Foe
Data Register
This
is
a bidirectional register. Write Function: 8-bit data
is
written
to
FDC
chip
as
commands
via
programmed I/O and
write
data
during disc transfers
via
DMA.
Read
Function: 8-bit data
is
read
from
FDC
chip
as
result
of
commands
via
programmed I/O and read data during disc
transfers
via
DMA.
Digital Input Register
Bit
Data
7
Definiton
State
of
the disc change line. Becomes active
when
the drive
door
is
opened and at power-on. It will
remain active until reset
when
a step pulse
is
issued.
It
is
active high.
FDC-to-Disc Drive Interface
The 5 1/4 inch disc drive interface
with
the
controller
is
through
control signals, status signals and data signals. The 5 1/4 inch
drives are daisy-chained on one connector and cable. The
following table shows the pin assignments
for
the
34-pin
connector. The input
or
output
of
the
signals are referenced
to
the
processor board.
In
the
HP
Vectra system the HP45812A 1.2 MB Internal Flexible
Disc
Drive provides a -
DISC
CHG
signal on
the
drive interface pin
34. This signal indicates the detection
of
the
drive
door
being
opened. The HP45811 A 360
KB
Internal Flexible
Disc
Drive does
not
provide a -
DISC
CHG
signal on pin 34. Thus, this signal will
always
be
inactive and the system cannot detect a possible media
Processor Board
49
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