JPH0321473A - Image output device - Google Patents

Abstract

PURPOSE:To make an image memory area available even if a system memory area is rapidly expanded by a method wherein, in a memory means having the system memory area, an image data memory area is set in an address area apart from the system memory area. CONSTITUTION:Since printing data is stored from the external in a user data area which is a part of a DRAM block part 42, this data is developed to bit map data by an MPU 30. The bit map data is again stored in a video band buffer(VBB) area which is a part of the DRAM block part 42. This data is read by using a VDG 35, converted to serial data, and transmitted by a laser scan unit(LSU) in synchronism with a horizontal synchronizing signal (HSYNC). At this time, a VBB mode change-over means 34 transmits memory capacity information to the VDG 35. The VDG 35 changes over a signal pattern to be issued to a VDG address path VDGA in accordance with the memory capacity information. In this manner, because the VBB area can be made variable, the user data area can be continuously ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image output device having an image memory for expanding and outputting bitmap data.

BACKGROUND OF THE INVENTION A conventional image output device will be described using a laser printer as an example, which is a common type of image output device.

FIG. 7 is a block diagram of a conventional laser printer. As shown here, the laser printer is composed of five blocks consisting of an interface means 2, a video data processing means 3, a laser scanning unit section 4 (abbreviated as LSU section), an engine control means 5 and an engine mechanical section 6. ing.

The outline of the laser printer with this configuration will be explained below. A laser printer connected to a host computer 1 receives text data sent from the host computer 1 via an interface means 2 and stores it in a memory within a video data processing means 3. Next, this text data is developed into bitmap data, which is image data, in the video data processing means 3, and output device L
In synchronization with a horizontal synchronizing signal (hereinafter abbreviated as HSYNC) sent from the SU section 4, the data is sent to the LSU section as video data (hereinafter abbreviated as VDOUT) which is a serial output. In addition, the video data processing means 3 also outputs VDOU.
In conjunction with outputting T, the engine control means 5, which controls the engine mechanical section 6 such as paper feeding and main motor drive, is managed. In this way, image formation of image data is performed.

In the laser printer configured as described above, a block diagram of a video data processing section, which is a conventional configuration of the video data processing means 3, is shown in FIG.

Here, 7 is an MPU, and 8 is a DRAM that has a DRAM.
Block part. , 9 indicate a VRAM block section.

Reference numeral 10 denotes an address decoding means, which inputs the address bus (MPUA) of the MPU 7, decodes the address, and identifies which memory, the DRAM block section 8 or the VRAM block section 9, the MPU 7 requests access to. However, compared to the DRAM arbitration stage 12 described later, the DRAM
access request signal (DRAMRQ) with
A request signal (VRAMRQ) for accessing the VRAM 9 is generated for the RAM arbitration means 16. 11 and 15 are refresh means for the DRAM block section 8 and VRAM block section 9, respectively, and are means for requesting refresh of the DRAM block section 8 and VRAM block section 9. The refresh means 11 sends a refresh request signal (DREFRQ) to the DRAM arbitration means 12, which will be described later.
The refresh means 15 generates a refresh request signal (VREFRQ) to the VRAM arbitration means 16, which will be described later.
) occurs. 12 and 16 are arbitration means for the DRAM block unit 8 and VRAM block unit 9, respectively;
The RAM arbitration stage l2 arbitrates between the access request signal DRAMRQ and the refresh request signal DREFRQ, and outputs a DRAM start command signal group (DSTC) indicating which arbitration has been taken for the DRAM timing stage l3, which will be described later.
OM) and the VRAM arbitration means 16 receives the access request signal VR.
Arbitration is made between AMRQ and refresh request compensation signal VREFRQ, and a group of VRAM start command signals (VSTCOM) indicating which arbitration has been taken is sent to VRAM timing stage 17, which will be described later.

l4 inputs the address bus MPUA and connects it to the DRAM described later.
This is a bank switching means that sends a group of bank switching status signals (BANKST) to the timing means 13. Here, when switching banks, the user area for storing text data in the DRAM block section 8 is fixed and limited, so it is necessary to expand the memory according to the amount of user text data to prevent memory overflow. , used during this DRAM expansion. 13 is a DRAM timing signal, and DRAM arbitration means 12
A timing signal group (DRAMT) for DRAM access is generated for the DRAM block unit 8 by the signal group DSTCOM sent from Bank information signal (B
Send ANKO〉. Although not shown in FIG. 8, the bank information signals BANKI and BANK are connected similarly to the DRAM block unit 8 for the bank information signal BANKO.
It is assumed that an extended DRAM block section for 2 exists. In this way, the address bus MPUA, the bank information signal BANKO, the timing signal group DRAMT1, and the data path MPUD are connected to the DRAM block unit 8, and the MPU
7 can access the DRAM. 17 is a VRAM timing means, and VRAM arbitration means 16
The timing signal group VRAMT for VRAM access is input to the VRAM block unit 9. The VRAM block section 9 is connected to the address bus MPUA and the data path MPUD, receives a signal group VRAMT, and outputs video data as a serial output in accordance with a clock sent from a video signal synchronization means 18 (described later) through video data (VDB). The video signal is sent to the 18th stage synchronously. In this way, the data path VDB is composed of a clock line, a serial data line, and a serial data line. Here, since the capacity of the memory buffer of the VRAM block section 9 is generally limited, if the sequential reading speed of the synchronization signal HSYNC is faster than the speed of developing image data into this memory buffer, the data before image data is expanded. An error state (hereinafter, this error state will be referred to as an overrun) occurs during the transfer. In order to widen this overrun limit, it is necessary to expand the memory buffer of the VRAM block unit 9. 18 is a video signal synchronization means, which receives a synchronization signal H sent from the LSU section (not shown).
Synchronizes with SYNC, counts the blanking time, generates a clock for the VRAM block section 9 so as to output the video data sent from the VRAM block section 9 to the effective print area, and outputs serial video data VDOU.
He is being sent to LSU as a T. Furthermore, the MPU 7 detects the synchronization signal HSYNC, counts the number of rask of output data, and controls and manages the VRAM block section 9 and the video signal synchronization means 18.

As described above, the system and user areas are stored in the DRAM block section 8, and the image data development is carried out on the VRAM block section 9.The memory is divided and made independent, and since the VRAM block section 9 is dual-ported, the MPU 7
The structure was easy to control, with easy access from the video signal synchronization stage 18 and clock access from the video signal synchronization stage 18.

On the other hand, each part board to expand the memory area is DRA.
The system structure was inconvenient for the user, as the M block unit 8 and the VRAM block unit 9 were required to be independent.

FIG. 9 shows characters developed as bitmap data, which is image data of an image. As an example, the development of characters A and B will be explained.

Here, for ease of explanation, each character is made up of 25 x 25 dots, each dot is defined as a 1-bit unit, a black dot is assumed to be 1, and an empty dot is assumed to be O. In the character font, each bit information of 25×25 is stored as a code of 1 or O. The text data stored in the DRAM is expanded as bitmap data into the VRAM buffer while referring to the character font via the MPU. Generally, this expansion involves sequentially expanding each character and writing them into a buffer. In FIG. 9, the character "A" is first developed into a bitmap in the VRAM, and each bit is written in accordance with the code of the character font. Next, we will perform bitmap expansion of the character "B", but here we will develop the character "A" and the character "B".
If the 25x25 bits are overlapped and a normal write operation is performed, the 25x25 bits will be written with the information of the character "rB" at the time of writing the character "B", and the information of the character "A" will be written.
will partially disappear. In order to prevent this, after expanding the character "A", perform a bitwise OR of the character "A" and the character "B", and write the overlapped information on the buffer, resulting in overlapping characters as shown in Figure 9. each can. This function is hereinafter referred to as overwriting. Generally VRA
M has this overwriting function, and the VRAMs discussed below are treated as having this function.

Next, using the flowchart in Figure 10, the MPU in Figure 9
The control performed by 7 will be explained. Here, the HSYNC interrupt routine interrupts MP every time a pulse is input to HSYNC.
U? The flowchart in which an interrupt occurs will be described below. First, in the main routine, step (a) initializes the variable X1Y. Here, X is MPU7 is VRA
This is the raster number written to the M area, and Y is HSYN.
This is the number of counters indicating the number of interrupts for each C. In step (b), the number of rasters to be printed is set in N. In step (c), HSYNC interrupt is enabled. In step (d), the planking time and other settings are set for the video signal synchronization means 18 and the video signal synchronization means 18 is activated. Step (e)
compares X and Y in order to determine whether there is an empty raster in the VRAM block section 9 for writing bitmap data. If there is no empty raster, go back to step (e); if there is an empty raster, go to step (f). In step (f), bitmap data for one raster is written to the VRAM block section 9,
Add +1 to the value. In step (g), it is determined whether the HSYNC counter number Y is equal to the number N of rasters to be printed, and if Xf. If Y, go to step (h). In step (h), the video signal synchronization means 18 is stopped and V
The writing of bitmap data to the RAM block section 9 is completed. Next, in step (i) of the HSYNC interrupt routine, +1 is added to the value of the output raster number Y. In step (j), Y and N are used to determine whether printing is finished or not.
If Y=N, go to step (k), Y
If ≠N, the process ends. In step (k), HSYNC interrupts are prohibited.

Problems to be Solved by the Invention However, in this case, VR as a bitmap memory
The memory capacity of the AM block section is fixed, and DRAM
Since the block section and the VRAM block section are separated into separate blocks, it is not easy to expand the storage area. To solve this problem, the DRAM block section and VR
It is conceivable to set the AM block part in one storage means, but the DR which the MPU uses as a system area
When the AM block section swells, the VRAM block section set as the image storage area may suddenly become unusable.

Means for Solving the Problem In order to solve this problem, the present invention includes an image area setting means for setting an image data storage area in an address area separate from the system storage area in a storage means having a system storage area. .

Effect: This arrangement provides an address space between the system storage area and the image storage area.

Embodiment An image output device according to an embodiment of the present invention will be described below.

First, FIG. 1 is a block diagram showing the structure of this embodiment. Here, 30 is a microprocessor unit (hereinafter referred to as MPU) for controlling the present image output device;
Which DR is selected when there are multiple DRAM block units 42?
Bank switching means for determining whether to access the AM block section; 32, address conversion means for converting the value of the address bus MPUA output from the MPU 30; 33, address decoding means; 34, storage in the DRAM block section 42. VBB mode switching means for switching the storage capacity of a video band buffer (hereinafter referred to as VBB) which is a part of the area; 35, video data generation means (hereinafter referred to as VDG) for outputting a video data output signal VDOUT; 36; is a DRAM address generating means, which generates an address bus DRAM to be output to the DRAM block section 42. Reference numeral 37 denotes a DRAM refresh means, which outputs a DRAM access request signal REFREQ at the period of the DRAM refresh cycle time. Reference numeral 38 denotes DRAM arbitration means, which arbitrates among a plurality of access request signals to the DRAM block section 42 and permits access to only one of the access requests. 39 is a DRAM timing means;
Timing signal group D for accessing M block section
RAMT output and bank signals BANKO, BANK1,
This is means for outputting BANK2. 40 is a bus switching means for switching whether or not to electrically connect the data path MPUD of the MPU.

Reference numeral 41 denotes an overwriting pattern generating means, and the overwriting is the function described above. 42 is a DRAM block section.

The operation of the video data processing unit block of the image output device of this embodiment configured as described above will be explained below. First, an overview of data processing in this video data processing block structure will be explained. Since the data to be printed from the outside is stored in the user data area which is a part of the DRAM block unit 42, this data is
0 is used to expand into bitmap data. At this time, if font data is required, processing such as referring to a font memory (not shown) is involved.The bitmap data is stored again in the VBB area, which is a part of the DRAM block unit 42.This VBB area data stored on the VD
Read the data using G35, convert this data to serial data, synchronize it with the HSYNC signal, and perform the above-mentioned L
Send as SU. The configuration for performing the above data processing will be described below.

There are a total of four modes for access requests in the DRAM block section 42. The first request is an access request from the MPU to the VBB area. The second is a request from the MPU to access an area other than the VBB area. The third is VDG3
5 is a request to access the VBB area. The fourth request is a refresh access request for refreshing data on the DRAM of the DRAM block unit 42 . In this way, the DRAM block section 42
There are four access modes, and at least two modes, and sometimes three modes, issue access requests at the same time, so some kind of arbitration is required. There are 3 ways to mediate these
This is the DRAM arbitration means shown in 8, and the VBB from the MPU.
Area access request signal VBBRQ and (7) access request signal MPUR from the MPU to areas other than the VBB area.
Q and the access request signal R from the refresh means 37
Inputs four EFRQ signals, performs internal arbitration, permits one access request signal among them, and outputs a start command signal group STCOM to notify the DRAM timing means 39 which access request is to be executed. . The DRAM timing means 39 uses the aforementioned signal group ST.
Bank switching means 3l for bank switching necessary when there are a plurality of COM and DRAM block units 42
This means inputs the output signal BANKST of BANoXBANK and generates the timing signal group DRAMT necessary for accessing the DRAM as well as the bank switching signal BANoXBANK.
Generate I BANK2. Further, the DRAM address generation means 36 informs the DRAM timing means 39 which access request is to be executed by the DRAM arbitration means 38.
Depending on the timing, it is determined which address bus should be sent to the DRAM block section 42. Therefore, D.R.
AM address generation means 36 is DRAM timing 1,000 stages 3
9 address switching control output signal group DAGCOM is D
When input to the RAM address generation means 36, the VBB address bus VBBA is generated according to this signal group DAGCOM.
, MPU address bus MPUA, VDG7 address bus v
It has a function of connecting to the address bus DRAMA which selects one of the DGAs and sends it to the DRAM block unit 42.

Next, the overwriting operation in the VBB area will be explained. As explained in the conventional example, it is necessary to overwrite in the VBB area, but since the DRAM block section 42 of the present invention does not have the additional function of the VRAM in the conventional example, a separate means for overwriting is required. First, write data is sent from the MPU 30 to the VBB area through the data path MPUD, so that this data can be input to the section A of the overwrite pattern generation stage 41. On the other hand, the read timing to the DRAM block section 42 is executed from the DRAM timing signal 39, and the data in the VBB area is transferred to the DRAM block section 42.
The signal is input to part B of the overwriting pattern generating means 41 through the M data path DRAMD. The input data to this section is latched by the output signal OvC of the DRAM timing means 39, a computation of overlapping with the data input to the A section is executed, and the data is output to the data path DRAMD as data to be written to the final VBB area. In this way, the data in the BB area is read and superimposed on the data sent from the MPU 30, and the result is written to the VBB area. Such a method is called read-modify-write, and is hereinafter referred to as RMW. As mentioned above, from the MPU 30's perspective, it can only recognize that there is one write cycle to the VBB area, but in actual hardware, the RM
The W cycle is automatically generated.

These cycles are all generated by the DRAM timing means 39.

Next, the VBB mode switching means 34 will be explained.

The VBB area will be explained in detail later, but the memory capacity of the VBB area can be made variable, and the DRAM block 4
In order to increase the memory capacity of 2, it is necessary to change the rotation of the VBB area when expanding to a plurality of DRAM blocks. Now suppose that the memory capacity of the VBB area is changed. In this operation, memory capacity information is input from the MPU 30 to the VBB mode switching means 34 via the data path MPUD. The VBB mode switching means 34 sends memory capacity information to each means, ie, the VDG 35, the address conversion means 32, and the bank switching means 31, via the VBB data path VBBD. VDG35
inputs the above memory capacity information and switches the signal pattern generated to the VDG address bus VDGA according to the memory capacity information. As will be explained later, since the VBB area uses a ring buffer method, it is necessary to convert the address information actually output from the MPU into physical address information on the VBB, so an address conversion means is used according to the memory capacity information. It is necessary to switch 32. Further, the bank switching means 31 is a means used when changing the location of the VBB area.

Next, the VDG 35 will be explained in more detail.

FIG. 2 is an internal block diagram of the VDG 35. 44 is a timing control means for synchronizing the internal timing of the VDG 35 with the external periodic signal HSYNC. 45 is a counter means for generating an address, which is a counter that counts up by +1, and its output is VBB.
Used as an address bus for accessing areas. 46 is a VBB memory capacity selection means, which inputs memory capacity information of the VBB area from the VBB bus VBBD;
This is a means for converting an address for actually accessing the VBB area and outputting it to the vDG address bus VDGA. 47 is a data latch means, which is a means for latching the data of the vBB area as it is input via the DRAM data bus DRAMD. 48
is a parallel-to-serial conversion means, which inputs data in the vBB area via the data bus VDQ, converts this data from parallel data to serial data, and sends it to the aforementioned LSU as a video data output signal VDOUT. 49 is a VDG control means which counts the number of pulses of the external synchronization signal HSYNC in order to know which raster the video data output signal VDOUT has been sent out.
MP to PU30. It has a function of sending data via the U data bus MPUD. In addition, when the number of raster to which the video data output signal VDOUT should be output is input from MPU3 via MPUD, and the output data is sent from VDOUT to the raster specified by MPU3, VDG35 is automatically stopped. Signal STOP
It has a function of sending out to the timing control means 44. It also has a start function via a start signal.

Next, the operation of the internal blocks of the VDG 35 will be explained. A clock synchronized with the external synchronization signal HSYNC is generated by the timing control means 44, and a signal PS obtained by dividing the main clock is generated.
Create CLKSLD and VDGRQ. VDGRQ is vDG
35 to VBB. I. DRA to access the rear
This is a request signal sent to the M arbitration means 38, and this DR
When permitted by the AM arbitration means 38, the data in the VBB area indicated by the address of the address bus VDGA output from the VDG 35 is read into the VDG 35. On the other hand, the address generation counter means 45 increments the counter by +1 by inputting the output signal ACLK of the timing control stage 44, and this output is sent to V via the bus Q.
It is sent to the BB memory capacity selection means 16. The VBB memory capacity selection means 46 receives the VB input from the VBB bus VBBD.
The data from the bus Q is processed according to the memory capacity of the B area and output to the VDGA as actual address information.

To explain the processing here, for example, when memory capacity is low, the upper bits of data from bus Q are deleted, and only the number of bits that fit the actual address space is stored in V.
This means outputting to the DG address bus VDGA, etc. The data in the VBB area indicated by the thus output address is latched into the data latch stage 47 via the DRAM data path DRAMD. This parallel data is converted into serial data via the parallel-to-serial conversion means 48, and VDGOU is output as a video data output signal.
Send from T. The signal flow of the video data processing section has been explained above using FIGS. 1 and 2.

Next, I will explain the VBB area. The memory map of the DRAM block unit 42 is shown in FIG. vS3. Reference numeral 50 indicates a real memory space of the DRAM block section 42.

51 is an area used by the system, 52 is a user data area for storing data sent by the user to the image format control device, and 53 is a VBB area.

54 is a virtual memory space of the VBB area seen from the MPU 30. In the memory mapped as described above, the virtual memory space 54 is a place to store data expanded into a bitmap for one page of printing paper output from the image forming apparatus.

Now, the MPU 3 writes addresses A to B in the virtual memory space 54.
When bitmap data is sequentially written into the address area 50, it is actually written sequentially from addresses a to b in the VBB area 53 of the real memory space 50. This data is read out in the order of addresses a to b through the VDG 35, converted to serial data, and sent to the LSU. Next, virtual memory space 5
Similarly, the data written from addresses C to d in No. 4 is actually written from addresses a to b in the VBB area. As described above, the VBB area 53 has a ring buffer configuration. Therefore, the data in the VBB area 53 is transferred from address a to b via VDG35.
From s a to b . . . are read out one after another and sent to the LSU. Furthermore, when bit map data is written from the MPU 30 to the virtual memory space 54 from addresses A to B, from C to D, etc., it is actually written to the VBB rear 53 from addresses a to bsa to b.

Next, the control performed by the MPU 30 in this embodiment will be explained using the flowchart shown in FIG. Here, in terms of hardware, the HSYNC interrupt routine inputs the external synchronization signal HSYNC shown in FIG. 1 to the interrupt terminal of the MPU 30.
An interrupt occurs to U30. This means that an interrupt occurs every raster. The flowchart will be explained below. First, in the main routine, the variable X%Y is initialized in step (a). X is MPU30 is V
BB. r. It is the raster number written to the rear,
Y is a counter number indicating the number of interrupts for each HSYNC. In the step (start), the number of rasters to be printed is set to V
Set to DG. In step (c), the HSYNC interrupt is enabled and the VDG is activated. In step (2), it is determined by referring to X and Y to check whether there is an empty raster for writing bitmap data in VBB. If there is no empty raster, return to step (2); if there is, proceed to step (e). Step (e) writes bitmap data into one raster sentence VBB and adds 1 to the value of X.

In step (go), it is determined whether the HSYNC counter number is equal to the number of rasters to be printed, and if Xf.Y, return to step (2), and if X=Y, write bitmap data to VBB. Exit. Next, HSYN
Read the C counter number from VDG and store it in V.

Step 〈C〉 compares Y with N to judge whether printing is finished or not, and if Y=N, step 〈〉
If Yv&N, the process ends. HSYNC interrupts are prohibited in step (ri).The operation of the video data processing unit block configuration shown in FIG. 1 has been described above with reference to FIGS. 2, 3, and 4.

Next, the case where the VBB area is made variable will be explained using FIG. When VBB rear is 64KB, address FFFFF (H) to FOOOO (
H) The virtual memory space addresses corresponding to bank 1 are 0 to FFFF (H) bank 2 is 10000 (H)
to IFFFF (H), bank 3 is 20000 (H
) to 2FFFF (H) . . . Therefore, by ignoring the upper bits of the address in the virtual memory space and validating only the lower four digits of the hexadecimal number, it is easily converted to an address in the real memory space. Next, when the VBB area is 48KB, the virtual memory space addresses corresponding to addresses FFFFF (H) to F4000 (H) in the real memory space are O to BFF (H) for bank l and COOO (H) for bank 2. to 17FFF (H), bank 3
is from 18000 (H) to 23FFF (H), so it is not possible to easily convert the address from virtual memory to real memory as in the case of 64 KB.

In general, it will look like this:

Ap=INV(A I-BpxINT(A I/Bp)
)・” (1) However, Ap is the address of the real memory space (physical address), and Al is the address of the virtual memory space (
Logical address) Bp indicates the memory capacity of VBB, and IN
V(X) means that when X is expressed as a binary number, 1 and O are reversed. Further, INT(X) indicates the integer part of X. As shown in Equation (1), the conversion means for converting into a logical address can generally be realized by using a multiplier/divider and an adder/subtractor. Further, when the VBB memory capacity is 2 to the nth power (n is an integer) as in the case of 64 KB, the upper bits can be ignored and only the necessary number of bits can be used, making the configuration simple.

As explained above, in order to make the VBB area variable capacity, the address conversion means 32 shown in FIG. 1 is used, and its interior is configured to satisfy the function of equation (1).

Next, FIG. 6 shows a memory map when expanding the DRAM block section. This is an example of a configuration in which only the DRAM block section is a separate printed circuit board (hereinafter referred to as an expansion RAM board), and the memory capacity can be expanded according to the user's wishes.In the left half of Fig. 6, the VBB area is 64 KB. This shows the case where there is no expansion RAM board and the case where one expansion RAM board is added.In the figure, address e
to h is the expanded part. Expanded RAM here
If the VBB area mapping is fixed when one board is added, it will be placed at addresses C to d in the figure. Therefore, the user data area is from address a to b.
Since the data area is divided into two from e to h, a continuous user data area cannot be secured and data processing becomes complicated.

To solve this problem, the VBB area can be mapped to the end of the memory, and the addresses f to h can be assigned as shown in the figure. In general, even if the memory capacity is expanded, the number of effective bits at the last address is often all 1, so
Since the address generation means generated from the VDG 35 shown in the figure can be used in common, the hardware can be easily implemented. On the other hand, another method to secure a continuous user data area is to map the VBB area adjacent to the system area, but in this case, the capacity of the system area may change due to the revision of the system area. When this happens, the hardware of the VDG35 must be changed, which is extremely inconvenient. For the above reasons, in this embodiment, the VBB area is mapped to the end of the mounted memory.

Next, the right half of FIG. 6 shows cases in which two expansion RAM boards are added and the VBB area is 64 KB and 128 KB. As shown in the figure, since the VBB area is made variable, it is easy to secure a continuous user data area, and the management of the user data area is also easy.

In addition, it is possible to optimize the VBB area capacity according to the amount of data input from the user manually from the outside, and the system system can be made resistant to overruns as described in the conventional example. In other words, determine the VBB memory capacity that can secure the maximum memory capacity as the VBB area in the empty area excluding the user data actually stored in the user data area, and
It can be seen that it is sufficient to set it to the VBB mode switching means shown in the figure. It also determines whether or not the VBB area can be secured sufficiently, and if possible, the memory capacity for one page is allocated to the VBB area.
It is also possible to fix it as area B, and in this case overrun will never occur. In addition, although FIG. 6 shows three cases where there are one, two, and no expansion RAM boards, in order to bring the VBB area location to the end, bank switching means 3 in FIG.
All you have to do is make the appropriate settings for 1. An embodiment of the present invention has been described above, focusing on the VBB area.

Effects of the Invention As described above, the present invention sets an image storage area in a storage means having a system storage area in an address area separate from the system storage area, so that the system storage area and the image storage area are combined into one. Even if the system storage area suddenly expands when provided in one storage means, it is possible to prevent the image storage area from becoming unusable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video data processing unit in an embodiment of the present invention, FIG. 2 is a block diagram of the inside of the VDG, and FIG. 3 is a memory map diagram showing the virtual memory space and real memory space. Figure 4 is the same flowchart, Figure 5 is the same V
Figure 6 is a memory map diagram when the BB area is made variable; Figure 6 is a memory map diagram when the DRAM block section is expanded; Figure 7 is a block diagram of the laser printer; Figure 8 is a diagram showing the block configuration of the laser printer.
The figure is a block diagram of a conventional video data processing unit.
The figure is a bitmap data development diagram for explaining overwriting, and FIG. 10 is a flowchart showing a conventional control procedure. 5... Engine control means, 6... Engine mechanical section,
42...DRAM block unit, 9...VRAM block unit, 12...DRAM arbitration means

Claims (1)

[Scope of Claims] 1) An image output device for bit-expanding and outputting image data processed by a processing means, comprising: a storage means having a system storage area used by the processing means; and a system storage area set in the storage means. An image output device comprising: image area setting means for storing bit-expanded image data in an address area separate from a system storage area. 2) The image output device according to claim 1, wherein the image area setting means sets the image storage area from the last address of the storage means.