = clock pulse */
  /*
     time_passed is equal to (count_passed / TIMER_MILLI_COUNT)
   */


  -- Jih-Shin Ho

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

#ifndef _TIMER_H
#define _TIMER_H
/* timer.h
 * Include file defining the timer routines.
 * Include this file in any program using them.
 */

#define TIMER_COUNT 1193181u /* Clock freq. = 1.193181 MHz */
#define TIMER_MILLI_COUNT 1193u

/*Calculate time elapsed (in milliseconds) between Start and Stop*/
unsigned int	elapsed_time(unsigned int start, unsigned int stop);

/*Reprogram the timer chip to allow 1 millisecond resolution*/
extern void	timer_on(void);

/*Restore the timer chip to its normal state*/
extern void	timer_off(void);

/*Read the timer */
extern unsigned int	read_timer(void);

extern unsigned int elapsed_count(unsigned int start, unsigned int stop);

#endif


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

/*
;timer.s
;Assembly language functions extracted from TIMER.C
;and recoded in *real* assembly language.
;(Too many incompatibilities in all the different
;implementations of inline assembly language ;-)
;
;David Kirschbaum
;Toad Hall
;
;Modified for DJGPP by Jih-Shin Ho, 1993
; u7711501 AT bicmos DOT ee DOT nctu DOT edu DOT tw
*/

	.text
        .align 2,0x90

	.globl _timer_on
        .globl _timer_off
        .globl _read_timer
        .globl _elapsed_time
        .globl _elapsed_count


/* ;void timer_on(void) */
_timer_on:
	movb   	$0x34,%al
	jmp    	LCommon	  	;/* common to return */

/* ;void timer_off(void) */
_timer_off:
 	movb  	$0x36,%al 	;/* outp(0x043,0x036); */
LCommon:
	movw  	$0x43,%dx
	outb  	%al,%dx
        jmp   	L1
L1:
   	movw  	$0x40,%dx 	;/* outp(0x040,0x000); */
   	xorw  	%ax,%ax
   	outb  	%al,%dx
        jmp   	L2
L2:
   	outb  	%al,%dx	  	;/* outp(0x040,0x000); */
	ret

	.align 2,0x90
/* ;unsigned long read_timer(void) */
_read_timer:
        xorl  	%eax,%eax
        movl  	%eax,%edx
        movl  	%eax,%ecx

	outb  	%al,$0x43	;/* Latch timer 0 */
	movw	(0xe000046c),%dx
	inb   	$0x40,%al	;/* Counter --> CX */
	movb  	%al,%cl	 	;/* LSB in CL     */
	inb   	$0x40,%al
	movb  	%al,%ch	 	;/* MSB in CH     */
	notw  	%cx    	 	;/* Need ascending counter */
        movw	%dx,%ax
        shll  	$16,%eax
        orl   	%ecx,%eax
 	ret

	.bss
	.lcomm flag,1
	.text
        .align 2,0x90

/* unsigned int elapsed_time(start,stop) */
_elapsed_count:
	movb $0,flag
	jmp L4

	.align 2,0x90
_elapsed_time:
	movb $1,flag
L4:
 	movl 8(%esp),%edx	;/* stop */
 	movl 4(%esp),%ecx	;/* start */
 	movl %edx,%eax
 	subl %ecx,%eax
  	jae L3
  	movl $-1,%eax
  	subl %ecx,%eax
  	addl %edx,%eax
  	incl %eax
        movl %eax,%ecx
        andl $0xffff0000,%ecx
        cmpl $0xffff0000,%ecx
 	jne L3
        andl $0xffff,%eax
L3:
	testb $1,flag
	jz L5
	movl $1193,%ecx
	xorl %edx,%edx
	divl %ecx
L5:
	ret