man4/man4.vax/rx.4

         Copyright (c) 1983 Regents of the University of California.
 All rights reserved. The Berkeley software License Agreement
 specifies the terms and conditions for redistribution.

 @(#)rx.4 6.1 (Berkeley) 05/15/85

 RX 4 ""
C 5  NAME
rx - DEC RX02 floppy disk interface
 SYNOPSIS
 "controller fx0 at uba0 csr 0177170 vector rxintr"
 "disk rx0 at fx0 drive 0"
 "disk rx1 at fx0 drive 1"  DESCRIPTION
The
 rx device provides access to a DEC RX02 floppy disk
unit with M8256 interface module (RX211 configuration).
The RX02 uses 8-inch, single-sided, 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-to-disk 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
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, and
have the form

#include <vaxuba/rxreg.h>
ioctl(fildes, code, arg)
int *arg;


The applicable codes are:
 RXIOC_FORMAT 18
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.
 ERRORS
The following errors may be returned by the driver:
 12
[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] 12
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) ).
 FILES
/dev/rx?

/dev/rrx?[a-d]
 SEE ALSO
rxformat(8V), newfs(8), mkfs(8), tar(1), arff(8V)
 DIAGNOSTICS
 "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.
 BUGS
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.