Sony SDX-1100V manual Read Buffer 3Ch, Bit Bite Operation Code 3Ch Reserved Mode, Buffer Offset

6.Command Specification READ BUFFER

6.15.READ BUFFER 3Ch

Bit	7	6		5	4		3	2		1	0
Bite
0					Operation		Code (3Ch)
1			Reserved						Mode
2						Buffer	ID
3	(MSB)				Buffer Offset
4
5											(LSB)
6	(MSB)				Allocation Length
7
8											(LSB)
9						Control

The READ BUFFER command is used in conjunction with WRITE BUFFER as a diagnostic function for testing the data buffer and the SCSI bus integrity of the drive. A REWIND command will be sent to the drive after WRITE/READ BUFFER diagnostic testing to return to normal operation.

The READ BUFFER command is executed only when there is no tape inserted in the drive or when the tape is positioned at BOT except in Echo buffer mode. Otherwise, the drive will return a CHECK CONDITION status with a Request Sense Key of ILLEGAL REQUEST.

Note:

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

Allocation Length: The Allocation Length specifies the maximum number of bytes that the initiator has allocated for returned data. An Allocation Length of ZERO indicates that no data will be transferred. Any other value indicates the maximum number of bytes that will be transferred. The drive terminates the DATA-IN phase when Allocation Length bytes of data have been transferred or when all available data has been transferred to the initiator, whichever is less. The Allocation Length must be greater than four (except in data only mode), else the drive will return a CHECK CONDITION status with an ILLEGAL REQUEST sense key set.

Mode: The drive supports the following values within this 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.

Table 6-72: READ BUFFER Mode values

Mode	Description
0000b	Combined Header and Data
0010b	Data
0011b	Descriptor
1010b	Echo Buffer
1011b	Echo Buffer Descriptor

Combined Header and Data (0000b) - Combined Header and Data Mode-in this mode, the drive returns a four-byte header followed by the data bytes. The drive terminates the DATA-IN phase when Allocation Length bytes of header plus data have been transferred or when the header and all available data have been transferred to the initiator, whichever is less. The four-byte READ BUFFER header is followed by data bytes from the drive's data buffer.

6-70 SONY AIT-5 drive SDX-1100V series Ver.1.0