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20
Sending Escape Sequences
Escape sequences can
be
sent
to the video interface
(as the
primary device)
from
the HP-41 keyboard
usinglAccHR
I
(in
Auto
mode),
as shown in
the following
example:
Keystrokes
27 1ACCHR
I
69
1ACCHR
I
The character
code
for
' < :
is sent
to
the
interface.
The
character code
for
liE"
is
sent
to
the
interface. A
Clear
Device
('<:
E) instruction is
completed.
A
Cursor
to Address instruction may be similarly
executed.
After keying
in the codes
for
' < :
and
%,
two
inputs
are
required
to specify
the
column (0
through
31)
and row
(0 through
15)
that
the cursor should
go
to.
Any number up
to
127 may be used to specify row and
column
locations; however, 10 and 13 should not
be used-they
are
redefined when
sent
in an
~
%
instruction.
The
following example shows
how
to instruct the
interface
to
move
the cursor to column
12,
row 8.
Keystrokes
271ACCHR
I
37 1ACCHR
I
12 1ACCHR
I
8
1ACCHR
I
Sends
the ' < : character code
to the
video
interface.
Sends the
%
character code to the interface.
Sends
the
column number to
the interface.
Sends the
row number to
the interface.
"'<:
%"
is now
executed. The
cursor is
positioned at column 12
and row 8
of
the video
display.
Escape sequences
can be combined with
displayable
characters
in ALPHA data
strings,
then sent using
lOUT AI,
~
or
I
ACA I.
The strings
are created
by specially building the
escape
character
in
the
X'register
with
I
BLDSPEC
I, recalling it
to
the
ALPHA register, keying
in the
remainder
of
the sequence
in
ALPHA
mode,
then
keying
in
words
to
be displayed,
as
shown
in
the
following
example:
Keystrokes
27 1BLDSPEC
I
IALPHA
I.
IARCLI[]x
.
%CDTOP
1
ALPHA
1
Builds
the ' < : character (HP-41
display
is
unintelligible).
Recalls the
' < :
character
into
the ALPHA
register.
The
sequence is completed and the word TOP is
added.
The character codes for C and D are
used
to determine
the
cursor
address.
The cursor is set at column 3,
row
4 and
the word
TOP is
written.
This
example shows how
standard
Hp·41 characters are
used
to specify the cursor address. Any character
(except 10 and 13) can be
used.
For your convenience, some easily
key
able address codes are shown
in
the
following
table.
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