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|  MIL-D-81347C(AS)
Function Generator Unit
3.5.3.4.3
Functional Description - The Function Generator Logic (FGL)
3.5.3.4.3.1
shall accept computer generated digital information, and convert it to an analog form suitable for dis-
playing conies on one of the Multipurpose Displays (MPD). The FGL shall process the computer data
and generate the appropriate analog sinusoidal waves and unblank signal which result in the display of
ellipses, circles, and vectors.
Figure 123 is a functional flow diagram of the FGL.
General Description - FGL receives 20-bit parallel words from
3.5.3.4.3.2
the computer via the MCP and TACCO MPD Logic and utilizes this data to generate the analog signals
necessary for conic presentation on the MPD. Two data w orals are required to define a conic. The
FGL shall transmit the unblank signal to the MPD Logic when it is in a state to receive data describ-
ing a new conic. It shall also receive diagnostic instructions and transmit diagnostic data via the
MTL.
Operating Requirements
3.5.3.4.3.3
Presentation
Requirements
3.5.3.4.3.3.1
Configurations to be Displayed
3.5.3.4.3.3.1.1
(1) Ellipse - The X and Y components of the semimajor and
semiminor axes are contained in Conic Data words 1 and 2 respectively. This data shall be refer-
enced to the center of the ellipse as shown in Figure 124, part A. The semiminor axis shall be
oriented at an angle of 90 degrees in the counterclockwise direction from the semimajor axis. Bit
allocations for the data are shown in 3.5.3.4.3.3.2(1) and 3.5.3.4.3.3. 2(2).
(2) Circles - Circles shall be transmitted as two words. The
length of the semimajor and semiminor axes shall be equal to each other. The first word shall con-
tain the X coordinate of the end point of the semimajor axis and zero for the Y coordinate data. The
second word shall contain the Y coordinate of the end point of the semiminor axis and zero for the X
coordinate data (Figure 124, part B). Bit allocations for the data are shown in 3.5.3.4.3.3. 2(1) and
3.5.3.4.3.3.2(2).
(3) Vectors or Straight Lines - Vectors or straight lines shall
The first word shall contain the X and Y components of the semimajor
be transmitted as two words.
axis. The second or semiminor axis word shall be transmitted as 0's (Figure 124, part C). Bit avo-
cations for the data are shown in 3.5.3.4.3.3.2(1) and 3.5.3.4.3.3.2(2).
Symmetry - The property of symmetry shall be utilized to re-
3.5.3.4.3.3.1.2
strict the semimajor axis to the first and our h quadrants. The semiminor axis, being oriented 90
CCW, is similarly restricted to lie in the first and second quadrants. Ellipses or straight lines which
have the Y axis as their semimajor axis, shall have the semimajor axis positioned in the first quad-
rant (Figure 124, parts D, E and F).
T i m i n g - Timing shall be in accordance with Figure 125. The
3.5.3.4.3.3.1.3
maximum generation time for one circle, ellipse or vector shall be 550 microseconds.
Data Transmission - Two sequential data transmissions shall be
3.5.3.4.3.3.2
required to describe a complete ellipse, circle or vector (Figure 126).
(1) First Transmission - This data word shall contain the X
and Y components of the semimajor axis (ax and ay). The transmission shall consist of a 20-bit
message; bits 5 through 14 representing ay and bits 20 through 29 representing ax. Bits 5 and 20 are
the LSB's and bits 14 and 29 the MSB's. Negative numbers shall be expressed in one's complement
code (Figure 126).
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