www.pudn.com > 8255_code_lib.rar > CHIPFN02.C

/*- 
 *  ---------------------------------------------------------------------- 
 *  File        :   CHIPFN02.C 
 *  Creator     :   Blake Miller 
 *  Version     :   01.00.00            February 1991 
 *  Language    :   Microsoft Quick C   Version 2.0 
 *  Purpose     :   Intel 8255 Compatible Digital IO Functions 
 *              :   80X86 IN Instruction Function 
 *  ---------------------------------------------------------------------- 
 */ 
 
void chp_portrd (int d_port, unsigned char *d_byte); 
 
/*- CHIP : Byte Get --------------------------** 
 *  Read a byte from one of the 80X86 ports. 
 *  Duplicates the library function inp() 
 */ 
void chp_portrd (int d_port, unsigned char *d_byte) 
	{ 
	unsigned char   t_byte = 0; /* temporary byte   */ 
 
	/*  set port address 
	 *  get data into AL 
	 *  store data into temporary variable 
	 *  Note: Use temporary variable because ASM has no idea 
	 *  what a pointer to an unsigned char is! 
	 */ 
	_asm    { 
		PUSH    AX 
		PUSH    DX 
 
		MOV     DX, d_port 
		IN      AL, DX          ; get byte into AL 
		MOV     t_byte, AL      ; transfer data to C temporary 
 
		POP     DX 
		POP     AX 
		} 
 
	*d_byte = t_byte;   /* transfer data back to C  */ 
	} 
 
/*- 
 *  ---------------------------------------------------------------------- 
 *  END CHIPFN02.C Source File 
 *  ---------------------------------------------------------------------- 
 */