main.c

Cygnal C8051F020 Dual UART Example

/*-----------------------------------------------------------------------------
-----------------------------------------------------------------------------*/
#include <C8051F020.H>
#include <stdio.h>                /* prototype declarations for I/O functions */


bit sio_port = 1;   /* SIO port to use (0 = SIO0) */

/*-----------------------------------------------------------------------------
The following putchar function replaces the one in the library.
-----------------------------------------------------------------------------*/
char putchar (char c)
{
if (sio_port == 0)
  {
  while (!TI0);
  TI0 = 0;
  SBUF0 = c;
  }
else
  {
  while (!(SCON1 & (1 << 1)));  /* While TI1 = 0 */
  SCON1 &= ~(1 << 1);           /* TI1 = 0 */
  SBUF1 = c;
  }

return (c);
}

/*-----------------------------------------------------------------------------
The following _getkey function replaces the one in the library.
-----------------------------------------------------------------------------*/
char _getkey (void)
{
char c;

if (sio_port == 0)
  {
  while (!RI0);
  c = SBUF0;
  RI0 = 0;
  }
else
  {
  while (!(SCON1 & (1 << 0)));  /* While RI1 = 0 */
  c = SBUF1;
  SCON1 &= ~(1 << 0);           /* RI1 = 0 */
  }

return (c);
}

/*-----------------------------------------------------------------------------
The main C function.
-----------------------------------------------------------------------------*/
void main (void) {

/*------------------------------------------------
NOTE:  You must properly configure the crossbar
for your application.
------------------------------------------------*/

/*------------------------------------------------
Disable the watchdog timer.  This should probably
be done in the STARTUP code.
------------------------------------------------*/
WDTCN = 0xDE;
WDTCN = 0xAD;

/*------------------------------------------------
Setup the serial port 0 for 1200 baud at 2MHz
using timer 2.

See http://www.keil.com/c51/baudrate.asp for
baudrate calculations and reload values.
------------------------------------------------*/
    SCON0  = 0x50;              /* SCON:  Mode 1, 8-bit UART, enable rcvr */
    T2CON  = 0x30;              /* T2CON: Use T2 for Baud Rate on SIO 0 */

    RCAP2L = 0xCC;              /* RCAP2: Reload value for 1200 baud */
    TL2    = 0xCC;
    RCAP2H = 0xFF;
    TH2    = 0xFF;

    TR2   = 1;                  /* TR2: T2 Run */
    TI0   = 1;                  /* TI0: Set TI0 to send first char of SIO 0 */

/*------------------------------------------------
Setup the serial port 1 for 2400 baud at 2MHz
using timer 4.

See http://www.keil.com/c51/baudrate.asp for
baudrate calculations and reload values.
------------------------------------------------*/
    SCON1  = 0x50;              /* SCON1: Mode 1, 8-bit UART, enable rcvr */
    T4CON  = 0x30;              /* T4CON: Use T4 for Baud Rate on SIO 1 */

    RCAP4L = 0xE6;              /* RCAP4: Reload value for 2400 baud */
    TL4    = 0xE6;
    RCAP4H = 0xFF;
    TH4    = 0xFF;

    T4CON |= 1 << 2;            /* TR4: T4 Run */
    SCON1 |= 1 << 1;            /* TI1: Set TI1 to send first char of SIO 1 */

/*------------------------------------------------
------------------------------------------------*/
  while (1) {
    char c;

    sio_port = !sio_port;       /* switch ports */
    printf ("Press a key: ");
    c = _getkey ();
    printf ("\r\nYou pressed %c\r\n", c);
  }
}