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 length + 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

MODE SENSE: The tape is write-enabled

 

1

MODE 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.

1The 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.

2The 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

Only the values 0 and 8 are valid. Any value other than 0 or 8, CHECK CONDITION status is

Length

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.

 

 

 

Commands

MODE SELECT 15h/55h 75