READ
Table 48. READ Command
| 7 | 6 | 5 | 4 |
| 3 |
| 2 | 1 | 0 |
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0 |
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| Operation Code (08h) |
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1 | Logical Unit Number (0) |
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| Reserved |
| SILI | Fixed | |||
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2 |
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: |
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| Transfer Length |
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4 |
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5 |
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| Control |
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The READ command causes data to be transferred from the tape medium to the initiator.
If the Fixed flag is clear and Transfer Length is not 0, then a single block of the length in Transfer Length is to be transferred. If the next block on tape is of this length or shorter, then it is transferred to the initiator. If the next block is longer than this length, then only the length requested is returned and the logical position is set to after the record. If the length of the block was the same as the Transfer Length field, then Good status is returned. For additional details about Suppress Illegal
Length Indicator (SILI) management, see
If the Fixed flag is set, the Transfer Length field is not 0, and the Suppress Illegal Length Indicator (SILI) flag is clear, then a sequence of blocks of the currently configured block length is to be returned, the number of blocks being indicated in the Transfer Length field. If there is a sequence of blocks of this length on the tape, they are returned to the initiator with Good status. If a block that is longer than the configured length is encountered before the sequence is complete, the blocks up to that block are returned, followed by the configured length from the record that was too long and Check Condition status. If a block that is shorter than the configured length is encountered before the sequence is complete, the blocks up to that block are returned, followed by all of that block and Check Condition status. The current position is set after the last block that was returned or partially returned.
If the Transfer Length field is 0, and if the Suppress Illegal Length Indicator and the Fixed bit are not both set, then no action is taken.
If Suppress Illegal Length Indicator (SILI) flag is set and the Fixed bit is set, then Check Condition status is returned. The Sense Key is set to Illegal Request and the ASC/ASCQ is set to Invalid Field in CDB (2400).
42Ultrium Internal Tape Drive and 3580 Ultrium Tape Drive: SCSI Reference
