Pioneer SCSI-2 - Manual (Page 166)

Write Buffer
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2.44 Write Buffer (3Bh)
Operation Code is (3Bh).
Mode specifies meaning of the Buffer Offset field.
Buffer ID is not supported. This byte must be 00h.
Buffer Offset is the byte offset in the buffer where the data shall be stored. This must be 0
through 15.
Transfer Length is the number of bytes to be transferred in the DATA OUT phase. This must
be the data length to be sent plus 4 bytes (header size).
This command is to be used with the READ BUFFER command to test the reliability of the
command buffer memory in the drive, and of the SCSI bus. The drive does not access any discs.
Mode Definition
00b Header, data, and buffer offset are 0s.
01b Buffer offset indicates the offset of the buffer at which data are to be stored.
10b Reserved
11b Reserved
The transfer length must include the 4-byte header, therefore, the actual data length to be stored
is the transfer length minus 4 bytes. As the buffer length of the drive is 16 bytes, the maximum
number of bytes that can be specified for Buffer Offset is 15, and the maximum for Transfer
Length is 20.
If Transfer length is larger than 20, a Check Condition is returned with the sense key "ILLEGAL
REQUEST." Check Condition will also be returned if the Buffer Offset + Transfer Length is
larger than 20.
If Buffer Offset is not 0 when Mode is 00h, Check Condition is returned.
Refer to Table 2-38A on the opposite page for the 4-byte header of 00h's must be sent preceding
the test data.