CP/M/CPM_CDROM.iso/simtel/sigm/vols000/vol073/dd6.doc

Text File | 1984-04-29 | 13KB | 274 lines

                       --- DISK DUMP ---

                       -- Version 2.15 --

                                        By Bill Bolton
                                        Software Tools,
                                        P.O. Box 80,
                                        Newport Beach,
                                        NSW, 2106,
                                        AUSTRALIA

Introduction
------------

    This program is an improved disk dump utility for CP/M.  Any
CP/M  file may be dumped to the console.  In addition any sector
or  group  of  sectors may be dumped in  the  same  format.  The
utility  can  be  made to handle any CP/M  2.X  disk  system  as
outlined later.

     The  program  is referred to as DD6 when  refering  to  the
latest    implementation   or   DDX   when   refering   to   all
implementations including the latest one.

                        --- OPERATION ---

    The program may be run either by typing DD6, or DD6 followed
by  the  file  name or track and sector.  If DD6  is  typed  the
program responds with a heading, followed by a '*' and waits for
more  user  input.  Operation in this mode is similar  to  other
utilities such as PIP or DDT.

     The operation desired may then be typed in as follows:

          DD6 file.nam
          DD6 A:file.nam
          DD6 C:file.nam

     or may be typed separately as:

          DD6

          *file.nam      (the * is the program prompt)
          *B:file.nam

    The  file  is  dumped by examining its  directory  entry  to
obtain   block  allocation,   number  of  records   and   extent
information.  The file is then dumped on a block by block basis,
this allows display of the track and sector numbers as a file is
dumped.  The  last block of a file is only dumped up to the last
sector actually used by the file.

    All   sector dumps display hex addresses in the range 00  to
7F  as a 2 digit hex number,   except in the case of a COM  file
dump.  When  a  COM file is being dumped,   the first sector  is
assumed  to  start  at 0100H and all  subsequent  addresses  are
incremented  from this base address and displayed as a  4  digit
hex number.

    A sector dump heading is displayed at the top of each sector
dumped   and  indicates  the drive selected,   whether  1  or  2
sided,  its  physical  sector size,  the track  number,  logical
sector number and a dump count:

 Drive A: 1S/2D/1024 - Track 2  Logical Sector 14  Dump Count 1

    The  dump count displays the running total of sectors dumped
from  a  single  command line.  This is useful  for  locating  a
particular sector of a file or block.  A modified version of the
CP/M  User's Group binary COMPARE utility,  which indicates file
differences   with  decimal  sector numbers that   are  directly
equivalent    to DDX Dump Count numbers,   is   available   from
Software Tools.

    The  program may also be used to dump disk sectors  directly
and  dump  any  CP/M  sector  block  (or  group)  - block   size
information  is  obtained from the CP/M 2.X DPB (Disk  Parameter
Block)  of  the  drive concerned.  The  sectors  containing  the
directory  may dumped with a simple single command and a map  of
the block allocations may be likewise displayed.

          DD6 TRACK 3 SECTOR 7
          DD6 TRACK 5   SECTOR 3 - 9
          DD6 TRACK 6  (dumps all sectors on the track)
          DD6 GROUP 19
          DD6 DIR
          DD6 MAP

     The  words  TRACK,  SECTOR and GROUP may be abbreviated  as
 follows:

          DD6 T 7 S 3-4
          DD6 G 4
          *TRACK 5 S 6
          *SECTOR 2-9 T 14
          DD6 B:    TRACK 3
          DD6 A: T 9    S 4-6
          DD6 B:   G    5
          DD6 B:MAP

    Note  that  the format is quite  free.  Spaces  are  usually
ignored.  They  are only required after the words TRACK,  SECTOR
and GROUP or T, S and G and after the word DD6.

     In  previous  versions  of DDX the  block  or  cluster  was
refered  to as a "group" as this term is still used as a command
to  maintain  compatibility  with  previous  versions.   Digital
Research  now  use the term "block" instead of "group" and  this
file   and most of the comments in the source file use the  term
"block".

                         -- EDITING ---

    A limited editing feature is included in the dump utility to
allow changing of data on disk.  The edit works as follows - any
single  logical sector of any drive may be edited by  requesting
display of the sector followed by the word EDIT.

          DD6 D:TRACK 4 SECTOR 2  EDIT

    The   requested   sector will be displayed  followed  by  an
edit prompt:

     EDIT -

    Enter  the  address of the first byte  to  be  changed.  The
program  will respond by typing back the address entered and the
present contents of that address.  To change the contents, enter
the  new byte followed by a carriage return.  The  program  will
display the next address and its contents. To stop entering data
type  a period,  the sector will then be redisplayed showing the
changes.  The  edit  feature works almost exactly like  the  'S'
command in DDT, typing only a carriage return omits entry.

    The  change is not made permanent until it is  written  back
onto the disk, you exit the edit mode by typing;

        WRITE  (write the changed sector back onto disk)
        STOP   (stop the edit without writing to disk)

    All  edit  entries  must be made in hex.  Entering  non  hex
characters results in an error message.  The permissable address
range is from 00 to 7F,  larger addresses give an error message.
When entering a block of bytes the addresses are computed modulo
128, the next address after 7F is 00.

    The  edit  feature  should be used with  caution  as  it  is
possible to edit CP/M to "death" by changing a single byte.  One
occasionally  valuable  use is to restore files which have  been
accidentally erased.  Erasing a file using the ERA command  does
not erase the data from the disk, but only writes an E5 into the
first byte of its directory entry.  To restore the file, display
the  directory  using  the  DD6 DIR  command.  Find  the  sector
containing  the entry in question and display it using the  EDIT
feature.  Change the byte preceeding the file name from E5 to 00
and  write the sector back on disk.  This will restore the  file
provided that you have not used any programs which write data to
disk since erasing the file. *** BE WARNED *** If you have run a
program that writes data to disk since erasing the file you  may
find  that the erased file's allocated blocks have been used for
another  file  and the integrity of the  erased  file  therefore
destroyed.

                        --- CP/M 2.X ---

     This latest version of DDX benefits from running under CP/M
2.X.  As the DPB location is now accessable via BIOS calls it is
possible to extract nearly all the  information needed to  allow
dynamic  determination  of a drives characteristics.

     There  are only two hardware dependent subroutines,  one is
optional  and simply sets up the sector display header  to  suit
your requirements. As it is not possible to determine the actual
density  or  number  of sides directly from  the  DPB,  as  CP/M
doesn't care about that information,   you must write the  code.
The 1791  controller chip has this available as  status  inform
ation  and  most other controller chips seem to  have  something
similar.

     The  other hardware dependent routine concerns the handling
of  Track  0.  In all IBM compatible formats Track 0  is  always
single  density  3740 format.  You must be able to  overide  all
dynamically    set  parameters  of  DD6  and  force  your   disk
controller  to  read Track 0 as single density,  26 x  128  byte
sectors.  The  Morrow Disk Jockey 2D and Godbout Disk 1 do  this
automatically  so it was simply a matter of feeding the  correct
sector  numbers to the controller.  Fortunately Track 0  is  not
involved  in file or block dumps  so  it is easy to treat it  as
an exception and  only  one subroutine needs to be altered.

    SECTOR  NUMBERING   - Single density CP/M maintains  a  skew
factor  of  6 on 8" IBM 3741 compatible disks (i.e the  standard
implementation).  This means that logical sector 1 on a track is
physical sector 1 while logical sector 2 is physical sector 7 on
that  track  etc.  This  is done to  provide  greatest  internal
efficency of operation for CP/M in accessing disks.

    CP/M  sees each 128 byte sector on a single density disk  as
one  logical  record so there is a direct  relationship  between
sector  size  and  data block size.  With  double  density  disk
recording  systems there are several possible sizes for sectors.
The IBM 2D standard allows for sector sizes of 256,  512 or 1024
bytes.  Double  density and Hard disk implementations which  use
physical  sectors sizes that are multiples of 128 bytes have  to
DEBLOCK the physical sector into  128 byte logical sectors.

     The BIOS handles all blocking and deblocking, so that legal
sector  numbers  for BIOS set sector calls are 1 to the  maximum
number  of 128 byte sectors for the track size,  the  BIOS  then
does  the deblocking and translation to physical sectors on  the
disk.  The  BIOS accesses all data bytes of a physical sector by
reading  them  into a buffer in memory and then  accessing   the
required 128 byte section of the buffer to give 128 byte logical
sectors.

    BLOCK  SIZE  - Standard CP/M 1.4 is set up to recognise  243
blocks per disk.  The block is the smallest amount of disk space
which  can  be allocated and disk space is allows  allocated  in
blocks.  In  a  standard  single  density  system  on  IBM  3741
compatible  8" disk the block size is 1K bytes or 8  sectors  of
128 bytes each.

     Block sizes for double density and hard disks vary but  are
always  a  multiple of 1K bytes.  The actual size is  determined
form the DPB.

    When  using  the DD6 GROUP N command a  calculation  of  the
sector  numbers  covered by any particular block is made  and  a
look  up  of the XLT (sector translation tables) in the BIOS  is
used to take into account the skew factor in use on the specific
CP/M implementation.

    The   current  source listing is for a Godbout "Disk 1" based
CP/M 2.X system and a 24 x 80 video display.  If you have a 16  x
64  video  display  you will need to remove some  of  the  spaces
inserted in the dump display by the PRTSEC routine.


     DD6 should be readily adaptable to other CP/M 2.X  systems,
including hard disk systems. As far as possible all values which
might  reasonably  be expected to exceed 256 in  any  realisable
disk  system  are manipulated as 16 bit  values.  Therefore  the
large  sectors  sizes,   sector numbers and track numbers likely
to  be found  on  a hard disks should present no  problem.   The
program  does  make  a few assumptions  about the way  CP/M  2.X
handles  the disk parameter block allocation,   it assumes  that
it  is all done dynamically  in the BIOS.   As all the  multiple
density  CP/M  2.X systems   that  I have come across manage  to
do  this (some  more elegently than others !) I think that it is
a safe assumption.

                     --- OTHER DETAILS ---

    As with other CP/M utilities a ^S 'freezes' the display  and
^C returns to CP/M.  Hitting the 'space bar' will abort the dump
currently  in  progress  and either exit or  return  to  command
level,  depending  on  how you entered the utility.  Dump  cont
ains   many  error  and  consistancy  checks.    The   resulting
messages  are generally self explanatory.

    DD6  was assembled using the CP/M MAC assembler and  uses  a
large  library  of macros called MACRO3.LIB which  is  available
from  Software  Tools.   (N.B.   MACRO3.LIB  is an  revision  of
MACRO.LIB, as used by Sam Singer's single density version,  with
extensions  to  the CALLBIOS  and DISKIO macros to  handle  CP/M
2.2,  and several new macros added).

    This disk dumper is in a continuing state of development and
refinement.  There  is now a version for the Morrow Designs Hard
Disk  controller  with a DJ2D or a Godbout  Disk  1  controller,
called DDH.   Many new features are planned and will be added in
the towards the end of 1981.