Digital Stroke Symbol Generation
The digital stroke method of symbol generation is
used in some AN/UYA-4(V) display groups that use
the console internally generated and refreshed
symbols (CIGARS) modifications of the digital stroke
symbol generator.
The CIGARS modified console
eliminates the need for a separate symbol generator
because each console contains its own symbol
generation circuitry.
The digital stroke symbol generator stores all
symbols as digital codes in a group of read-only-
memory (ROM) chips or programmable read-only-
memory (PROM) chips. In this example, we assume
that a PROM is the device that stores the symbol. The
computer sends a message to the display group
indicating what symbol needs to be painted. The
message is translated and the data bits that were used
to identify the symbol in the analog symbol generator
are sent to the stroke control logic and are used to
access stroke codes from a PROM.
There are eight distinct routine states or time
periods in the symbol routine process as shown in
table 1-1. During each routine time, a component of
the symbol to be displayed is mechanized. At the start
of the symbol generation process, the CRT beam is
moved to the location where the symbol is to be
painted.
Table 1-l.-Symbol Routine States
The stroke symbol generator paints the dot first,
then accesses the PROM to get the symbol strokes.
The PROM has eight outputs for each address. Each
output performs a particular function in the generation
of the symbol component. The eight output lines used
to mechanize the symbol are as follows:
Sign X, X, 2X
Sign Y, Y, 2Y
Z (unblank)
W (wait)
Figure l-12.—The symbol grid and stroke
PROM addresses.
Figure 1-12 shows the mechanization grid for the
hostile air symbol. A dot in the grid indicates the
function is active. The sign bits control the direction
of the beam. If the sign bit is active, the beam is
moved in a negative direction. The X, 2X, and Y, 2Y
bits combine to determine the amount of deflection:
1-12
