Question

微控制器PIC16F887 // 任务说：编写将反转PORTB的程序并将其作为输出端口，并且在每个SECOND中它将在Led Diods上进行反向ON / OFF

这是我的代码：

unsigned cnt ;

void interrupt(){
     if(TMR0IF_bit){ //if there is interrupt in timer0
      cnt++;         //increase the counter
      TMR0IF_bit=0;  //reset the timer
      TMR0 = 96;     //set the TMR0 to its default value
     }
}

void main() {
ANSEL = 0;
ANSELH = 0;
OPTION_REG = 0b00000100; //1:32 prescalar (last 3 bits are 100)
INTCON = 0xA0;          //enable interrupt generated by TMR0
TRISB = 0x00;           //make PORTB output port
PORTB = 0xFF;           //set PORTB to 1s
cnt =0;                 //initialize counter
TMR0 = 96;              //starting value of TMR0

do{
if(cnt==391){           
 PORTB = ~PORTB;       //invert PORTB
 cnt=0;                //reset the timer
}
cnt++;                 //increase counter if its not 391
}while(1);
}

重要 TMR0 = 96是起始值，256-96 = 160 OPTION_REG = 1:32所以预分类为32 我们需要接近2M，因为2M指令接近1秒，因为他们说

2 000 000/32（预分解）* 160（256-96）= ~391 所以当计数器达到391时，一秒延迟应为2M / 32 * 160 但是当我在8Mhz模拟时启动它时，LED DIODS的反转速度比1秒快得多。

那么你能帮我弄清楚问题是什么以及如何让它在每一秒都反转。谢谢

Answer 1

建议您阅读PIC16F系列的数据表。在开始使用之前理解每个寄存器及其重要性非常重要

您已经提到过，如果从while循环中删除cnt的增量，则需要10秒以上，这清楚地表明，时钟，TMR0值和循环值不同步。

对于简单计时器实现，请在下面的链接中解释，这可能会对您有所帮助

http://www.microcontrollerboard.com/pic-timer0-tutorial.html

Sudhee

Answer 2

距离这个作业问题的答案已有7个月了。几乎每学期都会分配此问题的变种，因此这里有一个可能的抄袭解决方案：

/*
 * file:        main.c
 * author:      dan1138
 * target:      PIC16F887
 * IDE:         MPLAB 8 v8.92
 * Compiler:    XC8 v1.45
 *
 * Description:
 *  program that will invert PORTB and will make
 *  it output port and in every SECOND it will make
 *  inverse ON/OFF on the Led Diodes.
 */
#include <xc.h>

/* Setup Configuration word 1 for the PIC16F887 */
__CONFIG( FOSC_INTRC_NOCLKOUT & WDTE_ON & PWRTE_OFF & MCLRE_ON & CP_OFF & CPD_OFF & BOREN_OFF & IESO_OFF & FCMEN_OFF & LVP_OFF );

/* Setup Configuration word 2 for the PIC16F887 */
__CONFIG( BOR4V_BOR21V & WRT_OFF );

#define FSYS 8000000L       /* target device system clock freqency */
#define FCYC (FSYS/4L)      /* target device instruction clock freqency */

#define _XTAL_FREQ FSYS     /* required for XC8 delay macros */

#define TIMER0_RELOAD_VALUE (250u)
/*
 * Handle Interrupt Events
 */
void interrupt ISR_Handler( void )
{
    static unsigned short OneSecondTick = 0;

    if(INTCONbits.TMR0IE)
    {
        if(INTCONbits.TMR0IF)
        {
            INTCONbits.TMR0IF = 0;
            TMR0 -= (TIMER0_RELOAD_VALUE - 3u);

            if(OneSecondTick == 0)
            {
                OneSecondTick = (FCYC / TIMER0_RELOAD_VALUE);
                PORTB ^= 0xFF;
            }
            OneSecondTick--;
        }
    }
}
/*
 * Main application
 */
void main(void)
{
    /* Initialisation */
    INTCON = 0x00;
    PIE1   = 0x00;
    PIE2   = 0x00;

    OSCCON = 0x70;          /* select 8MHz internal clock */
    CLRWDT();

    PORTA = 0x00;
    PORTB = 0x00;
    PORTC = 0x00;
    PORTD = 0x00;
    PORTE = 0x00;

    TRISA = 0x00;
    TRISB = 0x00;
    TRISC = 0xC0;  /* TRISC Bits 7 and 6 must be inputs when UART is used */
    TRISD = 0x00;
    TRISE = 0x00;

    OPTION_REG = 0xDF; /* PORTB pull up off, INT on low to high edge,           */
                       /* TMR0 clock is FCYC, WDT has prescaler, WDT rate 1:128 */

    /* Disable all analog inputs and use for digital I/O */
    ANSEL  = 0x00;
    ANSELH = 0x00;
    ADCON0 = 0xC0;
    ADCON1 = 0x00;

    /* Disable comparators */
    CM1CON0 = 0x00;
    CM2CON0 = 0x00;
    VRCON   = 0x00;

    /* Initialize TIMER0 */
    INTCONbits.TMR0IF = 0;
    INTCONbits.TMR0IE = 1;

    /* enable system interrupts */
    GIE   = 1;

    /* Application loop */
    for(;;)
    {
        CLRWDT();
    }
}

也许老师会为下一学期提出新的作业。

用PIC16F887将MicroC中的PORTB值反转1秒延迟

2 个答案: