t2_ledio.c

intel 196nt 例程

/*
** t2_ledio.c
**      Display some random patterns on the LEDs
**      mixed with a slightly highlighted LED
**      that runs from left to right.
*/

#include        <stdio.h>
#include        <stdlib.h>
#include        _SFR_H_

/* IMPORT functions */
extern  void    wait_ms( int );

/* LOCAL functions */
static  void            enable_led( void );
static  void            set_led( unsigned char );

void main(void)
{
    unsigned int        i;
    int                 j;
    unsigned char       mask;

    set_led( 0 );               /* Clear the LEDs before enabling. */
    enable_led();

    for ( j = 0, mask = 0x01; ; j++ )
    {
        if ( (j % 64) == 0 )
        {
            mask = mask & 0x80 ? 0x01 : mask<<1;
        }
        i = rand();
        set_led( i | mask );
        wait_ms( 3 );
        set_led( mask );
        wait_ms( 7 );
    }
}

/* LED I/O is connect to Port 1 */
static void enable_led( void )
{
    /* Set all pins of port1 to open-drain output (external pull-up). */
    asm stb     0,p1_dir;
}

static void set_led( register unsigned char b )
{
    /* Each bit is a LED in the LED array. */
    /* Note that there are ten LEDs,
       one is unused,
       one is for power-on indication. */
    asm stb     b,p1_reg;
}