M2488 PRODUCT GUIDE TAPE UNIT SCSI COMMANDS
April 1997 CG00000-011503 REV. A 4-103
4-3.23 REQUEST SENSE co mmand 03h
The REQUEST SENSE command requests that the target transfer sense data to the initiator. The con-
troller is capable of supplying 44 bytes (2Ch bytes) of sense. Refer to section 8-3 on page 8-4 for a
description of the sense data received via this command.
4-3.23.1 REQUEST SENSE CDB Descripti on
REQUEST SENSE is a six-byte command as shown bel ow and described in Table 4-99. Common
fields are described in paragraph 4-3.1 on page 4-4.
4-3.23.2 REQUEST SENSE CHECK CONDITI ON Status
The sense data is valid for a CHECK CONDITION status returned on the prior command. This
sense data is preserved by the target for the initiator until retrieved by the REQUEST SENSE com-
mand or until the receipt of any other command for the same logical unit from the initiator that
issued the command resulting in the CHECK CONDITION status. Sense data is cleared upon
receipt of any subsequent command (including Request Sense) to the logical unit from the initiator
receiving the CHECK CONDITION status.
The REQUEST SENSE command returns the CHECK CONDITION status only to report fatal
errors for the REQUEST SENSE command.
BITS
BYTES 7 6 5 4 3 2 1 0
000000011
1LUN Reserved
2Reserved
3Reserved
4Allocation Length
5Reserved Flag Link
Note: Changeable fields in the CDB are shaded.
Table 4-99. REQUEST SENSE Field Description
BYTE BIT VALUE DESCRIPTION
0 0-7 03h Operation code.
4 0-7 The Allocation Length field specifies the maximum number of sense data bytes
to be returned to the initiator. An allocation length of zero indicates that no sense
data is returned and is not considered an error. The target terminates the sense
data transfer when the allocation length bytes have been transferred or when all
of the sense data have been transferred to the initiator, whichever is less.
The additional sense length in the sense data is not altered to reflect truncation
due to insufficient allocation length.