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Maxtor Atlas 10K V 5-103
5.25 READ SKIP MASK Command (E8h)
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.
Table 5-143 READ SKIP MASK Command-Data Format
Table 5-144 READ SKIP MASK Command-Field Description
Bit
Byte
765 4 3210
0 Operation Code (E8h)
1 (MSB) Reserved (LSB)
2 - 5 Logical Block Address
6 Skip Mask Length
7 - 8 (MSB) Transfer Length (LSB)
9 VU Reserved
Flag Link
Field Description
Logical Block Ad-
dress
This field specifies the first logical block of the corresponding READ (10) COMMAND. This al-
lows a SEEK to begin immediately. The LBA of the following READ (10) command must be the
same as the LBA of the READ SKIP MASK command,
Skip Mask Length
This field indicated the length in bytes of the skip mask. The mask is up to 64 bytes, giving a data
address capability of 256K. 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) command. The transfer
length field must be equal to the number "1" bits in the skip mask. If a READ (10) is used with 0
as the transfer length, a transfer length of 256 data blocks is implied.