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5-102 Maxtor Atlas 10K V
5.24 READ LONG Command (3Eh)
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 5-140 and
Table 5-141 respectively.
Table 5-140 READ LONG Command Descriptor Block-Data Format
Table 5-141 READ LONG Command Descriptor Block-Field Descriptions
Table 5-142 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 60 ECC-related bytes.
Table 5-142 READ LONG Command-Returned Data
Bit
Byte
765 4 3210
0 Operation Code (3Eh)
1 Reserved Correct RelAdr
2 - 5 Logical Block Address
6 Reserved
7 - 8 Byte Transfer Length (578)
9 Control
Field Description
Correct
When the value in this field is 1, the drive corrects the data by the ECC before transferring it to
the initiator. When the value is 0, the drive does not perform ECC correction 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 578. This value reflects the number of bytes spanned by the ECC, including the ECC it-
self, 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 + 480 ECC bits + 6 pad bits
that are not written to media but are only needed for transfer = 4496 bits or 578 bytes). Any other
value in this field results in a CHECK CONDITION status and the appropriate sense data.
Bit
Byte
76543210
0 - 511 Data (512 Bytes)
512 - 513 Logical Block Address Bits + Force Error Bit
514 - 515 EDC (8 Bits)
516 - 577 60 ECC Bits + 8 Pad Bits