主文件代码：

/******************************************************************************/
/*  This file is part of the uVision/ARM development tools                    */
/*  Copyright KEIL ELEKTRONIK GmbH 2002-2004                                  */
/******************************************************************************/
/*                                                                            */
/*  HELLO.C:  Hello World Example                                             */
/*                                                                            */
/******************************************************************************/

#include                 /* prototype declarations for I/O functions */
#include               /* LPC21xx definitions                      */

/****************/
/* main program */
/****************/
int main (void)  {                /* execution starts here                    */

  /* initialize the serial interface   */
  PINSEL0 = 0x00050000;           /* Enable RxD1 and TxD1                     */
  U1LCR = 0x83;                   /* 8 bits, no Parity, 1 Stop bit            */
  U1DLL = 97;                     /* 9600 Baud Rate @ 15MHz VPB Clock         */
  U1LCR = 0x03;                   /* DLAB = 0                                 */

  printf ("Hello World\n");       /* the 'printf' function call               */

  while (1) {                     /* An embedded program does not stop and    */
    ;  /* ... */                  /* never returns.  We've used an endless    */
  }                               /* loop.  You may wish to put in your own   */
}                                 /* code were we've printed the dots (...).  */
串口程序代码：

/******************************************************************************/
/*  This file is part of the uVision/ARM development tools                    */
/*  Copyright KEIL ELEKTRONIK GmbH 2002-2004                                  */
/******************************************************************************/
/*                                                                            */
/*  SERIAL.C:  Low Level Serial Routines                                      */
/*                                                                            */
/******************************************************************************/

#include                      /* LPC21xx definitions               */

#define CR     0x0D

int putchar (int ch)  {                  /* Write character to Serial Port    */

  if (ch == '\n')  {
    while (!(U1LSR & 0x20));
    U1THR = CR;                          /* output CR */
  }
  while (!(U1LSR & 0x20));
  return (U1THR = ch);
}

int getchar (void)  {                    /* Read character from Serial Port   */

  while (!(U1LSR & 0x01));

  return (U1RBR);
}