RomWBW/Source/HBIOS/md.asm

;
;==================================================================================================
;   MD DISK DRIVER (MEMORY DISK)
;==================================================================================================
;
MD_DISPATCH:
	LD	A,B		; GET REQUESTED FUNCTION
	AND	$0F
	JP	Z,MD_READ
	DEC	A
	JP	Z,MD_WRITE
	DEC	A
	JP	Z,MD_STATUS
	DEC	A
	JP	Z,MD_MEDIA
	DEC	A
	JP	Z,MD_CAP
	DEC	A
	JP	Z,MD_GEOM
	CALL	PANIC
;
;
;
MD_MEDIA:
	LD	A,C		; DEVICE/UNIT IS IN C
	AND	$0F		; ISOLATE UNIT NUM
	CP	2		; CHECK FOR MAX UNIT EXCEEDED
	CALL	NC,PANIC	; PANIC IF TOO HIGH
	ADD	A,MID_MDROM	; SET CORRECT MEDIA VALUE
	RET
;
;
;
MD_INIT:
	PRTS("MD: UNITS=2 $")
	PRTS("ROMDISK=$")
	LD	HL,ROMSIZE - 128
	CALL	PRTDEC
	PRTS("KB RAMDISK=$")
	LD	HL,RAMSIZE - 128
	CALL	PRTDEC
	PRTS("KB$")
	XOR	A		; INIT SUCCEEDED
	RET			; RETURN
;
;
;
MD_STATUS:
	XOR	A		; ALWAYS OK
	RET
;
;
;
MD_CAP:
	LD	A,C		; DEVICE/UNIT IS IN C
	AND	$0F		; ISOLATE UNIT NUM
	JR	Z,MD_CAP0	; UNIT 0
	DEC	A		; TRY UNIT 1
	JR	Z,MD_CAP1	; UNIT 1
	CALL	PANIC		; PANIC ON INVALID UNIT
MD_CAP0:
	LD	HL,(HCB + HCB_ROMBANKS)	; POINT TO ROM BANK COUNT
	JR	MD_CAP2
MD_CAP1:
	LD	HL,(HCB + HCB_RAMBANKS)	; POINT TO RAM BANK COUNT
MD_CAP2:
	LD	H,(HL)		; H := # BANKS
	LD	E,64		; # 512 BYTE BLOCKS / BANK
	CALL	MULT8		; HL := TOTAL # 512 BYTE BLOCKS
	LD	DE,0		; NEVER EXCEEDS 64K, ZERO HIGH WORD
	XOR	A
	RET
;
;
;
MD_GEOM:
	; RAM/ROM DISKS ALLOW CHS STYLE ACCESS BY EMULATING
	; A DISK DEVICE WITH 1 HEAD AND 16 SECTORS / TRACK.
	CALL	MD_CAP		; HL := CAPACITY IN BLOCKS
	EX	DE,HL		; SWAP
	LD	D,1 | $80	; HEADS / CYL := 1 BY DEFINITION, SET LBA CAPABILITY BIT
	LD	E,16		; SECTORS / TRACK := 16 BY DEFINTION
	LD	B,4		; PREPARE TO DIVIDE BY 16
MD_GEOM1:
	SRL	H		; SHIFT H
	RR	L		; SHIFT L
	DJNZ	MD_GEOM1	; DO 4 BITS TO DIVIDE BY 16
	XOR	A		; SIGNAL SUCCESS
	RET			; DONE
;
;
;
MD_READ:
	CALL	MD_IOSETUP	; SETUP FOR MEMORY COPY
#IF (MDTRACE >= 2)
	LD	(MD_SRC),HL
	LD	(MD_DST),DE
	LD	(MD_LEN),BC
#ENDIF
	PUSH	BC
	LD	C,A		; SOURCE BANK
	LD	B,BID_BIOS	; DESTINATION BANK IS RAM BANK 1 (HBIOS)
#IF (MDTRACE >= 2)
	LD	(MD_SRCBNK),BC
	CALL	MD_PRT
#ENDIF
	LD	A,C		; GET SOURCE BANK
	LD	(HB_SRCBNK),A	; SET IT
	LD	A,B		; GET DESTINATION BANK
	LD	(HB_DSTBNK),A	; SET IT
	POP	BC
	CALL	BNKCPY		; DO THE INTERBANK COPY
	XOR	A
	RET
;
;
;
MD_WRITE:
	LD	A,C		; DEVICE/UNIT IS IN C
	AND	$0F		; ISOLATE UNIT NUM
	LD	A,1		; PREPARE TO RETURN FALSE
	RET	Z		; RETURN ERROR IF ROM UNIT

	CALL	MD_IOSETUP	; SETUP FOR MEMORY COPY
	EX	DE,HL		; SWAP SRC/DEST FOR WRITE
#IF (MDTRACE >= 2)
	LD	(MD_SRC),HL
	LD	(MD_DST),DE
	LD	(MD_LEN),BC
#ENDIF
	PUSH	BC
	LD	C,BID_BIOS	; SOURCE BANK IS RAM BANK 1 (HBIOS)
	LD	B,A		; DESTINATION BANK
#IF (MDTRACE >= 2)
	LD	(MD_SRCBNK),BC
	CALL	MD_PRT
#ENDIF
	LD	A,C		; GET SOURCE BANK
	LD	(HB_SRCBNK),A	; SET IT
	LD	A,B		; GET DESTINATION BANK
	LD	(HB_DSTBNK),A	; SET IT
	POP	BC
	CALL	BNKCPY		; DO THE INTERBANK COPY
	XOR	A
	RET
;
; SETUP FOR MEMORY COPY
;   A=BANK SELECT
;   BC=COPY SIZE
;   DE=DESTINATION
;   HL=SOURCE
;
; ASSUMES A "READ" OPERATION.  HL AND DE CAN BE SWAPPED
; AFTERWARDS TO ACHIEVE A WRITE OPERATION
;
; ON INPUT, WE HAVE LBA ADDRESSING IN HSTLBAHI:HSTLBALO
; BUT WE NEVER HAVE MORE THAN $FFFF BLOCKS IN A RAM/ROM DISK,
; SO THE HIGH WORD (HSTLBAHI) IS IGNORED
;
; EACH RAM/ROM BANK IS 32K BY DEFINITION AND EACH SECTOR IS 512
; BYTES BY DEFINITION.  SO, EACH RAM/ROM BANK CONTAINS 64 SECTORS
; (32,768 / 512 = 64).  THEREFORE, YOU CAN THINK OF LBA AS
; 00000BBB:BBOOOOOO IS WHERE THE 'B' BITS REPRESENT THE BANK NUMBER
; AND THE 'O' BITS REPRESENT THE SECTOR NUMBER WITHIN THE BANK.
;
; TO EXTRACT THE BANK NUMBER, WE CAN LEFT SHIFT TWICE TO GIVE US:
; 000BBBBB:OOOOOOOO.  FROM THIS WE CAN EXTRACT THE MSB
; TO USE AS THE BANK NUMBER.  NOTE THAT THE "RAW" BANK NUMBER MUST THEN
; BE OFFSET TO THE START OF THE ROM/RAM BANKS.
; ALSO NOTE THAT THE HIGH BIT OF THE BANK NUMBER REPRESENTS "RAM" SO THIS
; BIT MUST ALSO BE SET ACCORDING TO THE UNIT BEING ADDRESSED.
;
; TO GET THE BYTE OFFSET, WE THEN RIGHT SHIFT THE LSB BY 1 TO GIVE US:
; 0OOOOOOO AND EXTRACT THE LSB TO REPRESENT THE MSB OF
; THE BYTE OFFSET.  THE LSB OF THE BYTE OFFSET IS ALWAYS 0 SINCE WE ARE
; DEALING WITH 512 BYTE BOUNDARIES.
;
MD_IOSETUP:
	LD	HL,(HSTLBALO)		; HL := LOW WORD OF LBA
	; ALIGN BITS TO EXTRACT BANK NUMBER FROM H
	SLA	L			; LEFT SHIFT ONE BIT
	RL	H			;   FULL WORD
	SLA	L			; LEFT SHIFT ONE BIT
	RL	H			;   FULL WORD
	LD	C,H			; BANK NUMBER FROM H TO C
	; GET BANK NUM TO A AND SET FLAG Z=ROM, NZ=RAM
	LD	A,(HSTDSK)		; DEVICE/UNIT TO A
	AND	$01			; ISOLATE LOW BIT, SET ZF
	LD	A,C			; BANK VALUE INTO A
	PUSH	AF			; SAVE IT FOR NOW
	; ADJUST L TO HAVE MSB OF OFFSET
	SRL	L			; ADJUST L TO BE MSB OF BYTE OFFSET
	LD	H,L			; MOVE MSB TO H WHERE IT BELONGS
	LD	L,0			;   AND ZERO L SO HL IS NOW BYTE OFFSET
	; LOAD DESTINATION AND COUNT
	LD	DE,(DIOBUF)		; DMA ADDRESS IS DESTINATION
	LD	BC,512			; ALWAYS COPY ONE SECTOR
	; FINISH UP
	POP	AF			; GET BANK AND FLAGS BACK
	JR	Z,MD_IOSETUP2		; DO ROM DRIVE, ELSE FALL THRU FOR RAM DRIVE
;
MD_IOSETUP1:	; RAM
	ADD	A,BID_RAMD0
	RET
;
MD_IOSETUP2:	; ROM
	ADD	A,BID_ROMD0
	RET
;
;
;
MD_PRT:
	PUSH	AF
	PUSH	BC
	PUSH	DE
	PUSH	HL

	CALL	NEWLINE

	LD	DE,MDSTR_PREFIX	
	CALL	WRITESTR
	
	CALL	PC_SPACE
	LD	DE,MDSTR_SRC
	CALL	WRITESTR
	LD	A,(MD_SRCBNK)
	CALL	PRTHEXBYTE
	CALL	PC_COLON
	LD	BC,(MD_SRC)
	CALL	PRTHEXWORD
	
	CALL	PC_SPACE
	LD	DE,MDSTR_DST
	CALL	WRITESTR
	LD	A,(MD_DSTBNK)
	CALL	PRTHEXBYTE
	CALL	PC_COLON
	LD	BC,(MD_DST)
	CALL	PRTHEXWORD
	
	CALL	PC_SPACE
	LD	DE,MDSTR_LEN
	CALL	WRITESTR
	LD	BC,(MD_LEN)
	CALL	PRTHEXWORD
	
	POP	HL
	POP	DE
	POP	BC
	POP	AF

	RET
;
;
;
MD_SRCBNK	.DB	0
MD_DSTBNK	.DB	0
MD_SRC		.DW	0
MD_DST		.DW	0
MD_LEN		.DW	0
;
MDSTR_PREFIX	.TEXT	"MD:$"
MDSTR_SRC	.TEXT	"SRC=$"
MDSTR_DST	.TEXT	"DEST=$"
MDSTR_LEN	.TEXT	"LEN=$"