www.pudn.com > 8255_code_lib.rar > I8255F06.C

/*- 
 *  ---------------------------------------------------------------------- 
 *  File        :   I8255F06.C 
 *  Creator     :   Blake Miller 
 *  Version     :   0.00            June 1990 
 *  Language    :   Microsoft C     Version 5.1 
 *  Purpose     :   Intel 8255 Compatible Digital IO Functions 
 *              :   8255 Get Byte Function 
 *  ---------------------------------------------------------------------- 
 */ 
 
#define  I8255F06_C_DEFINED  1 
#include "I8255FN.H" 
#undef   I8255F06_C_DEFINED 
 
void I8255_get_byte (I8255DAT *data, int p_num, unsigned char *p_dat); 
 
/*- I8255 : Byte Get -------------------------** 
 *  Read one of the bytes in the 8255. 
 *  The port number should be 1 - 3 as follows: 
 *  1 = Port A,  2 = Port B,  3 = Port C 
 *  Reads the 8255 and returns data in variable as well as 
 *  loading port data area. 
 *  Passed: 
 *      pointer :   I8255DAT 
 *      integer :   port number 
 *      pointer :   unsigned char : returned port data 
 *  Returns: 
 *      nothing 
 *      Loads stat with appropriate error code. 
 *      Loads p_dat with returned data. 
 */ 
void I8255_get_byte (I8255DAT *data, int p_num, unsigned char *p_dat) 
	{ 
	int             padd;   /* port address */ 
	unsigned char   ival;   /* input value  */ 
 
	/*  Make sure the port requested is valid. 
	 *  Three ports. 
	 */ 
	if ( (p_num < 1) || (p_num > 3) ){ 
		data->stat = I8255_ST_BP; 
		return; 
		} 
 
	/*  Decrement the port so we have zero offset. 
	 *  port number = ( 0 - 2 ) 
	 */ 
	p_num--; 
 
	/*  Prepare to input data: 
	 *  Obtain port address. 
	 */ 
	switch ( p_num ){ 
		case 0:         /* port A   */ 
			padd = I8255_PORTA(data->base); 
			break; 
		case 1:         /* port B   */ 
			padd = I8255_PORTB(data->base); 
			break; 
		case 2:         /* port C   */ 
			padd = I8255_PORTC(data->base); 
			break; 
		} 
 
	chp_portrd ( padd, &ival );     /* input data   */ 
 
	/*  Save the input data. 
	 */ 
	switch ( p_num ){ 
		case 0:         /* port A   */ 
			data->adat = ival; 
			break; 
		case 1:         /* port B   */ 
			data->bdat = ival; 
			break; 
		case 2:         /* port C   */ 
			data->cdat = ival; 
			break; 
		} 
 
	*p_dat = ival; 
	data->stat = I8255_ST_OK; 
	} 
 
/*- 
 *  ---------------------------------------------------------------------- 
 *  END I8255F06.C Source File 
 *  ---------------------------------------------------------------------- 
 */