;**************************************************************
;              M DISK EQUATES
;**************************************************************
;

mdiskbase	equ	0c00h	;base paragraph
				;address of mdisk
;**************************************************************
;               DATBCB Definition
;**************************************************************

	drv	equ	byte ptr 0
	record	equ	byte ptr 1
	wflg	equ	byte ptr 4
	seq	equ	byte ptr 5
	track	equ	word ptr 6
	sector	equ	word ptr 8
	bufseg	equ	word ptr 10
	link	equ	word ptr 12
	pdadr	equ	word ptr 14
;**************************************************************
;             M DISK INITIALIZATION
;**************************************************************
init_m_disk:
	mov cx,mdiskbase
	push es ! mov es,cx
	xor di,di
	mov ax,0e5e5h		;check if already initialized
	cmp es:[di],ax ! je mdisk_end
	  mov cx,2000h		;initialize 16K bytes
	  rep stos ax		;of Mdisk directory to 0e5h's
mdisk_end:
	pop es
	ret

;**************************************************************
;            M DISK CODE
;**************************************************************

;=======
IO READ:			;Function 11 Read sector
;=======
; Reads the sector on the current disk, track and
; sector into the current DMA buffer.
;	entry:  AL = 00 if no error occurred
;	exit:	AL = 01 if an error occurred

read_m_dsk:
;-------------
	call mdisk_calc		;calculate byte address
	push es			;save UDA
	les di,dword ptr dmaoff ;load destination MDA address
	xor si,si		;setup source DMA address
	push ds			;save current DS
	mov ds,bx		;load pointer to sector in memory
	rep movsw		;execute move of 128 bytes....
	pop ds			;then restore user DS register
	pop es			;restore UDA
	xor ax,ax		;return with good return code
;========
IO_WRITE:			;FUNCTION 12: Write disk
;========
;Write the sector in the current Dma buffer
;to the current disk on the current
;track in the current sector
;      entry:  CL = 0 - Deferred Writes
;                   1 - nondeferred writes
;                   2 - def-wrt lst sect unalloc blk
;      exit:   AL = 00H if no error occurred
;                   01H if error occurred
;                   02H if read only disk

write_m_dsk:
;-----------
	call mdisk_calc		;calculate byte address
	push es			;save UDA
	mov es,bx		;setup destination DMA address
	xor di,di
	push ds			;save user segment register
	lds si,dword ptr dmaoff	;load source DMA address
	rep movsw		;move from user to disk in memory
	pop ds			;restore user segment pointer
	pop es			;restore UDA
	xor ax,ax		;return no error
	ret
mdisk_calc:
;----------
;	entry: IOPB variables on the stack
;	exit:  BX = sector paragraph address
;	       CX = length in words to transfer

	mov bx,track		;pickup track number
	mov cl,3		;times eight for relative
				;       sector number
	shl bx,cl
	mov cx,sector		;plus sector
	add bx,cx		;gives relative sector number
	mov cl,3		;times eight for paragraph
				;       of sector start
	shl bx,cl
	add bx,mdiskbase	;plus base address of disk
				;       in memory
	mov cx,64		;length in words for move
				;       of 1 sector
	mov al,mcnt
	xor,ah,ah
	mul cx			;length * multisector count
	mov cx,ax
	cld
	ret
;**************************************************************
;       M DISK - DISP PARAMETER BLOCK
;**************************************************************

dpb0	equ	offset $	;Disk Parameter Block
	dw	8		;Sectors Per Track
	db	3		;Block Shift
	db	7		;block mask
	db	0		;Extnt Mask
	dw	126		;Disk size - 1
	dw	31		;Directory Max
	db	128		;Alloc0
	db	0		;Alloc1
	dw	0		;Check Size
	dw	0		;Offset
	db	0		;Phys Sec Shift
	db	0		;Phys Sec Mask

xlt5	equ	0		;No Translate Table
als5	equ	16*2		;Allocation Vector Size
clss5	equ	0		;Check Vector Size
hss5	equ	(32 * 4)	;Hash Table Size

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