6.Command Specification | READ POSITION |
BPU: A Block Position Unknown (BPU) bit of one indicates that the First and Last Block Locations are not known or cannot be obtained. A BPU bit of ZERO indicates that the First contains valid position information.
Partition Number: This field reports the current partition number for the current logical position. This drive does not support multi partition.
First block location: This field indicates the Block Address associated with the current logical position. The value will indicate the Block Address of the next data block to be transferred between the initiator and the target if a READ or WRITE command is issued. See BT field for description of Logical Block Address. Note that the Logical Block Address at BOT/P is 0.
Last block location: This field indicates the Block Address associated with the next block to be transferred from the buffer to the medium. The value will indicate the Block Address of the next data block to be transferred between the buffer and the medium. If the buffer does not contain a whole block of data or is empty, the value reported for the last block location will be equal to the value reported for the first block location.
Number of Blocks in Buffer: This field indicates the number of data blocks in the buffer of the logical unit that have not been written to the medium.
Number of Bytes in Buffer: This field is not supported and is always set to ZERO.
Table 6-78: READ POSITION Data Format, long form
Bit | 7 | 6 | 5 |
| 4 |
| 3 | 2 | 1 |
| 0 |
Byte |
|
|
|
|
|
|
|
|
|
|
|
0 | BOP | EOP | Reserved |
|
| MPU | BPU |
| Reserved | ||
1 |
|
|
|
|
| Reserved |
|
|
|
| |
2 |
|
|
|
|
| Reserved |
|
|
|
| |
3 |
|
|
|
|
| Reserved |
|
|
|
| |
4 | (MSB) |
|
| Partition Number(0) |
|
|
|
| |||
7 |
|
|
|
|
|
|
|
|
|
| (LSB) |
8 | (MSB) |
|
|
| Block Number |
|
|
|
| ||
15 |
|
|
|
|
|
|
|
|
|
| (LSB) |
16 | (MSB) |
|
|
| File Number |
|
|
|
| ||
23 |
|
|
|
|
|
|
|
|
|
| (LSB) |
24 | (MSB) |
|
|
| Set Number |
|
|
|
| ||
31 |
|
|
|
|
|
|
|
|
|
| (LSB) |
The BOP, EOP, and Partition Number are as defined in the READ POSITION data returned when the TCLP bit is set to 0.
BPU: The Block Position Unknown (BPU) bit of ONE indicates the partition number or block number are not known or accurate reporting is not currently available. The BPU bit of ZERO indicates the partition number and block number fields contain valid position information.
MPU: The Mark Position Unknown (MPU) bit of ONE indicates the file number and set number are not known or accurate reporting is not currently available. The MPU bit of ZERO indicates the File number and Set number fields contain valid position information.
Block Number: Block Number reports the number of logical blocks between
File Number: File Number reports the number of Filemarks between
Set Number: Set Number reports the number of Setmarks between beginning
SONY |
