Read Long Command (3Eh) - Seagate SCSI Interface Product Manual

SCSI Interface Product Manual, Rev. J
5.26

Read Long command (3Eh)

The Read Long command (Table 132) requests that the target transfers data to the initiator. The data passed
during the Read Long command shall include the data bytes, followed by the ECC bytes of the single logical
block addressed by the command.
Table 132: Read Long command (3Eh)
Bit 7
Byte
0 0
1 0
Logical Unit Number [1]
2 Logical Block Address (MSB) [4]
3 Logical Block Address [4]
4 Logical Block Address [4]
5 Logical Block Address (LSB) [4]
6 0
7 Byte Transfer Length (MSB) [5]
8 Byte Transfer Length (LSB) [5]
9 0
Notes.
[1] The Logical Unit Number must be zero.
[2] A Corrected (Correct) bit of zero requests that a logical block be read without any ECC correction made by
the target. A Correct bit of one requests that the data be corrected by ECC, if necessary.
Other error recovery procedures separate from ECC are applied in accordance with the parameter set-
tings given in the mode sense Error Recovery page (01h). See individual drive's Product Manual, Volume
1, for a detailed discussion of the drive error recovery procedures.
If the DCR bit of the Read-Write Error Recovery page is equal to one and the Correct bit equals one, the
Read Long command shall be terminated with Check Condition status and the sense key shall be set to
Illegal Request with an additional sense code of Invalid Field in CDB.
[3] A Relative Address (RelAdr) bit of one indicates that the logical block address field is a two's complement
displacement. This negative or positive displacement is to be added to the logical block address last
accessed on the logical unit to form the logical block address for this command. This feature is only avail-
able when linking commands. The feature requires that a previous command in the linked group have
accessed a block of data on the logical unit.
A RelAdr bit of zero indicates that the logical block address field specifies the first RelAdr logical block of
the range of logical blocks to be operated on by this command.
[4] The Logical Block Address specifies the logical block at which the read operation shall occur. The most
recent data written in the addressed logical block shall be returned.
[5] The Byte Transfer Length specifies the number of bytes of data that shall be transferred. A transfer length
of zero indicates that no bytes shall be transferred. This condition shall not be considered as an error. The
byte transfer length requested must be equal to the current block size plus all ECC bytes for a data trans-
fer to occur. If an incorrect number of bytes is stated in the command block, this command terminates with
a Check Condition status. The correct number of bytes can be determined from the information returned
in the extended sense data bytes after issuing the Request Sense command. The Request Sense com-
mand shall result in the Illegal Field In CDB condition with the Illegal Request Sense Key. The extended
sense ILI bit shall be set. The extended sense information bytes contain the difference (residue) of the
requested length minus the actual length in bytes. (Negative values are indicated by two's complement
notation.)
[6] See "Control byte," paragraph 4.2.6.
6 5
0 1
0 0
0 0
0 0
4 3
1 1
0 0
0 0
0 0
2 1
1 1
0
Correct [2] RelAdr [3]
0 0
0 Flag [6] Link [6]
175
0
0
0