Sony SDX-800V/R manual Write Buffer 3Bh, Write Buffer Mode Field Description

6.Command Specification WRITE BUFFER

6.31.WRITE BUFFER 3Bh

Bit	7	6	5	4		3	2		1	0
Byte
0				Operation	Code (3Bh)
1		Obsolete		Reserved				Mode
2				Buffer ID
3	(MSB)			Buffer Offset
5										(LSB)
6	(MSB)			Parameter List Length
8										(LSB)
9				Control

WRITE BUFFER is used in conjunction with the READ BUFFER command as a diagnostic function.

WRITE BUFFER command is valid only when there is no tape inserted in the drive, or when the tape is positioned at BOT. An attempt to issue the Write Buffer command when the tape is not at BOT will result in a CHECK CONDITION status with a Request Sense Key of ILLEGAL REQUEST.

Note: The drive will write any buffered data to tape prior to executing this command. Any data that is then transferred by the WRITE BUFFER is not written to tape.

Mode: The drive supports the following values within the Mode field. If any other value is set, the drive will terminate the command with a CHECK CONDITION status and an ILLEGAL REQUEST sense key set.

Any Write Data, file-marks or set-marks in buffer will be transfer to tape before this command is executed.

Table 6-103: WRITE BUFFER Mode Field

Mode	Description
0000b	Write combined header and data
0010b	Write data
1010b	Echo Buffer

Combined Header and Data Mode - in this mode, the test data to be transferred must be preceded by a four-byte header. The four-byte header consists of all reserved bytes. The Parameters List Length specifies the maximum number of bytes that will be transferred during the DATA OUT phase. This number includes four bytes of header, so the data length to be stored in the buffer is transfer length minus four. The initiator should ensure that the transfer length is not greater than four plus the available length that is returned in the header of the READ BUFFER command.

Data Mode - in this mode, the DATA OUT phase contains only buffer test data.

Table 6-104: WRITE BUFFER Mode Field

Buffer ID: The supported values are:

Buffer ID	Description		Offset
0	Write Group Buffer	0	- 0x01000000
80	Write Group Buffer	0	- 0x01000000
81	Write Group Buffer	0x01000000 - 0x02000000
82	Write Group Buffer	0x02000000 - 0x03000000
83	Write Group Buffer	0x03000000 - 0x04000000

If an unsupported Buffer ID code is requested, the drive returns a CHECK CONDITION status with an ILLEGAL REQUEST sense key.

Buffer Offset: The buffer offset field contains the byte offset within the specified buffer from which data shall be transferred to. The initiator should conform to the offset boundary requirements returned in the WRITE BUFFER descriptor. If the target is unable to accept the specified buffer offset, it shall return CHECK CONDITION status, shall set the Sense Key to ILLEGAL REQUEST, and set the Additional Sense Code to ILLEGAL FIELD IN CDB.

6-108 SONY AIT-3Ex drive SDX-800V series Ver.1.1