external interrupt problem

Hello,

This problem begins to drive me crazy :
With a 87LPC767, I try to transmit a square signal via TXD.
With a button, I choose the period of the signal.
The button is linked to the interrupt pin 8 of the µcontroller and to another pin.

I define a baudrate in the initialize_system( ) function but I need to change the value of TH1 when the button is pushed.

When the com_baudrate() function is not in the code (like in the example beneath), everything works fine but when I move the // and I run the code, it goes once till the end of the main() and then enter the External_1() function and stay inside (TXD stays high).

I thought it was maybe a bank problem but adding "using 2" to the functions called in the External_1() function changes nothing…

Sorry to post all this code but I think it's easier to understand and not as long… :)

Thanks for any help and sorry for my English.

Arnaud Stoumont

/*---------------------------------------------------------------------------------------
IMPULSEUR
  ---------------------------------------------------------------------------------------*/
#include <stdio.h>
#include <rg_impuls.h>    /* SPECIAL FUNCTION REGISTER 87LPC767 */
#include <stdlib.h>

unsigned char debug;
unsigned char impulseur;

//------------------------------------------------------------------------------
// Support Function Prototypes
//------------------------------------------------------------------------------
void initialize_system (void);				// Initializes MCU, except I2C
void delay_time (unsigned int time_end);    // To pause execution for pre-determined time
void TESTSW(void);
void com_baudrate (unsigned char baudrate);


void TESTSW(void) using 2
{
	unsigned char LECTURESWITCH;	/*PERIODE DE LECTURE DES SWITCHES*/
	unsigned char BUTSELECTION;		/*Pour considéré le switch on doit etre > 90*/

	BUTSELECTION = 0;			
	LECTURESWITCH = 0;			/*Variable de comptage pour le nombre de lectures des boutons*/

do								/*Lecture de l'état des deux boutons*/
{
	if (BSELECTION == 0)		/*Lecture bouton selection*/
 	{
 		BUTSELECTION++;				/*Bouton sélection lu actionné*/
	}

	LECTURESWITCH++;			/*Variable de comptage pour le nombre de lectures des boutons*/
}
while (LECTURESWITCH < 100 );	/*Test pour 100 lectures du bouton sélection*/


			
if (BUTSELECTION > 90 ) /*Le bouton sélection est activé*/
{
	impulseur++;
}


if ( impulseur > 2 )
{
	impulseur = 0;
}

return;
}	

void initialize_system (void)
{
PCON &= 0x7F;							// Clear bit 7 of the PCON register (SMOD1 = 0) pour pouvoir diviser Fcpu par 192 et pas 96 

SCON = 0x50;			// 0101,0000 (Mode 1 and RxD enable)	
TMOD = 0x20;			// Timer #1 in autoreload 8 bit mode

TH1 = 0x11;			
											// Timer #1 overflow rate
											// Baud Rate = (Fcpu / 192) / (256 - TH1) avec TH1=230 --> 1202 bits/s
											// Fcpu = 8.00 MHz (XTAL)
TL1=TH1;
ET1 = 0;			    /* disable timer 1 interrupt */
TR1 = 1;			// Turn on Timer 1
REN=0;
//mettre la priorité de l'interrupt externe plus haute que celle du timer
IP0=0x84;
IP0H=0x84;
return;
}

/*------------------------------------------------------------------------------
------------------------------------------------------------------------------*/
void com_baudrate (unsigned char baudrate) using 2
{
/*------------------------------------------------
Clear transmit interrupt and buffer.
------------------------------------------------*/
TI = 0;				    /* clear transmit interrupt */
/*------------------------------------------------
Set timer 1 up as a baud rate generator.
------------------------------------------------*/
TR1 = 0;			    /* stop timer 1 */
ET1 = 0;			    /* disable timer 1 interrupt */
TH1 = baudrate;//(unsigned char) (256 - ((XTAL) / ((32L/2) * 12L * baudrate)));
TL1=TH1;
TR1 = 1;			    /*