Fujitsu M2488 Read Buffer command 3Ch, Read Buffer CDB Description, Read Buffer Field Description

TAPE UNIT SCSI COMMANDS M2488 PRODUCT GUIDE

4-3.16 READ BUFFER command 3Ch

The READ BUFFER command is used in conjunction with the WRITE BUFFER command as a diagnostic function for testing target memory and the SCSI bus integrity. Other than synchronizing any buffered write data to tape prior to performing the read buffer operation, the READ BUFFER command does not alter the tape medium of the target.

4-3.16.1 READ BUFFER CDB Description

READ BUFFER is a ten-byte command. The bytes are shown below and described in Table 4-63. Common fields are described in paragraph 4-3.1 on page 4-4.

									BITS
BYTES	7		6	5		4				3	2	1	0
0	0		0	1		1				1	1	0	0
1
			LUN						Reserved			Mode
2
									Buffer ID
3
		MSB
4
								Buffer Offset
5
														LSB
6
		MSB
7
							Allocation Length
8
														LSB
9
					Reserved							Flag		Link

Note: Changeable fields in the CDB are shaded.

Table 4-63. READ BUFFER Field Description

BYTE	BIT	VALUE	DESCRIPTION
0	0-7	3Ch	Operation code.
1	0-2		The Mode field is described in Table 4-64.
2			The Buffer ID field identifies a specific buffer within the target.
			The Buffer offset specifies the offset in the buffer for the beginning of the data
3-5			transfer. The Buffer Offset contains a multiple of the offset boundary field which
			is in the read buffer descriptor.
			The Allocation Length specifies the maximum number of bytes that are trans-
6-8			ferred during the DATA IN phase from the assigned buffer beginning at the
			buffer offset. The transfer length is the lesser of the Allocation Length or capac-
			ity of the requested buffer. The capacity of the buffer is shown in Table 4-65.

4-70 CG00000-011503 REV. A April 1997