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Commodore 128 CP/M v3.0
BIOS data structure macro definitions

;       Macro Definitions for CP/M3 BIOS Data Structures.

        ; dtbl  <dph0,dph1,...>         - drive table

	; dph	translate$table,	- disk parameter header
	;	disk$parameter$block,
	;	checksum$size,			(optional)
	;	alloc$size			(optional)

	; skew	sectors,		- skew table
	;	skew$factor,
	;	first$sector$number

	; dpb	physical$sector$size,	- disk parameter block
	;	physical$sectors$per$track,
	;	number$tracks,
	;	block$size,
	;	number$dir$entries,
	;	track$offset,
	;	checksum$vec$size		(optional)


;	Drive Table.  Contains 16 one word entries.

dtbl macro ?list
    local ?n
?n  set 0
    irp ?drv,<?list>
?n  set ?n+1
	dw	?drv
    endm

    if ?n > 16
.' Too many drives.  Max 16 allowed'
	exitm
    endif

    if ?n < 16
	rept (16-?n)
	dw	0
	endm
    endif
 endm

dph macro ?trans,?dpb,?csize,?asize
    local ?csv,?alv
	dw ?trans		; translate table address
	db 0,0,0,0,0,0,0,0,0	; BDOS Scratch area
	db 0			; media flag
	dw ?dpb			; disk parameter block
    if not nul ?csize
	dw ?csv			; checksum vector
    else
	dw 0FFFEh		; checksum vector allocated by
    endif			; GENCPM
    if not nul ?asize
	dw ?alv			; allocation vector
    else
	dw 0FFFEh		; alloc vector allocated by GENCPM
    endif
	dw 0fffeh,0fffeh,0fffeh	; dirbcb, dtabcb, hash alloc'd
				; by GENCPM
	db 0			; hash bank

    if not nul ?csize
?csv	ds	?csize		; checksum vector
    endif
    if not nul ?asize
?alv	ds	?asize		; allocation vector
    endif

    endm

dpb macro ?psize,?pspt,?trks,?bls,?ndirs,?off,?ncks
    local ?spt,?bsh,?blm,?exm,?dsm,?drm,?al0,?al1,?cks,?psh,?psm
    local ?n
;; physical sector mask and physical sector shift
    ?psh	set 0
    ?n		set ?psize/128
    ?psm	set ?n-1
	rept 8
	?n	set ?n/2
 	    if ?n = 0 
	    exitm
	    endif
	?psh	set ?psh + 1
	endm
    ?spt	set ?pspt*(?psize/128)

    ?bsh	set 3
    ?n		set ?bls/1024
	rept 8
	?n	set ?n/2
	    if ?n = 0
	    exitm
	    endif
	?bsh	set ?bsh + 1
	endm
    ?blm	set ?bls/128-1
    ?size	set (?trks-?off)*?spt
    ?dsm	set ?size/(?bls/128)-1

    ?exm	set ?bls/1024
        if ?dsm > 255
	    if ?bls = 1024
.'Error, can''t have this size disk with 1k block size'
	    exitm
	    endif
	?exm	set ?exm/2
	endif
    ?exm	set ?exm-1
    ?all	set 0
    ?n		set (?ndirs*32+?bls-1)/?bls
	rept ?n
	?all	set (?all shr 1) or 8000h
	endm
    ?al0	set high ?all
    ?al1	set low ?all
    ?drm	set ?ndirs-1
    if not nul ?ncks
    	?cks	set ?ncks
    else
	?cks	set ?ndirs/4
    endif
	dw	?spt		; 128 byte records per track
	db	?bsh,?blm	; block shift and mask
	db	?exm		; extent mask
	dw	?dsm		; maximum block number
	dw	?drm		; maximum directory entry number
	db	?al0,?al1	; alloc vector for directory
	dw	?cks		; checksum size
	dw	?off		; offset for system tracks
	db	?psh,?psm	; physical sector size shift
				; and mask
    endm

;
gcd macro ?m,?n
	    ;;	greatest common divisor of m,n
		    ;;	produces value gcdn as result
		    ;;	(used in sector translate table generation)
    ?gcdm	set ?m	;;variable for m
    ?gcdn	set ?n	;;variable for n
    ?gcdr	set 0	;;variable for r
	rept 65535
	?gcdx	set ?gcdm/?gcdn
	?gcdr	set ?gcdm - ?gcdx*?gcdn
	    if ?gcdr = 0
	    exitm
	    endif
	?gcdm	set ?gcdn
	?gcdn	set ?gcdr
	endm
    endm

skew macro ?secs,?skf,?fsc
;;	generate the translate table
    ?nxtsec	set 0	;;next sector to fill
    ?nxtbas	set 0	;;moves by one on overflow
    gcd %?secs,?skf
    ;;	?gcdn = gcd(?secs,skew)
    ?neltst	set ?secs/?gcdn
    ;;	neltst is number of elements to generate
    ;;	before we overlap previous elements
    ?nelts	set ?neltst	;;counter
	rept ?secs	;;once for each sector
	db	?nxtsec+?fsc
	?nxtsec	set ?nxtsec+?skf
            if ?nxtsec >= ?secs
	    ?nxtsec	set ?nxtsec-?secs
	    endif
	?nelts	set ?nelts-1
	    if ?nelts = 0
	    ?nxtbas	set ?nxtbas+1
	    ?nxtsec	set ?nxtbas
	    ?nelts	set ?neltst
	    endif
	endm
    endm


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This page has been created by Sami Rautiainen.
Read the small print. Last updated December 03, 1998.