TM 5-6675-316-14
3-3.2 DKA-3 Digitizing System. The digitizing system is a microprocessor device which can calculate all
necessary information to write machine control data for controls which process linear and circular interpola-
tion. The following components comprise and DKA-3 digitizing system and are housed (with the exception of
the keyboard and teletypewriter) in the card cage located-on the underside of the table frame:
Keyboard
Power Supply
Encoder Circuit Boards
Keyboard Interface Circuit Board
ROM Memory Circuit Board
Teletypewriter Interface Board (TTY)
Central Processing Unit Circuit Board
ASR-33 Teletypewriter
a. Keyboard. The keyboard contains 16 keys, BCD coded, 10 of which are numeric keys and 6 are alpha
keys. The minus key and alpha keys have two functions each while the numeric keys are for numeric en-
tries. The numeral 7 is also used to call the second function of the alpha keys (paragraph 3-4.1). The keys
control the digitizing operation and the numerical entries can be read on the digital display. The measuring
mode, coordinate presets, and scale factor entries are made via the keyboard. The four LED’s on the
keyboard indicate the various operations taking place and they will extinguish upon termination of the cur-
rent entry, The 7 segment digital LED indicates the current measuring mode of the digitizing operation
(Table 3-4). The push button on the keyboard starts the microprocessor after turning the display on, clears,
and resets the display to all zeros. The resetting of the microprocessor causes the system to default to the
English measuring system showing an E on the 7 segment LED. Depressing the X, Y, or B key allows the
digitized information to be sent to the teletypewriter from the TTY interface circuit card. The interface circuit
card enables the teletypewriter to produce the digitized information on a numeric control punch tape for the
automatic drafting operation.
b. Power Supply. The power supply provides the necessary voltage to the DKA-3 logic circuit boards for
the digitizing operation.
c. Encoder Circuit Boards. There are two encoder boards; one for the encoder on the X-carriage and one
for the encoder on the Y-carriage. The signals from the encoders are processed and routed to the X-Y
digital display. During the digitizing operation, the signals are stored in the RAM memory on the CPU circuit
board.
d. Keyboard Interface Circuit Board. The keyboard interface has two purposes; the first is to decode the
keyboard for use by the other circuits, and the second is to provide a common bus to the digital display.
e. ROM Memory Circuit Board. The ROM contains the complete operational program for the digitizing
mode.
f. Teletypewriter Interface Circuit Card. The TTY interface links the digitizing system to the teletypewriter
and allows the information to be passed to the teletypewriter which produces the numeric control punched
tape to be used in the automatic drafting operation.
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