displayed
as
blanks
that
occupy no
memory
locations.) The code entered immediately
follow-
ing the
"NEW
LINE"
code in memory
is
displayed
as
the
first
character on the
next
line.
If
the
80
character
by
25 line
format
must
be
retained, the Carriage Return-Line
Feed (CR-LF) functions may
be
keyed in
to
move the cursor
to
the
first
character position
on the
next
line.
After
all 2048
memory
loca-
tions are
used
up, the
memory
continues
to
receive data and scrolls up.
At
the end-of-
memory
indicator
(a
block
of
reverse video),
when a new character
is
received, a line
of
data
is
lost
from
the
top
of
the memory.
The cursor
is
always displayed on
screen and
if
any cursor
control
is
given
which
would
move the cursor
off
the display,
the display
will
be
scrolled up
or
down
so
that
the cursor wi!I remain displayed on the
screen.
With
efficient
paging, the cursor may
be
positioned
to
an
undefined location on a
particular line by moving
it
to
the
right
of
the
New Line
(N/L)
position. When this happens,
data cannot
be
entered on th
is
portion
of
the
line
to
the
right
of
where the
N/L
code was
entered.
If
insertions
are
to
be
made in a
particular line, the cursor must
be
positioned
to
a character located
to
the
left
or
under the
N/L
position.
Any
time
the cursor
is
under
the
N/L
position, the terminal automatically
operates
as
though in the Insert Character
mode.
1.3.5
Memory
Overwrite
When data
input
has
filled
all
memory
locations, Cursor Right and Cursor Down
are
inhibited
to
prevent the cursor
from
moving
through end-of-memory.
If
the last line
of
memory appears
as
the
first
line
of
the display,
Scroll Up,
Next
Page,
Cursor Right and Cursor
Down
functions
are
inhibited
so
that
they
do
not
move the cursor beyond the end
of
the
2048
memory
locations. Line
Feed
(LF),
Horizontal Tab
(HT),
and simply
writing
data
will
cause
Memory
Overwrite
to
occur. When
memory overwrite does occur, the
first
line
of
memory
is
filled
with
DEL
codes and made
available
for
additional data.
Care
must
be
taken
that
these
DEL
codes
do
not
cause
mistakes
if
the memory
is
to
be
retransmitted,
as
DEL
codes
are
interpreted
as
CR-LF codes
and
will
cause
the
ETX
code
to
be
missed
if
preceded
by
a
DEL
code in the
same
line.
Warning: Memory overwrite may occur
if
any
of
the
following
conditions occur:
a.
Cursor
is
on line 24, column 49-80 and
a Cursor Down
is
repeatedly attempted.
b.
Cursor
is
on line 25, column 0-48, and
a Cursor Down
is
repeatedly attempted.
c.
Cursor
is
on line 25, column 48, and a
Cursor Right
is
repeatedly attempted.
1.3.6
Space
Overwrite
(SPOW)
The
space
bar normally writes a
space
code in
memory
and advances the cursor one
character position
to
the right. However,
follow-
ing the operation
of
a Carriage Return (CR),
the
space
code re-acts
to
perform a Cursor
Right
function
but
does
not
write
a
space.
The
SPOW
latch
is
reset
by
performing a NEW
LINE,
Line Feed, HOME
or
TAB
function.
1.3.7 Character Overwrite
When
an
error
is
made in entering a
character (e.g., a misspelled word) a correction
can
be
made
by
overwriting the character. Note:
When terminal
is
in either On-Line
or
Print-On-
line
mode, character overwrite
will
overwrite
display
only
and
will
transmit
or
print
overwrite
characters
as
additional data. The
use
of
Delete
Character
or
Insert Character
functions
may
be
required
to
allow
for
a fewer
or
greater number
of
characters.
1.3.8 Special Function Keys
Eight
special
function
sequence keys (
F-1
through F8)
are
provided
to
allow
the user
to
call up routines unique
to
the
user.
Any
of
the eight
escape
sequence codes (ESC and p
through
ESC
and
w),
when generated
by
the
keyboard,
are
stored
as
a two-code sequence
starting at the cursor's location in the memory.
When the terminal
is
configured
to
"store
special
function",
the two-code sequence
is
stored in
page
memory. When the terminal
is
configured
to
"send special
function",
the
two-code sequence followed by
an
ETX
is
stored in memory and the ENTER
function
is
performed. During the ENTER
function,
if
the
terminal
is
configured
for
psudeopolling, the
1-6
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