1.6 Transport layerC141-C009 1-61If necessary, fill bytes are placed after the INFORMATION UNIT field so thatthe CRC field is aligned on a four-byte boundary. The number of the fill bytes isspecified by the NUMBER OF FILL BYTES field. If the transferred bytes in thelast DATA frame are not aligned on a four byte boundary, this field is set to thenumber of the extra bytes (4 - the remainder of (the number of transferredbytes/4) bytes).The CRC field contains a CRC value that is computed over the entire SSP frameprior to the CRC field including the fill bytes (i.e., all data dwords between theSOF and EOF).Drives ignore the Reserved fields.1.6.2 Information units1.6.2.1 COMMAND information unitTable 1.34 defines the command IU. The COMMAND frame is sent by an SSPINIT port to request that a command be processed by the device server in alogical unit.Table 1.34 COMMAND information unitBitByte 7 6 5 4 3 2 1 00 (MSB)7 LOGICAL UNIT NUMBER (LSB)8 Reserved9ENABLEFIRSTBURSTReserved TASK ATTRIBUTE10 Resered11 ADDITIONAL CDB LENGTH(n dwords) Reserved12 (MSB)27 CDB (LSB)2827+ n x 4 ADDITIONAL CDB BYTESThe LOGICAL UNIT NUMBER field contains the address of the logical unit.An ENABLE FIRST BURST bit set to "1" specifies that the first burst data itemis transferred as defined by the FIRST BURST SIZE field in the Disconnect-Reconnect mode page. However, drives do not support this bit. Therefore, adrive ignores the FIRST BURST SIZE field of the Disconnect-Reconnect modepage.Table 1.35 contains the definitions of the TASK ATTRIBUTE field. However,drives do not support ACA in Table 1.35. Moreover, when a reserved TASK
