www.pudn.com > 8255_code_lib.rar > DIOFNC03.C

/*- 
 *  ---------------------------------------------------------------------- 
 *  File        :   DIOFNC03.C 
 *  Creator     :   Blake Miller 
 *  Version     :   01.01.00        February 1991 
 *  Language    :   Microsoft C     Version 5.1 
 *  Purpose     :   Intel 8255 Compatible Digital IO Functions 
 *                  Bit Put Function 
 *  ---------------------------------------------------------------------- 
 *  Revision History: 
 *  022891 BVM  :   Change int to short. 
 *  070490 BVM  :   Creation 
 *  ---------------------------------------------------------------------- 
 */ 
 
#define     DIOFNC03_C_DEFINED  1 
#include    "DIOLIB.H" 
#undef      DIOFNC03_C_DEFINED 
 
void dio_bitput (DIODAT *data, short bit, short state); 
 
/*- DIO : Bit Put ----------------------------** 
 *  Set/Clear one of the bits in the 8255. 
 *  A state of !0 sets the bit and a state of 0 clears the bit. 
 *  The bit number should be from 0 - 23 as follows: 
 *   0 = Port A Bit 0;   7 = Port A Bit 7 
 *   8 = Port B Bit 0;  15 = Port B Bit 7 
 *  16 = Port C Bit 0;  23 = Port C Bit 7 
 *  Passed: 
 *      pointer :   DIODAT 
 *      short   :   bit number 
 *      short   :   state : TRUE (!0) = SET, FALSE (0) = CLEAR 
 *  Returns: 
 *      nothing 
 *      Loads stat with appropriate error code 
 */ 
void dio_bitput (DIODAT *data, short bit, short state) 
	{ 
	short           port;   /* port number  */ 
	unsigned char   mask;   /* byte mask    */ 
 
	/*  Make sure the bit requested is valid. 
	 *  Three ports of 8 bits each = 24 total bits. 
	 *  This will also validate the port number used later. 
	 */ 
	if ( (bit < 0) || (bit > 23) ){ 
		data->stat = DIO_ST_BB; 
		return; 
		} 
 
	/*  The bit number should have zero offset. 
	 *  This is useful for lining up the port with integer 
	 *  divide and it is also used for left shifting to 
	 *  create a mask. 
	 *  Get port number by doing integer division.  The port 
	 *  number should end up as 0, 1, or 2, corresponding to 
	 *  PORT A, PORT B, and PORT C respectively. 
	 *  Then do modulo 8 to get the corrsponding bit 
	 *  number to be used in the particular byte.  This 
	 *  value will end up being 0 - 7. 
	 *  Then form the bit mask, starting with 1 and 
	 *  left shifting to line it up with the proper port bit. 
	 *  If the bit is to be set, then this is bit ored (|) 
	 *  with the current port value and then output.  If it is 
	 *  to be cleared, then the mask bits are inverted and 
	 *  this vlaue is bit anded (&) with the current port value. 
	 */ 
	port = ( bit / 8);      /* port number (0 - 2)          */ 
	bit = bit % 8;          /* modulo to get the bit number */ 
	mask = 0x01;            /* assume low bit of byte       */ 
	mask = mask << bit;     /* shift left to requested bit  */ 
 
	/*  If bit is to be set: 
	 *  Switch to appropriate port and set bit. 
	 */ 
	if ( state ){ 
		data->pdat[port] = data->pdat[port] | mask; 
		} 
 
	/*  Otherwise bit is to be cleared: 
	 *  Invert bit mask. 
	 *  Modify appropriate port data by clearing bit. 
	 */ 
	else { 
		mask = ~mask; 
		data->pdat[port] = data->pdat[port] & mask; 
		} 
 
	/*  Prepare to output data: 
	 *  Obtain appropriate port data 
	 *  Obtain port address. 
	 */ 
	dio_bput ( data->base + port, data->pdat[port] ); 
	data->stat = DIO_ST_OK; 
	} 
 
/*- 
 *  ---------------------------------------------------------------------- 
 *  END DIOFNC03.C Source File 
 *  ---------------------------------------------------------------------- 
 */