main.c

来自「8051试验程序 基础教材」· C语言 代码 · 共 118 行

/*
02/01/2006: Petre M.
  -this program uses the watchdog timer (set at 2sec period) to send character
    strings using the UART whenever the watchdog interrupts are generated
*/
#include "ioADE7169F16.h"


//the character '0' at the end of the string shows the end of the message
__code const char Start_Message[]="\r\nCode is starting\r\n\0";
__code const char Watchdog_ISR_Message[]="\r\nReached watchdog ISR due to watchdog timeout\r\n\0";

__idata char b;


  void uart_init(void);
  void watchdog_init(void);
  void send_string(__idata char __code const *Message_ptr);
#pragma vector=0x5b
__interrupt void WATCHDOG_ISR(void)
{
  send_string(&Watchdog_ISR_Message[0]);
}



void main( void )
{

  watchdog_init();

  uart_init();

  send_string(&Start_Message[0]);




  while(1);

}


//this message sends the
void send_string(char __code const *Message_ptr) {

  char a;


  a=*Message_ptr;

  while (a!=0) {
    SCON_bit.TI=0; //make sure this bit is cleared

    SBUF = a; //send the character on the UART

    Message_ptr++;

    //wait until TI bit becomes 1
   while (SCON_bit.TI==0);
//    asm("nop");
//    asm("nop");
//    asm("nop");
//    asm("nop");


    a=*Message_ptr;
  }

  return;
}



//this function initializes the watchdog to 2 sec
void watchdog_init(void) {

  //disable interrupts
  IE_bit.EA=0;

  WDCON_bit.WDWR = 1;//before writing to WDCON, this bit must be 1

  /*WDCON=0111=2sec period
              1=watchdog generates an interrupt when times out
               0=status bit
                1=watchdog enabled
                 1=watchdog write enable bit
  */
  WDCON = 0x7b;
  //enable interrupts
  IE_bit.EA=1;


  return;
}



//this routine initializes the UART for 9600 baud
void uart_init(void) {

    /*01=Mode 1=8 bit UART, variable rate
        0=RI is set as soon as the data byte is received
         0=serial port reception disabled
          0=this bit represents the 9th data bit transmitted in Modes 2 and 3
           0=this bit represents the stop bit received in Mode 1 case
            0=Tx INT flag
             0=Rx INT flag
    */
  SCON = (SCON & 0x00) | 0x40;

  //for 9600baud@4.096MHz, DIV=4 and SBAUDF=0xab, real freq=9570baud
  SBAUDT = 0x04;
  SBAUDF = 0xab;
  return;
}