HP Q153090901, Technical Reference Manual

Page: 75 / 196

MODE SELECT 15h/55h
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Header fields
Mode Data Length
MODE SELECT:
Mode Data Length field must be zero.
MODE SENSE: Mode Data Length field is set to the number of bytes of data available to
return excluding itself (in other words, the number of actual bytes available is
mode data 1 for 6-byte MODE SENSE or +2 for 10-byte MODE
SENSE ).
NOTE:
The actual amount returned may be truncated to the allocation length
for the command.
Medium Type 00h The usual medium type when the drive is in normal tape drive mode.
01h WORM media is loaded
80h The tape drive is in CD-ROM emulation mode for OBDR.
WP Write Protect. Ignored for MODE SELECT .
0 M ODE SENSE : The tape is write-enabled
1 M ODE SENSE : The tape is write-protected
Buffered Mode 0 The drive will not report GOOD status on Write and Write Filemarks commands until all
data (blocks and filemarks) has been successfully written to tape.
1 The drive will report GOOD status for Write and Write Filemarks commands as soon as
all the data or marks specified in the command have been transferred to the data
buffer. Data for multiple commands from different initiators may be buffered. This is the
default value.
NOTE: It is strongly recommended that this field is set to 1, otherwise there will be
significant performance penalties. A method of flushing the buffer to tape without
changing logical position is available with the Write Filemarks command.
2 The drive will report GOOD status for Write and Write Filemarks commands as soon as
all the data or marks specified in the command have been transferred to the data
buffer and all buffered data from different initiators has been successfully written to the
tape.
Speed 0 The Speed field is not used and should be zero.
Block Descriptor
Length
Only the values 0 and 8 are valid. Any value other than 0 or 8, CHECK CONDITION status is
reported. See the Parameter List check for details of the sense data generated.
0 No block descriptor is being transferred.
8 The Mode Parameter header must be followed by the 8-byte block descriptor
described in the next section.