Short Form Block ID
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| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
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| 0 | BOP | EOP | LOCU (1) | BYCU (1) | Rsvd (0) | LOLU (0) | PERR | Rsvd (0) |
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| 1 |
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| Partition Number (0) |
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| 2 |
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| Reserved (0) |
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| 3 |
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| 4 | (MSB) |
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| First Block Location |
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| 7 |
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| 8 | (MSB) |
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| Last Block Location |
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| 11 |
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| (same as First Block Location) |
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| 12 |
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| Reserved (0) |
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| 13 | (MSB) |
| Number of blocks in buffer (0) |
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| 15 |
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| 16 | (MSB) |
| Number of bytes in buffer (0) |
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| 19 |
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Returned data fields:
BOP | 0 | The current logical position is not at BOM (beginning of media). |
| 1 | The current logical position is at BOM. |
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EOP | 1 | The current logical position is within the |
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LOCU | 1 | The number of blocks in the buffer is unknown. |
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BYCU | 1 | The number of bytes in the buffer is unknown. |
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LOLU | 0 | The Partition Number, First Block Location and Last Block Location fields are |
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PERR | 0 | No position error |
| 1 | There has been a position error caused by the overflow of some position field |
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| data. |
Partition Number This will always be zero.
First Block | The number of blocks and filemarks from BOM to the current position. Counting starts |
Location | at zero, so BOM is block location 0. |
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Last Block | Always set to the value of the First Block Location. |
Location |
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128 Commands