sstt -- Device Driver


The /ddeevv/rrsstt*  devices provide access to the  Archive SC-400 streaming tape
controller.   Each entry  is assigned  major device number  12, and  may be
accessed as a character-special device.

The  sstt tape  driver  handles one  0.25-inch  streaming-tape drive.   Minor
device 0  requests allocation  of a 256-kilobyte  tape cache and  should be
used unless the system has  minimal memory (e.g., less than 640 kilobytes).
Minor devices  1 through 127 request  allocation of a tape  cache of one to
127 kilobytes.   These devices normally  rewind the tape  during the close;
adding 128 to a minor-device number specifies non-rewind on close.

For an interface  to be accessible from the COHERENT  system, a device file
must be  present in  directory /ddeevv with  the appropriate type,  major, and
minor device numbers, and permissions.  The following gives an example form
of the command mmkknnoodd to creates a special file for a device:

/etc/mknod /dev/rst256 c 12 0
/etc/mknod /dev/nrst256 c 12 128

Tape-oriented commands under COHERENT (e.g., ttaarr) normally the disk devices
to store their output.  The following sample commands associate the generic
interface with the Archive streaming tape driver:

/bbiinn/llnn -ff /ddeevv/rrsstt225566  /ddeevv/rrmmtt
/bbiinn/llnn -ff /ddeevv/nnrrsstt225566 /ddeevv/nnrrmmtt

Depending on the  amount of memory available, you may  wish to restrict the
amount of memory used to buffer tape data.  This may be done by linking the
appropriate /ddeevv/rrsstt entry  to /ddeevv/rrmmtt.  For example, /ddeevv/rrsstt6644 allocates
64  kilobytes during  tape transfer  whereas  /ddeevv/rrsstt3322 allocates  only 32
kilobytes.

_H_a_r_d_w_a_r_e

The following  kernel variables define the  hardware interface to streaming
tape.

SSTTIIRRQQ     Specify the interrupt vector (default, 3).

SSTTPPOORRTT    Specify the input/output port (default, 0x200).

SSTTDDMMAA     Specify the DMA channel (default, 1).

Should these parameters conflict with other system hardware, you should use
the  command /ccoonnff/ppaattcchh  to  rebuild the  kernel  appropriately.  See  the
Lexicon article on hhss for sample commands.

_F_i_l_e_s
/ddeevv/rrsstt* -- Auto-rewind character-special file
/ddeevv/nnrrsstt* -- Non-rewinding character-special file
<ssyyss/mmttiiooccttll.hh>-- Tape iiooccttll commands

_S_e_e _A_l_s_o
ddeevviiccee ddrriivveerrss, ttaarr

_N_o_t_e_s
As delivered, the Archive tape controller uses interrupt vector 3.  If this
interrupt  is to  be  used, then  the  COHERENT kernel  must be  configured
without the second serial line driver (e.g., /ddeevv/ccoomm22*).
