@node fdrawcmd, floppycontrol, fdmount, Commands
@section fdrawcmd
@pindex fdrawcmd
@cindex raw command
@cindex low level interaction with floppy driver
@cindex direct interaction with floppy driver

@example
@code{fdrawcmd} [@code{drive=}@var{drive}] [@code{rate=}@var{rate}]
[@code{length=}@var{length}] [@code{repeat=}@var{repeat}]
[@code{cylinder=}@var{physical-cyl}] @var{command} [@var{paramters} @dots{}] [@var{mode}]
@end example

@code{fdrawcmd}
is used to send raw commands to the floppy disk controller, after
having selected a given drive. You must have write permission to the
selected drive.

When writing to a disk, data is read from stdin; when reading, data
is printed to stdout.  Diagnostic messages, return values from the
controller, and the value of the disk change line after the command are
printed to stderr.

@subsection Options

All numbers may be given in octal (0211), decimal (137), or hexadecimal
(0x89).

@table @code

@item drive=@var{drive}
Selects the drive.  The default is drive 0 (@file{/dev/fd0}).

@item rate=@var{rate}
Selects the data transfer rate. Use 0 for high density disks, 1 for
double density 5 1/4 disks (or 2 Mbps tapes, if the appropriate rate
table is selected), and 2 for double density 3 1/2 disks.

@item length=@var{length}
Describes the length of the transferred data for commands reading from
and writing to the disk.  The default is to continue until end of file.

@item repeat=@var{count}
Repeat the command @var{count} times.  This only works correctly for
commands which don't do any data transfer.

@item cylinder=@var{count}
Seek to the given cylinder before executing the command

@item @var{command}
The name of the command to send.  @var{command} may be a spelled out
name (like @code{read} or @code{write}), or a number representing the
commands floppy disk controller opcode.  A named command has already a
mode associated with it, whereas for a number the mode parameter should
be described using the @code{mode} option.


@item @var{parameters}
The parameters for the command (optional, not all commands need
parameters).

@item @var{mode}
Various flags or'ed together describing the properties of the command.

@end table


@subsection Commands

The description of the various floppy commands given in this manpage is
very sketchy. For more details get the 82078 spec sheet which can be
found at:
@example
http://www-techdoc.intel.com/docs/periph/fd_contr/datasheets/
@end example

Look for the chapter @code{COMMAND SET/DESCRIPTIONS}.  Older FDCs only
support a subset of the commands described therein, but the syntax for
the commands that do exist is the same.

@subsubsection Commands available on all FDCs

@table @code

@item read @var{drvsel cyl head sect szcod spt rw-gap szcod2}
Reads @var{length} bytes of data from the disk.  @var{drvsel} is the
drive selector. Bit 0 and 1 describe the drive, and bit 2 describes the
head.  The remaining parameters give the cylinder, head (yes, again),
sector, size of the sector (128 * 2 ^ @var{szcod}), sectors per track
(@code{spt}, this is used to switch to the second head when the first
side has been read), and size of the read-write gap. @var{szcod2} should
be 0xff.  @code{read} returns @var{ST0 ST1 ST2} and @var{cyl head sect
szcod} of the next sector to be read; see
@file{/usr/include/linux/fdreg.h} .

N.B. Certain newer floppy disk controllers are buggy, and do not
correctly recognize the end of transfer when operating in virtual DMA
mode.  For these, you need to set @code{spt} to the id of the last
sector to be read (for example, if you intend to read sectors 2, 3, 4,
set @code{spt} to 4, even if the disk has more sectors), and set the
@code{no-mt} flag.

@item write @var{drvsel cyl head sect szcod spt rw-gap szcod2}
Analogous to
@code{read}.

@item sense @var{drvsel}
Returns the third status byte (@var{ST3})

@item recalibrate @var{drvsel}
Recalibrates the drive and returns @var{ST0 ST1}.

@item seek @var{drvsel cyl}
Moves the head to @var{cyl} and returns @var{ST0 ST1}.

@item specify @var{drvsel spec1 spec2}
Specify various parameters to the drive.

@item format @var{drvsel szcod sect-per-track fmt-gap fmt-fill}
Formats the cylinder. The new sectors are filled with @var{fmt-fill}.
The header information comes from the input, which is made up of
@var{cyl head sect szcod} quadruples. The @var{szcod} parameter
from the command line is used to describe the actual size of the
sectors, and the @var{szcod} from the input is used to write into the
header. However, the first write to these sectors will use the header
information, and might overwrite the following sectors if the
@var{szcod} parameter from the command line was too small.

@item readid @var{drvsel}
reads the first sector header that comes and returns 
@var{ST0 ST1 ST2 }
and 
@var{cyl head sect szcod }
of the encountered header.
@end table

@subsubsection Commands available on 82072 and later

@table @code
@item dumpregs
Prints the contents of the FDCs registers, if supported.
@end table

@subsubsection Commands available on 82072A and later

@table @code
@item configure @var{conf1 conf2 conf3}
Configures FIFO operation.
@end table

@subsubsection Commands available on 82077 and later

@table @code
@item version
Echoes 0x90 if the FDC is more recent than 82072A, and 0x80 otherwise

@item perpendicular @var{rate}
Sets the perpendicular mode.  Use 0 for normal, 2 for 500kb/s
perpendicular, and 3 for 1 Mb/s perpendicular.

@item seek-out @var{drvsel n}
does a relative seek of
@var{n}
cylinders towards cylinder 0.

@item seek-in  @var{drvsel n}
does a relative seek of @var{n} cylinders away from cylinder 0.
@end table


@subsubsection Commands available on 82077AA and later

@table @code
@item lock
Locks the FIFO configuration, so that it survives a FDC software reset.
@item unlock
Unlock the FIFO configuration
@end table

@subsubsection Commands available on 82078

@table @code
@item partid
echoes a byte describing the type of the FDC in the 3 high bits, and
the stepping in the three low bits.

@item powerdown @var{powerconf}
configures automatic power down of the FDC. The old configuration is echoed

@item option @var{iso}
enables/disables ISO formats. Odd values of
@var{iso}
enable these formats, whereas even values disable them. ISO formats
don't have index headers, and thus allow to fit slightly more data on
a disk.

@item save
prints out 16 internal registers of the FDC.

@item restore @var{r1 r2 r3 ... r16}
restores the 16 internal registers of the FDC.

@item format_n_write @var{drvsel szcod sect-per-track fmt-gap fmt-fill}
formats the cylinder and writes initial data to it. The input data is
made up of a sequence of headers (4 bytes) and data:
@var{header1 data1 header2 data2 ... headern datan}

@item drivespec @var{dspec1 dspec2 ... specn terminator}
chooses rate tables for various drives. Each dspec byte describes one
drive. Bits 0 and 1 say which drive is described. Bits 2 and 3 describe
the rate table. Only tables 0 and 2 are interesting. Both tables only
differ in the meaning og rate 1. For table 0 (the default) rate 0 is 300
kb/s (used for 5 1/4 DD disks), whereas for table 1 it is 2 Mbps (used
for fast floppy tape drives). Bit 4 is the precompensation table select
bit. It should be set to 0. Bit 5-7 should be zero as well. The
@var{terminator} byte ends the @code{drivespec} command. It is either
0xc0 or 0x80. If it is 0xc0, no result phase follows; if it is 0x80, the
current data rate table configuration for the four drives is echoed.
@end table

@subsection Modes
The mode option is only needed when you describe the command as a
numerical value. Some mode names are also valid command names. They
are considered as command name if the command name has not yet been
given, and as mode name otherwise.

 If you give a command name followed by explicit modes, both the
implicit flags of the command name, and the explicit modes are or'ed
together.

 If on the other hand you give a command name preceded by explicit
modes, only the explicit modes are or'ed together.

@table @code
@item read
Read data from disk using DMA.

@item write
Write data to the disk.

@item intr
Wait for an interrupt.

@item spin
wait for the disk to spin up

@item disk
Aborts the operation if no disk is in the drive. This only works if you
also chose a physical cylinder to seek to.

@item no-motor
Don't switch on the drive motor while issuing the command

@item no-motor-after
Switch off the motor immediately after the command returns.

@item fm
Uses the FM version of the @code{read}, @code{readid}, @code{write} and
@code{format} commands.

@item no-mt
Do not use MT (multitrack) mode for the @code{read}, @code{readid} and
@code{write} commands. This is needed on certain broken FDC's which
don't recognize end of transfer when running in @code{nodma} mode. In
order to use these safely, set @code{no-mt}, and chose the id of the
last sector to be read as @code{sect-per-track}.

@end table

@code{fdrawcmd} opens the device node with the @code{NDELAY} flag. This
means that the driver should not try to autodetect the disk type (it
might not be formatted), and that it should not reset the FDC. If a
reset was needed, the command simply fails. If that happens, execute
@code{floppycontrol --resetnow 0} , and try again.