謝謝Master大的指導
原來是定義的時候就有限制了

你原來Long_Conut的型態是unsigned char，只要改成unsigned int就可以了。

各位大大好, 小弟現在在研究中斷程式的寫法, 並將W401的5-2練習改寫成以下的程式:

#include <p18f4550.h>
#include <timers.h>
#include <delays.h>
#include "P18F_LCD.h"


void isr_high(void);

volatile unsigned char Long_Count ;
volatile unsigned char Direct_LED ;
volatile unsigned char Dir_Count ;

void main(void)
{
TRISD=0x00;

RCONbits.IPEN=1;
IPR1bits.TMR2IP=1;
INTCONbits.GIEH=1;

ADCON0 = 0x01;
ADCON2 = 0x25;
ADCON1 |= 0x0F;

OpenI2C(MASTER, SLEW_OFF);
SSPADD = 59; // 100KHz and 24MHz

Long_Count=0;

PORTD = 0x0F;

/***********************************/
/* Interrupt Time */
/*(1/(24Mhz/4)) (16*10)(199+1)) = 5.3ms */
/***********************************/
OpenTimer2 ( TIMER_INT_ON & T2_PS_1_16
& _POST_1_10);

PR2 = 199;
while(1);
}

//************************************************
//* #pragma Interrupt Declarations *
//* *
//* Function: isr_high_direct *
//* - Direct execution to the actual *
//* high-priority interrupt code. *
//************************************************
#pragma code isrhighcode = 0x0008

void isr_high_direct(void)
{
_asm
goto isr_high
_endasm
}
#pragma code

//************************************************
//* Function: isr_high(void) *
//* High priority interrupt will *
//* - Received a serial data from RS-232 *
//* Save the received data to buffer Rec_Data*
//************************************************
#pragma interrupt isr_high

void isr_high(void)
{
PIR1bits.TMR2IF=0;

if (Long_Count <= 250) Long_Count++;
else
{
Long_Count=0;

PORTD=PORTD^0xFF;

}
}
#pragma code


預計讓high, low byte的LED每隔4秒交互亮, 可是當我更改Long_Conut超過250, 中斷程式就不會執行else裡面的程式, 請問這是因為我延遲的時間設的太久了嗎?

如果是, 我欲達到原程式設計目的, 我該怎麼修改?
Oscillator : HS : HS+PLL, USB-HS
DEMO Board : APP013
MCU : P18F4550
謝謝