di2726.txt
;************************************************************************************************
; LISTING 1 - TURBO C++ LISTING FOR PULSE GENERATION
;
; "Centronics port generates narrow pulse widths," EDN, Aug 2, 2001, pg 97
;
;************************************************************************************************

/****     Program to Generate Pulse Width  less then 1mSecond  ****/
/****     Written By: Darvinder Singh Oberoi 			       ****/
/****	  CEDTI, JAMMU, INDIA 								   ****/

#include <dos.h>
#include <conio.h>
#include <stdlib.h>
#pragma inline

/*** All values are in milli Second  ***/
#define Max_Time     0.750   /* Maximum Pulse Width Time(mS)       */
#define Neutral_Time 0.500   /* Neutral Width Time(mS)             */
#define Min_Time     0.250   /* Minimum Pulse Width Time(mS)       */
#define Time_Step    0.050    /* Time(mS) Steps for Pulse Change      */
#define Counter_Count_Time 0.0008380958 /* Counter2's single count period(mS) */
#define Off_Time  10              /* Pulse OFF Duration (mS)                      */

/* Address of Printer Port    */
#define Printer_Port 0x378
void screen_display(); 		/* Routine for displaying Instruction */
/***** Main Program Starts Here *****/
main()
{
	char ch;
	unsigned counter_data, count_elapsed,required_count;
	float desired_time,counter_time;
	desired_time=Neutral_Time;   /* Initial time               */
	clrscr();
	screen_display();
	/* Counter2 is set in Mode 2, control word  data is b4 	  */
	asm mov al, 0b4h	    /* Set the counter2 operation */
	asm out 043h,al
	for (;ch != 'q';)   /* Loop Till q/Q key is pressed */
	{
	 if (kbhit())       /* Check, if any key has been pressed or not */
	   ch = getch();
	   switch (ch)	    /* And take action depending upon the key pressed */
	   {
		   case 'Q': ch = 'q';break; /* If Q key is     pressed */
		   case 52: desired_time -=Time_Step; /* If 6 NUM Key is pressed */
			ch=' ';break;
		   case 54: desired_time += Time_Step;/* If 4 NUM Key is pressed */
			ch=' ';break;
		   case 53: desired_time=Neutral_Time; /* If 5 NUM Key is pressed */
			ch=' ';break;
		   case 56: desired_time =Max_Time; /* If 8 NUM Key is pressed */
			ch=' ';break;
		   case 50: desired_time =Min_Time; /* If 2 NUM Key is pressed */
			ch=' ';break;
	  }
/* Check the extreme positions and reset them in case of violation  */
	  if (desired_time > Max_Time)  desired_time = Max_Time;
	  if (desired_time < Min_Time)  desired_time = Min_Time;
/* Finds how many counter2 counts are required for the  desired time interval */
	  required_count = desired_time/Counter_Count_Time;
	  count_elapsed = 0;
/* Counter2 is loaded with initial with  count of ffff 		*/
	  asm mov al, 0ffh	   /* Load the initial count as ffff */
	  asm out 042h, al	   /* Done in two cycles 	    */
	  asm out 042h,al
	  asm mov al, 01h	   /* Enable the counter to Start the ON period */
	  asm out 061h, al
/* Desired Pulse is available at printer port's pin no.-2 */
/* The signal is  inverted by the buffer stage            */
	  asm mov al, 0
	  asm mov dx, Printer_Port
	  asm out dx, al
/* The read the data in this loop, till desired delay is obtained 	 */
	  while (count_elapsed < required_count)
	  {
		asm in al, 042h      /*  Get LSB        */
		asm mov cl, al
		asm in al, 042h		 /*  Get the MSB    */
		asm mov ah, al
		asm mov al, cl   	 /* Two bytes, combined to get 16 bit data */
		asm mov counter_data , ax
		count_elapsed = (0xffff - counter_data);  /* Calculate the elapsed counts  */
	  }
/*  Make pulse signal low here, after the desired counts have elapsed  */
		asm mov al, 1            /* Signal is inverted */
		asm mov dx, Printer_Port
		asm out dx, al
/* Disable the counter2 here */
		asm mov al, 00h
		asm out 061h, al
/* Print the information on the screen */
		counter_time=count_elapsed*Counter_Count_Time; /* Calculate counter time */
		gotoxy(8,12); cprintf("%f",desired_time);
		gotoxy(26,12); cprintf("%f",counter_time);
		gotoxy(45,12); cprintf("      ");
		gotoxy(60,12); cprintf("      " );
		gotoxy(45,12); cprintf("%u", count_elapsed);
		gotoxy(60,12); cprintf("%u",required_count );
/* OFF period taken as 20ms*/
		delay (Off_Time);
	}			/* End of FOR Loop */
	textcolor(LIGHTGRAY);   /* Set the text color and clear the screen */
	clrscr();
}				/* END of the MAIN program here */

/**** Routine Which display the instructions & Other Information	 ****/
void screen_display()
{
	textcolor(YELLOW);
	gotoxy(26,2); cprintf("Make Sure Num Lock is ON");
	gotoxy(5,11); cprintf("Desired Time(mS)  Counter Time(mS)  Count Elapsed  Required Count");
	textcolor(YELLOW);
	gotoxy(25,19); cprintf("< Press Q/q key to Quit the Program > ");
	gotoxy(15,21); cprintf("Press 4 NUM Key to Decrease Time        (By %f ms)",Time_Step);
	gotoxy(15,22); cprintf("Press 6 NUM Key to Increase Time        (By %f ms)",Time_Step);
	gotoxy(15,23); cprintf("Press 8 NUM Key For Maximum Pulse Width ( %f ms  )",Max_Time);
	gotoxy(15,24); cprintf("Press 2 NUM Key For Minimum Pulse Width ( %f ms  )",Min_Time);
	gotoxy(15,25); cprintf("Press 5 NUM Key For Neutral  Position   ( %f ms  )",Neutral_Time);
	textcolor(WHITE);
}
/*pulse.c*/