const char col_xlat[4]=
{
	0xe0,	/* column code 1110 */
	0xd0,	/* column code 1101 */
	0xb0,	/* column code 1011 */
	0x70,	/* column code 0111 */
};

void key_scan(void) 
{ 
char col; 
char row; 
char key; 

for(col=0; col<3; col++) 
{ 
P2=P2 | col_xlat[col];