* ipl.mac added

[avrcpm.git] / avrcpm / avr / dsk_fsys.asm

;    Filesystem functions for the Interaction with BIOS and Disks
;
;    Copyright (C) 2010 Frank Zoll
;
;    This file is part of avrcpm.
;
;    avrcpm is free software: you can redistribute it and/or modify it
;    under the terms of the GNU General Public License as published by
;    the Free Software Foundation, either version 3 of the License, or
;    (at your option) any later version.
;
;    avrcpm is distributed in the hope that it will be useful,
;    but WITHOUT ANY WARRANTY; without even the implied warranty of
;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;    GNU General Public License for more details.
;
;    You should have received a copy of the GNU General Public License
;    along with avrcpm.  If not, see <http://www.gnu.org/licenses/>.
;
;    $Id$
;

.equ DSKSEL_DEBUG = 0

; ---------------- Defines for the Filesystem Interface -------

;*****************************************************
;*        Disk-Manager constants                     *
;*****************************************************
	.equ	dskType_None		= 0
	.equ	dskType_CPM		= 1
	.equ	dskType_FAT		= 2
;	.equ	dskType_RAM		= 3

;*****************************************************
;*         CP/M to host disk constants               *
;*****************************************************
	.equ	MAXDISKS  = 8			;Max number of Disks (partitions)
	.equ    PARTENTRY_SIZE = 9		;Size of a Partitiontableentry
	.equ	blksize = 1024			;CP/M allocation size
	.equ	hostsize = 512			;host disk sector size
;	.equ	hostspt = 20			;host disk sectors/trk
	.equ	hostblk = hostsize/128		;CP/M sects/host buff
;	.equ	CPMSPT = hostblk*hostspt	;CP/M sectors/track
	.equ	CPMSPT = 26			;
	.equ	SECMSK = hostblk-1		;sector mask
	.equ	SECSHF = log2(hostblk)		;sector shift

;*****************************************************
;*        BDOS constants on entry to write           *
;*****************************************************
	.equ	WRALL = 0		;write to allocated
	.equ	WRDIR = 1		;write to directory
	.equ	WRUAL = 2		;write to unallocated
	.equ	WRTMSK= 3		;write type mask

	.equ	READ_FUNC  = 7
	.equ	WRITE_FUNC = 6
	.equ	BOOT_FUNC  = 5
	.equ	HOME_FUNC  = 4

;----------------------------------------------- Start of Data Segment

	.dseg

; The following 3 variables are copied from DRAM.
; Don't change order.

biosdrvtbl:	.byte	2	;
biosdirbuf:	.byte	2	;
biosenddat:	.byte	2	;

ndisks:		.byte	1		;Number of CP/M disks

; The following 5 variables are accessed from 8080/z80 via the
; virtual port interface. Don't change order.

biospar_base:
bcbadr:		.byte	2		;adr of BiosControlBlock
seekdsk:	.byte	1		;seek disk number
seektrk:	.byte	2		;seek track number
seeksec:	.byte	2		;seek sector number
dmaadr:		.byte	2		;last dma address

unacnt:		.byte	1		;unalloc rec cnt
unadsk:		.byte	1		;last unalloc disk
unatrk:		.byte	2		;last unalloc track
unasec:		.byte	1		;last unalloc sector

erflag:		.byte	1		;error reporting
wrtype:		.byte	1		;write operation type

hostbuf:	.byte	hostsize ;host buffer (from/to SD-card)
hostparttbl:	.byte	PARTENTRY_SIZE*MAXDISKS ;host partition table (type, start sector, sector count)
hostparttbltop:
hostdsk:	.byte	1		;host disk number
hosttype:	.byte	1		;host disk type (same entry as 1 parition entry)
hostlba:	.byte	3		;host sector number (relative to partition start)


; ------------------------------- Start of Code Segment
	.cseg

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

.if DSKSEL_DEBUG

dbg_prdrvtbl:
	push	xh
	push	xl
	push	temp3
	push	temp2
	push	temp
	printnewline
	printstring "drvtbl ("
	lds	xl,biosdrvtbl
	lds	xh,biosdrvtbl+1
	movw	temp,x
	rcall	printhexw
	printstring "): "
	ldi	temp3,16
dbg_pcpel:
	rcall	dram_readw_pp
	rcall	printhexw
	printstring " "
	dec	temp3
	brne	dbg_pcpel
	pop	temp
	pop	temp2
	pop	temp3
	pop	xl
	pop	xh
	ret
		
dbg_print_biosd:
	printnewline
	lds	temp,bcbadr
	lds	temp2,bcbadr+1
	rcall	printhexw
	printstring "  "
	lds	temp,biosdrvtbl
	lds	temp2,biosdrvtbl+1
	rcall	printhexw
	printstring "  "
	lds	temp,biosdirbuf
	lds	temp2,biosdirbuf+1
	rcall	printhexw
	printstring "  "
	lds	temp,biosenddat
	lds	temp2,biosenddat+1
	rcall	printhexw
	printstring "  "
	ret
.endif
	
; ====================================================================
; Function: Get a Pointer to a Partitiontable entry
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : [w] z			Pointer to the Partitionentry
;              [r] xl			Number of Diskentry to Read
;	       [w] _tmp0		scratch
;	       [w] _tmp1		"
; --------------------------------------------------------------------
; Description:
; ====================================================================
dsk_getpartentry:
	
	ldi	zl,PARTENTRY_SIZE
	mul	xl,zl
	ldiw	z,hostparttbl
	add	zl,_tmp0
	add	zh,_tmp1
	ret

; ====================================================================
; Function: Virtual Port Interface
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : 
; Variables  : 
;              
; --------------------------------------------------------------------
; Description:
; ====================================================================
	
dsk_param_getadr:
	ldiw	z,biospar_base
	add	zl,temp3
	adc	zh,_0
	ret

dsk_param_wr:
	rcall	dsk_param_getadr
	st	z,temp
	cpi	temp3,bcbadr+1-seektrk
	brne	dsk_param_wr1
	std	z+1,_0
dsk_param_wr1:	
	cpi	temp3,bcbadr+1-biospar_base
	breq	SetBCB
	ret

dsk_param_rd:
	cpi	temp3,seekdsk-biospar_base
	breq	dskDiskCheck
	rcall	dsk_param_getadr
	ld	temp,z
	ret

SetBCB:
	lds	xl,bcbadr
	mov	xh,temp
	ldiw	z,biosdrvtbl
	ldi	temp3,6
sbcb_l:
	rcall	dram_read_pp
	st	z+,temp
	dec	temp3
	brne	sbcb_l
	
;	rcall	dbg_print_biosd
	rcall	dsk_drvtblinit
;	rcall	dbg_prdrvtbl

	ret

; ====================================================================
; Function: Check if disk exists
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : 
; Variables  : 
;		return 0,  if selected disk not exist.
;		return !0, if disk exist
; --------------------------------------------------------------------
; Description:
; ====================================================================
dskDiskCheck:
	lds	temp,ndisks
	lds	temp2,seekdsk
.if	DSKSEL_DEBUG
	printnewline
	printstring "DiskCheck: "
	rcall	printhexw
.endif
	cpi	temp2,RAMDISKNR
	brsh	dsk_dchrd			;maybe ramdisk

; Check if selected disk # is less then # of disks.

	lds	temp,ndisks	
	tst	temp				;0 disks?
	brne	dsk_dchpart1

; No disks yet, need to init

	rcall	mgr_init_partitions		;disk chanched?
;	sbrs	temp,7	
;	 rjmp	dsk_dchpart0
	push	temp
	rcall	dsk_drvtblinit
;	rcall	dbg_prdrvtbl
	pop	temp
dsk_dchpart0:
	cbr	temp,0x80
	lds	temp2,seekdsk
	
dsk_dchpart1:
	cp	temp2,temp
	brsh	dsk_dch_err

.if	DSKSEL_DEBUG
	printnewline
	printstring "Select: "
	mov	temp,temp2
	rcall	printhex
.endif
	ldsw	x,biosdrvtbl
	lsl	temp2			;drive #
	add	xl,temp2
	adc	xh,_0
	rcall	dram_readw_pp		;get drive table entry

	or	temp,temp2		;if !0, drive is allready initialized
	brne	dsk_dchend
	lds	temp,seekdsk
	rcall	dsk_diskinit
	
dsk_dchend:
.if	DSKSEL_DEBUG
	push	temp
	ldsw	x,biosdrvtbl
	lds	temp,seekdsk
	lsl	temp			;drive #
	add	xl,temp
	adc	xh,_0
	rcall	dram_readw_pp
	printstring ", "
	rcall	printhexw
	pop	temp
.endif	

	ret

dsk_dch_err:
	ldi	temp,0			;error return
	ret	
	
;	Check RAMDISK

dsk_dchrd:
#if RAMDISKCNT
	cpi	temp,RAMDISKNR+RAMDISKCNT
	brsh	dsk_dchrd_err

	ldi	temp,0xff		;return ok
	ret
#endif
dsk_dchrd_err:
	ldi	temp,0			;error return
	ret


; ====================================================================
; Function: Return status of last disk i/o function
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : 
; Variables  : 
; --------------------------------------------------------------------
; Description:
; ====================================================================
dskErrorRet:
	lds	temp,erflag
	ret

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


	.dseg
tmpdpb:	.byte	15

	.cseg

; Test DPBs (avrcpm format)

dpblist:
;dpb243	
	.db 0x1A,0x00		;spt
	.db 0x03,0x07		;block shift, bock mask
	.db 0x00,0xF2		;extent mask, low(disk size -1), 
	.db 0x00,0x3F		;high(disk size -1), low(dir max)
	.db 0x00,0xC0		;high(dir max), alloc0
	.db 0x00,0x10		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
;dpb243	
	.db 0x1A,0x00		;spt
	.db 0x03,0x07		;block shift, bock mask
	.db 0x00,0xF2		;extent mask, low(disk size -1), 
	.db 0x00,0x3F		;high(disk size -1), low(dir max)
	.db 0x00,0xC0		;high(dir max), alloc0
	.db 0x00,0x10		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
;dpb243	
	.db 0x1A,0x00		;spt
	.db 0x03,0x07		;block shift, bock mask
	.db 0x00,0xF2		;extent mask, low(disk size -1), 
	.db 0x00,0x3F		;high(disk size -1), low(dir max)
	.db 0x00,0xC0		;high(dir max), alloc0
	.db 0x00,0x10		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
;dpb243	
	.db 0x1A,0x00		;spt
	.db 0x03,0x07		;block shift, bock mask
	.db 0x00,0xF2		;extent mask, low(disk size -1), 
	.db 0x00,0x3F		;high(disk size -1), low(dir max)
	.db 0x00,0xC0		;high(dir max), alloc0
	.db 0x00,0x10		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
;dpb243	
	.db 0x1A,0x00		;spt
	.db 0x03,0x07		;block shift, bock mask
	.db 0x00,0xF2		;extent mask, low(disk size -1), 
	.db 0x00,0x3F		;high(disk size -1), low(dir max)
	.db 0x00,0xC0		;high(dir max), alloc0
	.db 0x00,0x10		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
;dpb243	
	.db 0x1A,0x00		;spt
	.db 0x03,0x07		;block shift, bock mask
	.db 0x00,0xF2		;extent mask, low(disk size -1), 
	.db 0x00,0x3F		;high(disk size -1), low(dir max)
	.db 0x00,0xC0		;high(dir max), alloc0
	.db 0x00,0x10		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
;dpb243	
	.db 0x1A,0x00		;spt
	.db 0x03,0x07		;block shift, bock mask
	.db 0x00,0xF2		;extent mask, low(disk size -1), 
	.db 0x00,0x3F		;high(disk size -1), low(dir max)
	.db 0x00,0xC0		;high(dir max), alloc0
	.db 0x00,0x10		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
;dpb243	
	.db 0x1A,0x00		;spt
	.db 0x03,0x07		;block shift, bock mask
	.db 0x00,0xF2		;extent mask, low(disk size -1), 
	.db 0x00,0x3F		;high(disk size -1), low(dir max)
	.db 0x00,0xC0		;high(dir max), alloc0
	.db 0x00,0x10		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
#if 0
;rd1016	
	.db 0x20,0x00		;spt
	.db 0x04,0x0F		;block shift, bock mask
	.db 0x00,0xFB		;extent mask, low(disk size -1), 
	.db 0x01,0xBF		;high(disk size -1), low(dir max)
	.db 0x00,0xE0		;high(dir max), alloc0
	.db 0x00,0x30		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
;rd9192s
	.db 0x20,0x00		;spt
	.db 0x05,0x1F		;block shift, bock mask
	.db 0x01,0xFD		;extent mask, low(disk size -1), 
	.db 0x07,0xFF		;high(disk size -1), low(dir max)
	.db 0x01,0xF0		;high(dir max), alloc0
	.db 0x00,0x80		;alloc1, low(chk size)
	.db 0x00,0x02		;high(chk size), low(offset)
	.db 0x00,0x00		;high(offset), fill
#endif

; Test
cpy_dpb:
	push	zh
	push	zl
	push	yh
	push	yl
	ldiw	z,dpblist*2
	ldi	temp2,16
	mul	temp,temp2
	add	zl,_tmp0
	adc	zh,_tmp1
	ldiw	y,tmpdpb
cpydpb_l:
	lpm	temp,z+
	st	y+,temp
	cpi	yl,low(tmpdpb + 15)
	brne	cpydpb_l
	pop	yl
	pop	yh
	pop	zl
	pop	zh
	ret
	
; ====================================================================
; Function: Clear drive table
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : 
; Variables  : 
;              
; --------------------------------------------------------------------
; Description:
; ====================================================================

; For now, only  entries 1 - 7 are cleared.

dsk_drvtblinit:
	ldsw	x,biosdrvtbl
	adiw	x,2
	ldi	temp3,7
dsk_drvi_l:
	ldi	temp,0
	ldi	temp2,0
	rcall	dram_writew_pp
	dec	temp3
	brne	dsk_drvi_l
	
	lds	temp,biosenddat
	lds	temp2,biosenddat+1
	rcall	heap_init
	clr	temp
	ret

	
; ----------------------------------------------------------------------
; Init CP/M data structures 
; 	temp = drive #
;
;	return !0 if ok
;              0 on error


dsk_diskinit:
	mov	temp3,temp		;save disk #


; Test
	rcall	cpy_dpb
	
	


; get mem for DPH 
;         -----------------------------------------------------------------
; DPH:    |  XLT  |       |       |       |DIRBUF |  DPB  |  CSV  |  ALV  |
;         -----------------------------------------------------------------
;(offset)     0       2       4       6       8      10      12      14

	ldi	temp, low (16)
	ldi	temp2,high(16)
	rcall	heap_get
	brne	dsk_di_1
	rjmp	dsk_di_err		;
dsk_di_1:
	movw	x,temp
	movw	y,temp
	ldi	temp,0
	ldi	temp2,0
	rcall	dram_writew_pp		;XLT
	adiw	x,6
	lds	temp,biosdirbuf
	lds	temp2,biosdirbuf+1
	rcall	dram_writew_pp		;DIRBUF

; get mem for DPB	
;      -------------------------------------------------------------
; DPB: |  SPT  |BSH|BLM|EXM|  DSM  |  DRM  |AL0|AL1|  CKS  |  OFF  |
;      -------------------------------------------------------------
;          0                   5       7              11      13    
	
	ldi	temp, low (15)
	ldi	temp2,high(15)
	rcall	heap_get
	breq	dsk_di_err_p1
	movw	x,temp
	
	ldiw	z,tmpdpb
dsk_dicpl:
	ld	temp,z+
	rcall	dram_write_pp
	cpi	zl,low(tmpdpb + 15)
	brne	dsk_dicpl
	sbiw	x,15
	movw	temp,x
	movw	x,y
	adiw	x,10
	rcall	dram_writew_pp		;DPB
	
; get mem for dir check vector

	lds	temp,tmpdpb+11		;cks
	lds	temp2,tmpdpb+11+1
	cp	temp,_0
	cpc	temp2,_0
	breq	dsk_dicks0
	rcall	heap_get
	breq	dsk_di_err_p1
dsk_dicks0:
	rcall	dram_writew_pp		;CSV

; get mem for alloc vector

	lds	temp,tmpdpb+5		;dsm
	lds	temp2,tmpdpb+5+1
	subi	temp, low (-8)
	sbci	temp2,high(-8)
	lsr	temp2
	ror	temp
	lsr	temp2
	ror	temp
	lsr	temp2
	ror	temp			;(dsm+1+7)/8
	rcall	heap_get
	breq	dsk_di_err_p1
	rcall	dram_writew_pp		;ALV

; success, insert DPH into drvtbl

	lds	xl,biosdrvtbl
	lds	xh,biosdrvtbl+1
	lsl	temp3			;drive #
	add	xl,temp3
	adc	xh,_0
	movw	temp,y
	rcall	dram_writew_pp	
	ori	temp,0xff		;return ok
	ret

; error, free mem

dsk_di_err_p1:
	movw	temp,y
	rcall	heap_release
dsk_di_err:
	eor	temp,temp		;return 0 (+ Z-flag)
	ret
	

; ====================================================================
; Function: Does a Disk interaction
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : none
; Variables  : [r] seeksec		Sector to read
;              [r] seektrk		Track  to read
; --------------------------------------------------------------------
; Description:
; ====================================================================
dskDoIt:
.if DISK_DEBUG
	push 	temp
	sbrc	temp,READ_FUNC
	rjmp	dskdbgr
	sbrc	temp,WRITE_FUNC
	rjmp	dskdbgw
	rjmp	dskdbge

dskdbgr:
	printnewline
	printstring "Disk read:  "
	rjmp	dskdbg1
dskdbgw:
	printnewline
	printstring "Disk write: "
dskdbg1:
	lds		temp,seekdsk
	subi	temp,-('A')
	rcall	uartputc
	printstring ": track "
	lds 	temp2,seektrk+1
	lds 	temp,seektrk
	rcall 	printhexw
	printstring ", sector "
	lds 	temp,seeksec
	rcall 	printhex
	printstring ", dma-addr "
	lds 	temp2,dmaadr+1
	lds 	temp,dmaadr
	rcall 	printhexw
	pop		temp
	push	temp
	sbrs	temp,WRITE_FUNC
	rjmp	dskdbge
	printstring " wrtype "
	andi	temp,3
	rcall printhex
dskdbge:
	pop temp
.endif
	;See what has to be done.
	sbrc	temp,READ_FUNC
	rjmp	dsk_read
	sbrc	temp,WRITE_FUNC
	rjmp	dsk_write
	sbrc	temp,HOME_FUNC
	rjmp	dsk_home
	sbrc	temp,BOOT_FUNC
	rjmp	dsk_boot

	printstring "DISK I/O: Invalid Function code: "
	rcall	printhex
	rjmp	haltinv

dsk_boot:
	sts		ndisks,_0			;no active partitions
dsk_cboot:
	cbi		flags,hostact		;host buffer inactive
	sts		unacnt,_0			;clear unalloc count
	ret

dsk_home:
	sbis	flags,hostwrt		;check for pending write
	cbi		flags,hostact		;clear host active flag
	ret



; ====================================================================
; Function: Does a Disk read operation
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : in: temp			
; Variables  : [r] seekdsk		Number of Disk to Read
;			   [r] seeksec		Sector to read
;              [r] seektrk		Track  to read
; --------------------------------------------------------------------
; Description:
; ====================================================================
dsk_read:
	sts		erflag,_0
	sbi		flags,readop		; Set read operation flag

	;RAM disk?
	lds     xl,seekdsk
#if RAMDISKCNT
	cpi	xl,RAMDISKNR
	brlt	PC+2
	 rjmp	rdsk_read
#endif
	rcall 	dsk_getpartentry	; Get Paritiontableentry
	ld    	temp,z				; Get Partitiontype

; Isn't it a Disk ?
	cpi		temp,dskType_None
	brne	PC+2
	rjmp	dsk_read_err
; It must be a FAT16-Imagefile or CP/M Partition.
	sts		unacnt,_0
	sbi		flags,rsflag		;must read data
	ldi		temp,WRUAL			;write type
	sts		wrtype,temp			;treat as unalloc
	rjmp	dsk_rwoper			;to perform the read

dsk_read_err:
	ret

; ====================================================================
; Function: Does a Disk write operation
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : in: temp		Write type	
; Variables  : [r] seekdsk		Number of Disk to Read
;			   [r] seeksec		Sector to read
;              [r] seektrk		Track  to read
; --------------------------------------------------------------------
; Description:
; ====================================================================
dsk_write:
	;write the selected sector
	sts		erflag,_0
	cbi		flags,readop		; not a read operation
	;RAM disk?
	lds     xl,seekdsk
#if RAMDISKCNT
	cpi	xl,RAMDISKNR
	brlt	PC+2
	 rjmp	rdsk_write
#endif
	rcall 	dsk_getpartentry	; Get Paritiontableentry
	ld    	temp2,z				; Get Partitiontype

; Isn't it a Disk ?
	cpi	temp2,dskType_None
	brne	PC+2
	rjmp	dsk_write_err


; It must be a FAT16-Imagefile or CP/M Partition.

	cbi		flags,readop		;not a read operation

	andi	temp,WRTMSK
	sts		wrtype,temp			;save write type

	cpi		temp,WRUAL			;write unallocated?
	brne	dsk_chkuna			;check for unalloc

;	write to unallocated, set parameters
	ldi		temp,blksize/128	;next unalloc recs
	sts		unacnt,temp
	lds		temp,seekdsk		;disk to seek
	sts		unadsk,temp			;unadsk = sekdsk
	lds		temp,seektrk
	sts		unatrk,temp			;unatrk = sectrk
	lds		temp,seektrk+1
	sts		unatrk+1,temp		;unatrk = sectrk
	lds		temp,seeksec
	sts		unasec,temp			;unasec = seksec
;
dsk_chkuna:
	;check for write to unallocated sector
	lds		temp,unacnt			;any unalloc remain?
	tst		temp
	breq	dsk_alloc			;skip if not

;	more unallocated records remain
	dec		temp				;unacnt = unacnt-1
	sts		unacnt,temp
	lds		temp,seekdsk		;same disk?
	lds		temp2,unadsk
	cp		temp,temp2			;seekdsk = unadsk?
	brne	dsk_alloc			;skip if not

;	disks are the same
	lds		temp,unatrk
	lds		temp2,unatrk+1
	lds		temp3,seektrk
	lds		temp4,seektrk+1
	cp		temp,temp3			;seektrk = unatrk?
	cpc		temp2,temp4
	brne	dsk_alloc			;skip if not

;	tracks are the same
	lds		temp,seeksec		;same sector?
	lds		temp2,unasec
	cp		temp,temp2			;seeksec = unasec?
	brne	dsk_alloc			;skip if not

;	match, move to next sector for future ref
	inc		temp2				;unasec = unasec+1
	sts		unasec,temp2
	cpi		temp2,CPMSPT		;end of track? (count CP/M sectors)
	brlo	dsk_noovf			;skip if no overflow

;	overflow to next track
	sts		unasec,_0			;unasec = 0
	lds		temp,unatrk
	lds		temp2,unatrk+1
	subi	temp, low(-1)		;unatrk = unatrk+1
	sbci	temp2,high(-1)
	sts		unatrk,temp
	sts		unatrk+1,temp2
;
dsk_noovf:
	cbi		flags,rsflag		;rsflag = 0
	rjmp	dsk_rwoper			;to perform the write
;
dsk_alloc:
	;not an unallocated record, requires pre-read
	sts		unacnt,_0			;unacnt = 0
	sbi		flags,rsflag		;rsflag = 1
	rjmp	dsk_rwoper

dsk_write_err:
	ret

; ====================================================================
; Function: Does a Disk read/write operation
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : none
; Variables  : [r] seekdsk		Number of Disk to Read
;			   [r] seeksec		Sector to read
;              [r] seektrk		Track  to read
; --------------------------------------------------------------------
; Description:
; ====================================================================
dsk_rwoper:
	;enter here to perform the read/write
.if DISK_DEBUG
	printstring ", flags: "
	in		temp,flags
	rcall	printhex
.endif
	sts		erflag,_0	;no errors (yet)

	;Convert track/sector to an LBA address (in 128byte blocks)

	lds		xl,seeksec			;
	ldi		xh,0				;
	ldi		yl,0				;
	lds		temp3,seektrk		;
	lds		temp4,seektrk+1		;
	ldi		temp,CPMSPT			;
	mul		temp3,temp			;
	add		xl,r0				;
	adc		xh,r1				;
	mul		temp4,temp			;
	add		xh,r0				;yl:xh:xl := sec + trk * SectorsPerTrack
	adc		yl,r1				;

	mov		temp,xl
	andi	temp,SECMSK			;mask buffer number
	push	temp				;save for later

	;Convert from CP/M LBA blocks to host LBA blocks
	ldi		temp,SECSHF
dsk_sh1:
	lsr		yl
	ror		xh
	ror		xl
	dec		temp
	brne	dsk_sh1
					;yl:xh:xl = host block to seek
;	active host sector?
	in		_tmp0,flags			;host active flag
	sbi		flags,hostact		;always becomes 1
	sbrs	_tmp0,hostact		;was it already?
	rjmp	dsk_filhst			;fill host if not

;	host buffer active, same as seek buffer?
	lds		temp,seekdsk
	lds		temp2,hostdsk		;same disk?
	cp		temp,temp2			;seekdsk = hostdsk?
	brne	dsk_nomatch

;	same disk, same block?
	lds		temp,hostlba
	lds		temp2,hostlba+1
	lds		temp3,hostlba+2
	cp		xl,temp
	cpc		xh,temp2
	cpc		yl,temp3
	breq	dsk_match
;
dsk_nomatch:
	;proper disk, but not correct sector
	sbis	flags,hostwrt		;host written?
	rjmp	dsk_filhst
	push	xl
	push	xh
	push	yl
	rcall	dsk_writehost		;clear host buff
	pop		yl
	pop		xh
	pop		xl

dsk_filhst:
	;may have to fill the host buffer
	lds		temp,seekdsk
	sts		hostdsk,temp
	sts		hostlba,xl
	sts		hostlba+1,xh
	sts		hostlba+2,yl

	sbic	flags,rsflag		;need to read?
	rcall	dsk_readhost		;yes, if 1
	cbi		flags,hostwrt		;no pending write

dsk_match:

	;copy data to or from buffer
	ldiw	z,hostbuf
	ldi		temp,128
	pop		temp2				;get buffer number (which part of hostbuf)
	mul		temp2,temp
	add		zl,r0				;offset in hostbuf
	adc		zh,r1

.if DISK_DEBUG > 2
	push	r0
	push	r1
	printstring "; host buf adr: "
	pop		temp2
	pop		temp
	rcall 	printhexw
.endif

	lds		xl,dmaadr
	lds		xh,dmaadr+1
	ldi		temp3,128			;length of move
	sbic	flags,readop		;which way?
	rjmp	dsk_rmove			;skip if read

;	mark write operation
	sbi		flags,hostwrt		;hostwrt = 1
dsk_wmove:
	mem_read
	st		z+,temp
	adiw	xl,1
	dec		temp3
	brne 	dsk_wmove
	rjmp	dsk_rwmfin
	
dsk_rmove:
	ld		temp,z+
	mem_write
	adiw	xl,1
	dec		temp3
	brne	dsk_rmove
dsk_rwmfin:
;	data has been moved to/from host buffer
	lds		temp,wrtype			;write type
	cpi		temp,WRDIR			;to directory?
	breq	dsk_wdir
	ret							;no further processing
dsk_wdir:
;	clear host buffer for directory write
	lds		temp,erflag
	tst		temp				;errors?
	breq	dsk_wdir1
	ret							;skip if so
dsk_wdir1:
	rcall	dsk_writehost		;clear host buff
	cbi		flags,hostwrt		;buffer written
	ret

; ====================================================================
; Function: Does a Disk write operation
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : none
; Variables  : [r] seekdsk		Number of Disk to Read
;			   [r] seeksec		Sector to read
;              [r] seektrk		Track  to read
; --------------------------------------------------------------------
; Description:
; ====================================================================
dsk_writehost:
	lds    xl,hostdsk
	rcall  dsk_getpartentry
	ld     temp,z

#if FAT16_SUPPORT
; Is it a FAT16 Diskimage ?
	cpi		temp,dskType_FAT
	brne	PC+2
	rjmp	fat_writehost
#endif

; Is it a CP/M Partition ?
	cpi		temp,dskType_CPM
	brne	PC+2
	rjmp	cpm_writehost
; Disktype not supported -> Return 
	ret

; ====================================================================
; Function: Does a Disk read operation
; ====================================================================
; Parameters
; --------------------------------------------------------------------
; Registers  : none
; Variables  : [r] seekdsk		Number of Disk to Read
;			   [r] seeksec		Sector to read
;              [r] seektrk		Track  to read
; --------------------------------------------------------------------
; Description:
; ====================================================================
dsk_readhost:
	lds    xl,hostdsk
	rcall  dsk_getpartentry
	ld     temp,z

#if FAT16_SUPPORT
; Is it a FAT16 Diskimage ?
	cpi		temp,dskType_FAT
	brne	PC+2
	rjmp	fat_readhost
#endif

; Is it a CP/M Partition ?
	cpi		temp,dskType_CPM
	brne	PC+2
	rjmp	cpm_readhost
; Disktype not supported -> Return 
	ret