Fujitsu M2488, Руководство по эксплуатации продукта

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TAPE UNIT SCSI COMMANDS M2488 PRODUCT GUIDE
4-64 CG00000-011503 REV. A April 1997
4-3.14.2 READ CHECK CONDITION Status
The following table describes how a CHECK CONDITION occurs.
FIXED
BIT
SILI
BIT
BLOCK
MODE *
DESCRIPTION
1 1 Causes CHECK CONDITION status with the sense key being ILLEGAL REQUEST.
0 1 variable No CHECK CONDITION is set due to an actual block length being different than the
length specified in the Transfer Length field, except for the following condition.
The target still reports CHECK CONDITION status for an incorrect length condi-
tion if the overlength condition exists and the block length field in the mode param-
eter block descriptor is non-zero (a non-zero value in this field in the Mode Select
data implies fixed mode). The overlength condition exits after executing a Read
command when the length of the actual block read exceeds the requested transfer
length in the CDB.
0 0 variable With Fixed bit = 0, the transfer will take place in variable block mode independent of
the value in the mode parameters block descriptor. In variable block mode, a single
block is transferred with the bytes transferred being the lesser of the actual block
length or the requested Transfer Length.
A successful READ command with the fixed bit of zero, transfers the requested trans-
fer length in bytes to the initiator.
If the actual block length is different from the specified transfer length, CHECK
CONDITION status is returned to the initiator. The incorrect length indicator (ILI)
bit and valid bit in the sense data are set to one, and the sense key is set to NO
SENSE. The information bytes contained in the sense data are set to the difference
(residue) of the requested transfer length minus the actual block length, and this value
will be negative (two’s compliment) when the actual block length exceeds the
requested block length. Upon termination, the logical position is located after the
incorrect length block (EOM side).
1 fixed The transfer length specifies the number of blocks to be transferred to the initiator.
This form of the READ command is valid only if the logical unit is currently operat-
ing in fixed block mode. A logical unit is in fixed block mode if it has been instructed
by the MODE SELECT command to use fixed-length blocks. In this case, the current
block length is the block length defined in the MODE SELECT command.
A successful READ command with the fixed bit of one, transfers the requested trans-
fer length times the current block length in bytes to the initiator.
If the actual block length read is different from the current transfer length, as speci-
fied in the mode parameters block descriptor, CHECK CONDITION status is gener-
ated. The ILI bit and valid bit are both set to one, and the sense key is set to NO
SENSE. The information bytes in the sense data are set to the difference of the
requested transfer length minus the actual number of blocks read (not including the
incorrect length block). Upon termination, the logical position is located after the
incorrect length block (EOM side).
1 variable The target rejects the command by returning CHECK CONDITION status and by set-
ting the sense key to ILLEGAL REQUEST.