Seagate STT8000A - Manual (Page 62)

Chapter 5 ATAPI Interface
Page 54 STT8000A Product Manual
*These fields might appear to report the number of bytes/blocks in the buffer.
However, this information is not guaranteed to be accurate. You should not rely on
this information.
The only position that is guaranteed is the host logical block position. The First and
Last Block Locations both return the same host location, and Blocks and Bytes in
Buffer are reported as 0.
Because Read Position is DSC restrictive on all ATAPI tape drives, it can be used to
“wait” for any previous command to complete. This can be useful for applications
with ATAPI only access to determine the actual completion of a command. Note,
this will keep the ATA bus busy during the “wait”. DSC polling (to wait for DSC set)
is preferred when possible.