مشکل با وقفه gpio در lpc1768

#include "lpc17xx.h"
#include "lcd.h"
#include "delay.h" 
#include "ocf_lpc176x_lib.h"
#include "keypad.h"
void settings(void);
void EINT3_IRQHandler(){
 LPC_GPIOINT->IO0IntClr = 1<<15;
 LCD_DisplayString("interrupt");
 uint8_t key;
 key = KEYPAD_GetKey();
 if ( key == 83){
 settings();
 }
}
int main() 
{ 
 LPC_GPIOINT->IO0IntEnF = 1<<15;
 NVIC_SetPriority(EINT3_IRQn, 0);
 NVIC_ClearPendingIRQ(EINT3_IRQn);
 NVIC_EnableIRQ(EINT3_IRQn);
 SystemInit();
 /*Connect RS, RW, EN and data bus to PORT0.4 to PORT0.7*/
 LCD_SetUp(P0_0,P0_1,P0_2,P_NC,P_NC,P_NC,P_NC,P0_3,P0_4,P0_5,P0_6);
 LCD_Init(2,16);
 // Keypad setup
 KEYPAD_Init(P0_8,P0_9,P0_10,P0_11,P0_15,P0_16,P0_17,P0_18); // Keypad is connected to P0_8 - P0_18
 initTimer0(); //For delayMS()
 while(1)
 {
 LCD_DisplayString("main");
 delayUS(1000000); 
 LCD_DisplayChar(86);
 delayUS(1000000); 
 }
}
void settings(void){
 //LCD_GoToLine(0);
 LCD_DisplayString("settings");
 uint8_t key;
 key = KEYPAD_GetKey();
 if (key == 49){
 main();
 }else if(key == 50){
 LCD_Clear();
 while(1);
 }
}