I have successfully figured out how to keep an LED on for around 1 sec
(actual circuit, not a simulation) given a crystal of 3.57945 MHz.  As
you can see in the code snippet below, I have created algorithms for a
1 sec delay, 10 msec delay, 100 usec delay, and 1 usec delay.

What I'm having difficulty understanding is exactly how this works.  1
cycle is around 279 nsec.  But the code it took to create the 1 sec
delay makes it appear that it only takes .25 psec to increment the
value of a variable.  That implies a speed of 4 THz, and I know that
can't be possible for a through-hole microcontroller.

What's going on?  Does the microcontroller have a mechanism for
streamlining the process?

In applications for which timing is critical, how do you make sure the
timing is correct?

THE CODE SNIPPET:

#define __16F872
#include <stdlib.h>
#include <pic.h>
__CONFIG (XT&WDTDIS&PWRTDIS&BORDIS&UNPROTECT &  LVPDIS); // Set the
configuration bits:
// LVP must be disabled for LED8 to work.

unsigned char count, count1;

void delay_10_nsec (void)
	{
	count = 0;
	while (count < 200)
		{
		count1=0;
		while (count1 <200)
			{count1++;}
		count++;
		}
	}

void delay_1_usec (void)
	{
	count=0;
	while (count<100)
		{
		delay_10_nsec();
		count++;
		}
	}

void delay_100_usec (void)
	{
	count = 0;
	while (count<100)
		{
		delay_1_usec(); // 100 delays of 1 usec each.
		count++;
		}
	}

void delay_10_msec (void)
	{
	count = 0;
	while (count<100)
		{
		delay_100_usec(); // 100 delays of 100 usec each.
		count++;
		}
	}

void delay_1_sec (void)
	{
	count = 0;
	while (count<100)
		{
		delay_10_msec(); // 100 delays of 10 msec each.
		count++;
		}
	}

-- 
Jason Hsu
http://www.jasonhsu.com/swrwatt.html
http://www.jasonhsu.com/swrwatt-c.txt
http://www.jasonhsu.com/swrwatt-asm.txt
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