Abstract:
A monitoring circuit incorporated into a video game display device is operated responsively to first and second non-overlapping clock pulses and monitors raster line status in comparison to a stored raster address and provides a high speed raster scan interrupt when that address is achieved, triggering a SPRITE or other feature(s) display.

Description:
This application is a continuation of a pending U.S. application Ser. No. 455,975, filed Feb. 27, 1983, now abandoned, and directed to the same subject matter. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to monitoring circuits for a video game display device and specifically raster scan monitors for such display device where any of a plurality of objects are to be displayed at certain screen locations specified according to stored instruction words. 
     An object of this invention is to provide a high speed monitor or raster scan addresses. 
     A second object of this invention is to provide such a monitor which does not load down the raster address element. 
     A further object of this invention is to provide such a monitor which interrupts the background sweep to load and display a SPRITE or other feature display. 
     SUMMARY OF THE INVENTION 
     The objects of this invention are realized in a monitoring circuit for raster scan in a video game display circuit which is implemented in large scale integrated circuitry (LSI) utilizing NMOS technology. A raster line address or location is loaded into a register for each line on which the video display information is to be varied from the preestablished background display. These stored addresses are sequentially loaded responsive to a first clock pulse. 
     A second, non-overlapping clock pulse is utilized to initiate a comparison operation with the instantaneous raster line information to initiate a change in the display instructions for that line. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The features, operation and advantages of the invention can be learned from a reading of the following detailed description of the invention with the accompanying drawings in which like numerals refer to like elements and in which: 
     FIG. 1 is a block diagram of the video game display device and monitoring circuit invention interconnection; and 
     FIG. 2 is a circuit diagram of the monitoring circuit invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A video game device provides a color display to the operator or player comprised of a background, usually non-moving; of SPRITES, i.e. movable objects, usually player responsive; and of other features, either fixed or moving, usually player non-responsive. 
     The background to be displayed is loaded into the video game device from a program and usually comprises a background data instruction set. 
     The video, line-by-line display driver is operated according to the background data instruction set unless this format is interrupted to display SPRITE or other feature information. 
     SPRITE and other feature data is loaded into the video game device from a program, and as with the background data is dependent upon the &#34;game&#34; being played. The display addresses for SPRITES and other features, however, can be varied by the processor unit of the video game device or by controlled inputs. Instantaneous SPRITE and other feature addresses are held in an address register. 
     Information processing within the video game device utilizes two non-overlapping clock pulses. 
     The monitor 11, FIG. 1, of the invention receives instantaneous raster line information from the display driver 13, which driver 13 supplies signals to a color display 15, such as a color television. 
     Background data is stored in an active memory 17 which constantly feeds display information to the display driver 13. 
     SPRITE display data and data defining other display features is held in a second active memory 19. 
     Current or instantaneous addresses for SPRITES and other features are clocked into a third active memory 21. 
     The memory 21 is connected to the monitor 11. When the raster line information received from the display driver 13 equals the raster line address stored in memory 21 a signal is generated which interrupts the background data from the first memory 17 to the display driver 13 and substitutes (loads) the SPRITE or other feature data from the second memory instead. 
     The monitor 11 is an 8 bit word device, FIG. 2, but can be tailored to any size. Instantaneous raster line location information from the display driver 13 is connected onto the inputs 23(a) through 23(h). SPRITE or other feature address words from the third memory 21 appears on the inputs 25(a) through 25(i). Each letter &#34;a&#34; through (h), designates a repsective bit in the 8 bit word processing. 
     The signals on the inputs 25(a) through (h) are clocked into the circuit storage by a first clock pulse (Φ1) appearing on node 27. A comparison is made with the inputs 23(a) through (h) responsive to a second clock pulse (Φ2) appearing on node 29. 
     The 25 input node is connected to the drain pin of a first field effect transistor, FET 31, whose gate pin is connected to node 27. 
     The source pin of FET 31 is feed the two inverting amplifiers 33, 35 connected in series. 
     An FET 37 is connected as a recirculating gate feedback, drain-to-source pin across the two amplifiers 35, 33. An FET 39 is connected on the output of the amplifier 35 to input a comparator 41. The signals on the 23 input node are also connected to the comparator 41. 
     The interrupt signal is generated as the comparator 41 output to node 43. The FETs 37, 39 are switched to conduction by the second clock pulse (Φ2) on node 29 by a connection to the gate pins of the FETs 37, 39. 
     This architecture is duplicated for each bit to be processed with the plural comparators 41 output connected in common to the node 43. 
     The paired amplifiers 33, 35 form a register which is loaded responsive to the first clock pulse (Φ1). The register data is recirculated and &#34;dumped&#34; responsive to the second clock pulse (Φ2). 
     The description above is intended as illustrative and is not to be read in the limiting sense. Many changes could be made in the invention without departing from the intent and scope thereof.