Display Compatibility Interface
Introduction
An
HP
98546A Display Compatibility Interface enables
bit-mapped
video from
the
computer
to
be
compatible
with
the
HP
35721,
HP
35731,
and
HP
35741 monitors when one of
the
following
operating
systems is used:
•
HP
Series 200 BASIC 2.0, 2.1,
and
3.0.
•
HP
Series 200 Pascal 2.0, 2.1
and
3.0.
Two DIO cards
are
used
and
each may
be
individually replaced.
These
iterns
are
included in
the
package:
• Video
Card.
• Graphics
Card.
• Various video cables
Both
cards
are
installed in
adjacent
DIO
card
slots.
The
video
card
must
be
in a DIO interface
slot
with
the
graphics
card
in
the
accessory slot directly above
the
video card.
This
two-card set
has
the
following functions:
•
Bit-Mapped
Video
Input
•
Katakana
or
Roman
8
Character
font.
• 50 or 60 Hz Refresh
Rate
Selection
•
Alpha
and/or
Graphics Video
Output
Figures 3-31
and
3-33
are
block diagrams of
the
cards. Refer
to
these diagrams for functional
descriptions.
Video Card
Input Video
Bit-Mapped
video from a video
board
is
input
to
the
video
card
through
the
BNC
connector
labeled
Video In.
The
card
contains a relay
that
selects
either
the
externally supplied video
signal (from
another
video board)
or
the
on-board
generated
alpha/graphics
video
to
be
sent
to
the
monitor.
Timing and Drivers
Timing
clock signals
and
video driver circuits required
to
interface
the
graphics
card
are
on
the
video card. Vertical sync circuits
are
controlled by
the
position of
the
50/60
Hz
monitor
refresh
rate
switch.
Both
vertical
and
horizontal sync pulses
are
output
to
the
video circuits
to
be
part
of
the
composite video
output.
Functional Description
113
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