Figure 1 AS-11B-1 Automatic Analytical Stereoplotter
as a computer-controlled automatic plotting table, if
so desired.
COMPUTER AND SERVO EQUIPMENT
The new computer (Figure 1) employed in the
AS-11B-1 system is an 18-bit, parallel digital com-
puter with a 600-nanosecond 8,192-word random-
access memory.* The computer and interface system
utilizes silicon, monolithic, integrated circuits. The
computer organization provides the following fea-
tures:
(1) Dual accumulators with full arithmetic instruc-
tion repertoire.
(2) Hardware multiply and divide, including sign.
(3) Double-precision hardware add, subtract, store,
load, and clear.
(4) Hardware normalize for double-precision and
floating-point operations.
(5) Microprogramming ability.
(6) Two hardware index registers.
(7) Multilevel indirect or relative addressing with
post- or pre-indexing.
(8) Three-level hardware priority interrupt system
for input-output control.
Operation times for add, subtract, multiply, and
divide instructions, including memory access times,
are tabulated below.
Add or
Subtract, Multiply, Divide,
Operation Type Msec Msec sec
Single-Precision 1.2 4-5 4-5
Double-Precision 1.8 *25-37 *62-65
Floating-Point *16 *50 *75-95
*Subroutine
82
Two programs have been prepared for the computer
to aid in program preparation: a two-pass macro-
assembler and an on-line program checkout routine.
All servo control systemg in the AS-11B-1 have
been changed to dc servos, as compared to ac servos
and step-motors in the earlier systems. This change
was made to improve the system dynamic response
and because the components of the dc servo systems
are smaller and generate less heat. Use of dc servo
systems for the carriages simplifies accurate deflec-
tion of the scanner CRT scan patterns to compensate
for servo position error. Improvement of the servo
dynamic response reduces the servo error to be com-
pensated for and thus permits more accurate compen-
sation. Deflecting the scan patterns removes servo
errors from the automated system control loops; this
permits the use of higher gains and larger bandwidths
and enables higher plotting speeds to be achieved. In
addition, the change from step-motors to dc servo
systems for image rotation and magnification pro-
vides for a more convenient method for the operator
to adjust the base settings of the variables.
CONTROL PANELS
The operator's control panel at the viewer unit
contains all necessary controls for manual and auto-
matic operation of the system, except that some
infrequently used controls are located at the control
panel of the computer. The instrument control panel
also contains two display units, one numerical, the
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