source: Deliverables/D4.1/GCC/SerialWriteRead.c @ 297

#include "mcs51reg.h"

int factorial(int i)
{
  if(i == 0 | i == 1)
    return 1;
  else
    return i * factorial(i - 1);
}

void prepare_serial(void)
{
  SCON = SCON | 0x40;  // Change serial port mode to mode 1
  TMOD = TMOD | 0x20;  // Configure timer 1 to mode 2 (8 bit autoreload)
  TH1  = 0xFD;         // Baud rate to 19,200 with ~11mhz clock
  PCON = PCON | 0x80;  // PCON.7 set to double baud rate (needed?)
}

void write_serial(int d)
{
  TI   = 0x00;    // Clear the transmission bit
  SBUF = d;       // Write data to the serial buffer
  while(!TI) { }  // Wait until the data has been transmitted
}

int read_serial(void)
{
  while(!RI) { }  // Wait until receiver bit is set (we have data on the serial line).
  return SBUF;    // If so, we need to return SBUF, which contains the data.
}

int main(void)
{
  int x = 0;
  prepare_serial();
  write_serial(10);
  write_serial(20);
  write_serial(factorial(3));
  x = read_serial();
  return 5;
}