NOTE
This file is intended to be included with your CBIOS to provide disk definitions. A version of the file without the HTML codes is available here.
; CP/M 2.0 disk re-definition library
;
; Copyright (c) 1979
; Digital Research
; Box 579
; Pacific Grove, CA
; 93950
;
; CP/M logical disk drives are defined using the
; macros given below, where the sequence of calls
; is:
;
; disks n
; diskdef parameter-list-0
; diskdef parameter-list-1
; ...
; diskdef parameter-list-n
; endef
;
; where n is the number of logical disk drives attached
; to the CP/M system, and parameter-list-i defines the
; characteristics of the ith drive (i=0,1,...,n-1)
;
; each parameter-list-i takes the form
; dn,fsc,lsc,[skf],bls,dks,dir,cks,ofs,[0]
; where
; dn is the disk number 0,1,...,n-1
; fsc is the first sector number (usually 0 or 1)
; lsc is the last sector number on a track
; skf is optional "skew factor" for sector translate
; bls is the data block size (1024,2048,...,16384)
; dks is the disk size in bls increments (word)
; dir is the number of directory elements (word)
; cks is the number of dir elements to checksum
; ofs is the number of tracks to skip (word)
; [0] is an optional 0 which forces 16K/directory entry
;
; for convenience, the form
; dn,dm
; defines disk dn as having the same characteristics as
; a previously defined disk dm.
;
; a standard four drive CP/M system is defined by
; disks 4
; diskdef 0,1,26,6,1024,243,64,64,2
; dsk set 0
; rept 3
; dsk set dsk+1
; diskdef %dsk,0
; endm
; endef
;
; the value of "begdat" at the end of assembly defines the
; beginning of the uninitialize ram area above the bios,
; while the value of "enddat" defines the next location
; following the end of the data area. the size of this
; area is given by the value of "datsiz" at the end of the
; assembly. note that the allocation vector will be quite
; large if a large disk size is defined with a small block
; size.
;
dskhdr macro dn
;; define a single disk header list
dpe&dn: dw xlt&dn,0000h ;translate table
dw 0000h,0000h ;scratch area
dw dirbuf,dpb&dn ;dir buff,parm block
dw csv&dn,alv&dn ;check, alloc vectors
endm
;
disks macro nd
;; define nd disks
ndisks set nd ;;for later reference
dpbase equ $ ;base of disk parameter blocks
;; generate the nd elements
dsknxt set 0
rept nd
dskhdr %dsknxt
dsknxt set dsknxt+1
endm
endm
;
dpbhdr macro dn
dpb&dn equ $ ;disk parm block
endm
;
ddb macro data,comment
;; define a db statement
db data comment
endm
;
ddw macro data,comment
;; define a dw statement
dw data comment
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
;
diskdef macro dn,fsc,lsc,skf,bls,dks,dir,cks,ofs,k16
;; generate the set statements for later tables
if nul lsc
;; current disk dn same as previous fsc
dpb&dn equ dpb&fsc ;equivalent parameters
als&dn equ als&fsc ;same allocation vector size
css&dn equ css&fsc ;same checksum vector size
xlt&dn equ xlt&fsc ;same translate table
else
secmax set lsc-(fsc) ;;sectors 0...secmax
sectors set secmax+1 ;;number of sectors
als&dn set (dks)/8 ;;size of allocation vector
if ((dks) mod 8) ne 0
als&dn set als&dn+1
endif
css&dn set (cks)/4 ;;number of checksum elements
;; generate the block shift value
blkval set bls/128 ;;number of sectors/block
blkshf set 0 ;;counts right 0's in blkval
blkmsk set 0 ;;fills with 1's from right
rept 16 ;;once for each bit position
if blkval=1
exitm
endif
;; otherwise, high order 1 not found yet
blkshf set blkshf+1
blkmsk set (blkmsk shl 1) or 1
blkval set blkval/2
endm
;; generate the extent mask byte
blkval set bls/1024 ;;number of kilobytes/block
extmsk set 0 ;;fill from right with 1's
rept 16
if blkval=1
exitm
endif
;; otherwise more to shift
extmsk set (extmsk shl 1) or 1
blkval set blkval/2
endm
;; may be double byte allocation
if (dks) > 256
extmsk set (extmsk shr 1)
endif
;; may be optional [0] in last position
if not nul k16
extmsk set k16
endif
;; now generate directory reservation bit vector
dirrem set dir ;;# remaining to process
dirbks set bls/32 ;;number of entries per block
dirblk set 0 ;;fill with 1's on each loop
rept 16
if dirrem=0
exitm
endif
;; not complete, iterate once again
;; shift right and add 1 high order bit
dirblk set (dirblk shr 1) or 8000h
if dirrem > dirbks
dirrem set dirrem-dirbks
else
dirrem set 0
endif
endm
dpbhdr dn ;;generate equ $
ddw %sectors,<;sec per track>
ddb %blkshf,<;block shift>
ddb %blkmsk,<;block mask>
ddb %extmsk,<;extnt mask>
ddw %(dks)-1,<;disk size-1>
ddw %(dir)-1,<;directory max>
ddb %dirblk shr 8,<;alloc0>
ddb %dirblk and 0ffh,<;alloc1>
ddw %(cks)/4,<;check size>
ddw %ofs,<;offset>
;; generate the translate table, if requested
if nul skf
xlt&dn equ 0 ;no xlate table
else
if skf = 0
xlt&dn equ 0 ;no xlate table
else
;; generate the translate table
nxtsec set 0 ;;next sector to fill
nxtbas set 0 ;;moves by one on overflow
gcd %sectors,skf
;; gcdn = gcd(sectors,skew)
neltst set sectors/gcdn
;; neltst is number of elements to generate
;; before we overlap previous elements
nelts set neltst ;;counter
xlt&dn equ $ ;translate table
rept sectors ;;once for each sector
if sectors < 256
ddb %nxtsec+(fsc)
else
ddw %nxtsec+(fsc)
endif
nxtsec set nxtsec+(skf)
if nxtsec >= sectors
nxtsec set nxtsec-sectors
endif
nelts set nelts-1
if nelts = 0
nxtbas set nxtbas+1
nxtsec set nxtbas
nelts set neltst
endif
endm
endif ;;end of nul fac test
endif ;;end of nul bls test
endm
;
defds macro lab,space
lab: ds space
endm
;
lds macro lb,dn,val
defds lb&dn,%val&dn
endm
;
endef macro
;; generate the necessary ram data areas
begdat equ $
dirbuf: ds 128 ;directory access buffer
dsknxt set 0
rept ndisks ;;once for each disk
lds alv,%dsknxt,als
lds csv,%dsknxt,css
dsknxt set dsknxt+1
endm
enddat equ $
datsiz equ $-begdat
;; db 0 at this point forces hex record
endm
;