Maxtor D740X-6L 20.0 AT Product Manual page 75

length in sectors of the defect list in the Sector Count register (1F2), and the Sector
Number register (1F3), with the Sector Count register containing the LSB of the 2-
byte value (see Table 6-3). The defect list length is a fixed value for each Maxtor
product and can be calculated as follows:
length in sectors = (((maximum number of defects) * 8 + 4) + 511)/512
At the completion of the command, the task file registers 1F2 – 1F6 will contain bytes
necessary to execute the READ DEFECT LIST command, and the host will only
need to write the extended command code (F0h) to the Command register (1F7) to
proceed with the READ DEFECT LIST command execution.
READ DEFECT LIST LENGTH Command Bytes
6 C D N G  
8 # . 7 '
4 ' ) + 5 6 ' 4
$ G H Q T G
Sector 0
Count
Sector FFh
Number
Cylinder FFh
Low
Cylinder 3Fh
High
Device/ AXh (Drive 0)
Head
BXh (Drive 1)
Command F0h
Registers 1F2h through 1F5h must contain the exact values
0 Q V G
shown. These values function as a key. The drive issues the
message ILLEGAL COMMAND if the bytes are not entered
correctly.
The READ DEFECT LIST command is an extended AT command that enables the
host to retrieve the drive's defect list. The host begins by writing to address 1F6h to
select the drive. Then the host writes to addresses 1F2h – 1F5h using values indicated
in Table 6-4. When the host subsequently writes the extended command code F0h to
address 1F7h, the drive sets BSY, retrieves the defect list, sets DRQ, and resets BSY.
The host can now read the requested number of sectors (512 bytes) of data. An
INTRQ precedes each sector. Bytes 1F2h and 1F3h contain the 2-byte number of
sectors that the host expects to read, with address 1F2h containing the LSB (see Table
6-4). The sector count (1F2h – 1F3h) may vary from product to product and if the
wrong value is supplied for a specific product, the drive responds by setting the ABRT
bit in the Error register. If the host does not know the appropriate sector count for a
specific product, it can issue the Read Defect List Length command, described in the
previous section to set up the task file for the Read Defect List command.
ATA Bus Interface and ATA Commands
& ' ( + 0 + 6 + 1 0
Defect List Subcode
Password
Password
Password
Drive Select
—
Extended Command
Code
Maxtor D740X-6L 20.0/40.0/60.0/80.0GB AT
8 # . 7 '
# H V G T
Length in Sectors
(LSB)
Length in Sectors
(MSB)
FFh
3Fh
AXh = Drive 0
BXh = Drive 1
Status Register
6-9