5.23READ DEFECT DATA Command (12) (B7h)

The READ DEFECT DATA (12) command directs the drive to report defect information about the drive’s medium. Refer to the FORMAT UNIT command for information about defects. The data sent to the host in the command’s data-in buffer transfer consists of a four-byte Defect List header (Table 5-138and Table 5-139),followed by any Defect Descriptors (Table 5-136and Table 5-137).

The READ DEFECT DATA (12) Command Descriptor Block is shown in Table 5- 134; the data fields are described in Table 5-135.

Table 5-134READ DEFECT DATA (12) Command-Data Format

Bit

7

6

5

4

 

3

2

 

1

 

0

Byte

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

Operation

Code (B7h)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

Reserved

 

Plist

 

Glist

 

Defect List Format

 

 

 

 

 

 

 

 

 

 

 

 

2 - 5

 

 

 

Reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6 - 9

(MSB)

 

 

Allocation Length

 

 

 

 

 

 

 

 

 

 

 

 

(LSB)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10

 

 

 

Reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11

 

 

 

Control

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5-135READ DEFECT DATA (12) Command-Field Description

 

 

 

Field

 

Description

 

 

 

When the value is 0, the returned data does not include the Primary Defect List.

PList

When the value is 1, the returned data includes the Primary Defect List. The defects are returned

 

 

in ascending order.

 

 

 

 

When the value is 0, the returned data does not include the Grown Defect List.

 

When the value is 1, the returned data includes the Grown Defect List. The defects are returned in

GList

order of occurrence.

 

 

 

 

When both PList and GList are set to 1, the Primary Defect List and the Grown Defect List are

 

returned. The Plist is returned followed by the Glist (the lists are not merged). When both are set

 

to 0, only the Defect List Header (Table 5-138)is reported to the initiator.

Defect List

This field specifies the format in which the defect descriptors are to be returned. The supported

Format

formats are:

 

 

000b

Block Format (Table 5-136).1

 

100b

Bytes from the Index (Table 5-137). The data returned from this mode

 

 

does not include defects outside normal user space.

 

101b

Physical Sector Format (Table 5-137). Default format. The defects re-

 

 

turned from this mode do not include defects outside normal user space.

Allocation

If the number of defect

descriptors the SCSI device has assigned does not exceed the capability of

Length

the ALLOCATION LENGTH field size but contains a value that is insufficient to transfer all of

 

the defect descriptors, the defect list length shall not be adjusted to reflect the truncation and the

 

device server shall not create a CHECK CONDITION status. The initiator is responsible for

 

comparing the defect list length and the allocation length to determine that a partial list was

 

received. If the number of defect descriptors the SCSI device has assigned exceeds the capability

 

of the ALLOCATION LENGTH field size, the drive shall transfer no data and return a CHECK

 

CONDITION status and the sense key shall be set to ILLEGAL REQUEST and the additional

 

sense code set to INVALID FIELD IN CDB.

1All in-line spared blocks do not have an associated LBA, and, therefore, will not be seen in Logical Block Format.

5-100 Maxtor Atlas 10K V