5.25READ 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 5-143READ SKIP MASK Command-Data Format

 

Bit

 

7

6

5

4

 

3

 

2

1

0

 

Byte

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5-144READ SKIP MASK Command-Field Description

 

 

 

 

 

 

 

 

 

 

 

 

Field

 

 

 

 

 

 

Description

 

 

 

 

 

 

 

 

Logical Block Ad-

 

 

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

dress

 

 

 

 

same as the LBA of the READ SKIP MASK command,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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

Skip Mask Length

 

 

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.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This field must be equal to the transfer length in the linked READ (10) command. The transfer

Transfer Length

 

 

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.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maxtor Atlas 10K V

5-103

Page 161
Image 161
Maxtor 10K V manual Read Skip Mask Command E8h, 143READ Skip Mask Command-Data Format