Block Descriptor - Seagate Viper 200 Scsi Interface Manual

Page 68

Block Descriptor

Field Descriptions
Field Bytes Bits
Speed 3 0-3
Block 6-7
Descriptor
Length
Reserved
When Buffered Mode is 1, a Write command is terminated when the data is
transferred to the internal buffer of the drive. When Buffered Mode is 0 a Write
command is not terminated until all data has been transferred to tape.
Bits
Byte 7 6
0
1
2
3
4
5
6
7
Field Bytes Bits
Density 0
Code
Block 5-7
Length
Reserved
Description
This field indicates the tape speed.
0 = Default
3 = 2.077 m/sec (meter/second)
4 = 2.576 m/sec
5 = 3.097 m/sec
6 = 3.643 m/sec
7 = 4.153 m/sec
0 = No Block Descriptor follows.
8 = 8-byte Block Descriptor follows.
All reserved bits must be 0.
5 4 3
Density Code
Reserved
Reserved
Reserved
Reserved (0)
Block Length, MSB
Block Length
Block Length, LSB
Description
Identifies the format of the tape currently in the drive.
Mode Select: 00h = Default of Ultrium 1
40h = Ultrium 1
7Fh = No-op
Mode Sense: 00h = Default of Ultrium 1
0 = Variable length block mode. The Fixed bit in Read and Write
commands must be 0.
1 to FFFFFFh = The length of the fixed-length block to be read or
written when the Fixed bit is set in a Read or Write command.
All reserved bits must be 0.
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