JPH09222969A - Printer controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform storage control so that data does not overflow a buffer memory even when the image data of low compressibility exist in the case of transferring image data to a double-side printer. SOLUTION: A buffer memory 10 has storage capacity assuming that eight pieces of image data to be the basic unit of transfer to a printer are to be stored. Eight pieces of image data, namely, four image data pairs (pairs of front and rear sides) are stored in (A), and these pairs are read out and transferred to the printer. When the compressibility of image data is low, data overflow from the buffer memory like (B). Then, the overflowing pair is not stored in the buffer memory at this time of write like (C1) but secured to the next time of write like (C2). As for the overflowing pair, skip control for inhibiting paper feed is performed to deal with the prefeed of the printer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer control device for controlling a printer capable of double-sided printing.

[0002]

2. Description of the Related Art Generally, a printing system comprises a printer (printing device) and a printer control device (print server or the like) for controlling the printer. In the printer control device, the input image data is rearranged in a predetermined order and then transferred to the printer. That is, input image data corresponding to printing conditions (eg, double-sided / single-sided, number of prints, etc.) and printer operating conditions (eg, number of sheets to be fed at one time, sheet feeding method, output mode, etc.) The image data input in page order such as 1 page, 2 pages, 3 pages, 4 pages, etc. are sorted in the order of, for example, 2 pages, 1 page, 4 pages, 3 pages. Need to output. Note that such rearrangement is conventionally performed by using a buffer memory and an external storage device together. Here, the buffer memory is composed of a high-speed but relatively expensive semiconductor memory or the like, and the external storage device is composed of a low-speed but relatively inexpensive hard disk or the like.

When double-sided printing is performed by a printer, a buffer memory for transferring image data to the printer has at least two image data including front and back sides,
That is, it is necessary to have a storage capacity capable of storing the image data of the front surface (first printing surface) and the image data of the back surface (second printing surface) of the same sheet. In addition, a plurality of sheets (for example, four sheets) at a time on the sheet conveyance path (paper path) in the printer.
In order to adapt to a printer that enables high-speed printing by simultaneously presenting the sheets of paper, the buffer memory can store image data corresponding to both sides of a plurality of sheets of paper in accordance with such printer operating conditions. It is necessary to have a capacity.

Therefore, a printer capable of double-sided printing and high-speed printing requires a large capacity buffer memory. However, since the buffer memory is expensive, considering the system cost, the storage capacity of the buffer memory should be as small as possible.

[0005]

Since the amount of image data is enormous, the image data is compressed in order to efficiently use the storage device and shorten the transfer time. There is. That is, the input image data is compressed once, decompressed at the time of output and sent to the printer. Such data compression has the advantage that the storage capacity of the buffer memory can be reduced.

However, such data compression is
Usually, it is variable length compression, and the data amount of the compressed image data changes according to the image content. Therefore, if a predetermined number of image data is written in the buffer memory without considering the data amount, if a large amount of image data with a low compression rate is included, the data overflows from the buffer memory, and as a result,
There is a problem that printing of a specific page becomes defective.

This problem will be described with reference to FIGS. 1 (A) and 1 (B). The buffer memory 10 shown in FIG.
A printer in which the front side and the back side are alternately printed in units of M sheets, for example, the back side printing of the first to fourth sheets is performed after the front side printing of the first to fourth sheets. It is assumed that the image data is transferred to a printer that repeats the above for every four sheets. Therefore, the buffer memory 10 basically has a storage capacity capable of storing compressed image data of M sheets of paper corresponding to a transfer unit to the printer, that is, 2M (= n) compressed image data. To do.

As shown in FIG. 1A, in the normal case, the buffer memory 10 has eight pages (four sheets of paper).
Image data can be stored with a margin. In FIG. 1, an empty area 16 is created. Reference numeral 12 is a front side image data group, and 14 is a back side image data group.

However, when a large number of natural images are included, as shown in FIG.
When the image data is stored in the order of 1, 3, 5, 7, 2, 2, 4, 6, 8 with respect to 0, the image data of the last 8 pages is not completely stored, and the overflow data 20 becomes Occur. That is, the data portion 18 is stored, but the overflow data 20 portion is not stored. In such a state, when the image data of pages 1 to 8 is transferred from the buffer memory 10 to the printer through a predetermined process, only the partial printing is performed on the back surface of the fourth sheet, and a printing failure occurs. .

A conventional buffer memory management device is described in Japanese Patent Application Laid-Open No. 4-65259 and Japanese Patent Publication No. 5-19861. However, such a conventional device can effectively solve the above problem. Can not.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a printer control device for transferring image data to a double-sided printing device, even if image data having a low compression rate exists. Storage control is performed so that data does not overflow from the buffer memory.

Another object of the present invention is to prevent the data overflow from the buffer memory and to transfer the image data in conformity with the operation sequence of the double-sided printing apparatus in which the pre-feed is performed.

[0013]

In order to achieve the above object, the present invention relates to a printer control device for transferring image data to a printer for double-sided printing, and a buffer memory for storing a plurality of image data, Storage control means for writing a plurality of image data pairs to the buffer memory within a range where data overflow does not occur while using front and back image data pairs as a storage unit, and image data from the buffer memory according to operating conditions of the printer. And a transfer control means for reading and transferring to the printer.

According to the above structure, the buffer memory is
A plurality of image data pairs are stored in a storage unit corresponding to double-sided printing (that is, an image data pair of the front surface and the back surface of the same sheet). Normally, n pieces of image data (n / 2 pieces of image data pairs) corresponding to the transfer unit to the double-sided printing device are stored in the buffer memory, but when the data amount of a part of the image data is large, However, the n pieces of image data cannot be stored in the buffer memory, which may cause printing failure due to data overflow. Therefore, in the present invention, such data overflow is determined in advance, and a plurality of image data pairs are stored in the buffer memory within a range in which such data overflow does not occur.

In a preferred aspect of the present invention, the image data further includes compression means for performing variable length compression, and the image data after variable length compression is written in the buffer memory. That is, the present invention is particularly effective when compressed image data is stored in the buffer memory. In addition,
The image data read from the buffer memory is usually
After being decompressed, it is transferred to the double-sided printing device. The buffer memory preferably has a storage capacity that is premised on the storage of n pieces of image data forming a basic transfer unit. That is, according to the present invention, data overflow can be prevented without unnecessarily increasing the size of the buffer memory.

[0016] In a preferred aspect of the present invention, the storage control means sets the number of image data pairs which cannot be stored due to data overflow when n image data are to be stored in the buffer memory. Overflow pair number determining means for determining the number, storage pair number determining means for determining the storage pair number by subtracting the overflow pair number from the numerical value n, and writing for writing the image data for the storage pair number in the buffer memory And means.

According to the above configuration, n (basic transfer number)
When it is not possible to store n compressed image data in the buffer memory which is supposed to store the compressed image data of, there is not only the overflowed image data but also the front and back relation with the overflowed image data. Image data is also identified and the number of such overflow pairs is determined. Therefore, the numerical value n
If the number of overflow pairs is subtracted from, the subtraction result means the number of pairs that can be stored. Therefore, the image data for the number of storage pairs is stored in the buffer memory.

In a preferred aspect of the present invention, the storage control means further has a storage order management table in which a storage order of image data is associated with each storage pair number, and the writing means manages the storage order. Image data is written by referring to the table.

Further, in a preferred aspect of the present invention, the storage control means further comprises a data amount determination means for determining a data amount for each image data, and data in which the data amount for each image data is tabulated. Including a quantity table,
Overflow pairs are determined using the data amount table. That is, the data amount is managed for each image data, and when writing n image data to the buffer memory, the total amount of data is obtained, and the total amount of data is compared with the storage capacity to overflow. The pair is identified. of course,
The overflow pair is stored in the buffer memory on the next write and is therefore included in the next transfer unit. As the data amount of each image, when the image data is compressed, the compressed data is used.

In a preferred aspect of the present invention, when an overflow pair that cannot be stored due to data overflow occurs, the paper feed control means for prohibiting the printer from feeding the paper for the overflow pair is provided. Here, it is preferable that the paper feed control unit performs skip control that does not give a paper feed permission to the feed ready signal transmitted from the printer. That is, when an overflow pair occurs, it is not necessary to feed paper in advance, so skip control is performed to skip that paper feed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

First, the basic principle of the present invention will be described with reference to the example of FIG. As shown in (A), the buffer memory 10
In the above, storage of eight pieces of image data forming a basic transfer unit is assumed. In such a buffer memory 10, if data overflow is expected as shown in (B), the image data of the eighth page that partially overflows and the image of the seventh page that has a front-back relationship with it. The data is specified (ie, the overflow pair is specified), and as shown in (C1), the three image data pairs (the first and second page pairs, the third and fourth pages) excluding the overflow pair are identified. A pair of
The fifth and sixth page pairs) are written in the buffer memory 10 in a predetermined storage order.

Of course, when a plurality of overflow pairs occur, only the number of image data pairs obtained by subtracting the number of overflow pairs from eight are stored in the buffer memory 10. Here, the image data pair of the front surface and the back surface is used as a storage unit because it corresponds to double-sided printing. The reason that eight image data are the basic transfer unit is that the double-sided printing apparatus uses four sheets of paper. This is because it is a processing unit.

After the three image data pairs are stored as described above, the image data pairs are read from the buffer memory 10 and transferred to the double-sided printing device. In this case, since the double-sided printing device cannot acquire the image data for the basic transfer unit, the paper feed skip is executed as many times as the number of overflow pairs, as described later. Since each image data is compressed, the image data read from the buffer memory 10 is expanded before being sent to the double-sided printing device.

In the state shown in (C1), the overflow pair (image data of the 7th page and the 8th page) that could not be stored in the buffer memory 10 is as shown in (C2).
At the next writing, the data is written in the buffer memory 10 and transferred to the double-sided printing device together with other image data. As a result, for example, the first sheet after the paper feeding skip is
The image data of the page and the eighth page will be printed on both sides. This will be described in detail later.

Therefore, according to the above buffer storage management, it is possible to cope with the operation of the double-sided printing device and prevent printing defects without increasing the storage capacity of the buffer memory 10.

Next, the overall configuration of the printer control device 600 as an image processing device will be described with reference to FIG.

The printer controller 600 receives image data from a host computer via a network,
The input image data is transferred to the double-sided printing printer 610. The host interface 601 is
The image decompression unit 605 decompresses the image data received from the host computer into a bitmap, and the compression unit 6 receives the image data via the network.
03 compresses the image data expanded into the bitmap data. Hard disk 6 as a mass storage means
In 07, the compressed image data is stored in the input order.
The data amount storage unit 602 stores the size of each compressed image data. In FIG. 3, the data amount storage unit 6
The contents of the data amount management table 22 included in 02 are shown.

In FIG. 2, a buffer memory 608 (corresponding to 10 in FIG. 1) temporarily stores the image data read from the hard disk, and each image data read from the buffer memory 608 is decompressed. 60
After being decompressed at 4, the data is transferred to the printer 610 as a double-sided printing device via the printer interface 609. Here, the printer interface 609 manages communication with the printer 610 and transfer of image data. The main control unit 606 controls each component in the printer control device 600, and particularly performs write control and read control of the buffer memory 608. The main control unit 606 has the storage order management table 24 shown in FIG. This storage order table is referred to when writing image data to the buffer memory 608, and the number of writable image data without overflow of data and the storage order in that case are associated with each other. . The storage order is not represented by an absolute page number indicating the input order, but by a relative page number with the first data at the time of writing being number 1. The job information management unit 611 shown in FIG. 2 manages information regarding the print job received from the host computer.

The printer 610 of this embodiment has 1 to 4
After printing the first side of the first sheet of paper, print the second side of the first to fourth sheets of paper, and then print the first side of the fifth to eighth sheets,
The printing of the first side and the printing of the second side are alternately performed in units of four, such as printing the second side of the fifth to eighth sheets. Therefore, the basic transfer unit of data to the printer 610 is eight image data. When performing single-sided printing, there is no restriction on the operation during double-sided printing as described above, and printing is performed sequentially from the first sheet and then discharged.

FIG. 5 is a diagram showing a sheet conveying path (paper path) of the printer 610. The printer 610 is
Printing is performed by using a well-known electrophotographic method. A photosensitive member 701 is exposed by using a laser beam from a laser element (not shown), and an electrostatic latent image is formed on the photosensitive drum 701. The toner image is formed on the sheet supplied from the tray 700.

When double-sided printing is performed in this printer, after the surface (first surface) image is recorded on the photosensitive drum 701 on the paper supplied from the paper tray 700, the fixing process is performed by the fixing roller 702. The sheet is received and heads for the sheet reversing unit 703. The sheet is turned upside down in the sheet reversing unit 703, and again faces the photoconductor drum 701. The paper having the back surface (second surface) recorded on the photoconductor drum 701 is subjected to a fixing process by a fixing roller 702, and thereafter,
The sheet is discharged to the discharge tray 704. In this printer, four sheets of paper can be simultaneously present on the sheet conveyance path, and the sheet of the first side that has been recorded has the third sheet of the other three sheets before the second side is recorded. Recording on one side is performed.

Returning to FIG. 2, the buffer memory 608 is adapted to the above-described double-sided printing operation of the printer, and the buffer memory 608 has a required number of image data (compressed image data) for driving the printer 610 at the maximum speed. Has a storage capacity that can record. However, it is necessary that the storage capacity does not fall below the amount corresponding to two pages of uncompressed image data. This is because even if pages with poor compression ratio continue
This is for ensuring the transfer of at least image data corresponding to the front and back of one sheet. Here, the storage capacity of the buffer memory 608 is the compressed page amount of 8 sheets in consideration of the front and back sides of 4 sheets that are simultaneously present in the sheet conveyance path (paper path) of the printer 610. The storage order of the image data in the buffer memory 608 basically corresponds to the transfer order of the image data required to drive the printer 610 at the maximum speed. In this example, the transmission order is the first page, the third page, the fifth page, the seventh page, the second page, the fourth page, the sixth page, and the eighth page.

Next, the printer controller 600 shown in FIG.
The image input operation will be described. First, image data described in the printer description language (PDL) is input from the host interface 601. The input image data is expanded into bitmap data by the image expansion unit 605, and then compressed by the compression unit 603. Then, the compressed image data is sequentially stored in the hard disk 607. At this time, the size of the compressed image data is determined, and the data amount is stored in the data amount storage unit 602 for each page. Job information such as the number of pages of the job is stored in the job information management unit 611.

When a predetermined amount of image input processing is completed, the image output processing is started via the buffer memory 608.
Here, the predetermined amount is determined by the difference between the image input speed and the image output speed. When the printing speed of the printer is higher than the image input speed as in the present embodiment, the predetermined amount of image input is finished. Image output starts from.

FIG. 6 is a flowchart showing the specific contents of buffer management performed by the main control unit 606.

First, in S1, the total page of the print job is set to a variable "number of remaining pages", and in S2, "write top page number" is set to 1. Then, S
In 3, it is determined whether or not the "number of remaining pages" is less than eight pages. In S4, if the “remaining page number” is 8 pages or more, the “write page number” is set to 8. This means that the writing unit of the buffer memory is the image data of 8 pages.

When the "remaining page number" is less than eight pages, the "remaining page number" is directly set to the "write page number" in S5. Next, in S6, it is determined whether or not the set "write page number" of image data can be stored in the buffer memory 608. In this case, the data amount management table 2 of the data amount storage unit 602
2 (see FIG. 3), the amount of data for each page stored is referred to, and the total amount of data is compared with the storage capacity of the buffer memory.

In this case, if the image data for "the number of pages to be written" cannot be stored in the buffer memory 608,
In S7, 2 is subtracted from the "write page number". This means that the image data for two pages corresponding to the front surface and the back surface of one sheet is excluded from the storage target. 2
The reason for subtracting is that a pair of front and back image data is used as a storage unit in correspondence with double-sided printing.
That is, for example, when the back side image data overflows from the buffer memory 608, the corresponding front side image data is also excluded from the writing this time. In addition, in FIGS. 7A to 7D, four, three, two and one are respectively shown.
The state where one image data pair is stored in the buffer memory is shown.

After the execution of S7, it is checked again in S6 whether or not the image data for the "write page number" obtained by subtracting 2 can be stored in the buffer memory. If the storage is still impossible, another page is drawn in S7. .

By repeating this, the maximum even-numbered "write page number" of 8 or less at which data overflow does not occur is obtained. When the "write page number" is obtained, in S8, "write start page number" + "write page number" is calculated and the "write start page number" is updated in preparation for writing to the next buffer memory 608. To do. In S9, the storage order is determined. In that case, the storage order table 24 shown in FIG. 4 is referred to, and the storage order is determined from the number of written pages. Although the storage order is specified by the relative page number, it can be converted into an absolute page number by using the "writing first page" of this time. That is, the storage order represented by the relative address may be added to the "write first page" -1 of this time.

When the storage order is determined, in S10,
Image data is read from the hard disk 607 in this order and written in the buffer memory 608. The buffer memory 608 is a ring buffer and can be written as long as there is a free area. When the storage of the image data for the “number of pages to be written” is completed, the main control unit 606 sends a buffer memory 608 to the printer interface 609.
Request transfer of the above image data. On the other hand, after predetermined communication is performed, the decompressed image data is sent to the printer 610 via the printer interface 609.

This will be specifically described. When the writing of the image data to the buffer memory 608 is completed, the printer 610 sends signals such as a feed ready signal and an image request signal to the printer control device 600. On the other hand, the printer control device 600 sends the image data in synchronization with the page synchronization signal generated by the printer 610. As a result, the printer 610 prints. Here, the feed ready signal is a signal that is generated for each page and requests the printer control device 600 for sheet feeding permission.

FIG. 8 is a flow chart for explaining the operation of the printer interface 609 when receiving the feed ready signal.

In S10, when the feed ready signal requesting the Nth page is input to the printer interface 609, the printer interface 609
It is determined whether or not the image data of the Nth page exists in the buffer memory 608. In this case, if it exists, a permission signal is output in S11 to permit feeding of the sheet corresponding to the Nth page. On the other hand, if it does not exist, the feed is not permitted in S12.

FIG. 9 is a timing chart showing the relationship between the feed ready signal and the permission signal. It should be noted that T indicates a writing unit to the buffer memory.

FIG. 9A shows a case where image data for 8 pages are prepared in the buffer memory as shown in FIG. 1A. In this way, if all of the eight image data are stored in the buffer memory, 1, 3,
In response to the feed ready signals generated in the order of page numbers 5, 7, 2, 4, 6, and 8, permission signals are output for all pages to permit feed.

On the other hand, FIG. 9B shows a case where the image data corresponding to the 7th page and the 8th page is not stored in the buffer memory as shown in FIG. 1C1. . In this case, in response to the feed ready signals generated in the order of page numbers 1, 3, 5, 7, 2, 4, 6, the sheets other than the sheet of page 7 are permitted to be fed, and the sheet of page 7 is fed. No permission is given (no permission signal is sent), that is, skip control (shown by S in FIG. 9) is performed. It should be noted that paper conveyance and printing are performed in synchronization with the page synchronization signal, and a feed ready signal is also generated in synchronization with the page synchronization signal.

Incidentally, in the printer 610, when the fourth sheet of paper whose front surface corresponds to the seventh page is not fed, the feed signal corresponding to the eighth page corresponding to the back surface thereof is not generated.

After allowing the feed, the image data is transferred from the buffer memory 608 to the printer 610 at a predetermined timing. Printer interface 60
When the image transfer is completed, 9 notifies the main control unit 606 of this fact. The main control unit 606 enables the buffer memory 608 that has been transferred to be overwritten, and writes the image data of the subsequent page in the buffer memory 608 by the above-described algorithm.

The operation of the printer 610 is schematically shown in FIGS. As described above, this printer carries out continuous printing by feeding four sheets at the same time in the paper transport path while performing the preceding paper feeding. FIG.
1 shows the operating state of the printer to which the image data of 8 pages is supplied from the buffer memory in the state as shown in FIG. In this case, as shown in FIG. 9A, printer control is performed so that double-sided printing is performed on all four sheets on the sheet conveyance path. on the other hand,
FIG. 11 shows an operating state of the printer to which the image data of 6 pages is supplied from the buffer memory in the state as shown in FIG. 1 (C1). In this case, as shown in FIG. 9B, the skip control (shown by S in FIG. 9) which does not give the feed permission is executed in the missing data portion, so that as shown in FIG. The paper is removed and only three sheets are fed. That is, the printing speed is slightly reduced, and one sheet of paper is skipped. In FIG. 12, the operation progresses from the state of FIG.
The state where the input of eight pieces of image data as shown in (C2) is started is shown. In that state, the double-sided printing of the papers # 1 and # 2 has been completed and the papers are discharged into the discharge tray. Image data for 8 pages is printed on both sides. That is, printing on the front surface of the paper # 4 is performed after printing on the back surface of the paper # 3.
Is fed back and the back side is printed.

According to such control, when a prescribed number of image data pairs cannot be stored in the buffer memory and an overflow pair occurs, the paper feed for the overflow pair is prohibited and wasteful paper conveyance is performed. It can be prevented and efficient printing can be realized.

[0053]

As described above, according to the present invention, in a printer control device for transferring image data to a double-sided printing device, data does not overflow from the buffer memory even if image data having a low compression rate exists. As described above, the storage control can be performed, and by adapting to the operation sequence of the double-sided printing apparatus in which the pre-feed is performed, it is possible to realize the efficient control while eliminating the unnecessary paper feeding.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a configuration diagram of a printer control device according to the present invention.

FIG. 3 is a diagram showing the contents of a data amount management table.

FIG. 4 is a diagram showing the contents of a storage order management table.

FIG. 5 is a diagram schematically showing the operation of the printer.

FIG. 6 is a flowchart showing the operation of the printer control apparatus according to the present invention.

FIG. 7 is a diagram showing a state of writing image data in a buffer memory.

FIG. 8 is a flowchart showing the operation of the printer interface.

FIG. 9 is a diagram showing communication between the printer control device and the printer.

FIG. 10 is a diagram schematically showing the operation of the printer.

FIG. 11 is a diagram schematically showing the operation of the printer.

FIG. 12 is a diagram schematically showing the operation of the printer.

[Explanation of symbols]

10 buffer memory, 16 free space, 602 data amount storage unit, 606 main control unit, 607 hard disk, 608 buffer memory, 609 printer interface, 610 printer.

Claims (8)

[Claims] 1. A printer control device for transferring image data to a printer for double-sided printing, wherein a buffer memory for storing a plurality of image data and a front and back image data pair are used as a storage unit and data overflow occurs. A storage control unit that writes a plurality of image data pairs to the buffer memory within a range that does not occur, and a transfer control unit that reads image data from the buffer memory and transfers the image data to the printer according to the operating conditions of the printer. Characteristic printer control device. 2. The printer control device according to claim 1, further comprising a compression unit that compresses the image data in a variable length, and the image data after the variable length compression is written in the buffer memory. 3. The printer control device according to claim 2, wherein the buffer memory has a storage capacity that is premised on the storage of n image data forming a basic transfer unit. 4. The apparatus according to claim 3, wherein the storage control unit determines the number of image data pairs that cannot be stored due to data overflow when n image data are stored in the buffer memory. Overflow pair number determining means, a storage pair number determining means for determining the storage pair number by subtracting the overflow pair number from the numerical value n, and a writing means for writing the image data for the storage pair number in the buffer memory And a printer control device. 5. The apparatus according to claim 4, wherein the storage control unit further has a storage order management table in which a storage order of image data is associated with each number of storage pairs, and the writing unit stores the storage. A printer control device for writing image data by referring to an order management table. 6. The apparatus according to claim 4, wherein the storage control unit further includes a data amount determination unit that determines a data amount for each image data, and data that tabulates the data amount for each image data. And a quantity table, wherein an overflow pair is determined using the data quantity table. 7. The apparatus according to claim 1, further comprising paper feed control means for prohibiting the printer from feeding the paper for the overflow pair when an overflow pair that cannot be stored occurs due to data overflow. Characteristic printer control device. 8. The printer control apparatus according to claim 7, wherein the paper feed control unit performs a skip control that does not give a paper feed permission to a feed ready signal transmitted from the printer. .