Filter
Top Products
4.4 Maintenance, Diagnostic Commands
C141-C013 271
(1) Mode = 0, 0, 0, 0: Header + data, without address specification
When this mode is specified, the data stored in the HDD's data buffer are
transferred to the INIT after the 4-byte header. Zero must be specified in the
"Buffer offset" field in the CDB.
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 HDD 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 HDD'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 HDD'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 Table 4.63.
Table 4.63 READ BUFFER command: buffer data (mode = 0000, 0001)
Bit
Byte
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0 0
1 Effective Buffer Data Length (MSB)
2 Effective Buffer Data Length
3 Effective Buffer Data Length (LSB)
4 Buffer Data (Byte 0)
5 Buffer Data (Byte 1)
n Buffer Data (Byte n–4)
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 HDD'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 HDD'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.
~
~
~
~
~
~
Header
Data