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SCSI Description
Maxtor Atlas 10K III 5-117
The READ LONG command is used in conjunction with the WRITE LONG
command to allow the initiator to issue raw reads and writes of physical data blocks,
but address them as logical blocks with an assumed sector length of 512 bytes. These
two commands are used to verify the correction capability of the drive’s ECC and to
create a known kind and location to verify the drive’s recovery and bad sector
handling policies. The data format and field descriptions are shown in Table 5-146 and
Table 5-147 respectively.
READ LONG Command Descriptor Block-Data Format
READ LONG Command Descriptor Block-Field Descriptions
Table 5-148 shows the format of the data that is returned during the READ LONG
Command's data-in buffer transfer. The returned data always consists of 512 bytes of
data, followed by a two LBA bytes, two EDC bytes, and 46 ECC-related bytes.
READ LONG Command-Returned Data
0 Operation Code (3Eh)
1 Reserved Correct RelAdr
2 - 5 Logical Block Address
6 Reserved
7 - 8 Byte Transfer Length (562)
9 Control
Correct
When the value in this field is 1, the drive corrects the data by the ECC before trans-
ferring it to the initiator. When the value is 0, the drive does not perform ECC cor-
rection on the data.
NOTE: This bit, not the DCR bit of the Read Recovery page, governs the effect of
error correction for the READ LONG command.
RelAdr Relative addressing is not supported by the drive. This value must be 0.
Logical Block Ad-
dress
Specifies the logical sector to read.
Byte Transfer
Length
Must be 562. This value reflects the number of bytes spanned by the ECC, including
the ECC itself, rounded up to the next word (this is easiest understood in bits: 4096
data bits + 1 force error bit + 15 Logical Block Address bits + 16 cross check bits
+ 2 pad bits + 360 ECC bits + 6 pad bits that are not written to media but are only
needed for transfer = 4496 bits or 562 bytes). Any other value in this field results
in a CHECK CONDITION status and the appropriate sense data.
0 - 511 Data (512 Bytes)
512 - 513 Logical Block Address Bits + Force Error Bit