Read Command
August 2016 Commands 141
Read Command
The Read command transfers the next record or records from tape to the host. After
successful completion of a Read Command, the tape is positioned after the last block
read.
Notes:
• Setting of the Fixed bit is only allowed if the fixed block length is not zero. In
fixed block mode, the record size is specified by the block length. The Mode
Sense command reports the fixed block length.
TABLE 3-93 Read Command
Byte
Bit
76543210
0 Operation Code (08h)
1 Reserved SILI Fixed
2
thru
4
(MSB)
Transfer Length
(LSB)
5 Control Byte
Parameter Value
SILI:
Suppress Illegal Length Indication
0 = Check condition status is returned if the record length
does not match Transfer Length. ILI (Illegal Length Indication)
and Valid bits in sense data are set.
In variable block mode, the Information bytes are set to the
Transfer Length minus the actual record size.
In fixed block mode, Information bytes are set to the
Transfer Length minus the number of blocks transferred,
not including the incorrect length block.
1 = Return Check Condition status only when the actual
record length is larger than transfer length, and the Mode
Sense block length field in not zero.
Note – This option is not allowed if the fixed bit is 1.
Fixed Indicates the block mode for data transfer:
0 = Variable block mode. Transfer Length is the number of
bytes requested.
1 = Fixed block mode. Transfer Length is the number of blocks
requested.
Transfer Length Number of blocks or bytes requested.
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