3.5.3.2.1 External Function Words. used to control the DGU as follows:

External Function Words (EFWs) shall be

Master Reset Reset DITEG DGU and consoles

Update - Causes file memory data to be converted for display on a specified video channel

Hard Copy Initiate/Terminate a hard copy

MEP Switch Extinguish - Extinguish an amber illumination of a switch
MEP Switch Illuminate - Illuminate a switch amber

Read Control Read a File Memory, etc.

MIS Mask Enable/Disable MEP's

3.5.3.2.2 Output Data Words. Any data necessary to define the image such as radius length or coordinates shall be sent as an Output Data Word.

3.5.3.3 Computer/DITEG DCU Input Channel Requirements. The Computer/DITEG DGU Input Channel shall be used by the DITEG DGU to transfer operator entered MEP data, status information and cursor position to the computer. This information shall be transferred as External Interrupt Words and Input Data Words. Word formats shall be supplied to the procuring activity for approval within 60 days after award of the contract.

3.5.3.3.1 Preliminary External Interrupt Word List

Interrupt

MEP Data
Status

Source

MEP switch depression
Error condition or computer
request

3.5.3.3.2 Input Data. The DITEG DGU shall generate input data words for the computer to retrieve the following types of data when commanded by an interrogate EFW: File Memory readback, Cursor position, Video Memory readback, Diagnostic results.

3.5.4 File Memory. The File Memory shall be a 65536 x 32-bit memory which stores the Computer specified image data for use in producing all hard copy and video displays, plus display aids. Memory for each channel shall be allocated by the computer, based on the data load per channel. The File Memory shall be expandable to 131072 x 32 bits, in increments of 32768 x 32-bits.

3.5.5 Function Generators. the DITEG DGU shall contain two independent and redundant function generators, each consisting of a conic, vector. and symbol generator. Either function generator shall have access to all file memory locations and any video memory. They may process different updates simultaneously or one may be disabled by the computer (in case of a fault) and the DITEG DGU will operate in a degraded mode.

The function generators shall perform the following functions:

a. Provide for Range Scaling of Coordinates

b. Provide for Offsetting of the display

c.

d.

3.5.5.1

Provide for Category Selection of data items

Provde for conversion of file memory data into video memory data.

Range Scaling. The function generator shall provide for the 1024 x 1024 display element grid to be defined by display radii of 2 mi, 4 mi, 8 mi, 16 mi, 32 mi, 64 mi, 128 mi, 256 mi, 512 mi or 1024 mi, such that in the 2 mile range pixel 7.8 yards and on the 1024 mile range 1 pixel - 2 miles. The range scale of the display may be changed by the computer and a new image shall be generated by the DGU upon computer command. Selected data items may be range scale disabled to provide for their display at the display element coordinates corresponding to a centered 1024 mile range presentation regardless fo range scale and offset of the display presentation. The display grid coordinate system to be used shall be defined by Figure 3.5.5.1-1.

3.5.5.2 Offset. The function generator shall provide for positioning the display other than at the center of the defined universe. The perimeter of the resulting display shall not extend beyond the 4096 mile x 4096 mile defined universe. Any data which is range-scale-disabled shall also be

offset-disabled.

3.5.5.3 Category and Source Selection. The function generator shall selectively inhibit the display of data items as a function of their computer assigned category and source. Category Select Override shall be provided to cause individual data items to be displayed regardless of whether their category or source is inhibited or not.

3.5.5.4 Data Conversion. The function generator shall provide for the conversion of computer supplied data defining conics, vectors, symbols and alphanumerics into a video data base for display on the specified channel.

3.5.5.4.1 Conic Generator. The Conic Generator shall accept conic information from the computer defining conics (circles or ellipses) from the size of a dot to one with a major axis of 2048 display elements. The center of the conic shall be positionable anywhere on the 2048 by 2048 element grid. The Conic Generator shall provide for the display of the conic or the portion of the conic which falls in the concentric 1024 by 1024 element grid. either dashed or solid. Conics shall be defined by the parameters A, B, sin theta and cos theta. (See Figure 3.5.5.4.1-1). The conic generation circuitry shall generate the data necessary to load the video memory.

AREA

NOTE:

THE ANGLE IS ALWAYS MEASURED CLOCKWISE FROM THE POSITIVE AXIS TO THE AXIS OF THE ELLIPSE THAT LIES WITHIN THE 1ST QUADRANT

Figure 3.5.5.4.1-1.

3.3.5.4.2 Vector Generator.

The Vector Generator. shall accept vector

information from the computer defining vectors of any length between two points on a 4096 by 4096 mile grid. The Vector Generator shal! provide for the display of the vector or the portion of the vector which falls in the concentric 1024 by 1024 element grid. Vectors shall be generated from one of three types of data:

Start Point and End Point (normal lines)

Start Point, Tan theta and Longest Side Magnitude

Start Point and delta x, delta y

Normal and tan theta lines shall be scalable and offsetable. Lines defined by delta x, delta y shall be range scale disabled.

The Vector Generator shall permit the display of any vector, whether single or contained in a vector string to be either continuous or dashed. When dashed, the vector shall be displayed with 24 -8 elements illuminated then 24 +8 elements blank. The illuminated and blank portions shall alternate along the length of the vector. The vector generation circuitry shall generate the data necessary to load the video memory.

3.5.5.4.3 Character Generator. The Character Generator shall contain a repertoire of 256 symbol and alphanumeric types. Of these, 224 are predefined as shown in Figure 3.5.5.4.3-1. The remaining 32 fonts shall be alterable and definable by the computer.

A character is which are blanked. x, delta y of each

composed of connected line segments (strokes). some of The computer definable symbols shall be defined by delta stroke and whether the stroke is visible or blanked.

All symbol and alphanumeric types shall be available in four sizes:

Singly anywhere on the display area

Alphanumeric text string with carriage return/line feed
With an associated Tag and/or Non-scalable Leader (see Figure
3.5.5.4.3-2).

3.5.5.4.3.1 Tags A Tag is any alphanumeric character string Tan theta vector string, or conic that is associated with some other displayed data. Positioning of the Tag data items relative to the associated data item shall be as specified by the computer. Alphanumeric Tags may utilize CR/LF, be single, double or triple spaced, and be unlimited in length.