IDLE MODE EXIT PROBLEM

You already had an earlier thread
http://www.keil.com/forum/60312/
where Erik did give you suggestions two weeks ago.

That you now wonder what an ISR is, means that you can't have spent very much time with Google to figure out how to implement that external interrupt that Erik did mention then.

Learning doesn't come magically - it takes own work to get some progress. If you do get stuck, don't start new threads asking the same question a second time. Instead post links to text you have spent time reading through, and ask about specific sentences or concepts that you don't understand.

In the end, the processor is no much different from you. It wakes up when it gets interrupted by some external interrupt (like an alarm clock) or an internal sleep timer interrupts it.

You already had an earlier thread
http://www.keil.com/forum/60312/
where Erik did give you suggestions two weeks ago.

That you now wonder what an ISR is, means that you can't have spent very much time with Google to figure out how to implement that external interrupt that Erik did mention then.

Learning doesn't come magically - it takes own work to get some progress. If you do get stuck, don't start new threads asking the same question a second time. Instead post links to text you have spent time reading through, and ask about specific sentences or concepts that you don't understand.

In the end, the processor is no much different from you. It wakes up when it gets interrupted by some external interrupt (like an alarm clock) or an internal sleep timer interrupts it.

First hit was:
http://www.keil.com/download/docs/188.asp"

Second hit was:
www.circuitstoday.com/external-interrupts-handling-in-8051

Third hit was:
www.embeddedcraft.org/interrupt.html

Fourth hit was:
stackoverflow.com/.../8051-external-interrupt

...

So Google would quickly bring in all the required information to
- tell what an external interrupt is
- tell the meaning of ISR
- tell how to connect a signal
- tell how to initialize your external interrupt
- show what the ISR should look like
- ...

The only way to "unconfuse" yourself is to spend time making selective searches for information. Google supports queries written i normal english, so most questions you can ask here can be asked directly on the Google text input line with decent result. If the result isn't good, then your question wouldn't be good here either because Google will fail for the same reason thread questions fails - lack of enough information.

So - spend some time reading through the above links.

Then try that same search expression I used and see if you can't find some other interesting links.

Then come back after you have done some own work. And come back in this thread instead of starting a third thread. The people on the forum can help you forward. But it isn't populated by payed consultants that will come sit down beside you and write the code for you. People will only find it meaningful to help you if you show some interest in putting in some own work too.

Any time you see a term you don't understand - don't directly jump to a forum and ask what it means. Try Google instead. That is faster and easier. Google can supply long descriptions and illustrations that are not practical for any forum visitor to spend time creating just for you and your personal needs.

www.danlhenry.com/.../80C51_FAM_ARCH_1.pdf
www.danlhenry.com/.../80C51_FAM_HARDWARE_1.pdf
www.danlhenry.com/.../80C51_FAM_PROG_GUIDE_1.pdf

Erik

So you never did look at the data in the ZIP file available on this link?
http://www.keil.com/download/docs/188.asp
which happens to be:
http://www.keil.com/download/files/8051_ex0.zip
which happens to contain source code:

#include <REG52.H>

/*=============================================================================
=============================================================================*/
unsigned char ex0_isr_counter = 0;

void ex0_isr (void) interrupt 0
{
ex0_isr_counter++;   // Increment the count
}

/*=============================================================================
=============================================================================*/
void main (void)
{

/*-----------------------------------------------
Configure INT0 (external interrupt 0) to generate
an interrupt on the falling-edge of /INT0 (P3.2).
Enable the EX0 interrupt and then enable the
global interrupt flag.
-----------------------------------------------*/
IT0 = 1;   // Configure interrupt 0 for falling edge on /INT0 (P3.2)
EX0 = 1;   // Enable EX0 Interrupt
EA = 1;    // Enable Global Interrupt Flag

/*-----------------------------------------------
Wait forever.
-----------------------------------------------*/
while (1)
  {
  }
}

/*=============================================================================
=============================================================================*/

By the way - your original post does show C code. Now you start talking about RET or RETI - which implies you suddenly are talking about the instruction set of the processor. RETI is the special instruction needed to return from an ISR, while RET is the instruction to return from a normal sub-routine. And the C compiler already knows this - so if you write an ISR in the way documented in the compiler manual you will automatically get the correct return instruction.

You don't seem to be a problem solver. When you get stuck you don't spend much time trying before giving up or dropping off in a different direction. Programming is about logic. So spend some logic thinking on your problems. It will really improve your progress. Wildly testing random statements like some magical arcane spells (like what you listed in your previous post) isn't a good way to solve your problem.