TITLE 'CF cold boot loader'

    ; Port Address Equates

	include config.inc
	include z180reg.inc

    ; IDE Task File Register Definitions

IDEDat	equ	IDEBASE+0	; Data Register
IDEErr	equ	IDEBASE+1	; Error Register
IDEFeat	equ	IDEBASE+1	; Feature Register
IDESCnt	equ	IDEBASE+2	; Sector Count
IDESNum	equ	IDEBASE+3	; Sector Number
IDECLo	equ	IDEBASE+4	; Cylinder Low
IDECHi	equ	IDEBASE+5	; Cylinder High
IDESDH	equ	IDEBASE+6	; Drive and Head
IDECmd	equ	IDEBASE+7	; Command / Status

    ; IDE Hard disk commands:

CmdNOP	equ	00h		; NOP Command
CmdHome	equ	10h		; Recalibrate
CmdRd	equ	20h		; Read Sector
CmdWr	equ	30h		; Write Sector
CmdId	equ	0ECh		; Read ID
CmdSF	equ	0EFh		; Set Feature

    ; Partition Table Structures

PTYPE	equ	4
PSTART	equ	8
PSIZE	equ	12

    ; Partition table id
    ; (see http://www.win.tue.nl/~aeb/partitions/partition_types-1.html)

PARTID1_FAT16	equ	00EH
PARTID2_FAT16	equ	006H
PARTID_CPM	equ	052H


DEBUG		equ	false		; not used
DO_WAIT_NBSY	equ	false
RUN_TPA		equ	false

   if RUN_TPA
base		equ	0100h
   else
base		equ	0
   endif

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

	aseg

	org	base

	jr	start

para:		equ	$
loadaddr:	dw	base+100h
sec_start:	db	0
sec_cnt:	db	7
part_id:	db	PARTID_CPM
timeout:	dw	10000
stages:		db	number_of_stages
done:		db	0
result:		db	0
ide_result:	db	0,0

o_part_id	equ	part_id - para
o_stages	equ	stages - para
o_done		equ	done    - para
o_result	equ	result  - para

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

start:
	ld	sp,stack
	pop	ix
	pop	de
loop:
	dec	(ix+o_stages)
	jp	m,stop

	pop	hl
	push	de
	push	hl
	exx
	ld	hl,(loadaddr)
	ret
continue:
	exx
	ld	(ix+o_result),a
	or	a
	jr	z,loop
stop:
	in	a,(Idecmd) 	;2
	ld	l,a     	;1
	in	a,(IdeErr) 	;2
	ld	h,a     	;1
	ld	(ide_result),hl	;3 	9
	dec	(ix+o_done)
	halt

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

chk_to:
	xor	a	;
to_l:
	dec	a
	ex	(sp),hl
	ex	(sp),hl
	jr	nz,to_l	;
	dec	hl	; 4
	ld	a,h	; 4
	or	l	; 4
	ret	nz	; 10/5
	ccf		; 3
	ret		; 9

   if base = 0
     if 044h-$ > 0
	rept	044h-$
	db	0
	endm
     endif
   endif

part_start:
;	dw	0
;	dw	0	; part_start is 4 byte long, but stack gets free
stack:
	dw	para
	dw	continue
stage_table:
   if	DO_WAIT_NBSY
	dw	s_wait_not_bsy
   endif
	dw	s_wait_rdy
	dw	s_check_io
	dw	s_set_xfermode8
	dw	s_read_parttbl
	dw	s_check_signature
	dw	s_find_partition
	dw	s_read_sectors
	dw	s_go
number_of_stages equ ($-stage_table)/2

   if	DO_WAIT_NBSY
;-------------------------------------------------------------------------------
; Wait while device is busy with time out
;     return:
;	 a = 0 if ok
;	 a = ff in timeout
;     destroys hl

s_wait_not_bsy:
	ld	hl,(timeout)
wnb_l:
	in	a,(IdeCmd)
	rla
	jr	nc,wnb_e
	call	chk_to
	jr	nc,wnb_l
wnb_e:
	sbc	a,a
	ret
   endif

;-------------------------------------------------------------------------------
; Wait for ready signal with time out
;     return:
;	 a = 0 if ok
;	 a = ff in timeout
;     destroys hl

s_wait_rdy:
wait_rdy_to:
	ld	hl,(timeout)
wrdy_l:
	in	a,(IdeCmd)
	xor	01000000b
	and	11000000b	; clears carry
	jr	z,wrdy_e
	call	chk_to
	jr	nc,wrdy_l
wrdy_e:
	sbc	a,a
	ret

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

s_check_io:
	ld	a,0E0h		; unit 0, lba mode
	out	(IdeSDH),a	;

	xor	a		; execute NOP command
	call	do_ide_cmd	; should return error
	ret	c
	xor	1
	ret	nz
	ld	a,CmdHome	; execute RECALIBRATE command
	jr	do_ide_cmd

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

s_set_xfermode8:
	ld	a,1		; Enable 8-bit data transfer.
	out	(IDEFeat),a
	ld	a,CmdSF		; Set feature command

;	fall thru
;	jr	do_ide_cmd

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

do_ide_cmd:
	out	(IdeCmd),a	;
	call	wait_rdy_to
	ret	c
	in	a,(IdeCmd)
	and	10001001b	;
	ret

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

s_check_signature:
;	ld	hl,(loadaddr)
	inc	h		; Point to last byte of MBR
	inc	h
	dec	hl
	ld	a,0aah
	cp	(hl)			; Test, if it has a valid MBR
	ret	nz
	dec	hl
	cpl				; a=055h
	sub	(hl)			;
	ret				; should be 0

;-------------------------------------------------------------------------------
; Read partition table (lbr)

s_read_parttbl:
;	ld	hl,(loadaddr)
	ld	bc,1*256 + 0	; sector 0 (lba)
	ld	e,c
	ld	d,c
	jr	read_sectors

;-------------------------------------------------------------------------------
; Find CP/M paartition
; 	Look for first CP/M partition
;	and save partition offset

s_find_partition:
;	ld	hl,(loadaddr)
	ld	de,512-2-64+PTYPE	; Point to  partition type of first first partition table entry
	add	hl,de
	ld	de,16
	ld	b,4			; Max # of partition table entries
ploop:
	ld	a,(ix+o_part_id)
	sub	(HL)			; Test for CP/M Partition
	jr	nz,pnext
	ld	bc,4
	add	hl,bc			; Point to partition start (lba)
	ld	de,part_start
	ldir
	ret				;a=0
pnext:
	add	hl,de
	djnz	ploop
	ret


;-------------------------------------------------------------------------------
; Read sec_count sectors, beginning at part_start+sec_start

s_read_sectors:
;	ld	hl,(loadaddr)
	push	hl
	ld	bc,(sec_start)		;b=sec_count, c=sec_start
	ld	e,c
	ld	d,0
	ld	hl,(part_start)		;add partition offset to sector number
	add	hl,de
	ld	a,(part_start+2)
	adc	a,d			;d=0
	ld	c,a
	ex	de,hl
	pop	hl

;	fall thru

;-------------------------------------------------------------------------------
; Read a number of sectors
;	hl:  memory address
; 	cde: sector number (24 bit)
;	b:   sector count

read_sectors:
	ld	a,e		; lba 0..7
	out	(IdeSNum),a
	ld	a,d		; lba 0..7
	out	(IdeClo),a
	ld	a,c		; lba 0..7
	out	(IdeCHi),a
	ld	a,b		; number of sectors to read
	out	(IdeSCnt),a	; set sector count

	ld	a,CmdRd
	out	(IdeCmd),a	; command: read sector data
	ld	d,b
	ld	bc,IdeDat	; I/O address
wdrq:
	in	a,(IdeCmd)	; wait for DRQ to become active
	bit	3,a
	jr	z,wdrq
	inir			; read 512 data bytes (2 x 256)
	inir
wnb:				; wait while busy
	in	a,(IdeCmd)	;
	rlca
	jr	c,wnb
	rrca			; restore status
	bit	0,a
	jr	nz,err_out
	dec	d
	jr	nz,wdrq
err_out:
	and	10001001b	; Busy, DRQ, or Error?
	ret			; return 0, if everything is ok

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

s_go:
;	ld	hl,(loadaddr)
	dec	(ix+o_done)
	jp	(hl)


;-------------------------------------------------------------------------------
   if base = 0
     if $ > 100h
	.printx Error: Program to large to fit in page 0!
	db "Stop
     endif
   endif

	end