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SCSI Interface Product Manual, Rev. B
8.58
WRITE BUFFER command (3Bh)
The WRITE BUFFER command may be used in conjunction with the READ BUFFER command as a diagnos-
tic function for testing the drive's data buffer memory and the SCSI bus integrity. When used in a diagnostic
mode, the medium shall not be accessed during the execution of this command. Additional modes are provided
for downloading and saving executable microcode.
The function of this command and the meaning of the fields within the Command Descriptor Block depend on
the mode field (Byte 1, data bits 0, 1, 2). See note [2] of Table 246.
Table 246:
WRITE BUFFER command (3Bh)
Bit
7
Byte
0
0
1
Reserved [1]
2
BUFFER ID [5]
3
(MSB)
4
5
6
(MSB)
7
8
9
CONTROL [4]
[1]
Formerly, the LOGICAL UNIT NUMBER. Must be zero.
[2]
The MODE field is defined in the following table and in the referenced sections.
Check with individual drive's Product Manual, Volume 1, to see which modes are supported by the drive in
question.
DB3
DB2
DB1
0
0
0
0
0
0
0
0
1
0
1
0
0
1
0
0
1
1
0
1
1
1
0
1
1
0
0
1
0
0
1
0
1
:
:
:
1
1
1
[3]
Use a READ DATA BUFFER command with mode bits set to 0011b to get the drive buffer capacity to use
with the WRITE BUFFER command.
[4]
See Table 61, "CONTROL field," in Section 7.2.1. All bits are zero for all modes.
[5]
These bytes used only for modes 0110b and 0111b. See sections 8.58.6 and 8.58.7 for descriptions of
their usage in these modes.
6
5
0
1
Reserved
BUFFER OFFSET [5]
BYTE TRANSFER LENGTH [3]
DB0
Mode definition
0
Write combined header and data (Section 8.58.1)
1
vendor-specific (Section 8.58.2)
0
Write data (Section 8.58.3)
0
Download microcode (Section 8.58.4)
1
Download microcode and save (Section 8.58.5)
0
Download microcode with offsets (Section 8.58.6)
1
Download microcode with offsets and save (Section 8.58.7)
0
Write data to echo buffer (Section 8.58.8)
0
Reserved
1
Reserved
1
Reserved
:
Reserved
1
Reserved
4
3
1
1
2
1
0
1
MODE [2]
(LSB)
(LSB)
317
0
1
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