SCS I Description
M axtor Atlas 10K III 5-117
The READ LONG command is used in conjunction with the WR ITE LONG
command to allow the initiator to issue raw reads a nd writes of physical data blocks,
but address them a s logical blocks with a n assumed sector length of 512 bytes. These
two commands are used to verif y the c orrection capabili ty 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
Tab l e 5-147 res p e ctively.
READ LON G Com mand De s cri p t or Blo ck-Data Format
READ LONG Com mand De s cri pto r B lock-Field Desc ri p t i ons
Table 5-148 shows the format of the data that is retu rned during the R EAD LONG
Command's data-in buffer transfe r. The returned data always consists of 512 bytes of
data, followed by a two LBA bytes, two EDC bytes, and 46 ECC-related bytes.
REA D LO NG Com m and-Re t urned Data
0 Opera tion C ode (3 Eh )
1 Reserved Correct RelAdr
2 - 5 Logical Bl ock Address
6 Reserved
7 - 8 By te Transfer Lengt h (562)
9 Control
Correct
When t he value in this f ield is 1, the dri ve c orrect s the da ta b y the ECC be for e trans -
fer ring it to th e in it ia to r . W h e n the value is 0, the driv e d o e s no t p e rf or m E C C co r-
rection on the data.
NOTE: This bit, not the DCR bi t of th e Read Recovery page, governs the eff ect of
error corr ect ion f or the READ LONG command.
RelAdr Relative addres sing is not supported by the drive. This value m ust be 0.
Logical Block Ad-
dress Specifi es the l ogical sector to read.
Byte Transfer
Length
Must be 562. This value r efl ects the number of bytes spa nned by the ECC, i ncluding
the ECC i tself , rounded up to the next word ( this is easi est underst ood in bit s: 4096
data bits + 1 force error bit + 15 Logical Block Addre ss bits + 16 cross check bits
+ 2 pad bits + 360 ECC bits + 6 pad bits that ar e not written to media but are only
needed for transfer = 4496 bits or 562 bytes). Any other val ue in this field results
in a CHECK CONDITION status and the appropriate sense data.
0 - 511 Data (5 12 Bytes)
512 - 513 Logical Block Address Bits + Force Error Bit