User`s manual

IOP - I/O Physical (Direct Disk Access)
3-96
3
Flag Byte =00?
The ßag byte is used to specify variations of the same command,
and to receive special status information. Bits 0 through 3 are
used as command bits; bits 4 through 7 are used as status bits.
The following bits are deÞned for streaming tape read and write
operations.
Retension/Erase =R (R/E)?
After all the required parameters are entered, the disk access is
initiated. If an error occurs, an error status word is displayed. Refer
to Appendix F for an explanation of any error status codes that are
returned.
Bit 7 Filemark ßag. If 1, a Þlemark was detected at the end of
the last operation.
Bit 3 Disk formatting. It is ignored on tape operations.
Bit 2 Reset Controller Flag. If 1, a controller reset will take
place if possible before the requested operation takes
place.
Bit 1 Ignore File Number (IFN) ßag. If 0, the Þle number Þeld
is used to position the tape before any reads or writes are
done. If 1, the Þle number Þeld is ignored, and reads or
writes start at the present tape position.
Bit 0 End of File ßag. If 0, reads or writes are done until the
speciÞed block count is exhausted. If 1, reads are done
until the count is exhausted or until a Þlemark is found.
If 1, writes are terminated with a Þlemark.
R Retension tape when a format operation is scheduled
E Erase and retension tape when a format operation is
scheduled