;	Absolute Disk Read:  GETSEC  ( uses BIOS interrupt 0x25 )

;

;	Interfaces to Computer Innovations C-86 "c" compiler V1.32 (& later)

;	See DOS 2.10 Technical Reference page 5-10, and Technical Reference

;	page A-32.  This code was written by Mike Sirmans (05-25-84).

;	--------------------------------------------------------------------

;       THIS ROUTINE IS POWERFUL. (AND AS SUCH, IS DANGEROUS IN THE WRONG

;       HANDS).  BE CAREFUL HOW YOU USE IT.  I ASSUME NO RESPONSIBILITY.

;	--------------------------------------------------------------------

;

;	Synopsis:	int getsec(drive,numsec,begsec,buffer)

;			unsigned int drive;	/* 0=A, 1=B, etc. */

;			unsigned int numsec;	/* Number of sectors to read */

;			unsigned int begsec;	/* Beginning logical sector */

;			char *buffer;		/* Transfer address */

;

;	Function:	The number of sectors specified are transferred 

;			between	the given drive and the transfer address. 

;			LOGICAL SECTOR NUMBERS are obtained by numbering

;			each sector sequentially starting from track 0, head 0,

;			sector 1 (logical sector 0) and continuing along the

;			same head, then to the next head until the last sector

;			on the last head of the track is counted.  Thus, 

;			logical sector 1 is track 0, head 0, sector 2,

;			logical sector 2 is track 0, head 0, sector 3,  & so on.

;

;	Returns:	NULL if the operation is successful.

;			otherwise, error codes are as follows:

;

;			hex 80	Attachment failed to respond.

;			hex 40	SEEK operation failed.

;			hex 20	Controller failure.

;			hex 10  Bad CRC on diskette read.

;			hex 08	DMA overrun on operation.

;			hex 04	Requested sector not found.

;			hex 03	Write attempt on write-protected diskette.

;			hex 02	Address mark not found.

;			hex FF	Unspecified (error other than those above).

;

code	segment	byte public		;segment registers remain intact

	assume	cs:code			;all other registers will be destroyed

	public	getsec



getsec: push	bp			;save old frame pointer

	mov	bp,sp			;get new frame pointer

	mov	ax,4[bp]		;put drive number into AL

	xor	ah,ah

	mov	cx,6[bp]		;number of sectors to fetch

	mov	dx,8[bp]		;logical record number of 1st sector

	mov     bx,10[bp]		;pointer to transfer address

	int	25h			;BIOS call

	jc	error			;error has occurred if carry flag = 1

	mov	al,00H			;NULL to indicate sucessful completion

	jmp	done

error:	cmp	al,00H			;detect unspecified error code 00H

	jne	done			;...change to 0FFh if found to 

	mov	al,0FFH			;...differentiate it from success code

done:	xor	ah,ah			;return AL only

	popf				;remove flags int 0x25 left on stack

	pop	bp			;restore original frame pointer

	ret				;all done



code	ends

	end



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