US 4,342,991 A · Partial scrolling video generator

Abstract

A raster scan cathode ray tube (CRT) display system which is capable of indirectly addressing data to be displayed in an manner presenting the data on any selected row or group of rows, in any order. A scrolling system according to the invention includes a cathode ray tube controller (CRTC) coupled to an indirect address counter which is coupled together with a presettable counter through a multiplexer (MUX) to the address port of a CRT display refresh memory (RAM), a segment of the data output port of the refresh memory being coupled to the preset port of the presettable counter. The invention operates by generating a refresh address indirectly through the presettable counter which addresses pointers in the refresh memory, each pointer containing the absolute address of the beginning of a specific line of data in the refresh memory which is to be displayed. During the blanking interval of the display, data is addressed by the indirect address counter. During other intervals, the address presented to the refresh memory is generated by the refresh address counter (the presettable binary counter). The address which is provided at the refresh address counter dictates the line of characters which are therafter displayed.

Claims8

Dependent claims

A method for use in scrolling display rows in a raster scan type cathode ray tube display system wherein the display system includes a video display, refresh logic, a refresh memory, a first counter and a second counter, said refresh memory having storage locations arranged in a first matrix and a second matrix, said first matrix comprising storage for indirect address pointers of preselected base address locations for rows of said second matrix, said second matrix comprising fixed address storage for data to be presented for output to said video display, said method comprising the steps of:

(a) writing a base address pointer for each row into said first matrix;
(b) reading, according to an address value in said first counter, a base address pointer from a location in said first matrix which points to the base address of a row in said second matrix so as to supply the base address to the address input of said refresh memory;
thereupon
(c) reading for output to said video display, according to a value in said second counter containing the current column address, data in said second matrix at the current column and row address;
(d) incrementing said second counter containing the current column and row address to advance the column address;
(e) repeating steps (c) and (d) until the end of the row is serviced;
(f) incrementing said first counter to access a next sequential address in said first matrix;
(g) repeating steps (b) through (f) to present a plurality of rows of data in said second matrix to said video display.

5 more elements

A method for use in scrolling rows in a raster scan type cathode ray tube display system wherein the system includes a video display, refresh logic and a refresh memory operative in response to write signals to store data information for subsequent display according to address information and operative in response to read signals at an address input to present data information at a data output, said refresh memory having storage locations arranged in a first matrix and a second matrix, said first matrix comprising storage for indirect address pointers of base addresses of rows of said second matrix, said second matrix comprising storage for data to be presented to said video display, said method comprising the steps of:

(a) writing display data into said refresh memory in said second matrix;
(b) writing base address information into said refresh memory in said first matrix, said base address information being arranged in a queue in said first matrix;
(c) causing said refresh memory to read a base address of a row from a current location of said first matrix as an indirect address and supplying said base address as a current location to the address input of said refresh memory;
(d) causing said refresh logic to read into said video display the data at the current location of the specified row in said second matrix in order to provide a video output signal;
(e) incrementing a column counter in response to a character clock in order to increment column location from said base address location in said second matrix;
(f) repeating steps (c) and (d) until said column counter is preset;
(g) incrementing an indirect address counter synchronously with a preset signal to said column counter in order to advance the current location of said first matrix;
(h) repeating steps (c) through (g) in order to present all rows of said second matrix for refreshing said display.

5 more elements

Dependencies are inferred from the claim text.

Partial scrolling video generator

Life of this patent

Partial scrolling video generator

Life of this patent

Abstract

Claims8