Abstract:
A comparator circuit incorporated into a video game device and operated responsive to first and second non-overlapping clock pulses can be used to compare background information location to SPRITE information location for both raster line (vertical) and column (horizontal) coordinates to provide a high speed interrupt signal to a central processor unit (CPU) triggering a processing of SPRITE or other features&#39; display instead of a processing of background display, the comparator being implemented in less silicon area and having a lower power usage than other types of circuit implementations.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to monitoring circuits for a games and specifically to raster line comparators which compare display location to stored location instructions. 
     Video games are played using circuits which supply video and audio signal information to the antenna leads of a color television type display. Video information comprises background data; and fixed object data and movable object (called a &#34;SPRITE&#34; data. The fixed object data becomes a part of the background data for any specific game. SPRITE location and movable features location (and therefore data instructions) change from instant to instant as the game is played. 
     Additional predetermined trajectory or vector information can also be displayed according to the game played. This additional vector information can include moving &#34;bullets&#34;, &#34;missiles&#34;, swing vines, moving balls of all varieties and anything else the game inventor can think of. 
     It is important to display all of the game information accurately. One approach is to display the background in raster line fashion with background data instructions being provided for all 525 scan lines on the display screen. An object to be displayed, appears in front of the background and therefore is displayed instead of background information at that particular screen location. 
     A high speed comparator circuit is needed to switch the game circuitry from background to object data. 
     Video games find a marketplace either as a consumer item, or an arcade item. They need to use as little power as possible and be capable of being made as inexpensively as possible, i.e. be implemented with as little circuitry as possible. 
     An object of this invention is to provide a high speed raster location and column location comparator circuit. 
     A second object of this invention is to provide such a circuit which minimizes D.C. power use. 
     A further object of this invention is to provide such a circuit which can be implemented in LSI and NMOS circuitry in a minimal amount of silicon area. 
     SUMMARY OF THE INVENTION 
     The objects of this invention are realized in a digital circuit which when implemented in duplicate monitors raster scan line location and column scan location in the video display driver circuit of a video game device or computer. The circuit is implemented in large scale integrated circuitry (LSI) utilizing NMOS technology. A raster line address (or vertical address) instruction for any object to be displayed is loaded into a register and compared with the video display driver instantaneous raster line (or vertical) location. The stored addresses are recirculated into the device to assure current data. 
     Any stored raster line (or vertical) address, for any instantaneous object data instruction, is 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 (or vertical) information to initiate an interrupt signal which is used by another circuit to change the display for that line (or vertical). 
     Power drain is minimized. Silicon area need for implementation is minimized. 
    
    
     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 digital video game device and the digital comparator circuit invention (as illustrated for raster line compare); and 
     FIG. 2 is a circuit diagram of the comparator circuit invention as represented for processing a single digital bit of information or plural bit instructions (whether raster line or vertical information). 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Video game devices provide a color display to a 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. 
     Such video game devices are commonly implemented by circuits connected to home computers which then become dedicated to a game program entered into memory, or commonly implemented by special purpose circuits, i.e. video games which provide input signals to the antenna leads of a color television (or black and white), or implemented as a stand-alone video arcade-type machine. Regardless of the type of implementation, game information signal processing can produce the same video display. 
     When implemented as a special purpose &#34;video game&#34; of the type popular in the consumer marketplace, the circuit implementation is desirable to be of low cost and low power consumption design. These design goals are impressed on the present invention. 
     Background to be displayed is loaded into the consumer video game device from a program and usually comprises a background data instruction set (data) and object, i.e. SPRITE instruction set (data). 
     The device provides an output signal which is translated into line-by-line (or column-by-column) display signals received by the television display device. The device operates to generate a background display only and unless this format is interrupted to display SPRITE or other features information. 
     SPRITE and other features data is loaded into the video game device from the program, and as with the background data is dependent upon the &#34;game being played&#34;. The display addresses for SPRITES and other features, however, can be varied by the central processor unit (CPU) of the video game device and by player controlled inputs. Instantaneous SPRITE and other feature addresses are held in memory. 
     Information processing within the video game device can utilize two non-overlapping clock pulses which are provided to the circuit environment. LSI implementation, especially in NMOS technology provide the possibility for a low power and inexpensive circuit design. 
     To completely determine SPRITE position a horizontal &#34;compare&#34; is accomplished using the comparison device of the invention. The circuit compares the horizontal position (x-direction) with the stored SPRITE vector. It is this comparison function which necessitates high speed performance since it must compare locations at the dot frequency of a typical color TV set display, i.e. about 8 MH z . A vertical position (y-direction) &#34;compare&#34; is accomplished with the comparison device of the invention at an approximate 63 microsecond repetition rate. Boot strap circuit conditioning principles assure fast operation and low power drain. 
     FIG. 1 shows the video game device environment in which the present invention operates and the intra-circuit connection with the circuit comprising the present invention. Shown is only the raster line (y-direction) location determination circuitry. A central processing unit (CPU) 11 receives background data information and SPRITE data information (as well as other feature information) from memory registers 13. These memory registers 13 are loaded from a game program 15. The game program provides data in the form of digital signals stored on a magnetic tape or other storage mediums. 
     The CPU 11 also receives game information from a game player input device 17. CPU 11 generates two non-overlapping clock pulses (φ1) 19 and (φ2) 21 for its own use and for use by other circuit components. An output of the CPU 11 is connected to a line-by-line display driver 23. This display driver 23 provides signals to a color display (or black and white) 25. Most typically in consumer home applications this color display is implemented by the television set. 
     A raster line comparator circuit 27 receives instantaneous line location information from the line-by-line display driver 23 and raster line address instruction locations for object display (SPRITES or other features) from the CPU 11. The non-overlapping clock pulses 19, 21 are each fed into the raster line comparator circuits 27. The raster line comparator circuit provides an interrupt signal output 29 which is sent back to the CPU 11. 
     The raster line comparator circuit 27 of FIG. 1 can be implemented as shown in FIG. 2 to process a single bit &#34;word&#34; or a plural bit &#34;word&#34;. Most often with commercially available CPU&#39;s 11 the circuit, FIG. 2, is required to process 8 bit words. As the circuit implementation is duplicated for each bit, only one bit processing is shown in full in FIG. 2. 
     Instruction location information received from the CPU 11 is input to the circuit at node 31. Instantaneous line location information received from the line-by-line display driver 23 is input to the circuit at node 33. The first clock pulse (φ1) 19 is input to the circuit at node 35, while the second non-overlapping clock pulse (φ2) 21 is input to the circuit at node 37. 
     The first clock pulses 19 are utilized to load information into a register, which is a part of the circuit of FIG. 2 and to recirculate the information through the register so that information is not lost and/or information is updated. The second clock pulse 21 is then used to clock the operation of the comparison function while the comparison portion of the circuit 27 is isolated from the CPU 11, thereby minimizing D.C. power drain (power usage). The first clock pulse 19 is utilized to precondition the circuit enabling faster operational speeds. 
     Circuit node 31 is connected to the drain pin of a first field effect transistor (FET) 39, while FET 39 has its gate pin connected to the node 35. 
     The source pin of FET 39 is connected to a first operational amplifier 41 and to the drain pin of a second FET 43. This second FET 43 has its gate pin connected to the circuit node 37. 
     The output from the first operational amplifier 41 is connected to a second operational amplifier 45 and to the drain pin of a third FET 47. The output from the second operational amplifier 45 is connected to the source pin of the second FET 43, the drain pin of a fourth FET 49 and the drain pin of a fifth FET 51. 
     The fourth FET 49 has its source pin connected to the circuit node 31 and its gate pin connected to the circuit node 35. 
     The gate pins of each of the third and fifth FETs 47, 51 are connected to the circuit node 37. The source pin of the third FET 47 is connected to the gate pin of a sixth FET 53, while the source pin of the fifth FET 51 is connected to the gate pin of a seventh FET 55. These sixth and seventh FETs 53, 55 have their drain pins connected together and to circuit ground. 
     The source pin of the sixth FET 53 is connected to the drain pin of an eighth FET 57, while the source pin of the seventh FET 55 is connected to the drain pin of a ninth FET 59. The gate pin of the eighth FET 57 is connected to the circuit node 33 through an amplifier 61, while the gate pin of the ninth FET 59 is directly connected to this circuit node 33. The source pins of the eighth and ninth FETs 57, 59 are connected together and to circuit node 63 which provides the interrupt signal 29 connection to the CPU 11. 
     The amplifiers 41, 45, and 61 are each of the inverting type. Amplifier 41 serves as the storage register while amplifier 45 provides an inverted or complementary output signal to that of the first amplifier 41. The third and fifth FETs 47, 51 provide a switch function which isolates the register amplifiers 41, 45 from the comparison portion of the circuit. 
     FETs 53, 55, 57, 59 are connected to form a cross coupled NAND gate circuit which performs the actual comparison function. The circuit is designed to simultaneously compare both the signals and their inverse as a check on a logical zero versus the absence of a signal. Amplifier 61 on its output provides the inverse of the line location information appearing on circuit node 33. 
     For (x-direction) column (vertical line) location comparison, the line-by-line display driver 23, FIG. 1, (vertical display driver for horizontal line location) is replaced by a horizontal display driver. The circuit of FIG. 2 remains identical. 
     The implementation as disclosed above may be modified or changed without departing from the intent or scope of the invention. It is therefore intended that this disclosure be interpreted in the illustrative sense and not read in the limiting sense.