I am having problem on while loop.

I wonder why this code is not working:

waitForHostReady = 1;
while(waitForHostReady);

while this one is working:

waitForHostReady = 1;
while(waitForHostReady)
	__delay_us(0);

Here is how I define the variable:

unsigned char waitForHostReady = 0;

Also, I use interrupt to change the variable value to 1 to break the while loop. Here is the simplified code:

void ISR(void) {
	if(waitForHostReady)
		waitForHostReady = 0;
}

Does this have to do with the interrupt?

 

You don't mention your compiler but the better it is the more likely you are to see this. C does not merely translate your code to machine language but in some cases tries to out think your logic.

Try defining waitForHostReady as volatile. That will force C not to make assumptions about it's value.
volatile unsigned char waitForHostReady = 0;

 

ErnieM, thanks for your suggestion, will try that out soon.

By the way, I am using MPLAB C30 C Compiler. Sorry that I didn't mention earlier.

 

ErnieM, as you suggested, I tried using the volatile and it works!

Thank you so much!

By the way, could anyone briefly explain how does volatile help in this situation?