Figure 3.36 Read Buffer Command: Buffer Data (Mode = 0000, 0001) - Fujitsu MAX3073NC - SCSI,80, Dell DC961,Hard Drive Scsi Logical Interface Specifications

Command Specifications
The "Transfer byte count" field in the CDB specifies the total number of bytes of the header and buffer
data which can be received by the INIT. The IDD reads the data from the data buffer from the top
(Address X '000000'), then adds the 4-byte header to it and transfers it to the INIT. Data transfer is
completed at the point when the number of bytes of the header and data from the IDD's data buffer,
specified in the "Transfer byte length" field, has been transferred, or at the point when transfer of the
header and all the data in the IDD's data buffer, to the final byte position, has been completed. When
zero is specified in the "Transfer byte length" field, this command is terminated without executing a data
transfer.
The format of the data transferred to the INIT when this mode is specified is shown in Figure 3.36.
Byte
0
1
Header
2
3
4
5
Data
~
~
n

Figure 3.36 READ BUFFER command: buffer data (Mode = 0000, 0001)

The "Effective buffer data length" field in the header indicates the size of the data buffer (byte length).
This value indicates the size of the IDD's data buffer that can be used by the WRITE BUFFER and
READ BUFFER commands without relation to the length specified in the "Transfer byte length" field in
the CDB or the length of the data actually stored in the data buffer by the WRITE BUFFER command.
When this mode is specified, the "Effective buffer data length" shows the size (cache segment volume)
of the IDD's entire data buffer area. Also, the length of the buffer data transferred to the INIT by this
command is the value for the number of bytes in the ["Transfer byte length" field in the CDB – 4 bytes]
or the value indicated in the "Effective buffer data length" field in the header, whichever is smaller.
(2) Mode = 0, 0, 0, 1: Header + data, with address specification
The format of the data transferred to the INIT when this mode is specified is the same as the format of
the data in the case of Mode = 0, 0, 0, 0, with the data stored in the IDD's data buffer transferred to the
INIT following the 4-byte header. In this mode, the address in the data buffer can be specified in the
"Buffer offset" field in the CDB.
3-116
Bit
7 6
0 0
Effective Buffer Data Length (MSB)
Effective Buffer Data Length
Effective Buffer Data Length (LSB)
Buffer Data (Byte 0)
Buffer Data (Byte 1)
~
~
Buffer Data (Byte n–4)
5 4 3 2
0 0 0 0
1 0
0 0
~
~
C141-C010