JP2001213011A - Method for managing memory and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a bit map at a high speed by eliminating overhead in the management of band, and to develop PDL data to a bit map with no break. SOLUTION: A memory managing section (16) manages a page memory such that image data is developed to a bit map using memory management in units of page of sheet size when a memory area developable to a page of bit map is present in a page memory otherwise switching is made to memory management in units of band where a page of image data is sectioned into bands and developed to a bit map in units of band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a memory management method and an image forming apparatus, and more particularly to a PD transmitted from a host device.
The present invention relates to an image forming apparatus such as a page printer that develops L data in a page memory as a bit map.

[0002]

2. Description of the Related Art Conventionally, when performing band memory management, only memory saving is prioritized. Therefore, a memory is used in a manner other than band memory management (in page units). As an example,
Japanese Patent Application Laid-Open No. 9-164729 (hereinafter referred to as Conventional Example 1)
Then, it is necessary to divide the bitmap memory into a plurality of blocks, manage whether or not the bitmap is stored for each block, and divert unused block memory to expanded work memory when the work memory is full By
A memory without a bitmap is obtained from the page memory, but is not used as a drawing memory because it is used as a work memory.

In a page printer that develops page description language (hereinafter abbreviated as PDL) data into a bitmap, if high-speed printing is required, CPU power is allocated to how the PDL data is developed into a bitmap.
One point is whether the operation can be performed without interruption. Furthermore, if a relatively large-capacity page memory is mounted and bitmaps are created in advance on a plurality of page memories, the performance of the print engine will not be impaired even if processing that takes a long time to develop the bitmap occurs. In addition, the possibility of printing without delay increases.

[0004]

However, a high-speed print engine tends to have a long paper-passing path, and the page memory is retained until the discharge is completed even after the transfer of the page memory to the print engine for jam recovery. However, there is a problem that sufficient memory is not necessarily mounted because of the necessity and the cost of mounting the memory. Also, when the required amount of memory to be allocated to the page memory is no longer allocated, the page memory previously created by the development from the PDL to the bitmap is released even though there is ample room for CPU resources. Will be completely stalled until the

[0005] Generally, as a memory saving technique, a method is generally used in which a memory is divided into predetermined bands and no memory is allocated to a band without a bitmap. The overhead caused by band memory management adversely affects the development of PDL data requiring the most CPU power into bitmaps.

The present invention has been made to solve these problems. When there is room in the memory area, the overhead of band management can be eliminated, the bitmap can be expanded at a high speed, and the memory has no room. In this case, the purpose is to change the development of the page and subsequent pages to band memory management so that the development of the PDL data into the bitmap is executed without interruption.

[0007]

In order to solve the above-mentioned problems, according to a memory management method for managing a memory for expanding data stored in a bitmap and storing the data in a bitmap, one memory is used in a memory area of the memory. If there is a memory area that can be developed in the bitmap for the block, the memory area is developed into the bitmap in block units using the memory management in block units. On the other hand, when there is no expandable memory area in the bit map of one block in the memory area of the memory, the memory management is switched to a band unit divided into bands smaller than the memory area of one block, and is expanded into a bit map in band units. Therefore, the overhead of band management can be eliminated and bitmap development can be performed at high speed. If there is no more memory area to be allocated by band-based memory management, the previously created page-based memory area is switched to band-based memory management, and unprocessed data is allocated to the memory area of the band where no bitmap exists. By developing the data into a bitmap, the development into the bitmap is executed without interruption. Furthermore, the speed can be increased by setting the memory area of the band where the physical address is continuous to the memory area of one band.

According to another aspect of the present invention, an image forming apparatus having a page memory for expanding page description language data transmitted from a host into a bitmap and storing the same in a bitmap for one page in a memory area of the page memory. If there is a memory area that can be expanded, it is expanded into a bitmap using the memory management of the page unit for the paper size. If there is no memory area that can be expanded into a bitmap for one page in the memory area of the page memory, the image data is It is characterized in that it has a memory management unit that manages a page memory so that one page is switched to band-based memory management divided into bands and developed into a bitmap in band units.
When the memory area to be allocated by the band-based memory management runs out, the memory management unit switches the previously created page-based memory area to the band-based memory management, and leaves the memory area of the band where no bitmap exists in the memory area. The image data of the band to be processed is allocated and developed into a bitmap. Further, the memory management unit sets the memory area of the band where the physical address is continuous to the memory area of one band. Therefore, when there is room in the memory area, the overhead of band management can be eliminated, and bitmap development can be performed at high speed. When the memory has no room, the development after the page is changed to band memory management, thereby enabling PDL. The development of data into a bitmap can be executed without interruption.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When there is a memory area that can be expanded into a bit map for one page in a memory area of a page memory, the memory area is expanded into a bit map by using memory management of a page unit for a paper size, and the page memory is expanded. When there is no memory area that can be developed in a bitmap for one page in the memory area, the page memory is managed so that one page of the image data is switched to the memory management in a band unit divided into bands and developed into a bitmap in band units. And a memory management unit.

[0010]

FIG. 1 is a block diagram showing the configuration of an image forming apparatus according to the present invention. In FIG. 1, the image forming apparatus according to the present invention includes, via a bus 11, a CPU 12, a reception buffer 13, a program execution memory 14, a page memory 15, a memory management unit 16, a host I / F 17
, Host 18 and intermediate code / font ROM 19
, Print control unit 20, input / output panel 21, video I
/ F22 and a print engine 23.

Next, a description will be given of the memory management operation of the page memory in the image forming apparatus having such a configuration. The memory management operation is performed by the host 18 via a host I / F 17 such as Centronics, RS-232C, a network, or a USB. The PDL data is temporarily stored in the reception buffer 13. The PDL data stored in the reception buffer 13 is interpreted by a data development module 32 shown in FIG. 2 showing a software configuration required for operation, and is developed into a bit map in the page memory 15. This operation is divided into two steps. In other words, the data is expanded into an intermediate code suitable for bitmap expansion by the data expansion module 32 in FIG. 2, and the rendering module may expand the intermediate code into a bitmap, but this does not affect the description here. Omitted. Then, when the creation of the page memory 15 is completed, the memory management unit 16 transfers the management of the page memory 15 to the print control module 33 of FIG. 2 that operates independently of the data development module 32.
The print control module 33 holds the page memory 15 and, when it is time to print the page, sends to the print control unit 20 of FIG.
After setting the sub-scanning width and the like, video transfer is performed, the page memory 15 is held until the page is discharged in consideration of a jam backup, and then the page memory 15 is released.
For jam backup, there is a method of releasing the page memory and saving it in the form of intermediate code, and a method of compressing and saving the page memory after printing.However, saving in the intermediate code involves saving the page memory at the time of jam backup. In the method of compressing and saving, the CPU cost of compression is generated during normal printing, which causes a reduction in printing speed, and is not adopted here. Next, since the page memory creation of the data development module 32 and the operation of the print engine 23 are performed asynchronously, the print control module 33 manages a plurality of page memories 15 at the same time. When it is necessary to change the order of the pages due to the double-sided printing mechanism, the print control module 33 of FIG. 2 changes the order of the page memory 15 sent to the print engine 23 of FIG.

Next, the basic operation of the data expansion module will be described with reference to FIG. 3 showing an operation flow. The page size is determined from the acquired data (step S1).
01, S102). Then, the page memory 15 in FIG. 1 is allocated, and if the allocator processing is not successful, a wait processing is performed and the page memory 15 is allocated again (steps S103 to S105). Step S1
If the allocator processing is successful in 04, the data is received and 1
Bitmap development is performed until the page data is completed (steps S106 and S107). When the bitmap is developed for the data of one page, the memory management unit 16 transfers the management of the page memory 15 to the print control unit 20 and moves to the next page processing (steps S108 and S10).
9). The print control module 33 is an aggregation of small modules having functions corresponding to the following events, although the description is omitted because the print control module 33 operates in response to events from the data expansion module 32 and the print engine 23.
For the page memory creation completion event, the page memory is placed under management (for example, added to a queue), and for the print preparation completion event, search of the page memory to be transferred next and video setting are performed. In addition, video transfer start is performed for a video transfer request event, jam backup processing is started for a jam occurrence event, and the corresponding page memory is released for a paper discharge completion event. Such an event can be both a hardware interrupt and a software event using a flag or the like.

The above is the general printing operation. Here, the allocation of the page memory will be described. All page memories 15 in FIG. 1 are managed by virtual addresses.
When the data expansion module 32 in FIG. 2 requests the page memory 15 from the operating system 34, the operating system 34 returns a virtual address to which a physical memory has not been allocated. Therefore, the allocation failure shown in FIG. 3 cannot actually occur as described above, and the wait processing does not occur when the page memory is allocated. And the data expansion module 3
2 writes the bitmap to the page memory 15 assigned to the virtual address, an exception of the CPU 12 in FIG. 1 occurs because the physical memory is not assigned. Therefore, the memory management module in the operating system 34 allocates the physical memory to the page memory of the virtual address for the first time when this exception occurs. The wait process is realized by a method such as not performing a context switch to the data expansion module until the allocated physical memory can be secured when the physical memory allocated to the page memory is insufficient.

By performing such memory management,
The data development module can perform processing without regard to whether the memory to be drawn is managed in page units or band units.

Normally, when there is room in the remaining memory, the memory management module allocates one page of real memory to the virtual page memory when data is written to the page memory at the virtual address. However, when the allocable memory is less than one page, the memory is allocated only to the band including the address where the writing has been performed.
This is the timing to start allocation in band units, but it does not matter if there is no memory for one page,
Further, it may be a time when a predetermined remaining memory capacity is reached.

FIG. 4 is a diagram showing an example of allocation on a page basis. This figure shows a state in which one page of memory is allocated to pages 1 to 4, and it is detected that there is no memory of one page when allocating the memory of page 5. Therefore, as for page 5 that could not be allocated in page units, as shown in FIG. 5, an allocatable memory was searched, and page 5 was allocated in band units according to the memory area of the allocatable memory, and allocated. Arrow 1 in FIG.
Bitmaps are expanded as in to 4 to prevent drawing from being delayed. However, as shown in FIG. 5, the character “MO”, which is one of the image data, cannot be allocated from the allocatable memory in the memory of FIG. Therefore, at this time, the page 4 that has been created and is waiting to be printed is divided into band units, and the band L without the bitmap is used for the last band of the page 5, so that the character “mo” in FIG. It can be allocated on the memory from the allocatable memory and expanded into a bitmap.

FIG. 6 is a flowchart showing the operation of the memory management module. First, if there is a memory allocation request, it is determined whether there is one page in the allocatable memory,
If there is, memory for one page is allocated (step S2).
01 to S203). In step S202, if there is no allocable memory for one page, but there is less allocable memory for one page, the memory is allocated in band units (steps S204, S205). Then, it is determined whether or not all the assignments in band units have been completed. If the assignment has not been completed, and if there is no memory that can be assigned in step S204, a page waiting for printing is searched from the upper address (step S206). , S207). It is determined whether the searched page waiting for printing is band-managed, and if not managed, the process proceeds to band management (steps S208, S209). Then, a band without a bitmap is searched, and if the band is found, the band memory is removed from page management and assigned (steps S210 to S212). If no band without a bitmap is found in step S211, step S2 is executed.
Returning to step 207, the page waiting for printing is searched again from the next higher address, and steps S208 to S211 are repeated until a band without a bitmap is found. As described above, for example, a method of searching for a band having no bitmap of page 4 is possible. However, it is possible to scan the memory of one page. Even if they are assigned, it is desirable to perform processing such as marking a band having a bitmap on a band-by-band basis in the data expansion module.

Next, consider that the print control module prints page 4 shown in FIG. Here, page 4 is divided into bands A to L, and band L is allocated for page 5. The print control module addresses the number of bands from A to K for the video transfer of page 4,
Settings such as width and height are made to the print control unit. The DMA of the band L of the band L used for the page 5 may be prepared with a memory of one band, but the print control unit 20 of FIG. If it has a function of performing blank transfer only by designation, there is no need for the memory. Normally, the print control unit 20 has at most about one to three stages of FIFOs, so that settings other than the head of a page must be made during DMA.

As shown in FIG. 1, in this configuration, the bus 1
Since one is one, the CPU arbitrates during DMA by bus arbitration.
The time during which the memory 12 can access the memory is limited. In fact, since it is normal to actually perform much finer memory division than that shown in FIG. 5, the address calculation for the DMA and the setting to the print control unit become a CPU time and a bus occupation time that cannot be ignored. Appears. Further, even if only the set number of times is taken, for example, when printing on A4 size paper at 600 dpi, a memory of about 4.2 megabytes is required for one page. If this is divided into bands of 32 kilobytes, it is divided into about 130 bands,
In short, in the case of the page unit, it is necessary to perform the setting with one setting 130 times. This time is overhead, and when performing band management even during normal operation, the CPU time that can be used by the data expansion module due to this overhead and the bus time for memory access, which is a problem during DMA, are always required. It is in a restricted state.

In FIG. 5, page 4 is divided into bands A to L, but since physical memory for one continuous page is originally allocated, even if L is allocated for page 5, It is a continuous real memory. Therefore, although not shown, if the memory of page 1 is released before the creation of page 6 and subsequent pages, there is no further division of the physical memory. At this time, if A to K are treated as one band, the video setting can be completed only twice in the band with the physical memory and in the band without the physical memory.

For the above reasons, when allocating a memory without a bitmap from a page that has already been created, the memory is allocated from the highest possible address. By doing so, when the paper ejection is completed in order from page 1, the possibility of allocating a continuous space in the allocation of the memory after the next page becomes very high.

When it is necessary to allocate memory for page 6 and subsequent pages, the memory is reallocated from page 4. The next memory that can be allocated is I, H, G without a bit map in FIG. is there. At this time, I, H,
G is assigned in the order of G. However, if the required bands correspond to three bands, they may be assigned in the order of G, H, and I. By doing so, GI becomes a continuous area, and the number of times of video setting can be reduced to 1/3.

However, since the reallocation of the memory is performed when an exception occurs due to the writing to the virtual memory having no actual physical memory, it cannot be detected that the next band is at a continuous address.

Thus, when there is a request for physical memory,
It is necessary to take measures such as releasing G1 to I as a once assignable memory from page 4 and assigning it from a lower address (memory that was G). In page 4, there is no difference that the memory is divided into two even if one band is released or three consecutive bands are released, so that the number of video settings itself does not change.

For the same reason, the two bands at the top of page 5 shown in FIG. 5 are allocated from a continuous space. Therefore, by treating them as one band, the time for video setting is reduced to half. Can be reduced.

The operation of the above-described memory management module will be described with reference to FIG. 7 showing an operation flow of another memory management module. The operations in steps S201 to S212 in FIG. 6 are the same as the operations in steps S301 to S312 in FIG. 6, except that the band memory is removed from the page management in step S312 and allocated.
It is determined whether or not the allocated band is a physical address that is continuous with the band allocated immediately before. If the allocated physical address is a continuous physical address, the band is managed as one band together with the band allocated immediately before (steps S313 and S314). If it is not a continuous physical address in step S313, the address is allocated as it is and the process is terminated.

It should be noted that the print control module only performs video setting in order according to the information provided by the memory management module, and there is no difference other than the number of times of setting.

The present invention is not limited to the above embodiment, and needless to say, various modifications and substitutions can be made within the scope of the claims.

[0029]

As described above, according to the present invention,
An image forming apparatus having a page memory for developing PDL data transmitted from a host into a bit map and storing the developed data, wherein if there is a memory area that can be expanded into a bit map for one page in the memory area of the page memory, It is developed into a bitmap using memory management in page units for the size. On the other hand, when there is no expandable memory area in the bit map for one page in the memory area, 1
Switch to page-by-band memory management by dividing the page into bands, and expand to bitmaps in band units. Therefore, the development of the PDL data into the bitmap can be executed without interruption.

When a memory area to be allocated is exhausted during creation of a page being drawn by band-based memory management, the previously created page-based memory area is switched to band-based memory management, and a bit map is created. By releasing the memory area of the band where there is no, and developing the released memory area into bitmaps in band units for the page being drawn, the overhead of band management can be eliminated and bitmap development can be performed at high speed.

Further, if there is a memory area of a continuous band, the memory area of the continuous band is set as a memory area of one band, so that the maximum processing time of the CPU can be allocated to bitmap development. The printing speed can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating a relation of software in the image forming apparatus of the present invention.

FIG. 3 is a flowchart showing a basic operation of the data expansion module.

FIG. 4 is a diagram illustrating an example of a state in which a page is allocated to each page of a page memory according to the embodiment;

FIG. 5 is a diagram illustrating a state in which page memories according to the present embodiment are allocated in band units.

FIG. 6 is a flowchart illustrating an operation of the memory management module according to the embodiment.

FIG. 7 is a flowchart illustrating another operation of the memory management module of the embodiment.

[Explanation of symbols]

11: bus, 12: CPU, 13: reception buffer, 1
4: Program execution memory, 15: Page memory, 1
6: memory management unit, 17: host I / F, 18: host, 19: intermediate code / font ROM, 20: print control unit, 21: input / output panel, 22: video I / F, 2
3: Print engine.

Claims (6)

[Claims] 1. A memory management method for managing a memory for expanding data stored in a bitmap sent from a host and storing the expanded data in a bitmap, wherein when there is a memory area in the memory area of the memory which can be expanded to a bitmap of one block. Is expanded into bitmaps in block units using block-by-block memory management, and when there is no expandable memory area in the bitmap for one block in the memory area of the memory, the memory area is divided into bands smaller than the memory area of one block. A memory management method characterized by switching to band-based memory management and developing a bitmap in band units. 2. When there is no more memory area to be allocated by band-based memory management, the previously created page-based memory area is switched to band-based memory management, and the unprocessed memory area of the band in which no bitmap exists exists. 2. The memory management method according to claim 1, wherein data is allocated and developed into a bitmap. 3. The memory management method according to claim 1, wherein a memory area of a band in which physical addresses are continuous is a memory area of one band. 4. An image forming apparatus having a page memory for expanding page description language data transmitted from a host into a bitmap and storing the bitmap, wherein the memory can be expanded into a bitmap for one page in a memory area of the page memory. If there is an area, it is developed into a bitmap using the page size memory management for the paper size. If there is no memory area that can be developed into a bitmap for one page in the memory area of the page memory, one page of image data is stored. An image forming apparatus, comprising: a memory management unit that manages the page memory so that the page management is switched to a band-by-band memory management divided into bands and developed into a bitmap in band units. 5. When the memory area to be allocated by the band-based memory management runs out, the memory management unit switches the previously created page-based memory area to the band-based memory management, and selects a band in which no bitmap exists. 5. The image forming apparatus according to claim 4, wherein the image data of the unprocessed band is assigned to the memory area and is developed into a bitmap. 6. The image forming apparatus according to claim 4, wherein the memory management unit sets a memory area of a band in which physical addresses are continuous to a memory area of one band.