Video terminal character generator

Claim 2

Apparatus for generating raster line dot information for use in displaying character fields on a raster scan video display monitor, each character field consisting of a plurality of raster line segments, each raster line segment consisting of a portion for displaying a raster line character dot pattern and at least one portion for providing intercharacter spacing, said apparatus comprising: means for supplying signals identifying the character to be displayed in each of said character fields; means for supplying signals identifying which of said plurality of raster line segments within said character field is to be displayed; memory means, containing at least a plurality of raster line character dot patterns, for supplying individual ones of said plurality of raster line character dot patters in response to said character identifying signals and said raster line segment identifying signals; means for generating a first set of input signals; means for generating a second set of input signals; means for generating a selection signal for each of said raster line segments; and means, responsive to said selection signal, for selecting between said first set and said second set, the selected set to be used as the dot pattern for said at least one intercharacter spacing portion.

Claim 3

The apparatus of claim 1 wherein each said selection signal is stored in said memory means such that each of said plurality of character dot patterns has a selection signal associated therewith.

Claim 4

The apparatus of claim 1 or 2 wherein said first set of input signals is connected to a substantially constant voltage level and said second set of input signals is connected to at least one of the character dot pattern output signals from said memory means such that each signal of said second set of input signals has the same state as the character dot pattern output signal to which it is connected.

Claim 5

The apparatus of claim 3 wherein said second set of input signals includes at least one signal connected to the dot signal within said character dot pattern which will be displayed leftmost within the character field and at least one signal connected to the dot signal within said dot pattern which will be displayed rightmost within said character field.

Claim 7

The apparatus of claim 2 wherein said outputs of said read only memory are a character dot pattern of seven bits and a selection signal of one bit.

Claim 8

In a raster scan video display terminal having means for defining a plurality of character rows, means for defining a plurality of character fields in each character row, each character field having a character display portion and at least one intercharacter spacing portion, means for identifying the character to be displayed in each character field, memory means containing a plurality of raster line character dot patterns, said character dot patterns being smaller than the width of said character fields and means for identifying which of said plurality of character dot patterns is to be displayed, a method of generating the dot information to be displayed on each character field raster line, said method comprising the steps of: (a) retrieving, in response to signals indicating the character to be displayed and indicating the raster line within the character field to be displayed, the character dot pattern to be displayed; (b) monitoring a selection signal indicating the status of said at least one intercharacter spacing portion; (c) selecting in response to said selection signal one of a plurality of sets of signals to be used as the source of the dot signals for the dots in said at least one intercharacter spacing portion; and (d) repeating steps (a)-(c) at each character time during terminal operation.

Claim 9

In a raster scan video display terminal having means for defining a plurality of character rows, means for defining a plurality of character fields in each character row, each character field having a character display portion and at least one intercharacter spacing portion, means for identifying the character to be displayed in each character field, memory means containing a plurality of raster line character dot patterns, said character dot patterns being smaller than the width of said character fields and means for identifying which of said plurality of character dot patterns is to be displayed, a method of generating the dot information to be displayed on each character field raster line, said method comprising the steps of: (a) retrieving, in response to signals indicating the character to be displayed and indicating the raster line within the character field to be displayed, the character dot pattern to be displayed; (b) monitoring a selection signal indicating the status of said at least one intercharacter spacing portion; (c) selecting in response to said selection signal one of a plurality of sets of signals to be used as the source of the dot signals for the dots in said at least one intercharacter spacing portion; and (d) repeating steps (a)-(c) at each character time during terminal operation.

Claim 10

The method of claim 7, wherein each of said character dot patterns has a selection signal associated with it, said selection signal being stored in said memory means and being retrieved simultaneously with its associated character dot pattern.

Claim 11

The method of claim 7, wherein said selection signal is supplied to the select input of a multiplexer and wherein said plurality of sets of signals are supplied to the inputs of said multiplexer.

Claim 12

The method of claim 7, wherein a first set of said plurality of sets, if selected, will result in the dots in said at least one intercharacter spacing portion being off and wherein a second set of said plurality of sets, if selected, will result in each dot in said at least one intercharacter spacing portion having the same state as the dot in the character dot pattern nearest to said each of said intercharacter spacing portion dots.