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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
The READ DEFECT DATA (12) Command Descriptor Block is shown in Table 5- 134; the data fields are described in Table
Table
Bit | 7 | 6 | 5 | 4 |
| 3 | 2 |
| 1 |
| 0 |
Byte |
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0 |
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| Operation | Code (B7h) |
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1 |
| Reserved |
| Plist |
| Glist |
| Defect List Format |
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2 - 5 |
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6 - 9 | (MSB) |
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| Allocation Length |
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10 |
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11 |
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| Control |
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Table | ||
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Field |
| Description |
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| 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 | |
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| in ascending order. |
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| 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. |
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| 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 | |
Defect List | This field specifies the format in which the defect descriptors are to be returned. The supported | |
Format | formats are: |
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| 000b | |
| 100b | Bytes from the Index (Table |
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| does not include defects outside normal user space. |
| 101b | Physical Sector Format (Table |
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| 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. |
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