Specifications

ATAPI For Streaming Tape QIC-157 Rev B
70
For the MODE SENSE command, the density code field reflects the current operating density of the
Device. For some Devices, the default density code value returned in response to a MODE SENSE
command may change dynamically to match the most recently selected density. The density code
value returned in response to a MODE SENSE command shall be as described below:
1. Following a UNIT ATTENTION condition for a power on or hard reset condition, while not ready,
the Device shall report the default density.
2. Following a UNIT ATTENTION condition for a not-ready-to-ready transition, the Device shall:
a) report the default density if no attempt has been made by the Device to determine the
density.
b) report the default density if the Device cannot automatically determine the density from the
medium.
c) report the current recorded density if the Device can automatically determine the density
from the medium.
3. Following a successful read operation at or after beginning-of-medium, the Device shall report a
density code value reflecting the recorded density of the medium. For some implementations, the
Device may automatically determine this value from the medium. For Devices not capable of
automatic density determination, the default density is reported if the density code value is not
provided by the preceding MODE SELECT command.
4. Following an unsuccessful read operation or a successful write operation, while at beginning-of-
partition, the Device shall:
a) report a density code value as described for item (2) if a previous MODE SELECT
command has not established a density code for the currently loaded cartridge.
b) report a density code value as provided by the last successful MODE SELECT command
for the currently loaded cartridge.
5. Following a successful unload operation the Device shall report the most recent density code value
as determined by items (2) through (4) above.