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RX(4)

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NAME    [Toc]    [Back]

     rx - DEC RX02 floppy disk interface

SYNOPSIS    [Toc]    [Back]

     rx* at mscpbus? drive?

DESCRIPTION    [Toc]    [Back]

     The rx device provides access to a DEC RX02 floppy disk unit
with M8256
     interface  module  (RX211  configuration).   The  RX02  uses
8-inch, singlesided,
 soft-sectored floppy disks (with pre-formatted industry-standard
     headers) in either single or double density.

     Floppy  disks  handled  by  the RX02 contain 77 tracks, each
with 26 sectors
     (for a total of 2,002 sectors).   The  sector  size  is  128
bytes for single
     density, 256 bytes for double density.  Single density disks
are compatible
 with the RX01 floppy disk unit and with IBM 3740  Series
Diskette 1
     systems.

     In  addition  to  normal (`block' and `raw') I/O, the driver
supports formatting
 of disks for either density and the ability  to  invoke a 2 for 1
     interleaved sector mapping compatible with the DEC operating
system
     RT-11.

     The minor device number is interpreted as follows:

           Bit       Description
           0         Sector interleaving  (1 disables  interleaving)
           1         Logical sector 1 is on track 1 (0 no, 1 yes)
           2         Not used, reserved
           Other     Drive number

     The two drives in a single RX02  unit  are  treated  as  two
disks attached to
     a  single  controller.   Thus,  if there are two RX02's on a
system, the
     drives on the first RX02 are ``rx0'' and ``rx1'', while  the
drives on the
     second are ``rx2'' and ``rx3''.

     When the device is opened, the density of the disk currently
in the drive
     is automatically determined.  If there is no floppy  in  the
device, open
     will fail.

     The  interleaving  parameters  are represented in raw device
names by the
     letters `a' through `d'.  Thus, unit 0, drive 0 is called by
one of the
     following names:

           Mapping          Device name      Starting track
           interleaved      /dev/rrx0a       0
           direct           /dev/rrx0b       0
           interleaved      /dev/rrx0c       1
           direct           /dev/rrx0d       1

     The  mapping  used  on the `c' device is compatible with the
DEC operating
     system RT-11.  The `b' device accesses the  sectors  of  the
disk in strictly
  sequential  order.  The `a' device is the most efficient
for disk-todisk
 copying.  This mapping is always used by the block  device.

     I/O requests must start on a sector boundary, involve an integral number
     of complete sectors, and not go off the end of the disk.

NOTES    [Toc]    [Back]

     Even though the storage capacity on a floppy disk  is  quite
small, it is
     possible  to  make filesystems on double density disks.  For
example, the
     command

           % mkfs /dev/rx0 1001 13 1 4096 512 32 0 4

     makes a file system on the double density disk in  rx0  with
436 kbytes
     available for file storage.  Using tar(1) gives a more efficient utilization
 of the available space for file storage.  Single density diskettes
     do not provide sufficient storage capacity to hold file systems.

     A number of ioctl(2) calls apply to the rx devices:

     RXIOC_FORMAT   Format the diskette.  The density to  use  is
specified by
                    the  arg  argument, zero gives single density
while non-zero
                    gives double density.

     RXIOC_GETDENS  Return the density of the diskette  (zero  or
non-zero as
                    above).

     RXIOC_WDDMK     On  the  next  write, include a deleted data
address mark in
                    the header of the first sector.

     RXIOC_RDDMK    Return non-zero if the last sector read  contained a
                    deleted data address mark in its header, otherwise return
                    0.

FILES    [Toc]    [Back]

     /dev/rx?
     /dev/rrx?[a-d]

DIAGNOSTICS    [Toc]    [Back]

     rx%d: hard error, trk %d psec %d cs=%b, db=%b,  err=%x,  %x,
%x, %x.  An
     unrecoverable error was encountered.  The track and physical
sector numbers,
 the device registers and the extended error status are
displayed.

     rx%d:  state  %d (reset).  The driver entered a bogus state.
This should
     not happen.

ERRORS    [Toc]    [Back]

     The following errors may be returned by the driver:

     [ENODEV]  Drive not ready; usually because no disk is in the
drive or the
               drive door is open.

     [ENXIO]    Nonexistent  drive (on open); offset is too large
or not on a
               sector boundary or byte count is not a multiple of
the sector
               size  (on read or write); or bad (undefined) ioctl
code.

     [EIO]     A physical error other than ``not ready'',  probably bad media
               or unknown format.

     [EBUSY]   Drive has been opened for exclusive access.

     [EBADF]   No write access (on format), or wrong density; the
latter can
               only happen if the disk is changed without closing
the device
               (i.e., calling close(2)).

SEE ALSO    [Toc]    [Back]

      
      
     intro(4), mscpbus(4), mkfs(8), newfs(8)

HISTORY    [Toc]    [Back]

     The rx driver appeared in 4.2BSD.

BUGS    [Toc]    [Back]

     A  floppy  may not be formatted if the header info on sector
1, track 0 has
     been damaged.  Hence, it is not possible to format completely degaussed
     disks  or disks with other formats than the two known by the
hardware.

     If the drive subsystem is powered down when the  machine  is
booted, the
     controller won't interrupt.

OpenBSD      3.6                          March      27,     1991
[ Back ]
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