JPH0562350B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a display controller used for computer terminals, video games, and the like. [Prior art] In recent years, under the control of a CPU (central processing unit),
Various display controllers have been developed that display moving images and still images on the screen of a CRT (cathode ray tube) display device. FIG. 1 is a block diagram showing the configuration of a color display device using this type of display controller a. In this figure, b is a CPU, and c is a ROM (read-only memory) in which programs used in the CPU and b are stored. ) and RAM (random access memory) for data storage, d is VRAM
(video RAM), e is a CRT display device. In this color display device, CPU・b is
First, still image data and moving image data to be displayed on the display screen of the CRT display device e are sequentially output to the display controller a. Display controller a sequentially processes the supplied data.
Write to VRAM・d. Next, when CPU b outputs a display command to display controller a, display controller a receives this command, reads the still image data and video data in VRAM d, and displays them on the display screen of CRT display device e. . By the way, in this type of display device, for example, when you want to move a still image displayed in area R1 of the display screen shown in FIG. 2 to area R2, or when you want to display a still image stored outside the display area, There are often cases where you want to transfer data to an area. In such cases, the VRAM typically used
If an external memory for expansion is provided in addition to the above, the space in the non-display area will be expanded when exchanging image data between the display area and the non-display area.
A large amount of image data can be stored in the non-display area, which is extremely effective. However, in the above case, it is difficult to decide whether to set the source or destination in VRAM or external memory, or to set the source and destination in VRAM, or to set the source and destination in external memory. It is necessary to control switching each time, depending on the data transfer mode, such as whether to set the This problem arises. In addition, if the CPU can directly access external memory that can be accessed by the display controller as a source or destination area, data transfer and display control modes will increase, resulting in various display effects. It is convenient to play. For example, if the data in the external memory is rewritten by the CPU and then transferred from the external memory to the VRAM after this rewriting, the image on the display screen can be instantly changed. [Object of the invention] This invention was made in view of the above circumstances,
The purpose is to provide a display controller that can easily specify VRAM and external memory as source and destination areas as appropriate, and that allows a CPU to access the external memory as appropriate. [Characteristics of the Invention] In order to achieve the above-mentioned object, the present invention includes an expansion memory whose address input terminal is connected to an address bus for display memory, and a source area and a destination area by the central processing unit. is specified, and a command processing circuit that transfers the color code between the specified areas or between the specified area and the central processing unit, and the source area is set to either expansion memory or display memory. and whether the destination area is set to expanded memory or display memory, and whether the central processing unit accesses via the display controller is set to display memory or expanded memory, respectively. A memory selection data storage means into which designated information is written; and, based on the contents of the memory selection data storage means, either the display memory or the expansion memory at the time of accessing the source area and the time of accessing the destination area. The present invention is characterized in that it includes strobe signal switching means for switching and supplying a memory address strobe signal to the memory address strobe signal. [Embodiment] FIG. 3 is a block diagram showing a schematic configuration of a color display device to which a display controller (hereinafter referred to as VDP) 1 according to an embodiment of the present invention is applied, and in this figure, 2 is a CPU;
3 is a memory, 4 is a VRAM, and 5 is a CRT display device. In VDP1, image data processing circuit 1
0 reads the still image data and video data in the VRAM 4 via the interface 11 in accordance with the scanning speed of the screen of the CRT display device 5, and also sends a synchronization signal SYNC necessary for scanning the screen to the CRT display device 5. Output. In this case, the still image data and the moving image data each consist of a color code (2, 4, or 8 bits) that specifies the color of a dot on the display screen, and the image data processing circuit 10 converts the read color code into a color palette 12. Output to. The color palette 12 converts the supplied color code into an RGB (red, green, blue) signal and supplies it to the CRT display device 5. In addition, the image data processing circuit 10 processes the image data supplied from the CPU 2 via the interface 13 during the non-display period of the screen (vertical retrace period, etc.).
, write to VRAM4, and then write to VRAM4.
4, and when CPU2 directly accesses
VRAM4 or external RAM (DRAM) for expansion
17, a signal S1 is supplied to the command processing circuit 15 to notify that it is being accessed. In this case, VRAM4 (or
Access to the DRAM 17) is prioritized in the order of image data processing circuit 10, CPU 2, and command processing circuit 15, and the image data processing circuit 10 accesses the CPU 2 at a predetermined timing when it is not accessing itself. Outputs the signal TAC to allow access. Further, the image data processing circuit 10 can access only the VRAM4, and the CPU 2 and the command processing circuit 15 can access the VRAM4.
4 and DRAM 17 are both accessible.
And CPU2 is VRAM4 or DRAM17
When accessing directly, write the row address and column address in sequence to the access control unit 13a provided in the interface 13,
Next, these address data, a row address strobe, and a column address lobe CAS are outputted to determine the access address, and then data transfer is performed via the interface 13.
Note that in FIG. 3, the row address strobe output from the access control unit 13a is not shown; however, this row address strobe is
and is directly supplied to the DRAM 17. This also applies to the image data processing circuit 10 and the command processing circuit 15, so these row address strobes are omitted from illustration. Also, CDB shown in Figure 3 is a common data bus, and CAB
is a common address bus. In addition, the command processing circuit 15 receives from the CPU 2,
This circuit performs processing corresponding to various commands supplied via the interface 13, and its details are shown in FIGS. 8 and 9. Next, still image display in this embodiment will be explained. In this embodiment, multiple still image display modes are set, which can be roughly divided into 8×8
Alternatively, the mode is divided into a pattern mode in which a pattern of 8×6 pixels is appropriately selected and displayed on the display screen, and a dot map mode in which colors are individually specified for all dots making up the screen. In this case, since the pattern mode is substantially the same as the processing of a conventional display controller, its explanation will be omitted, and only the dot map mode will be explained. In this example, the dot map mode includes:
There are four modes: G, G, G, G.
The correspondence relationship between the still image data in the VRAM 4 and the display position in each mode is as follows. G mode This G mode is 256
The screen has a screen configuration of 192 x 192 dots, and the color codes of all the dots making up this screen are stored in the still image data area 4a of the VRAM 4 shown in FIG. The color code in G mode is composed of 4 bits, and this color code is applied to the still image data area 4 in the order shown in C of the same figure.
It is stored in a. In other words, at address 0 of VRAM4, there is a color code of a dot whose (x coordinate, y coordinate) is (0,0) on the display screen and (x, y coordinate).
A dot color code with y) of (1,0) is stored, and a (2,0) color code and a (3,0) color code are stored at address 1, respectively. The same applies below. Furthermore, since the color code in this G mode is 4 bits, up to 16 colors can be specified per 1 bit. Further, the capacity of the still image data area 4a is required to be 24,576 bytes as shown in the figure. Area 4c in VRAM 4 is an area where various data necessary for displaying moving images are stored, and area 4b is a reserve area.
In this case, the spare area 4b is allocated to a contiguous address of the still image data area 4a, and can store a color code for still image display as required. G mode This G mode is 512
The screen has a screen configuration of ×192 dots, and the color codes of all dots are stored in the still image data area 4a as in the G mode. The color code in the G mode is composed of 2 bits, and four color codes are stored at each address in the still image data area 4a in the order shown in FIG. Further, the capacity of the still image data area 4a is required to be 24,576 bytes, similar to the G mode.
This means that in G mode, the number of dots in the x-axis direction is G.
This is because the number of bits of the color code is 1/2 that of G mode, although it is twice that of G mode. Since the color code is 2 bits, up to 4 colors can be specified for 1 bit. Note that areas 4b and 4c in the VRAM 4 are the same as in the G mode. G mode This G mode is 512
It has a screen configuration of ×192 dots, and the color code is made up of 4 bits like the G mode. As a result, the capacity of the still image data area 4a is 49,152 bytes, which is twice that of G mode (FIG. 2), and the order of color codes in the still image data area 4A is shown in FIG. It's becoming like that. G mode In this G mode, the color code is 8.
It consists of bits, and as a result, 256 colors can be specified for one bit on the display screen. Also, the screen configuration is as shown in Figure 7 A.
The size of the still image data area 4a is 256×192 dots, and the capacity of the still image data area 4a is 49152 bytes, similar to the G mode. And still image data area 4
The color codes in a are stored one at each address as shown in FIG. 7c. Next, details of the command processing circuit 15 will be explained. This command processing circuit 15 is a circuit that decodes various commands supplied from the CPU 2 and processes data corresponding to the decoding results. CPU2
The commands supplied from the controller are broadly classified into a high-speed move command group and a logical move command group. The high-speed move command is a command that instructs to transfer a color code in units of bytes, and the logical move command is a command that instructs to transfer color codes in units of dots. Furthermore, each command has an 8-bit configuration, and the upper 4 bits are a data processing command,
The lower 4 bits are used for logical operation (below)
(abbreviated as LOP) command. in this case,
The data processing instruction is an instruction for instructing the type of data processing, and the LOP instruction is an instruction for instructing to perform transparency processing and logical operation, which will be described later, when transferring a color code. Note that the high-speed move command does not include the LOP command (lower 4
bit becomes “0”). FIG. 8 is a block diagram showing the configuration of the command processing circuit 15. In this figure, 19 is a CPU bus (hereinafter referred to as CBUS), which is connected to the CPU 2 via an interface 13 (FIG. 3). 20 is a command register in which commands supplied from the CPU 2 are stored, and the upper 4 bits (data processing instructions) of this command register 20 are decoded by a command decoder 21 and then stored in a microprogram ROM (hereinafter referred to as μ program ROM). 22, a jump control 23, and a high-speed move detection circuit 24. The μ program ROM 22 stores a plurality of microprograms corresponding to various commands, and the microprogram selected by the output signal of the command decoder 21 responds to the count up of the count output OT2 of the program counter 25. The μ instruction decoder (hereinafter abbreviated as μID) 2 is read out sequentially.
6. μID26 is μ program ROM
Three-step instructions are created based on the instructions read from the program counter 22, and each of these instructions is sequentially decoded and output in accordance with the count up of the count output OT1 of the program counter 25. The output signals are supplied to an arithmetic and register circuit (hereinafter abbreviated as ARC) 27 as a control signal group CONT. Also, μID26 is μ program ROM2
control signal based on the instruction read from 2.
Create and output VAS, JMP1, JMP2, TS, and TD. The program counter 25 outputs its count.
OT1 is ternary, OT2 is hexadecimal, and
The count output OT2 is incremented by 1 every time the count output OT1 completes one cycle. Furthermore, the terminal CK of the program counter 25 is a clock input terminal.
R is a reset terminal, PS is a preset terminal,
C is a count interruption terminal. 28 is a VRAM access controller, which performs the processing described below. If the instruction output from the μ program ROM 22 is an instruction that requires access to the VRAM 4, the μ ID 26 transfers the signal VAS to the VRAM 4.
The data is supplied to the access controller 28. VRAM
The access controller 28 determines whether the signal S1 is being output when the signal VAS is supplied.
(In other words, the image data processing circuit 10
If the signal S1 is output, the signal S3 is sent to the program counter 25.
is supplied to terminal C of the program counter 25 to interrupt the counting operation of the program counter 25. As a result, μID26
cannot move on to instruction analysis processing, and enters an access standby state. On the other hand, if the signal S1 is not output, the VRAM access controller 28 does not output the signal 3, and as a result, the μID 26 can immediately proceed to the instruction analysis process, and access to the VRAM 4 is executed. In this way, VRAM
In the access controller 28, the command processing circuit 15 and the image data processing circuit 10 are both VRAM.
This is a circuit that gives priority to the access of the image data processing circuit 10 and temporarily interrupts the processing of the command processing circuit 15 when the access of the command processing circuit 15 is required. Next, the jump controller 23 controls jump destination addresses for various jump instructions in the microprogram.
It has FF2. In this case, the flip-flop FF1 is connected to the operation result discriminating circuit 41 in the ARC27.
(See Figure 9) Signals output from <->, <0
>, <256>, <512> (the meanings of these detection signals will be explained later) and the signal
JMP1, and flip-flop FF2 is set by either signal <-> or <0> and signal JMP2 (the reset signal paths for FF1 and FF2 are complicated to explain). (omitted from illustration to avoid problems). The jump controller 23 operates on flip-flops FF1 and FF2.
A jump destination address is created based on the state of , the value of the count output OT2, and the output signal of the command decoder 21, and this jump destination address is output to the preset terminal PS of the program counter 25. When the jump destination address is supplied to the terminal PS, the program counter 25 outputs this address as a count output OT2, and as a result, the processing of the microprogram being executed shifts to the instruction at the jump destination address. Based on the output signal of the command decoder 21, the high-speed move detection circuit 24 detects whether the command currently being processed is a command belonging to the high-speed move command group, and detects that the command is a high-speed move command. Then, the signal S2 is sent to the image data processing circuit 10.
Output to. The image data processing circuit 10 receives a signal
While S2 is being supplied, video display processing is prohibited. That is, in the high-speed move command, the command processing circuit 15 can also access the VRAM 4 using the time slot assigned to the moving image processing of the image data processing circuit 10. Next, the LOP decoder 30 decodes the data (LOP command) in the lower 4 bits of the command register 20, and supplies the decoding result to the ARC 27 as a signal LOPS. Reference numeral 31 denotes a mode register, into which data specifying one of the aforementioned dot map modes G to G is written by the CPU 4. The output of this register 31 is supplied to the ARC 27 as data MOD. 32 is an argument register. This argument register 32 is an 8-bit register as shown in FIG.
One-bit data MXS, MXD, and MXC are written into the fifth and sixth bits by the CPU 2, respectively. The outputs of the second and third bits of this register 32 are supplied as data ARD to the ARC27, and the outputs of the fourth to sixth bits are respectively controlled by AND gates AN1, AN2 and switch means SW2 as shown in FIG. It is supplied to terminal d. In this case, the switch means SW2 selects the output terminal a when a "1" signal is supplied to the control terminal d, and selects the output terminal b when a "0" signal is supplied. Note that the functions of data MXS, MXD, MXC, and DIRY will be explained later. Reference numeral 33 is a flag register in which various flags are set. Setting and resetting of each flag is performed by a flag control circuit 34, and the contents of this flag register 33 are as follows.
Output to CBUS19. Next, the ARC27 will be explained. This ARC
27, 10 registers SX, as shown in FIG.
SY...LOR, address shifter 43, addition/subtraction circuit 44, data shifter 45, LOP unit 40, operation result determination circuit 41, CBUS 19
, IBUS (internal bus) 47, and VDBUS (VRAM
data bus) 48 and VABUS (VRAM address bus) 49. register sx
... Each LOR has a load terminal, an output buffer, and an output control terminal that controls enabling and disabling of the output buffer, and each of the LORs has a control signal group CONT (eighth
The specific control signals in Figure) are provided. Then, for example, register the data in register SX
When transferring data to SXA, first, a control signal that enables the output buffer is supplied to the output control terminal of register SX, and at the same time, a control signal that instructs data loading is supplied to the load terminal of register SXA. This causes the data in register SX to
Transferred to register SXA via IBUS47. The calculation result determination circuit 41 is a circuit that determines the calculation result in the addition/subtraction circuit 44, and when the calculation result is negative, "0", "256", or "512", the signal <
->, <0>, <256>, <512> are output. In addition,
Components 40 and 43-45 will be described later. Next, the operation of the above-mentioned command processing circuit 15 will be explained. This command processing circuit 15 is designed to be able to process 12 types of commands.
Memory) commands and HMMM (High Speed
The processing process of the Move Memory to Memory) command is explained below. These commands both move the image in area S (source) of the display screen shown in Figure 11A to area D (destination), or move the image shown in Figure 11B, C, and D.
Between VRAM2 and DRAM17 and DRAM17
This is a command to transfer data in the source area to the destination area within the . In this case, the transfer shown in A of the same figure sets both MXS and MXD in the argument register 32 to “0”.
MXS and MXD are respectively (“0”, “1”) and
This is a transfer in the case of (“1”, “0”), (“1”, “1”) (details will be described later). Furthermore, there are three differences between the LMMM command and the HMMM command: (Details will be described later.) First point: In the LMMM command, color codes are transferred dot by dot. In contrast, HMMM commands are executed in byte units. Second point: Transparency processing and logical operation processing are possible in the LMMM command. In contrast, these processes are not possible with the HMMM command. Third point: In the LMMM command, display processing in the image data processing circuit 10 (FIG. 3) takes priority over command processing. In contrast,
In the HMMM command, command processing is performed by temporarily stopping the moving image display processing in the image data processing circuit 10. Next, an outline of the processing process of the LMMM and HMMM commands is as follows. □ LMMM command For example, in the case of movement shown in Figure 11, first move dot P1.
The color code of dot Q1 is read out from VRAM4, and then the color code of dot Q1 is read out from VRAM4. Next, transparency processing and logical operation processing are performed on each color code of dots P1 and Q1, and the processing results are written into the storage area of VRAM 4 corresponding to dot Q1. Thereafter, the same process is repeated for dots P2, Q2, dots P3, Q3, . . . . □ The case of HMMM command mode G will be explained as an example. For example, as shown in Figure 12, the color codes of dots P1 and P2 are stored at address <85> of VRAM4.
The color codes of dots P3 and P4 are stored at address <86> of VRAM4, respectively.
Also, the color code of dots Q1 and Q2 is
Dots Q3 and Q are placed at address <215> of VRAM4.
The color code of 4 is the address of VRAM4 <216>
It is assumed that each of... is memorized. In this case, in the HMMM command processing, first read the color code in address <85>, write this read color code in address <215>, then read the color code in address <86>, and write the read color code in address <215>. Write in <216>,
This process is repeated hereafter. Next, various processes necessary for the above command processing will be explained. (1) Transparency processing If the color code of area S is a color code indicating transparency (ALL “0” in this example), this color code (ALL “0”) is not transferred to area D,
It may be convenient to leave the color code of area D as it is. This processing is called transparent processing, and in this embodiment, whether the CPU 2 performs transparent processing or not is determined by the LOP command (lower 4 bits of the command).
It can now be specified by (2) Logical operation processing This processing is a process of performing logical operations between each bit of the color code of the dot in the area S and each bit of the color code of the dot in the area D. In this embodiment, it is possible to perform AND, OR, EXOR (exclusive or), and NOT operations, and the CPU 2 determines the type of logical operation and whether or not to perform the logical operation in the LOP instruction. It is now possible to specify. Table 1 shows the types of LOP instructions in this embodiment. In this table, SC indicates the source color code (color code of the dots in area S), DC indicates the destination color code, and D indicates area D.

〔Effect of the invention〕

As described above in detail, according to the present invention, a source area and a destination area are specified by an expansion memory whose address input terminal is connected to an address bus for display memory, and the central processing unit, a command processing circuit that transfers a color code between the designated areas or between the designated area and the central processing unit;
Displays whether the source area is set to expansion memory or display memory, whether the destination area is set to expansion memory or display memory, and the access performed by the central processing unit via the display controller. A memory selection data storage means in which information specifying whether to set the memory or expanded memory is written, and based on the contents of this memory selection data storage means, each time the source area is accessed and the datening area is accessed. Since the strobe signal switching means is provided to switch and supply a memory address strobe signal to either the display memory or the expansion memory, the source area and destination area can be set appropriately for each of the VRAM and the external memory. In addition to allowing the CPU to access either VRAM or external memory via VDP, these accesses can be switched extremely easily (without the need for program processing on the CPU side). It can be carried out. Therefore, the amount of data that can be stored in the non-display memory area increases dramatically, and since the data can be transferred in many ways, various display effects can be achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a display device using a conventional display controller.
FIG. 2 is a diagram for explaining the movement of an image, FIG. 3 is a block diagram showing a schematic configuration of a color display device using a display controller according to an embodiment of the present invention, and FIGS. 4 to 7 are each 8 is a block diagram showing the configuration of the command processing circuit 15 in FIG. 3, and FIG. 9 is an arithmetic and register circuit (ARC) in FIG. 8. 10 is a block diagram showing the configuration of the argument register 32 in FIG. 8, FIGS. 11 to 14, and 16.
17 are explanatory diagrams for explaining the operation of the command processing circuit 15 shown in FIG.
FIG. 5 is an operational flowchart of the command processing circuit 15, and FIG. 18 is a block diagram showing the configuration of an applied example of the same embodiment. 4...VRAM (extended memory), 15... Command processing circuit, 32... Argument register (memory selection data storage means), AN1 to AN3...
...AND gate (strobe signal switching means),
OR1 to OR4...OR gate (strobe signal switching means), SW1, SW2...switching means (strobe signal switching means).

Claims (1)

[Claims] 1. A display that, under the control of a central processing unit, reads a color code stored in a display memory corresponding to each dot on a display screen from said memory, and displays dots on said display screen based on the read color code. In the controller, a source area and a destination area are specified by an expansion memory whose address input terminal is connected to the address bus for the display memory and the central processing unit, and between the specified areas or between the specified areas. a command processing circuit that transfers a color code between the designated area and the central processing unit; a memory selection data storage means in which information is written specifying which of the display memories is to be set and which of the display memory or the expansion memory is to be accessed by the central processing unit via the display controller; Strobe signal switching means for switching and supplying a memory address strobe signal to either the display memory or the expansion memory at each time of accessing the source area and accessing the destination area, based on the contents of the memory selection data storage means; A display controller comprising: