106 Product Manual - Disc Drive SCSI-2/SCSI-3 Interface (Vol. 2; Ver. 2), Rev. E
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5.1.2.4
Read Data Buffer command (3Ch)
Table 5.1.2-3. Read Buffer
Bit
7
6
5
4
3
2
1
0
Byte(s)
0
0
0
1
1
1
1
0
0
1
Logical Unit No [1]
RSVD
Mode [2]
0
0
0
0
0
0
0
0
2
Buffer ID [5]
3
(MSB)
[6]
4
Buffer Offset
[6]
5
[6](LSB)
6
(MSB)
7
Allocation Length [2]
8
(LSB)
9
0
0
0
0
0
0
Flag [4] Link
The Read Buffer command is used in conjunction with the Write Buffer command as a diagnostic function for
testing disc drive memory and the SCSI bus integrity. This command shall not alter the medium. Command
format is shown in Table 5.1.2-3.
Notes.
[1] LUN must be zero.
[2] Read Buffer Mode Field. The interpretation of data bits 0-2 is given in the following table and in para-
graphs following the table.
DB2
DB1
DB0
0
0
0
Read combined descriptor header and data (section 5.1.2.4.1)
0
1
0
Read data (section 5.1.2.4.2)
0
1
1
Read descriptor (section 5.1.2.4.3)
5.1.2.4.1
Read Combined Descriptor Header and Data mode (000b) (see Table 5.1.2-4)
In this mode, a four byte Read Buffer header followed by the data bytes are returned to the initiator during the
Data In phase. The buffer ID and the buffer offset fields are not used by drives supported by this manual, and
must be zero.
Table 5.1.2-4. Read Buffer Header (Mode 000b)
Bit
7
6
5
4
3
2
1
0
Byte(s)
0
0
0
0
0
0
0
0
0
1
(MSB)
2
Buffer Capacity
3
(LSB)
