Fujitsu MBC2036RC, MBC2073RC, MBA3300RC, MBA3147RC Read Buffer command buffer data mode = 0000, Lsb

4.4 Maintenance, Diagnostic Commands

(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)

Header

Data

	Bit	7	6	5		4	3	2	1	0
Byte
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.

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