A-44
HP
9895A
Disc
Memory
Command Set
Requirements for Execution:
Parallel
Poll:
Unbuffered Write
Type:
Purpose:
Description:
1. 2 data bytes in command
2.
0
<=
Unit
<=
3
3.
DSJ
<>
2
4. Disc present
and
ready
5. First status bit not set
6.
Stat 1 = Normal completion,
1/
0 program error or illegal
opcode
error
7. Disc not write protected
The parallel poll response
is
re-enabled after the operation
is
completed, normally or abnormally.
Disc write.
The unbuffered write allows more than one sector to
be
transferred from the bus controller to the disc using a single
HP-IB command sequence. Due to the inability
to
share
the
HP-IB during the transfer, the unbuffered write is not
the preferred mode when
HP-IB performance is desired.
Following reception of the Write command, parallel poll
response
is
disabled
and
status of the specified unit
is
checked. The 9895A now waits for the receive data secon-
dary
and
then
fills
its internal buffer with
one
sector from
the
bus
controller. When the buffer
is
full, the 9895A
searches for the target sector
and
writes the buffer to it.
When the buffer has
been
emptied, the 9895A accepts
another sector from the
HP-IB
and
in turn writes it to the
next sector of the disc. This process continues until a byte
tagged with
an
EOI
is
received
or
an
error occurs. The
buffer containing the byte tagged with the
EOI
is
written to
the disc before the write completes.
If
an
error occurs (Le., drive goes not ready,
an
HP format
D bit
is
encountered, the sector
can't
be
found, etc.), writ-
ing to the disc
will
stop,
but
the 9895A
will
continue accept-
ing bytes until
an
EOI tagged byte
is
received.
If
an
error occurs, the target address
will
point to the sector
in which it occurred.
Otherwise, the target address
will
pOint to the sector following the last sector written. When
writing has
been
completed, parallel poll response
will
be
re-enabled.
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