fdrawcmd - send raw commands to the floppy disk controller
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fdrawcmd [drive=drive] [rate=rate]
[length=length] [repeat=repeat]
[cylinder=physical-cyl] command [parameters ...] [mode]
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.
All numbers may be given in octal (0211), decimal (137), or
hexadecimal (0x89).
- drive=drive
- Selects the drive. The default is drive 0
(`/dev/fd0').
- rate=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.
- length=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.
- repeat=count
- Repeat the command count times. This only works correctly for
commands which don't do any data transfer.
- cylinder=count
- Seek to the given cylinder before executing the command
- command
- The name of the command to send. command may be a spelled out name
(like read or 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 mode
option.
- parameters
- The parameters for the command (optional, not all commands need
parameters).
- mode
- Various flags or'ed together describing the properties of the
command.
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:
http://www-techdoc.intel.com/docs/periph/fd_contr/datasheets/
Look for the chapter 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.
Commands available on all FDCs
- read drvsel cyl head sect szcod spt rw-gap szcod2
- Reads length bytes of data from the disk. 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 ^ szcod), sectors per track
(spt, this is used to switch to the second head
when the first side has been read), and size of the read-write gap.
szcod2 should be 0xff. read returns ST0
ST1 ST2 and cyl head sect szcod of the next sector to be
read; see `/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 spt to the id of the last
sector to be read (for example, if you intend to read sectors 2, 3, 4, set
spt to 4, even if the disk has more sectors), and
set the no-mt flag.
- write drvsel cyl head sect szcod spt rw-gap szcod2
- Analogous to read.
- sense drvsel
- Returns the third status byte (ST3)
- recalibrate drvsel
- Recalibrates the drive and returns ST0 ST1.
- seek drvsel cyl
- Moves the head to cyl and returns ST0 ST1.
- specify drvsel spec1 spec2
- Specify various parameters to the drive.
- format drvsel szcod sect-per-track fmt-gap fmt-fill
- Formats the cylinder. The new sectors are filled with fmt-fill. The
header information comes from the input, which is made up of cyl head
sect szcod quadruples. The szcod parameter from the command
line is used to describe the actual size of the sectors, and the
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 szcod parameter from the
command line was too small.
- readid drvsel
- reads the first sector header that comes and returns ST0 ST1 ST2
and cyl head sect szcod of the encountered header.
Commands available on 82072 and later
- dumpregs
- Prints the contents of the FDCs registers, if supported.
Commands available on 82077 and later
- version
- Echoes 0x90 if the FDC is more recent than 82072A, and 0x80 otherwise
- perpendicular rate
- Sets the perpendicular mode. Use 0 for normal, 2 for 500kb/s
perpendicular, and 3 for 1 Mb/s perpendicular.
- seek_out drvsel n
- does a relative seek of n cylinders towards cylinder 0.
- seek_in drvsel n
- does a relative seek of n cylinders away from cylinder 0.
Commands available on 82077AA and later
- lock
- Locks the FIFO configuration, so that it survives a FDC software
reset.
- unlock
- Unlock the FIFO configuration
Commands available on 82078
- partid
- echoes a byte describing the type of the FDC in the 3 high bits, and the
stepping in the three low bits.
- powerdown powerconf
- configures automatic power down of the FDC. The old configuration is
echoed
- option iso
- enables/disables ISO formats. Odd values of iso enable these
formats, whereas even values disable them. ISO formats don't have index
headers, and thus allow one to fit slightly more data on a disk.
- save
- prints out 16 internal registers of the FDC.
- restore r1 r2 r3 ... r16
- restores the 16 internal registers of the FDC.
- format_n_write 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: header1 data1 header2
data2 ... headern datan
- drivespec 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 of 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
terminator byte ends the 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.
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.
- read
- Read data from disk using DMA.
- write
- Write data to the disk.
- intr
- Wait for an interrupt.
- spin
- wait for the disk to spin up
- disk
- Aborts the operation if no disk is in the drive. This only works if you
also chose a physical cylinder to seek to.
- no-motor
- Don't switch on the drive motor while issuing the command
- no-motor-after
- Switch off the motor immediately after the command returns.
- fm
- Uses the FM version of the read,
readid, write and
format commands.
- no-mt
- Do not use MT (multitrack) mode for the read,
readid and write commands.
This is needed on certain broken FDC's which don't recognize end of
transfer when running in nodma mode. In order to
use these safely, set no-mt, and chose the id of
the last sector to be read as sect-per-track.
fdrawcmd opens the device node with the
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 floppycontrol --resetnow 0
, and try again.