System information

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
;
diskdefmacro 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&dnequ css&fsc ;same checksum vector size
xlt&dn equ xlt&fsc ;same translate table
else
secmaxset 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&dnset (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
Appendix F : CP/M Disk Definition Library CP/M Operating System Manual
F-3