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Operating Modes - IBM 1620 Manual Of Instruction

Data processing system, model 2; plotter control unit; plotter feature
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r,'\
+y
~
...
~It-""""'----
-x
7
Pen
9 - Raise Pen
0-
Lower Pen
NOTE: The encircled numerical figures are the
1620
characters
that correspond to the indicated direction of plotting movement
as viewed from the front of the plotter. Normally, graphs are
plotted so that their horizontal axes are, in reality, the X axis
as shown above.
Figure 1-2. Output Record Control Digit
Table 1.
Proper Output Characters
Numerical
Alhhameric
Plotter
Character
C aracter
Action
Op Code
35
~
38
Op Code
39
0,0
70
Lower Pen
1,1
71,51
-+y
Increment
2,2
72,52
+X, -y Increment
3,3
73,53
+x
Increment
4,4
74,54
+x,
-y Increment
5,5
75,55
-y Increment
6,6
76,56
-x,
-y
Increment
7,7
77,57
-x Increment
8,S
78,58
-x,
-+y
Increment
9,C,
79,59
Raise Pen
Operating Modes
An output record of 3' s or 7' s produces a paper move-
ment by the plotter along the x-axis. An outputrecord
of l' s or 5' s produces a pen movement by the plotter
along the y-axis. The digits 2, 4, 6, or 8 in an out-
1.2
put record produces simultaneous motion of paper and
pen which results in a diagonal movement (Figure 1-2).
The distance moved diagonally is 1. 4 times a hori-
zontal or vertical movement.
Single Character (Overlap) Mode
The P-address of a write instruction can refer to any
size record, but
by
using single-character records,
each successive increment can be computed while the
previous increment is being drawn.
In
this manner,
1620 computation instructions for the next increment
or other processing are "overlapped" with plotting
operations.
For example, a Write Numerically instruction
and a data record consisting of the digit five followed
by a record mark (5
:j:)
produces the result shown in
Figure 1-3. This operation requires 3.3 miliseconds
(ms) for the 1627, Modell, or 5 ms for the 1627,
Model 2. However, the 1620 CPU is not held up, but
is disconnected and allowed to proceed to the next in-
struction 200 microseconds
(/-l
sec) after the write
plotter instruction is initiated ..
If
a second 1620 plotter instruction is attempted
before completion of a previous plotter operation, the
1620 waits until the plotter can accept the next com-
mand. Plotter instructions that occur more than 3. 3
ms apart, operate the plotter properly, but at less
than the maximum rate of 300 increments per second
(1627 Modell speed). Both 1627 models require 100
ms for pen status change (0 or 9 in the output record).
!--I/IOO"
Start
Finish
( assume pen in down status )
Figure 1-3.
Plotter Result for Data of 5
:I:
Multiple Character Record (Nonoverlap) Mode
When a record in core storage consists of more than
one character, only the last character can
be
over-
lapped with processing. For example, a record con-
sisting of 05555922077779:1: is translated as follows:
lower pen, move pen four increments in the -y direc-
tion, raise pen, move two increments diagonally (+x,
+y), lower pen, move drum four increments in the -x

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