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b. Command: Write
c. Data: First byte of X data with blanklng
bit set to
L
d. Command: Set Buffer Address and
start, Address N.
Example 3: Alphameric Keyboard Operation
A. Problem: With the buffer contents the same
as in Example 1, and with the display regenerating,
insert a box name using the alphameric keyboard.
42
B. Sequence:
1. The operator observes the cursor to de-
termine where the first character will be
inserted. The cursor inserted in buffer
location N +
42
is displayed two spaces to
the right of E in the word NAME (Figure
16,
Table
10).
Note that the cursor bit in
a buffer location is not associated with the
data bits in that location; this bit causes a
cursor to be displayed beneath the charac-
ter selected by the data bits. In this ex-
ample, the data bits in locations N
+
42
through N +
47
specify space codes, caus-
ing six consecutive spaces to be left on the
display for the insertion of data.
2. The operator presses a key on the alpha-
meric keyboard: either a character key
(to insert a character) or the space bar
(to move to the next position without dis-
playing a character). In either case, the
cursor automatically moves to the next
position.
3. The operator inserts the box name in the
manner described in sequence 2, using a
maximum of six positions. The characters
that have been inserted are stored in buf-
fer locations N +
42
through N +
47
and
are displayed on the CRT display area.
If
buffer location N
+
47
is used for inser-
tions, the cursor remains in that location
until it is moved (either by program or by
the alphameric keyboard BACKSPACE or
JUMP key).
If
the JUMP key is activated,
the cursor is moved to location N +
42,
which, because of regeneration, is the
first location following N
+ 49 that con-
tains unprotected data.
4. The operator checks the name and makes
changes, as necessary, by positioning the
cursor with the BACKSPACE, ADVANCE,
and/ or JUMP key and keying in the de-
sired change.
5. When the desired message is displayed,
the operator presses the END key, locking
the keyboard and setting the Attention bit
in the status byte.
6. The program responds to the
I/
0 interrupt
and CSW containing Attention status with a
Read Manual Input command.
7.
The
2840
responds to this command with
three bytes that specify to the program
that the Attention status was caused by the
alphameric keyboard END key.
8. The program then analyzes this informa-
tion and issues the following command
sequence to retrieve the inserted data:
a. Set Buffer Address Register and Stop,
address N +
42.
b. Read Buffer, specifying a byte count
of 6 to the channel.
GRAPHIC DESIGN OPERATIONS
The following paragraphs describe graphic design
techniques that can be programmed for a
2250-3.
Included are sample buffer programs which illus-
trate several of these techniques.
Entities
In general, data will be composed of vectors, points,
and characters; these groups are called entities.
The
2250-3/2840-2
orders provide great flexibility
in the storage, linkage, pen detection, identifica-
tion, and manipulation of such entities. A sample
entity is shown in Table 11.
Table 11. Sample Entity Routine
Buffer
Location
Contents
Comments
E, E+ 1
GDPD
+2
G:MVD
+4
Adr
Program-specified location for
+6
LABEL
saving Entry name (i.e., LABEL)
+8
GDRD
Entry
+10
GEPM or GEVM
+12
x
+14
y
+16
GEVI2
+18
x, y
+20
X,Y
+22
GTDD
+24
Adr E
+26
GEN SD
+28
GTRU
Exit
E+30, E+31
Adr (next)
At entry, the Defer Response to Light Pen De-
tects order defers detects on any element of the
entity to be deferred to a single sampling time of
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