CA1237207A - High resolution video graphics system - Google Patents

Abstract

Abstract of the Disclosure A high resolution video graphics system for use with a processor and characterized by improved memory expandability particularly in connection with color display. The high resolution video graphics system includes a video memory which is preferably comprised of a plurality of video memory planes and video counter means for providing display timing. There are basically four buses that are used with the system including a control bus, a read bus, a write bus, and an address bus. A multiplexer means is provided for receiving either video counter addresses or direct addresses from the processor. There is associated with the video memory means for converting to serial output data which the preferred embodiment includes a series of shift registers corresponding to the number of separate memory planes employed. In the preferred embodiment the system has three memory planes, each of 16k by 16 capacity. The shift register output is coupled to a high speed static palette RAM with the shift register outputs being the addresses thereto. The data outputs of the palette RAM
couple to guns on a color monitor or to the back plane in connection with black and white graphics.

Description

The present inven-tion relates in general to a hiyil resolution video graphics sys-tem. More parti-cularly, the invention pertains to such a high resolu-tion system that is adapted for display of either black and white or colour format and which is expand-able in the number of colors displayed.
~ mong the o'ojects of the present lnvention is an object to provide a new and uni~ue bus archi-tecture referred to herein as a split bus system. The split bus system in particular pertains to the system write bus which is split into a plurality of separate buses corresponding to the number of memory planes employed.
~ nother object of the present invention is to provide a high resolution video graphics system which is readily expandable in both the number of memory planes employed and memory width. The greater the number of memory planes employed the greater the number of colors that can be derived. As far as width is concerned this may be, for example in widths of 8, 16 or 32 bits.
A further object of the present invention is to provide a high resolution video graphics system interfacing with a processor to form a part of an overall computer system and in which the high resolu-tion graphics is substantially entirely transparen-t as far as the processor is concerned.
Still another object of the present inven-tion is to provide an improved high resolution video graphics system in which the number of memory addres-ses does not change with the number of memory planes ~x~o~

employed. The same number of memory addresses are used regardless of the number of memory planes that are employed.
Still another object of the present inven-tion is to provide improved memory control circuitry which is instrumen-tal in providing maximum access speed using only a relatively small number of compo-nent circuits.
To accomplish the foregoing and other objects of this inventlon there is provided a high resolution video graphics system adapted for use in a computer system employing a processor. The video portion of the system has the capability of displaying both graphics and alpha numeric characters. The system employs a unique split bus architecture. The split bus system is advantageous in reducing the total number of parts employed and also enables expand-ability of the system particularly with respect to the number of memory planes that are employed. With this technique there is provided very fast screen updates.
The split bus architecture means that there are actually a plurality of write buses. In addition to this there is also a read bus, a control bus and an address bus. The control bus couples signals from the processor to the high resolution video graphics circuitry. Typlcally, the control bus couples such signals as memory read and write signals, peripheral select signals and data ready signals. These signals are buffered and decoded to provide the proper memory timing.

.,. ~v .

~ t~ 7 The data communication between the proces-sor and the graphics memory is provided by the read and write buses. It is noted that the read bus is isolated from the write bus so that the processor may read the graphics memory while displaying data to the screen all occurring simultaneously. In order to accomplish this the write bus is preferably split from the read bus by a buffer means. The write bus split into separate write buses then couples to the memory planes. The write bus goes directly to the black and white plane which has been identified as plane 0 and is gated by bidirectional buffers splitting the bus into second and third buses for coupling to the respective buses. The address bus, which is coupled from the processor is used to read and write graphics data. The addresses for the display data since they are sequential, are generated by a scan counter which provides column and row signals. These signals are coupled to a high speed multiplexer which selects between the addresses that are coupled to the memory.
It selects between either scan counter addresses or processor generated addresses.
The system disclosed herein comprises three memory planes each of 16K by 16 capacity. The outputs of the memories are fed to 16 bit shift registers where the data is serialized. All of the shift registers operate in parallel from the common clock.
The shift registers couple to a high speed static palette RAM as the addresses to the palette RAM. The data output from the RAM goes to the respective guns on the color monitor or to the black plane for the black and white graphics if using a standard video monitor.
Numerous other objects, features and advantages of the invention should now become apparent upon a reading of the following detailed description taken in conjunction with the accompanying drawings, in which:
Figs. lA to lE show circuit details for a portion of the high resolution video graphics of the present invention;
Figs. 2A to 2D show the remainder of the detailed circuitry of the high resolution graphics system of the invention;
Fig. 3 is a timing diagram associated with the circuitry of Figs. 1 and 2;
Fig. 4 shows additional circuit details including the video display chip.
For a detailed description of the video control system of the present invention, reference is now made to the drawings which show all of the circuit elements and associated interconnections for carrying out the features of the present invention. In the drawings, the central processing unit and other parts of the overall computer system are not described in detail. However, connections are noted in the draw-ings illustrating wherein connections are made to other parts of the computer system including the central processing unit, ~LX~7~7 In a general overview, the system employs a split bus architecture to minimize the total number of componen-ts employed while at the same time providing an expandable upgrade path. This technique permits fast screen updates, on the order of 23 million pixels per second. The system employs four buses including a control bus, a read bus, a write bus, and an address bus. All of these buses intercouple with the central processing unit. The control bus contains signals from the processor which may be a type l86 processor.
These control bus signals may include such signals as memory read and write signals, peripheral select signals and data ready signals. These signals are buffered and decoded to provide proper memory timing as to be described ln further detail hereinafter.
The read bus RD-BUS and the write bus WR-BUS are the data lines to and from the graphics memory. The read bus RD-BUS is isolated from the write bus WR-BUS so that the processor may read the graphics memory while displaying data to the screen simultaneously. The write bus WR-BUS is split off from the read bus RD-BUS by a tri-state buffer. The write bus WR-BUS then passes to the three memory planes. It also goes directly to the black and white plane (plane 0), and is gated by bi-directional buffers into planes 1 and 2. Reference is made hereinafter to the aforementioned buffers and memory planes.
The address bus BUSAOO-BUSAl9 is coupled from the aforementioned 186 processor, and is used to read and write graphics data. The addresses for the ~z ~ t7 display data, since they are sequential, are generated by a 14 bit counter. A very high speed 4:1 multiplexer selects between the addresses, where they go to the memorles.
The system has three memory planes, each 16K by 16. The outputs oE the memories are fed to 16 bit shift registers, where the data is seriali~ed.
All the shift registers operate in parallel from common clocks. The shift register outputs go to a high speed static RAM as the address inputs to the RAM. The data outputs of the RAM go to the guns on a color monitor which may be a standard CM-l color monitor, or to the back plane for the black-white graphics on a VM-l monitor. Further details are described hereinafter in connection with the aforesaid operation relating to the addressing and the video shift registers and associated RAM.
Prior to initiating a detailed description of the circuitry in the drawings, reference is now

2~ made to a discussion on the design considerations associated in particular with graphics operation. In any computer graphics system, there are basically three objectives:
1. The storing of data from the host computer into the graphics memory.
2. Displaying the stored data on the monitor.

3. Retrieving stored data in the graphics memory for communication back to the host computer.
Of the above objectives, generally speak-ing, the second objective has the highest priority. Auser does not want the CRT monitor to blink rapidly, "hash" or go blank for any length of time. Thus, the display objective is relatively critical. As such, graphic systems have been designed so tha~ the host computer can access (read or write) data to the graphics memory only during certain times, so as not to disturb the CRT monitor. The common way to accom-plish this is to delegate accesses so as to allow them only during a blank time of the CRT beam; i.e. when the CRT beam is turned off. This occurs during retrace times, when the beam goes from the right side of the screen to the next line down on the left side ~horizontal retrace), or from the lower right corner of the screen to the upper left corner of the screen (vertical retrace).
Although the technique of using blank time is easy to implement, the problem is that it is relatively slow. With this technique, the processor can only access the monitor, approximately 6 ms out of a total cycle of 16.6 ms. Of course, the faster the 24 processor/graphics memory is, the more data that can be written in the 6 ms time interval. Another way to access more data is to use a wide data path; i.e.
change from an 8 bit processor to a 16 bit processor.
However, perhaps the best means of speeding up graph-ics speed is to use an interleaving technique. This is the technique used in accordance with the high resolution graphics techniques of this invention.
In connection with the objective of provid-ing a proper continuous display, the aforementioned "hash" problem happens when the host computer is trying to access data at the same time that the .

~'7 ~

graphics circuitry is loading the video shift regis-ters. This may be referred to as "memory contention";
when two different circuits essentially vie over who hdS control of the memory. The contention happens because processor access can happen virtually at any time, while shift register loading happens at a certain time frame. Thus, if the processor tries to access memory when the shift register is being loaded, the register is loaded with incorrect data (usually all ones) and the "hash" effect appears, at least for a brief instant of time on the screen.
In the interleaved technique of the present invention, the memory contention is eliminated by guaranteeing access when the shift register is not being loaded with data to be displayed. Since the shift register, once loaded, is not disturbed by the data being changed on its inputs, one can access memory while the data is being shifted out.
An interleaved memory is controlled by an 2~ interleave clock which divides the accesses up between the processor and the shift register. In the pre-ferred embodiment as described in detail hereinafter, there is provided a 50% duty cycle clock of 714 ns period. This clock, identified by the signal DISCYC*.
The interleave clock divides the accesses into two equal time slots, each of 357 ns. This means that the processor has 357 ns to access data and the shift registers have 357 ns to fetch the data to be dis-played next. This may be referred to as a 1:1 inter-leave since the time slots are equal.

~3'7 ~)7 The previously referred to two accesses arecarried out as follows. During a processor access, the 186 processor address is used as the memory address. Data is either written into memory or latched from memory. During a display access, the scan counter address is used to look up the data in all three memory planes. The shift registers are simul-taneously loaded and then control goes back to the processor.
Before considering the details of the drawings, reference is now made to timing aspects of the system. In order to provide fast memory access, a fast processor is used with a wide data path. In the disclosed embodiment, the processor may be a type 186 which is a conventional readily available processor circuit. The processor can access 16 bits of data in 500 ns. To also provide proper operation, there are used high speed RAMS of sufficient size to hold all of the pixels for a full screen. The given screen size is 640 x 400 which provides a total of 256,000 pixels.
With the use of a 16 bit processor, this translates into 16,000 16 bit words. A standard 16K RAM array, 16 bits wide can thus be used to hold all the data.
In the disclosed embodiment, the RAMS that are chosen are 16K x 4, 150 ns dynamic memories. In this regard, refer to the circuit diagram which shows these memo-ries as memory devices U2-U13. See Figs. 2A to 2C.
Each of these is of type TMS 4416-15. The cycle times of these memories is under the aforementioned 357 ns parameter.

~2~ 7 The equation for the horizontal scan frequency of the video controller is given by equation 1 :

~ number of visible scan -lines) Horizontal Scan Ereq. =
(vertical display time) (1) The system of the invention has 400 visible lines. The vertical display time is less than 16.66 ms, and depends on the size of the CRT that is being used. For a 13" tube, this time is 15.15 ms. There-fore, the horizontal scan rate is 26.403 KHz.
The next calculation is for the dot clock frequency for the video shift registers:

(number of horizontal dots) dot clock freq. = (2) (horizontal display time) The number of horizontal dots is given as 640. The horizontal display time is less than 37.87 us, which is the horizontal period. Since the SMC
9007 video display chip shown in FIG. 4 as circuit U16, which is providing the monitor signals, is character oriented, all the calculations for dot clock are based on this fact. First, the 640 dots are chosen so that 80 characters may be displayed, with each character having an 8 cell width. The CM-l and VM-l monitors require at least 2 us sync pulses; the aforementioned SMC 9007 chip can provide 8 character-wide sync pulses. Therefore, the 37.87 us horizontal time may be bro}~en down into 80 characters displayed, eight characters for sync, and 18 for blanking (also due to monitor size). This gives the active display time as 28.59 us and a dot clock frequency of 22.3854 MHz.
Because of the use of a 16 bit wide shift register, the shift register is loaded in accordance with the following.

(shift register width) S.R. load =

(dot clock frequency) As indicated previously, this load is 714 ns. A 1:1 interleave requires two time slots, each of 357 ns.
The data from the shift registers goes to a high speed static RAM referred to herein as a palette RAM. This is identified in the drawing in FIG. 2D as RAM U16 which is of type 74S189A. The palette RAM U16 holds a list of color data for the color monitor. The palette RAM has its own input addresses taken either from the shift registers or the processor and also has a data input from the processor. The output from the palette RAM U16 is a data bus to the video monitor, one data bit per gun. The CM-l monitor which is not shown in the drawings has four inputs which inputs are labeled in the drawing. These inputs are RED, GREEN, BLUE, and INTENSITY. Hence, the palette RAM U16 has four data outputs. The processor can load any of l6, four bit data values into the palette RAM, allowing any address from the shift registers to be any color.
Reference is made to this important feature and a further discussion of the details tha~ now fo]lows.

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For a discussion of the details of the hardware, reference is now made to the drawings, and in particular FIGSo lA to lE and 2A to 2D~ The de-tailed circuitry described herein basically interfaces with two units, including the processor not actually shown herein, and a video monitor also not actually shown herein. It is understood that the video monitor is of conventional design and is a color monitor. The processor has been identified previous],y as a 186 processor which is a 16 bit machine and which also is of conventional design. Interconnections are labeled in the drawing to indicate connections to and from these other components of the overall system.
The internal timing signals used in the video controller are derived from a 22.38 MHz dot clock whose output is buffered by means of the inver-ter Ul~ pins 10 and 11. ~he output of this inverter is the signal DOT CLK shown in FIG. lE. The signal DOT CLK is coupled to video shift registers and also to the high speed counter Ul9. The signal DOT CLK
couples to the clock input at pin 11 of each of the shift registers U22, U24, U26, and U28. Refer to FIG.S 2A and 2C. Similarly, the signal DOT CLK
couples to the clock input at pin 2 of the counter or divider Ul9, shown in FIG. lE.
Thus, the counter Ul9 forms part of a video divider chain. The output at pin 12 from counter Ul9 provides a divide by 8 count to give the character clock signal. The output from pin 12 of counter Ul9 couples to inverter U18, pins 8 and 9 with the output at pin 8 being the character clock signal CCLK. This signal couples to both delay line U31 and also to the gate U66 at pin 9 in FIG. lC.
The delay line U31 is of type DDU4-5200 having three separate output taps at 40 ns, 80 ns and 120 ns. The signal at pin 12 is coupled by way of inver-ter U18, pins 5 and 6 to provide the signal RAS*.
At pin 4 there is provided directly the signal MUX.
At pin 10 the signal is coupled by way of the inverter U18, pins 1 and 2 to provide the signal CAS*. The signals RAS* and CAS* are for row and column address selection, respectively. All of these signals RAS*, CAS*, MUX as well as DISCYC couple to FIG. lC.
The signal DOT CLK is also divided by 16 to provide the signal DIS CYC and the negation signal DIS
CYC* which is the aforementioned interleaving clock signal. In this regard, refer to the counter Ul9 and its output at pin 11 which directly provides the signal DIS CYC. This signal is also coupled by way of NOR gate U14 functioning as an inverter, pins 1, 2, and 3 to provide the signal DISCYC*.
The signal DOT CLK is different than a character clock signal generated from the central processing unit and is out-of-phase with this CPU
signal. Because the SMC 9007 is used to generate the monitor timing signals (horizontal and vertical sync and blankino) using the out-of-phase character clock of the processor, there is the need for special circuitry to assure that these timing signals are synchronized. A first circuit to carry this out is comprised of D flip-flop U64A. It is noted that the Q
;, - 13 -'7;~

output at pin 5 of the flip-flop U64A connects to the load input at pin 9 of the counter Ul9. The clock input to the flip-flop U64A is the signal 9007 VSYNC.
when the machine is first powered up -the master reset signal MRST- goes low for about 100 ms.
This forces the counter Ul9 to load all ~eroes to its outputs~ The Q output at pin 5 from the flip-flop 64A
stays low until the signal MRST* goes away and then a vertical sync signal is issued. The leading edge of the vertical sync signal sets the flip-flop U64A so that the Q output goes high, thus allowing the counter Ul9 to count. Because the vertical sync signal is aligned with the character clock of the SMC9007, this scheme lines up the graphics clock with the character clock; the graphics clock being the signal CCI,K taken by way of inversion at an output of the counter Ul9 as previously referred to.
However, the other signals from the SMC9007 video display chip delayed from the signal CCLK due to circuitry on the main processor board and due to part-to-part variations between different SMC9007 chips. Therefore, the monitor signals are also lined up using the four bit latch U70 shown in FIG. lA. The latch U70 is clocked by the signal DIS CYC*~ The aforementioned circuits now make all of ~he SMC 9007 signals power up in a known synchronous state.
Reference is now made to the timing diagram pertaining to memory timing signals and illustrated in FIG. 3. Reference is made to the counter Ul9 pre-viously discussed which generates, in addition to thecharacter clock and interleaving clock signals the shift register load pulse signal S/L*. It is notedthat in this regard the output of the counter at pin 15 couples by way of inverter U18 pins 12 and 13 to provide the aforementioned signal S/L*. This signal is coupled to pin 2 of each of the shift registers U20, U22, U24, U26, U28 and U38. See FIGS 2A to 2C.
This signal controls the ]oading of the respective shift registers. With regard to the timing reference has been herein before to the delay line U31. The delay line receives the character clock signal CCLK.
The dynamic RAMS U2-U13 refer to FIGS. 2A to 2C are clocked by delayed versions of the signal CCLK gener-ated from the delay line U31. The row address strobe signal RAS* is the signal CCLK inverted and delayed 45 ns. The signal MUX, which switches the 4:1 address multiplexer between row and column addresses, is the signal RAS* delayed 40 ns. The address multiplexer just referred to is comprised of multiplexer devices U34-U37 shown in FIG. lD. The column address strobe signal CAS* is the signal MUX delayed 40 ns.
In accordance with the system of this invention, in order to conserve address space, all of the memory planes occupy the same physical address space. This technique differs from previous graphic systems which had their memory planes formed as a contiguous memory block.
With regard to the operation relating to the multiple memory planes, there is provided a plane select register U56 (refer to FIG. lB) which is used to select which of the three planes is to be accessed by the processor. During display cycles, this regis-3~

ter is essentially ignored. The register U56 alsoprovides control in the event that the video shift registers are enabled. In this regard note the signal GROF* at the output pin 10 of the register U56. The register U56 also controls what video plane is accessed by the processor. In this regard, note the signal G/A* at output pin 12 from the register U56.
The signal GROF* couples to pin 1 of each one of each of the latches U21 (FIG. 2B), U23 (FIG. 2A), U25 (FIG.
2A), U27 (FIG. 2C), U29 (FIG. 2C) and U39 (FIG. 2B).
The signal G/A* couples to inverter gate S38 which in turn connects to gate U67 and pin 10 as illustrated in FIG. 2D.
When the signal GROF* is low, the shift registers are continuously loaded with O's. When the signal G/A* is high, graphic's data is displayed on the color monitor. On the other hand when the signal G/A* goes low the alpha numeric text from the SMC9007 video character display chip is displayed.
It is also noted that the signal G/A*
couples to gate FOOA at pin 2 and to gate FOOB at pins

4 and 5 as shown in FIG. 2D. The output of gate FOOA
at pin 3 couples to one input of gate FOOD. The output of gate FOOB at pin 6 couples to one input pin 9 of gate FOOC. Gate FOOC at pin 10 also receives an output from the blanking delay register U63. The register U63 at FIG. 2D is of type LS164 and is clocked from the signal DOTCLK. The output of gate FOOC at pin 8 forms the second input to the gate FOOD.
The output of the gate FOOD controls the color and intensity output gates U15A, U15B, U14A and U14B
coupled from the output of the palette RAM U16. The palette RAM is of type 74S189A.
~ s indicated previously, the high resolu-tion graphics of the system of this invention provides 640 X 400 pixels on the VM-l and CM-l video monitors.
The system has 96K bytes of high speed RAM for storage of graphics data and a user proqrammable color palette U16 for color assignment. The graphics memory is organized in a planar fashion. If two color video is desired, then plain O is installed~ Installing planes 1 and 2 provides 8 color video. AS indicated pre-viously, all three memory planes occupy -the same physical address space. Thus, to determine which of the three planes the CPU is reading or writing to there is provided the aforementioned plane select register U56 (see FIG. lB) which is set up prior to accessing the graphic's RAM.
With regard to memory organization, the memory starts at address EOOOOH in the 186 address space. This address corresponds to the upper left of the video screen. The next address is to the right.
The lower right corner is the last address. The full screen uses 32,000 bytes or 16,000 words to fully describe a single plane. The system responds to ~oth byte and word accesses. Word accesses are on even addresses only. Either the high byte or the low by-te may be transferred during byte accesses.
The graphics memory may be accessed at any time. The high resolution circuitry uses WAIT states to synchronize the data transfer between the CPU and the graphlcs memory. The average speed at which data is transferred is 16 bits per us. Each bit of the graphics memory represents a DOT (pixel) on a video screen. The MSB (most significant bit) of the byte or word is the left most pixelr The Lss (least signi-ficant bit) is the last pixel to the right.
With regard to the three planes that have been mentioned herein, reference is made to the drawing. The video RAMS U10-U13 (see FIG. 2C) are associated with plane 0. The video RAMS U2-U5 are associated with the plane 1. Finally, the video RAMS
U6-U9 are associated with plane 2. In this regard note the outputs signal POVID at pin 12 from the shift register U28. Also note the output signal PlVID from the output pin 12 from the shift register U20. Also note the output signal P2VID at the output pin 12 from the shift register U22. The signals POVID, PlVID, and P2VID couple respectively to the multiplexers U17A, U17B and U17C illustrated in FIG. 2D. Each of these multiplexers may be of type 74F257 as noted in the drawing. The video plane signals couple to the B
input of each of these multiplexers. The A inputs receive the respective signals PAl, PA2 and PA3. The signals PAl, PA2 and PA3 are directly controlled CPU
signals from the input address bus. See FIG. lA.
The outputs from the multiplexers U17A, U17~ and U17C at the respective output pins 4, 12 and 7 couple to inputs A0, Al and A2 of the palette RAM
U16 also illustrated in FIG. 2D. The palette RAM
"looks up" a color by forming an address by using the data from each installed plane. Plane 0 is palette ~ r.J ~ 13 ~J

address bit A0, plane 1 is palette address bit Al and plane 2 is palette address bit A2. Palette address bit A3 as noted in the drawin~ is tied to a high voltaqe by way of a resistor at pin 13 to the palette RAM. This maintains the A3 input to the palette RAM
at a high or one state. If a plane is not installed, the palette address bit is a 1. Therefore, if plane 0 contains a 1, plane 1 a 0 and plane 2 a 0 the palette would "look up" the color at address 1001 in the palette memory.
As indicated previously, because there are three memory planes at a maximum, there can be up to 8 colors displayed at once on the screen. The CM-l color monitor can display 15 colors. Therefore, any of the available 15 colors up to 8 at a time may be displayed.
In accordance with one feature of the present invention it is to be noted that the CPU may write the palette to change the color look up table.

The palette is located in the 186 processor I/0 space and is on word (even address) boundaries. The 186 processor uses PCS3 as the I/0 port decode for graph-ics .
As far as the programming is concerned, thepalette appears to the pro~rammer as 16 word addres-ses, starting at I/0 address 0180H. The palette is a write-only device. I/0 address 0180H is the first palette address, 0182H is the second, etc. Data is stored in the palette by data bits DO-D3. In this regard, note the inputs to the palette RAM tJ16, signals RDO-RD3 to respective pins 4, 6, 10 and 12.

The control is carried out by means of a signa] at pin 3 which is signal WR-PMS. The upper data bits are ignored. In this regard also recall that these addresses are not the addresses formed to "look up" a color or a particular pixel. Those were addresses A0-A3 shown in the diagram of the palette RAM U16.
The four data outputs from the palette RAM, signals D01-D04 are taken at respective pins 5, 7, 9 and 11.
Although a program may access the palette RAM IJ16 at any time, it is possible to generate an undesirable "tear" or horizontal bar on the screen during a palette write from the CPU. To prevent the video monitor from doing this, the palette RAM is written to only during the vertical blank time. The SMC9007 video controller has a status register which reflects the status of the vertical sync signal. Alsol the SMC9007 can provide interrupts to the CPU each vertical sync. It is up to the individual programmer which option is preferred.
With respect to the generation of colors, reference is again made to the palette RAM U16. The data in the palette RAM is tied to the video guns of the CN-l color monitor in accordance with the table below. It can be seen that the data signal DO con-trols the blue gun, Dl controls the green gun, D2 controls the red gun, and D3 controls half intensity.
A "1" for data D3 is full intensity and a "0" is half intensity. The table shows posslble colors versus data bits.
D3 D2 Dl D0 COLOR ON CM-l 0 0 0 0 black 0 0 0 1 dark blue C 0 1 0 dark green 0 0 1 1 dark yellow 0 1 0 0 dark red 0 1 0 1 dark magenta 0 1 1 0 dark cyan 0 1 1 1 gray 1 0 0 0 black 1 0 0 1 blue 1 0 1 0 green 1 0 1 1 yellow 1 1 0 0 red 1 1 0 1 magenta 1 1 1 0 cyan 1 1 1 l white Because, as mentioned previously, the three memory planes occupy the same address base, there has to be a way to determine which one of the memory planes the CPU is trying to read or write to. This is done by writing the proper data into the plane select register U56. The plane select register is I/O mapped as address 01AOH. It is write only and is 6 bits wide using data bits DO~D5. In this regard, note the 6 inputs RDO-RD5 to the data inputs DO-D5 of the select register U56. The register U56 is of type LS174. The signals RDO-RD5 are derived from the CPU data bus signals BUS D00-BUS DO5.
The plane select register U56 has basically three functions. First, it selects which plane of memory the CPU has access to. Only one plane at a time is selected. If more than one plane is selectedthen the register deselects all planes. Second, the register determines if the graphics planes are dis-played or turned off. If they are turned off, the address into the palette is 08H, i.e. the plane data is forced to a 0. This does not erase the data in the planes, but simply forces the palette address to 08H.
Third, the register determines if addresses into the palette are from the internal memory planes or from the SMC 9007 video memory.
In the following table is presented a chart for the bits contained in the plane select register U56 and their associated function.
BIT FUNCTION
0 Select plane 0 1 Select plane 1 2 Select plane 2 3 No connection 4 Graphics on/off Graphics/Alpha switch 6 and 7 No connection To select a particular plane, a "1" is in the corresponding bit while the remaining two plane selects are "0"~ If plane 1 is -to be selected, then data bits D0 and D2 contain a "0" while data bit Dl contains a "1". The graphics on/off bit which is bit D4 contains a "1" to turn on (display) the graphics data in the installed planes. A "0" forces the palette to ignore the memory plane data and display the color contained at palette address 08H corres-ponding to processor 186 I~0 0190H. The graphics/-- 22 ~

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alpha bit, namely, data bit D5, determines which data is used as palette addresses. If this bit is a "1", the high resolution memory planes are used. If this bit is a "0", the data from the SMC9007 video controller is used for displaying text on the CMl color monitor.
As indicated previously, circuitry is provided for switching between the internal memory planes or external data for use as palette addresses.
Refer to the multiplexers U17A-V17C of FIG. 2D. The external data is hard wired on the bus as the SMC 9007 video and the video attribute bit intensity. If the external mode is selected, referred to as the alpha mode, the video data is palette address A0 and the attribute bit for intensity is palette address bit Al.
Palette address bits A2 and A3 are tied high. This allows four color text to be displayed on the CM-1 color monitor.
In connection with the video RAMS, it is noted that a gated CAS* signal is used to selectively access the different memory planes. In this regard, note the signal CAS OHR (see FIG. 2A) associated with RAMS U6-U9, the signal CAS lHR (see FIG. 2D) associ-ated with RAMS U2-U5, and the signal CAS 2HR (see FIG.
2C) associated with the video RAMS U10-U13. It is also noted that all of the planes receive the signal RAS*, a common write signal VWRR* and of course also receive memory addresses. The signal CAS* couples to the memory control PAL U55 (see E'IG. lC) and is J~

selectively gated in to access memory. Planes which do not receive the signal CAS* are refreshed by the signal RAS*.
The three plane select lines from the register U56 identified as signals PP0, PPl and PP2, along with the signal CAS* go to the memory control PAL U55. Attached hereto is a logic format for the PAL U55. The device U55 is a programmable logic array programmed to send the signal CAS* to each memory plane. The nature of the signal changes but it is noted in FIG. lC that at the output of the PAL U55 there are signals CAS OH at pin 18, CAS lH at pin 16 and CAS 2H at pin 14. These signals couple to the package RP 4 (FIG. 2A) and generate corresponding signals CAS OHR, CAS lHR and CAS 2HR. It is this set of signals that controls the video RAMS as noted.
The 186 processor can do either byte or word transfers. Two status lines are provided from the processor which tell external devices, the type of transfer which is about to occur. These signals include a bus high enable signal BHE* and the address line signal PAO (see FIG. lA). The following chart shows how the lines are decoded:
PAO BHE* TRANSFER
word 0 1 byte on DO-D7 1 0 byte on D8-D15 1 1 not used Note the signal BHE* coupled to pin 6 of the PAL ~55 (FIG. lC) and -the signal PAO coup]ed to pin 7 of the 0 PAL ~55. The slgnal BHE* couples from an input latch U61 rela-ting to the CPU signal BUS BHE. The pal U55 recelves all of the aforementioned signals along with signal DIS CYC* and signal 186/SCN* and determines which plane is selected and then which of the memories receive the signal CAS*.
There are basically two instances when the signal CAS* is sent. The first is during a display cycle, when the shift registers are loaded. All three planes get the signal CAS*, or a signal derived thereErom, so that the data to be displayed can be fetched. Note that CAS* signal is thus split into upper and lower byte signals for each plane. On a word access, both upper and lower bytes go low during the time the signal CAS* is low. On a byte access, the high or low side goes low, depending on the status of the signals BHE* and PAO.
In connection with the upper and lower byte categories, note for example, with respect to the video RAMS U2-U5, the RAMS U2 and U3 receive the signal CAS IHR relating to upper bytes and the video RAMS U4 and U5 receive the signal CAS ILR relating to lower bytes. The same also applies with respect to the video RAMS U6-U9 and U10-U13. Note the signals CAS OHR; CAS 2HR, and CAS OLR; CAS 2LR.
The second instance when a CAS* signal is sent is during a processor access when the signal 186SCN* is high. Again, the PAL U55 looks at the status of the signals BHE* and PAO, but also checks the plane select register and then the proper signal ~ J~3~1 CAS* is then generated. The checking of the plane select register occurs by virtue of the inputs P0, Pl and P2 that couple from register U56 to the PAL U55.
It is noted that in addition to the column address select signals at the output of the PAL U55, there are also provided output enables for planes 1 and 2 referred to as signa]s OEl* and OE2*. These signals are used to enable the bidirectional buffers U40, U41, U43 and U44. See FIGS. 2A and 2C. Each of 10 these buffers is of type 74F245. These buffers isolate the planes from each other. Plane 0 does not need such a buffer since it is on the bottom of the write bus. This topology allows any number of addi-tional planes to be easily added. These signals go low when their associated plane is being accessed by the 186 processor. In this regard note the signal OEl*
coupled to buffers U40 and U43 (FIG. 2C) and the signal OE2* coupled to buffers U41 and U44 (FIG. 2A).
The buffers U40 and U43 along with U41 and U44 have their terminals A0-A7 coupled to the write bus (WR-BUS). This is referred to herein also as the signal W2BUS. At the terminals BO-B7 of these bi-directional buffers, are identified the signals WlDO-WlD15 associated with buffers U40 and U43 and signals WOD0-WOD15 associated with bidirectional buffers U41 and U44. It is also noted that there are provided 8 bit latches U42 and U45. Each of these is of the type 74LS374. The data side of each latch corresponding to data terminals DO-D7 couples to the write bus WR-BUS.

The Q output sides identified as outputs Q0-Q7 couples to the read bus. Note the signals RDO-RDlS coupling to the read bus signal RD-BUS.
The graphics memory starts at system address EOOOOH. Although there are three 16K memory planes, each is mapped at address EOOOOH. In this regard refer to the comparator U51 shown in FIG. lA
which is a device of type 74LS85 having A inputs A0-A3 and B inputs BO-B3. The input BO is tied to ground and inputs Bl-B3 are tied to a positive voltage. The address lines PA16-PAl9 are coupled to the respective AO-A3 inputs of the comparator. Thus, the comparator 51 looks at the addresses and issues a valid graphics memory address when an "E" is detected on the upper address lines. Also, the comparator is gated by the signal EQIN which is generated by the logic array U69 shown in FIG. lB. The array U69 may be of type 825153 and may be a programmable array logic. The comparator U51 is gated by the signal EQIN so that the false accesses are blocked when the SCM9007 controller is transferring video in memory.
When a valid address is detected, the array U69 determines if a read or write is requested.
Depending on the access, the signal BUFDIR* switches the data bus buffers U57 and U58 of FIG. lB to the correct direction. Note the signal BUFDIR* at pin 17 at the array U69 coupling to pin 1 of the bidirec-tional data buffers U57 and U58. Also note the signal BUFEN* at the output pin 18 of the logic array U69.
This signal enables the data bus for the access. This signal couples to the enable input at pin 19 of the buffers U57 and U58. The logic array U69 then assertsthe signal MACC, signifying a valid memory access is requested. This signal couples to the memory arbi~
trator flip-flop U48 ~FIG. lC) and also couples to gate U46 at pins l and 2.
The memory arbitration logic is comprised of two flip-flops U48 and U64. The flip-flop U48 is a J-K flip-flop of type LS73. Flip-flop U64 is a clocked D-type flip-flop of type F74. The assertion output of the fllp-flop U64 is the signal DATA-RDY.
The data input to the flip-flop U64 at pin 12 is the signal PUP which is taken from the counter Ul9 of FIG.
lE. The flip-flop U64 is clocked at pin ll from the output of the gate U66 at pin ll. The J-K flip-flop U48 has at its assertion output at pin 12 the signal 186/SCN*. The K input to the flip-flop U48 is grounded and the J input is the signal MACC pre-viously referred to. The flip-flop U48 is clocked from the outpu of gate U30 at pin 8. The gate U30, pins 8, 9 and lO determines when the shift registers are loaded.
The assertion output of the flip-flop U48 also connects to gate U30 at pin 2 with the output of gate U30 at pin 3 being the read latch signal RDLTH.
The negation output from the flip-flop IJ48 couples to gate U66 at pin 5. The other input to the gate U66 at pin 4 receives a signal VMWR*. The output from the gate U66 a-t pin 6 is the signal VWR*. This signal controls, inter alia, the buffers U59 and U60 also depicted in FIG. lC. The gate U66 pins 4-6 assumes that the signal VWR* is asserted only upon a write request. In connection with the memory arbi-tration circuitry, it is also noted that the gates U66 pins 8-10 and U66 pins 11-13 determine the end of access and involve a resetting of the flip-flop tJ48. The output of the gate U66 at pin 11 also clocks the flip-flop U64.
The system of the invention uses a "data ready" handshake scheme for external memory. In this technique the 186 processor automatically goes into a WAIT state after requesting access. It is then up to the external memory to assert the signal ARDY when the access is completed. The processor then goes Ollt of the WAIT state, and -the external device clears the data-ready signal before the next processor 186 memory cycle.
FIG. lC also shows the AND gate U30 pins 4 and 5 as inputs and pin 6 as an output. l'his gate senses whether the signal DISCYC is low thus signify-ing tha~ the shift registers have been loaded and a processor access can now occur. As soon as the signal DISCYC goes low, the flip-flop U48 at pin 1 clocks the signal MACC which appears at pin 14 and which is high to the Q output of flip-flop U48 at pin 12. This makes the signal 186/SCN at the output pin 12 go high which switches the address multiplexers U34-U37 (FIG.
lD) from the scan counter addresses to the processor addresses and similarly, the Q* output of the flip-flop U48 at pin 13 goes low, which enables the video writes signal, VWR*. The gate U66 pins 4, 5 and output pin 6 makes sure that the signal VWR* is asserted only if a write has been requested. Also, 7~7 the Q output of pin 12 from -flip-flop U48 is gated with the signal RAS* to form the read latch signal RDLTH which clocks the two 8 bit latches on the read bus, namely latches U42 and U45. Note the input clock signal at pin 1 which is a signal RDLTH coupling to both 8 BIT latches U42 and U45 (E`IG. 2C). These latches may be of type 74LS374.
It is noted that the address multiplexers U34-U37 each have A and B inputs. The aEorementioned signal 186/SCN* is coupled in common to all of the B
inputs of these multiplexers. When this signal is high it switches the multiplexers from the scan counter addresses to processor generated addresses.
The input A inputs are tied in common from the signal MUX. In this regard the RO-R7 signals and CO-C5 signals are the scan counter signals and the processor generated addresses are the PAl-PA14 addresses. By way of example, with respect to the multiplexer U35 pins 5 and 6 along with pins 10 and 11 receive scan counter addresses and pins 3 and 4 along with pins 12 and 13 receive processor generated addresses. From the multiplexers the signals are identified as signal VA4 at pin 9 and VA5 at pin 7. Similar arrangements occur with respect to the other multiplexers U34, U36 and U37.
The end of an access is basically deter-mined by the gates U66, pins 8-10 and 11-13. The end of an access is determined when the signals CCLK and MUX are both low. When this occurs, the flip-flop U64 is clocked from the output of gate U66 at pin 11 thus asserting the data ready signal DATA-RDY. This signal r ~ t~

is driven to the bus in an inverted state by opencollector driver U67, pins 1-3 shown in FIG. lA. The control then waits until the processor acknowledges the access. The signal MACC then goes low after the access, which clears the flip-flop U64 by way of gates U46, pins 1-3 and U46 pins 4-6. This then drops the data ready signal DATA-RDY. The cycle is now completed and the logic is ready for the next request.
Additional circuitry described in the drawings is concerned with displaying the graphics on the CRT monitor. As mentioned previously, the graph-ics planes are mapped to the screen so that the upper left corner of the monitor is address EOOOOH, with increasing addresses going to the right. To synchro-nize the display properly, there is provided a scan counter (FIG. lD) which is composed of four separate counters U32, U33, U49 and U50. Each of these coun-ters may be of type 74F161. These counters have a clock input at pin 2, a load input at pin 9 and a clear input at pin 1. The clock input is the signal SCNCLK taken from NAND gates U46 pins 8-10 and pins 11-13. The signal SCNCLK is derived from the signal CBLANK* and also from the two inputs to the gate U30 at pins 4 and 5, namely, the signals MUX and DISCYC*.
The output of gate U30 at pin 6 couples to pin 12 of gate U46. Gate U46 at pins 9 and 10 are tied together and this gate functions as an inverter with the output at pin 8 being the signal SCNCLK for clocking the scan counter.

The scan counter is reset each vertical retrace from the flip-flop U48A at its Q output, pin 8. The flip-flop U48A is of type LS73 and is a J-K
flip-flop. The J input is tied to a positive voltage and the K input is tied to ground. The clock input at pin 5 to the flip-flop U48A is the signal VSYNC*. The output from the flip-flop U48A at pin 8 ties to the clear inputs of each stage of the scan counter at pin 1. Thus, the vertical sink signal VSYNC* clears the counters to scan address O corresponding to processor address EOOOOH until the signal CBLANK goes low thereby clearing the flip-flop U48A. Note the signal CBLANK coupling to the reset input of the flip-flop U48A.
The siqnal CBLANK is the composite blank signal, and is low during active display time.
The scan counters U32, U33, U49 and U50 are clocked by the signal DISCYC* gated by the signal MUX
and the signal CBLANK*. This clocking signal is the aforementioned signal SCNCLK. The gating occurs by way of the aforementioned gate U46 pins 8-10, gate U46 pins 11-13 and gate U30 pins 4-6. This clocking assures that the counters advance during active display times. The scan counters produce 8 row outputs RO-R7 corresponding to the scan counters U32 and U33. The outputs RO-R3 are from the counter U32 and the outputs R4-R7 are from the counter U33. The scan counter also produces six column outputs CO-C5.
The output CO-C3 are taken from the counter U50 and the output C4 and C5 are taken from the counter U49.

. , ~ ~ ~ 4y~",Q~OEl The row ou-tputs RO-R7 along with the column ou-tput CO-C5 couple to the 4:1 multiplexer which is comprised of multiplexer circui-ts U34-U37.
As noted in the drawing, the row outputs couple as follows. Signals RO and Rl to multiplexer U37, signals R2 and R3 to multiplexer U36, signals R4 and R5 to multiplexer U35 and signals R6 and R7 to multiplexer U34. With respect to the column outputs, output CO couples to multiplexer U37, outputs Cl and C2 couple to multiplexer U36, outputs C3 and C4 couple to multiplexer U35 and output C5 couples to multi-plexer U34. The column and row outputs always couple to the O and 1 inputs of these multiplexers either at pins 5 and 6 or at pins 10 and 11. These are the sean eounter inputs to the multiplexers. The processor inputs are at pins 3, 4, 12 and 13. These column and row outputs from the scan counter address the graphics memory during display cycles. The outputs from the multiplexers are identified as signals VAO-VA7. These signals couple to the package RP3 (FIG. 2A) shown in the drawing and the outputs therefrom are converted to signals VAOR-VA7R eouple to the graphies memory.
I'he graphies memory is comprised of 12 dynamie RAMS. Eaeh dynamie RAM is of type TMS 4416-15 and eaeh is a 16K by 4 dynamic RAM. The graphics memory is arranged in three planes. The first plane is eomprised of RAMS U10-U13 (FIG. 2C) the seeond plane is comprised of RAMS U2-U5 lFIG. 2B) and the third plane is comprised of RAMS U6-U~ (FIG. 2A). The plane O is the black and white plane and as mentioned is comprised of RAMS U10-U13. The other memory planes 7~

are added to upgrade to color. Each plane has four RAMS and also comprises two latches of type 74LS273 and also two shift ,registers of type 25LS22. Thus, the plane 0 has latches U27 and U29 and shift registers U26 and U28. The plane 1 has latches U21 and U39 and shift registers U20 and U38. The plane 2 has latches U23 and U25 and shift registers U22 and U24. The latches of type 74LS273 have a clock input which receives the signal LD-VID. These latches also receive the signal GROF*. The shift registers are loaded by means of the signal S/L*. The output plane video signals are taken at pin 12 of one of the shift registers of each pair. Thus, the signal POVID is taken at pin 12 of shift register U28. The signal PIVID is taken at the output pin 12 of the shift register U20. The signal P2VID is taken at the output pin 12 of the shift register U22. These signals POVID, PlVID and P2VID couple to the multiplexers U17A, U17B and U17C. These multiplexers also receive processor addresses PAl, PA2 and PA3, respectively.
In addition to the latches and shift registers, there are also provided bus isolation buffers U40,U41 and U43,U44. These buffers are associated only with planes 1 and 2. I-t is noted that the write bus (signal WR-BUS) couples directly to the latches U27 and U29. However, the write bus couples by way of bus isolation buffers U40 and U43 to the bus Wl-BUS, and also couples by ~ay of bus isolation buffers U41 and U44 to the bus W0-BUS. The bus 30 isolation buffers U40,U41 and U43,U44 are necessary because during display cycles all three planes are simultaneously reading data out of their memories into the latches, therefore, each plane needs a dedicated path to its associated latches. Also, the particular type of RAM used has common I/0 pins, so data input from the processor cannot be separated from the data going to the latches.
The memory latches such as the latches U27 and U29 of plane 0 hold the data until the shift registers are empty. After 16 pixels have been shifted out, the signal S/L* goes low and the data in the latches are loaded into the shift registers. The OUtpllt of the shift registers go to a 2:1 multiplexer U17 comprised of separate multiplexer circuits U17A, U17B and U17C. These are the aforementioned signals POVID, PlVID and P2VID coupling respectively to the B
inputs of the multiplexers U17A, U17B and U17C.
The multiplexer selects which address lines go to the palette RAM U16. It selects between pro-cessor information represented by the signals PAl, PA2 and PA3; and shift register data as represented by the signals POVID, PlVID and P2VID.
In connection with the multiplexers U17A, U17B and U17C it is noted that control is provided from the signal WR-PAL*. This signal is normally high and thus the shift register outputs form the palette address. However, during palette writes, when the 186 processor assigns colors, the signal WR-PAL* goes low, switching the multiplexer to the processor 186 addresses. In this regard also note the signal WR-PM*
which controls the read/write operation of the palette RAM U16.

J~ ~

Associated with the multiplexers U17A-U17C
is a buffer that permits direct character data from the 9007 vide~ controller. In this regard, note the signals AGVID and AINT in FIG. 2D. These signals couple to the drivers Ul at respective pins 5 and 12.
These drivers are enabled from a signal at the output of the gate U67 at pin 8 derived from the graphics/-alpha numerics signal G/A* under control of the signal WR-PAL which is the assertion of the signal used for control of the multiplexers.
The multiplexer comprised of multiplexer circuits U17A-U17C has tri-state outputs, so that a video from the central processor can be used instead of the graphic data. This allows four color text on the CM-l monitor. The 9007 video in attribute BIT for intensity can be routed to the palette RAM U16 by buffer Ul which is comprised of four drivers, pins 1-3, pins 4-6, pins 7-9, and pins 11-13. This routing of the 9007 video to the palette RAM is controlled by the status of the graphics/alpha numerics line, namely signal G/A*. Also, the buffer Ul can send the data from plane 0 to the CPU if desired. Note the signal POVID coupling to the gate U30 at pin 12 which can couple by way of the buffer U1 pins 2 and 3 to the signal line AGVID.
The outputs of the palette RAM U16 pins 5, 7, g and 11 corresponding to data outputs D01-D04 couple to video line drivers U14A, U14B and U15A-U15D.
Blanking is also provided at these drivers U14 and U15 by means of NAND gate circuitry including gates FOOA

and FOOD and the blanking delay device U63. The blanking is selected by the discrete 2:1 multiplexerU47 which is comprised of the aforementioned gates FOOA-FOOD. The blanking is selected so that either the aligned composite blank for graphics is used or the original blanking delayed 8 DOT clocks for text is used. Note that there is associated with the multi-plexer U47 a shift register U63 which i.s of type LS164 and which is used to delay the original blanking signal which is the signal 9007 BLANK shown on the drawing and inputted into the shift register U63. The signal DOTCLK controls the clocking of the blankinq shift register U63.
Ha~ing now described a preferred embodiment of the present invention, it should now be apparent to those skilled in the art that numerous other embodi-ments are contemplated as falling within the scope of this invention as now defined by the appended claims.

Claims (31)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A high resolution video graphics system comprising a processor having a control bus, a read bus, a write bus, and an address bus, said video graphics system comprising; video memory means having address lines and data lines, video counter means adapted to generate video divider signals for row and column selection, multiplexer means, means coupling the output of the video counter means to a first input of said multiplexer means, means coupling address signals from said processor to a second input of said multiplexer means, means coupling the output of said multiplexer means to said video memory means for providing address inputs at said address lines of said video memory means, and means coupled from said data lines of said video memory means to convert to a serial output signal for control of a video monitor.

2. A video graphics system as set forth in claim 1 wherein said video memory means comprises multiple memory units with the address inputs thereto tied in common to each memory unit.

3. A video graphics system as set forth in claim 2 wherein said video memory means comprises a video random access memory.

4. A video graphics system as set forth in claim 3 wherein said write bus is separated into separate write buses corresponding to the number of memory units.

5. A video graphics system as set forth in claim 1 including latch means for isolating the write bus from the read bus.

6. A video graphics system as set forth in claim 5 wherein said write bus is separated from the read bus by isolation buffers.

7. A video graphics system as set forth in claim 1 including means for receiving the write bus and means for separating the write bus into a number of separate write buses corresponding to the number of memory planes employed.

8. A video graphics system as set forth in claim 7 wherein said means for separating the write bus comprises tri-state buffer means.

9. A video graphics system as set forth in claim 1 wherein said video counter means comprises a scan counter having multiple bit row outputs and multiple bit column outputs.

10. A video graphics system as set forth in claim 9 wherein said means coupling from the video counter means to the multiplexer means comprises conductor means.

11. A video graphics system as set forth in claim 10 wherein said multiplexer means comprises a plurality of separate multiplexer circuits.

12. A video graphics system as set forth in claim 11 wherein said scan counter is controlled from a vertical synchronization signal.

13. A video graphics system as set forth in claim 1 wherein said means for converting to serial output comprises shift register means.

14. A video graphics system as set forth in claim 1 wherein said means for converting comprises a like plurality of shift register means for providing multiple serial outputs.

15. A video graphics system as set forth in claim 14 including a multiplexer circuit for receiving the outputs from said shift register means and receiving a second input thereto from the address bus.

16. A video graphics system as set forth in claim 15 further including a palette RAM means and means coupling the output of said multiplexer circuit to said palette RAM means address inputs.

17. A video graphics system as set forth in claim 16 wherein said multiplexer circuit is controlled so as to couple to the palette RAM means either processor addresses or shift register generated addresses.

18. A video graphics system as set forth in claim 17 further including multiple output lines from said palette RAM means including color generating lines and an intensity line and further including output driver means for coupling these signals to a color video monitor.

19. A video graphics system as set forth in claim 1 wherein said video memory means comprises a plurality of memory planes each having the same address coupled thereto and thus being expandable so as to provide any number of separate memory planes.

20. A video graphics system as set forth in claim 1 wherein said video memory means comprises a plurality of video memory planes having the same number of addresses coupled thereto regardless of the number of planes employed.

21. A video graphics system as set forth in claim 1 including memory control means for the generation of timing signals for controlling said video counter means.

22. A high resolution video graphic system comprising a processor having a control bus, a read bus, a write bus, and an address bus, said video graphics system comprising; video memory means having address lines and data lines, video counter means adapted to generate video divider signals for row and column selection, signal steering means including first and second inputs, means coupling the output of the video counter means to the first input of said signal steering means, means coupling the address signals from said processor to the second input of said signal steering means, means coupling the output of said signal steering means to said video memory means for providing address inputs at said address lines of said video memory means, and means coupled from said data lines of said video memory means to convert to a serial output signal for control of a video monitor.

23. A video graphics system as set forth in claim 22 wherein said signal steering means comprises a multiplexer means.

24. A video graphics system as set forth in claim 22 wherein said video memory means comprises multiple memory units planes.

25. A video graphics system as set forth in claim 22 wherein said video counter means comprises a scan counter having multiple bit row outputs and multiple bit column outputs, said means coupling from the video counter means to the multiplexer means comprising conductor means and wherein said scan counter is controlled from a vertical synchronization signal.

26. A video graphics system as set forth in claim 22 wherein said means for converting comprises a like plurality of shift register means for providing multiple serial outputs.

27. In a high resolution video graphics system comprising a processor having a control bus, a read bus, a write bus, and an address bus, a method of coupling signals for control of a video monitor comprising the steps of: providing a video memory means having address lines and data lines, providing a video counter means adapted to generate video divider signals for row and column selection, providing a signal steering means having first and second inputs, coupling the output of the video counter means to the first input of said signal steering means, coupling the address signals from said processor to the second input of said signal steering means, coupling the output of said signal steering means to said video memory means for providing address inputs at said address lines of said video memory means, and coupling the data lines of said video memory means to convert to a serial output signal for control of the video monitor, said signal steering means including first multiplexer means and said coupling to convert to a serial output including second multiplexer means.

28. A method of control for high resolution video graphics comprising a processor having a control bus, a read bus, a write bus, and an address bus, said method comprising the steps of, providing a video memory means having address lines and data lines, providing video counter means adapted to generate video divider signals for row and column selection, providing multiplexer means, coupling the output of the video counter means to a first input of the multiplexer means, coupling address signals from said processor to a second input of said multiplexer means, coupling the output of said multiplexer means to said video memory means for providing address inputs at said address lines of said video memory means and coupling from said data lines of said video memory means to convert to a serial output signal for control of a video monitor.

29. A high resolution video graphics system comprising a processor having a control bus, a read bus, a write bus, and an address bus, said video graphics system comprising; video memory means having address line and data lines, video counter means adapted to generate video divider signals for row and column selection, multiplexer means, means coupling the output of the video counter means to a first input of said multiplexer means, means coupling address signals from said processor to a second input of said multiplexer means, means coupling the output of said multiplexer means to said video memory means for providing address inputs at said address lines of said video memory means, and means coupled from said data lines of said video memory means to convert a serial output signal for control of a video monitor, said write bus being separated into separate write buses corresponding to the number of memory planes, latch means for isolating the write bus from the read bus, said write bus being separated from the read bus by isolation buffers, video memory means comprising a plurality of memory planes and said means for converting comprising a plurality of shift register means for providing multiple serial outputs, a multiplexer circuit for receiving outputs from said shift register means and receiving a second input thereto from the address bus, including a palette RAM
means and means coupling the output of said multiplexer circuit to said palette RAM means address inputs.

30. A video graphics system as set forth in claim 29 wherein said multiplexer circuit is controlled so as to couple to the palette RAM means either processor addresses or shift register generated addresses.

31. A video graphics system as set forth in claim 29 further including multiple output lines from said palette RAM means including color generating lines and an intensity line and further including output driver means for coupling the signals to a color video monitor.