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SCSI Description
Maxtor Atlas 10K III 5-119
The READ SKIP MASK command allows the initiator to condition the function of
the READ commands to allow only selected data to be transferred over the SCSI
interface. A READ SKIP MASK command precedes a READ (10) command; the
READ (10) command must be linked to the READ SKIP MASK command or the
skip mask is lost and a CHECK CONDITION status is returned. The data format and
field descriptions are shown in Table 5-149 and Table 5-150 respectively.
READ SKIP MASK Command-Data Format
READ SKIP MASK Command-Field Descriptions
0 Operation Code (E8h)
1 Reserved
2 - 5
(MSB)
Logical Block Address
(LSB)
6 Skip Mask Length
7 - 8
(MSB)
Transfer Length
(LSB)
9 VU Reserved Flag Link
Logical Block Address
This field specifies the first logical block of the corresponding READ (10)
COMMAND. This allows a SEEK to begin immediately. The LBA of the fol-
lowing READ (10) command must the same as the LBA of the READ SKIP
MASK command.
Skip Mask Length
This field indicates the length in bytes of the skip mask. The mask is up to
2048 bits, giving a data address capability of 1 MB in 512-byte block
length. The mask consists of a sequence of bits where a “1” bit is for the
blocks of data to be transferred, and a “0” for the blocks of data that are to
be skipped. The first “1” bit of the mask corresponds to the first LBA to be
transferred. Any unused bits at the end of the last byte in the mask must
be set to 0. The mask is transferred in the data-out buffer transfer of the
skip mask command.
Transfer Length
This field must be equal to the transfer length in the linked READ (10) com-
mand. The transfer length field must be equal to the number of “1” bits in
the skip mask. If a READ (10) is used with 0 as the transfer length, a trans-
fer length of 256 data blocks is implied.