IBM Ultrium Internal Tape Drive T200, Reference Manual

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If the Buffered Mode is 0, then the drive does not report Good status on WRITE
and WRITE FILE MARKS commands until the data is written to tape. If Buffered
Mode is 1, then the drive reports Good status as soon as data has been transferred
into the drive’s data buffer. The default value is 1.
The Speed field is not used and should be set to 0.
The Block Descriptor Length is 0 if no Block Descriptor is transferred or 8 if a Block
Descriptor is transferred. The Mode parameter value is stored for each initiator.
Mode Block Descriptor
Table 33. Mode Block Descriptor
7 6 5 4 3 2 1 0
0 Density Code
1
:
3
Number of Blocks (0)
4 Reserved
5
:
7
Block Length
The Density Code field returns a code identifying the format of the tape currently
loaded in the drive. If there is no tape loaded, the code for the highest capacity
format supported by the drive is returned. See Table 75 on page 57 for details of
supported density codes.
The Number of Blocks field is 0.
The Block Length field indicates the block length to be used in subsequent READ,
WRITE, and VERIFY commands, with the Fixed bit set. (See “READ” on page 42,
“VERIFY” on page 82, and “WRITE” on page 83.) The default is 1024. The block
size may only be an even number. (For variable block transfers, which do not use
this field, both odd and even values are supported.)
Chapter 2. Command Support
29