在PIC16F87上使用__delay_ms（）时出现奇怪行为

我正在学习中断，似乎偶然发现了一些非常奇怪的行为。至少在我的设置中，它的行为很奇怪。我已经删除了我所有的其他代码，并将其缩小到以下条件。在我的设置中，我有2个LED连接到RB4＆AMP；RB5。我的伪代码基本上是这样做的，打开两个LED。等待X秒。打开一个LED，等待Y秒。在我的代码中，如果我使用值为Y-YelayaysMs（）最多1000，一切似乎都很好，表现正常。如果我开始增加值，保持X和Y的相同，“ON”时间似乎是正确的，但是“off”时间大大减少到1/5秒。我开始以100ms的增量增加值直到1900毫秒，然后LED似乎永远保持不变。根据文档（我使用XC8 1.42）-“延迟参数必须是常数，小于50463240”任何可能导致这一点的想法，我的完整代码如下。



      以下为原文

    I was learning about interrupts and seem to have stumbled across some really weird behaviour of the __delay_ms() function.  At least on my setup it's behaving odd.

I've stripped out all my other code and narrowed it down to the following conditions.  In my setup I have 2 LEDs connected to RB4 & RB5.  My pseudo code basically does this;

Turn both LEDs on.
Wait x seconds.
Turn one of the LEDs off
Wait y seconds.

In my code if I use values up for  __delay_ms() up to 1000, everything seems fine and behaves apparently normally.  Howevef if I start increasing the values, keeping the same for x & y the "on" time seems correct but the "off" time is greatly reduced to what seems like 1/5 second.  I started increasing values in increments of 100ms up to 1900ms and then the LEDs seem to stay on permanently.

According to the documentation (I'm using XC8 1.42) - "The delay argument must be a constant and less than 50,463,240"

Any ideas what could be causing this, my full code is below.

// PIC16F87 Configuration Bit Settings

// 'C' source line config statements

// CONFIG1
#pragma config FOSC = INTOSCIO // Oscillator Selection bits (INTRC oscillator; port I/O function on both RA6/OSC2/CLKO pin and RA7/OSC1/CLKI pin)
#pragma config WDTE = ON // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = ON // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is MCLR)
#pragma config BOREN = ON // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF // Low-Voltage Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF // Data EE Memory Code Protection bit (Code protection off)
#pragma config WRT = OFF // Flash Program Memory Write Enable bits (Write protection off)
#pragma config CCPMX = RB0 // CCP1 Pin Selection bit (CCP1 function on RB0)
#pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off)

// CONFIG2
#pragma config FCMEN = ON // Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor enabled)
#pragma config IESO = ON // Internal External Switchover bit (Internal External Switchover mode enabled)

// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

#include

// We're going to be using the __delay_ms() functions so we need to define the clock frequency we've set.
#define _XTAL_FREQ 4000000
void main(void) {
    // Set up the clock frequency. Make sure the _XTAL_FREQ definition matches.
    //
    // 000 = 31.25 kHz
    // 001 = 125 kHz
    // 010 = 250 kHz
    // 011 = 500 kHz
    // 100 = 1 MHz
    // 101 = 2 MHz
    // 110 = 4 MHz
    // 111 = 8 MHz
    //
    OSCCONbits.IRCF = 0b110;
        
    // Set up our ports.
    TRISBbits.TRISB5 = 0;
    TRISBbits.TRISB4 = 0;

    // Make sure all LEDs are off.
    PORTBbits.RB5 = 0;
    PORTBbits.RB4 = 0;
                    
    // Enter inifinite loop.
    while(1) {
      
        // Turn 2 pins on.
        PORTBbits.RB4 = 1;
        PORTBbits.RB5 = 1;
        
        // Wait 3 seconds.
        #ifndef __DEBUG
        __delay_ms(1000);
        #endif

        // Turn off one of the LEDS.
        PORTBbits.RB5 = 0;
              
        // Wait 2 seconds.
        #ifndef __DEBUG
        __delay_ms(1000);
        #endif
    }
   
    return;
}

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