READ BUFFER
7. ATAPI Packet Command Specification
SONY AIT-1 Turbo drive SDX-470V series Ver.1.0
7-53
Data Mode
– in this mode, the DATA TRANSFER contains buffer data only.
Descriptor Mode
– in this mode a maximum of four bytes of READ BUFFER descriptor information are returned.
The drive returns the descriptor information for the buffer specified by the Buffer ID. In this mode, the drive does
not reject the valid Buffer Ids with a CHECK CONDITION status but returns 3F 68 00h when Buffer ID is set to 0,
80 00 00h when Buffer ID is set to 1 in the READ BUFFER descriptor.
Table 7-49: Read Buffer Descriptor
Bit
Byte
7 6 5 4 3 2 1 0
0
Reserved
1
(MSB)
2
3
Buffer Capacity
(LSB)
Buffer ID:
The supported values are:
Buffer ID
Description
0 Read
Interface
Buffer
1
Read Group Buffer
Buffer Offset:
The Buffer Offset field contains the byte offset within the specified buffer from which data shall be
transferred. The host should conform to the offset boundary requirements returned in the READ 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.
Allocation Length:
The Allocation Length specifies the maximum number of bytes that the host 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 TRANSFER when
Allocation Length bytes of data have been transferred or when all available data has been transferred to the host,
whichever is less. The Allocation Length must be greater thatn four (except in data only mode), else the drive will
return a CHECK CONDITION status with an ILLEGAL REQUEST sense key set.
