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|  MIL-D-81347C(AS)
The other operations, Vector, Type, and Conic, require more computer information, so the Logic
stores the command, and raises the Output Data Request line. Timing for the analog operations is
illustrated in Figure 104. The operations are as follows:
(1) Analog Channel 1 - The Set Position word generates the
necessary
signals to open the MPD's analog gates for display of the stored radar scan converter pre-
sentation.
The Logic will also generate an enable signal to the MTL which will return a timed scan
converter
read enable signal to the MPD Logic. The trailing edge of this signal will cause the MPD
Logic to
close the channel and request a new computer word.
(2) Analog Channel 2- The Set Position word generates the
proper signals to open the MPD's analog gates for LLLTV readout. The LLLTV presentation will
continue until the next 57.1 Hz Sync signal is received, at which time channel 2 will be closed and a
request for a new computer word will be initiated.
(3) Analog Channel 3 - The Set Position word for analog
channel 3 initiates the same chain of events for channel 3 as it did for channel 1, for Spare Scan
Converter.
(4) Analog Channel 4 - The Set Position word for analog channel 4
will control the display of conies on the TACCO MPD and a raw radar video on the Sensor Operator's
MPD. Upon receipt of the appropriate Set Position word, enable signals shall be generated in the
MPD Logic which will open the MPD's analog gates for the positioning, unblank, and video information
from either Function Generator or Radar Interface Unit.
At the end of each conic presentation, as signaled by the
change of state of the Function Generator Unblank signal from Unblank to Blank, the Logic Unit shall
send an Output Data Request signal to the computer. Raw radar video presentation shall be enabled
from the time that the Logic Unit receives a Set Position word containing a Control Field Code of 11
until the time the next 40 Hz Sync pulse is received.
(5) Vector - If the previous Set Position word requested a
vector, the MPD Logic will interpret the next word as such. The vector major axis length is loaded
into a nine-bit, two MHz length counter. The nine-bit slope signal is sent out to the MPD as are the
major axis and sign bits. The Logic releases the clamp (sweep enable) on the MPD sweep generator,
starts the Vector Unblank, and starts the length counter de cementing toward zero. When the length
counter reaches zero, the MPD Logic stops the Vector Unblank, reinstitutes the clamp on the sweep
generator, and raises the Request line to the computer. The vector requires 1/2 microsecond for
every plotting point of length: Negative minor axis components require the slope to be expressed in
one's complement form. This shall be done automatically by the computer. The timing constraints
for vector generation are illustrated in Figure 105.
(a) Analog Vector Generator - The MPD contains a device
whose purpose is to draw straight lines in any of 2048 different directions and with any of 512 different
lengths, on the CRT screen. It does this by generating x - axis and Y - axis components of a constant
rate sweep waveform whose time duration is proportional to the desired line length, as shown in
Figure 106. The major axis sweep is multiplied by 1, the minor axis sweep by the slope, a fraction
of 512.
(6) Type - If the Set Position word requested the `Typewriter mode,
the series of words following will be interpreted as Type words. The Logic examines each character
code for the special codes Carriage Return and End of Message on the selection lines. The position
from the Set Position word is stored in a margin register, a horizontal position register, and a vertical
position register. The Logic gates the first six bits of the Type word onto the character selection
lines to the display, waits approximately four microseconds, and if the character is not a special code,
raises the Character Unblank for 24 microseconds. The Logic then gates the next group of six bits
onto the selection lines, advances the horizontal position register, and repeats the process. Altogether,
the MPD Logic performs the above process for all five six-bit groups in the input register, i.e;, one
computer word, then raises the request line to the computer for the next word. However, if a Carriage
Return code is encountered, the MPD Logic will suppress the Unblank, reload the horizontal position
172
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