scsi interface specification - Plasmon

DRIVE COMMAND SETMODE SENSE (1AH)Allocation LengthThe Allocation Length specifies the maximum number of bytes that the Initiator has allocated for returnedMODE SENSE data. The LaserDrive terminates the DATA IN phase when Allocation Length bytes havebeen transferred or when all available MODE SENSE data has been transferred to the Initiator, whicheveris less. An Allocation Length of zero indicates that no MODE SENSE data is transferred. The LaserDriveMode Sense Allocation Length must be 36 bytes or greater to return all supported pages (3FH option).MODE SENSE DATAThe Mode Sense data returned by the LaserDrive consists of a 4-byte header, followed by an 8-byte blockdescriptor, followed by one or more pages.The Sense Data Length specifies the length in bytes of the following MODE SENSE data that is availableto be transferred during the DATA IN phase. The Sense Data Length count does not include this byte.The contents of the Media Type field is two. This indicates the WORM media type.MODE SENSE DataBITBYTE7 6 5 4 3 2 1 000 Sense Data Length01 Media Type (02H)02 WP Reserved EBC03 Block Descriptor Length (0 or 8)Write Protect (WP)A Write Protect (WP) bit of zero indicates that the LaserDrive or media is write enabled. A WP bit of oneindicates that the LaserDrive or media is write protected or that an RTPM condition is present.Enable Blank Check (EBC)An Enable Blank Check (EBC) of one indicates that blank checking during write operations is enabled.Block Descriptor LengthBLOCK DESCRIPTOR00 Reserved01 Number of Blocks (00H) (MSB)02 Number of Blocks (00H)03 Number of Blocks (00H) (LSB)04 Reserved05 Block Length (MSB) (00H)06 Block Length (04H)07 Block Length (LSB) (00H)PAGE(S)The Block Descriptor Length specifies the length in bytes of the block descriptor. The LaserDrive supportsone block descriptor; thus the value in this field is either a zero or eight.The LaserDrive will return a block descriptor in a MODE SENSE command only when the media is readyand available for access. If not ready, the Block Descriptor Length will be zero and the block descriptorfields will be omitted.97653978 HPage 77