JPH11249832A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the burden of a system bus by simplifying video data transfer processing. SOLUTION: When expanding print data as dot image data in a page memory 101 of a RAM 10, the pattern of respective blocks in image data at the time of dividing respective lines into four is decoded, and the print data are expanded while adding the data of 8 bits to the head of image data for one line with that information as a line header 102. Corresponding to the line header 102 in the head of respective lines of image data in the page memory 101, an image correcting part 11 discriminates whether the data of respective blocks are white or black fixed data or any other pattern data and when they are white or black fixed data, the white or black fixed data are outputted as video data. When the data of respective blocks are discriminated as any pattern data excepting for fixed data, video image data are outputted by DMA transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer or a multifunctional copying machine, and more particularly to a method for reducing a load on a system bus.

[0002]

2. Description of the Related Art When printing black-and-white document data from a host device to a printer device and printing it, image data for one page is developed in a page buffer of a RAM in a controller of the printer device, and the developed image For all lines from the first line to the last line in the printing direction, binary print image data of white or black is read in order and sent to the printer engine and printed on recording paper.

[0003]

However, if the binary print pixel data of white or black is sequentially read and sent to the printer engine for all the lines irrespective of the content of the developed image data of one page, Video DMA processing for reading all the data for one page from the RAM is required. Although the access speed of the RAM is increased, the bus is occupied during the access, and other systems cannot process. In particular, in a high-speed printer with a high printing speed, the video clock frequency is high and often causes a bottleneck in image processing. In some cases, the bus for the image memory is dedicated to support the system bus separately from the system bus. However, in this case, the number of data buses increases, and the layout of the substrate and the design of the gate array become complicated and cost increases. .

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages and to obtain an image forming apparatus capable of reducing the number of accesses to a memory, simplifying a video data transfer process and reducing the load on a system bus. .

[0005]

An image forming apparatus according to the present invention receives a character information or image information from a host device and generates image image information, and a recording medium receiving the image image information formed by the controller. In an image forming apparatus having a printing unit for forming an image thereon, when print data is developed in a memory of a controller, one line at the beginning of one line data is all black or white fixed data or other data. Image mask information indicating whether the pattern data includes the pattern data described above, and whether or not to perform the video data transfer processing is determined based on the information.

It is preferable that the image mask information is provided with N-bit mask information obtained by dividing one line into N, and whether or not video data transfer processing is performed for each block is determined based on the information.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A printer according to the present invention has a controller and a printer engine. The controller is a host interface and a CPU that communicate with the host device.
ASIC, program ROM, font ROM, RA
M, an image correction unit, and an engine interface.
The page memory of the RAM has a block image data area obtained by dividing, for example, video image data into four for each line, and has an 8-bit line header at the head of each line. The line header indicates image mask information indicating whether the data is all black or white fixed data or other pattern data for each block obtained by dividing one line into four.

When print data is sent from the host device to the printer device and is developed as dot image data in the page memory of the RAM, the pattern of each block of image data when each line is divided into four is decoded. Information is used as a line header, and 8-bit data is added to the head of one line of image data and developed. The image data expanded in the page memory is processed by the image correction unit, and the video data is transmitted to the printer engine. The image correction unit determines whether the data of each block is white or black fixed data or other pattern data based on the image mask information indicated in the first line header of each line of the image data in the page memory, In the case of black fixed data, white or black fixed data is output as video data. When the data of each block is determined to be pattern data other than white or black fixed data,
The video image data is DMA-transferred and output. In this way, the DMA transfer is reduced and the load on the system bus is reduced.

[0009]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. As shown in the figure, a printer device 1 is connected to a host device 2, prints print data sent from the host device 2, and has a controller 3 and a printer engine 4 for actually performing printing. The controller 3 has a host interface 5, a CPU 6, an ASIC 7, a program ROM 8, a font ROM 9, a RAM 10, an image correction unit 11, and an engine interface 12. Host interface 5 is Centro I / F or RS2
32C, and communicates with the host device 2. CPU
Reference numeral 6 controls the entire controller 3 by a program in the program ROM 8 or a command from the host device 2.
The ASIC 7 controls a bus to a device of the controller 3 or an external interface. Program RO
The control program of the controller 3 and the image correction pattern of the image correction unit 11 are stored in M8. Font R
The OM 9 stores font pattern data and the like. The RAM 10 is used as a work memory for the CPU 6, an input buffer for input data, a page memory for print data, and the like. As shown in FIG. 2, the page memory 101 of the RAM 10 has, for each line, a block image data area 103 obtained by dividing video image data into four, for example, and has an 8-bit line header 102 at the head of each line. The image correction unit 11 is a page memory 10 of the RAM 10
The image data is corrected for image data and sent to the engine interface 12, and includes a video buffer 111, a frequency divider 112, a block selector 113, and a video selector 114 as shown in FIG. The video buffer 111 is the page buffer 101 of the RAM 10
Is temporarily stored. Frequency divider 112
Receives a line gate signal and a video clock and generates, for example, a pulse obtained by dividing the number of video clocks (line gate length) for one line into four. Block selector 11
Reference numeral 3 switches the information of the line header 102 every １ ／ line (one block) of each line of the video image data. The video selector 114 is a block selector 11
Line header 102 in the block output from 3
The video image data is switched according to the information. The engine interface 12 communicates commands, statuses and print data with the printer engine 4.

When print data is sent from the host device 2 to the printer device 1 configured as described above, the sent print data is developed as dot image data in the page memory 101 of the RAM 10. At this time, the pattern of each block of the image data when each line is divided into four, for example, is decoded, and the information is used as a line header 102 as 8 lines.
Bit data is added to the head of one line of image data and developed. Assuming that the line header 102 has a pattern as shown in FIG. 2 when, for example, the first three lines are focused and each line is divided into four, as shown in FIG. And the identifiers B / W1 to B / W4. The masks M1 to M4 indicate whether the corresponding block is black or white fixed data or other pattern data, and the identifiers B / W1 to B / W4 indicate the data when the mask M of the corresponding block is fixed data. Indicates whether it is black or white. For example, taking the first line of the image data shown in FIG. 2 as an example, since all data is white (L) in block 1 of the block image data area 103 divided into four, M1 = 1 is fixed data. B / W1 = 0 indicates white data. In block 2, all data is black (H),
M2 = 1 indicates fixed data, and B / W2
= 1 indicates black data. In block 3, since all data is not white or black, M3 = 0, B
/ W3 = (-) indicates pattern data.
In block 4, since all data is black, M4 = 1, B
/ W4 = 1. When all the image data of one page is expanded to the last line in the page memory 101 in this manner, a print start signal is sent to the printer engine 4, and the video data is transmitted to start printing.

The operation when the image data expanded in the page memory 101 is processed by the image correcting section 11 and the video data is transmitted to the printer engine 4 will be described with reference to the flowchart of FIG. When printing starts, the page memory 102 sequentially reads the image data from the top line, stores the read image data in the video buffer 111 of the image correction unit 11, and reads the top line header 102 of each line into the block selector 113. A signal obtained by dividing one line gate length by four from the frequency divider 112 is input to the block selector 113, and the masks M1 to M4 of the line header 102 and the identifiers B / W1 to
B / W4 is switched for each block. First, in block 1 of the first line, the mask M1 of the line header 102
And the identifier B / W1 are output and sent to the video selector 114. The video selector 114 switches video data according to the contents of the headers M and B / W. In the case of the image data shown in FIG.
Since 1 and B / W1 = 0, white (L) fixed data is selected and output as video data. This process is repeated for blocks 2, 3, and 4. That is, in block 2, M2 =
1, B / W2 = 1, so that black fixed data is output. In block 3, M3 = 0, and B / W3 = (-), a video DMA request is issued to the ASIC 7, and the page memory 102 outputs video image data of block 3. To DM
A is transferred and the data is output. In block 4, since M4 = 1 and B / W4 = 1, black fixed data is output as video data. This process is performed for each line. For example, in the case of the image data shown in FIG. 2, since there is no fixed data which is all white or black in line 2 in any block, DMA transfer processing for one line data is required and the time occupying the system bus increases. In line 3, since all blocks are white fixed data,
It is not necessary to perform the MA transfer even once, and the load on the system bus can be reduced.

Although the above embodiment has been described in connection with the case where the video image data is divided into four for each line, the load on the system bus can be reduced in the same manner without dividing the video image data for each line. . In this case, the line header is 2 bits and the block selector 113
In the case of the image data shown in FIG. 2, since all of the lines 1 and 2 are not fixed black or white data, DMA transfer processing for one line data is required. 3 is all white data, the video selector 114 selects white data and outputs it as video data, thereby eliminating the need for video DMA transfer processing.

[0013]

As described above, according to the present invention, when print data is developed into image data, one line of data is fixed to black or white at the beginning of one line data, or a pattern other than that is used. Because image mask information indicating whether or not data is included is provided, and whether or not video data transfer processing is performed is determined based on the information, and video data transfer processing is performed only when one line is not all black or white fixed data. Thus, the burden on the system bus can be reduced.

Further, the video data transfer processing is further improved by providing the image mask information with N-bit mask information obtained by dividing one line into N, and determining whether or not to perform the video data transfer processing for each block based on the information. This can be simplified, and the load on the system bus can be further reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a page memory of a RAM.

FIG. 3 is a block diagram illustrating a configuration of an image correction unit.

FIG. 4 is a configuration diagram of a line header of a page memory.

FIG. 5 is a flowchart showing the operation of the embodiment.

[Explanation of symbols]

 Reference Signs List 1 printer device 2 host device 3 controller 4 printer engine 5 host interface 6 CPU 7 ASIC 10 RAM 11 image correction unit 12 engine interface 101 page memory 102 line header 103 block image data area 111 video buffer 112 frequency divider 113 block selector 114 video selector

Claims (2)

[Claims] An image forming apparatus comprising: a controller that receives character information and image information from a host device to generate image image information; and a printing unit that receives image image information formed by the controller and forms an image on a recording medium. When the print data is developed in the memory of the controller, the first line of the line data has image mask information indicating whether all lines are fixed black or white data or include other pattern data. An image forming apparatus for determining whether to perform a video data transfer process based on the information. 2. The image forming apparatus according to claim 1, wherein the image mask information includes N-bit mask information obtained by dividing one line into N, and whether or not video data transfer processing is performed for each block is determined based on the information.