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9
The video
interface
features
top-around scrolling. The
first line
of
memory will follow the last line
of
memory
onto
the
screen
in
a
repeated roll-up
operation.
The last line will follow the first if a roll-down
operation is continued.
31 Lines
01
Display
Memory
Roll Up
Roll Down
Controlling the Video Interface
)
16 Lines
On Screen
Most
controllers perform a specified operation
by
automatically sending a preprogrammed sequence of
Hp·IL
messages around
the
interface
loop. You
would not
be using the
actual Hp·IL
messages in this
case,
but
rather you would be
using
the
HP·IL
capabilities
built into
your calculator, computer, or
Hp·IL
extension.
This
section describes
how
the
HP
82163 Video
Interface responds
to
the
individual
Hp·IL
messages.
The
video
interface
operates
according
to
information
it
receives
on the interface
loop. Specifically, it
responds
to the
standard HP·IL messages (listed
on
page 10), including
special
Data Byte messages
(in
the form of
escape
sequences,listed
on
page 10) that
are
interpreted as instructions.
Startup Conditions.
The
video
interface is
automatically turned on
when
the ac adapter
is plugged
into
it. While
the
ac adapter
is
plugged in,
the interface
retains
its display memory
whether or
not
the
TV
or
monitor is
turned on or connected.
When
the video interface is
first connected to its power source and
is linked
with
HP-IL,
it
is
in
an
inactive
mode
and its
default Hp·IL
address
is
set
to
3.
(In
most
applications
this default
address
isn't
used,
since
controllers
usually
assign addresses to
loop devices.)
Escape Sequences.
The
HP
82163 Video
Interface
responds to
14
escape sequences. An escape sequence
is
a
string
of characters that
is
sent out
on
the
loop
as
a
series of
Data
Bytes
and
interpreted
as a special
instruction by the device receiving it. An escape
sequence
always starte with'"
(escape)-code
number
27-
and is
followed
by
one or
more characters that define
the instruction.
Escape sequences are used by
the video
interface
to
position
the cursor, scroll
through display memory,
and
clear
the
display.
Many
different escape sequences can
be passed through
HP-IL; however,
the
video
interface
responds to
only a
few
of these.
When the interface receives an
escape sequence
that
it
does not recognize,
it
displays
all
but
the first two characters in
the
sequence. Escape sequences recognized
by the interface
are shown
in
the following table.
•
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