JP2006217007A - Interface apparatus for companding module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interface apparatus between a DMAC and a companding module, the interface apparatus having simple configuration and capable of efficiently transferring image data. <P>SOLUTION: The interface apparatus calculates a setting value of a line length being a processing unit of a compander on the basis of line length information of data transferred from a DMA controller and a line memory capacity of the compander. When the data amount transferred from the DMA controller is greater than the line memory capacity of a compression apparatus in the case of compression, the interface apparatus divides data of one line into data whose capacity is the line memory capacity or below, and the interface apparatus transfers the divided data several times to the compression apparatus. When the data amount transferred from the DMA controller is greater than the line memory capacity of an expansion apparatus in the case of expansion, the interface apparatus merges a plurality of line data outputted from the expansion apparatus as one line and transfers the resulting data to the DMA controller. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an interface device for a compression / decompression module, and more particularly to an interface device for an image compression / decompression module incorporated in an ASIC and a general-purpose DMAC in a copying machine, a printer, or an MFP.

  Image processing apparatuses such as printers and MFPs are equipped with a compression / decompression device for the purpose of reducing the amount of data when storing images in storage such as RAM and HDD. There are various compression / decompression methods, but in the case of a compression / decompression device that is built in hardware and built into the ASIC and performs compression / decompression using line memory, the main scan of the processed image to be input to the compression / decompression device The width is limited.

Generally, the line memory is used for storing image data for one line. There are the following reasons for using a line memory.
(1) When the compression / decompression method is a two-dimensional compression method referring to the previous line.
(2) When the compression / decompression device scans an image of one line and selects an optimal compression method or internal parameters.
(3) To eliminate speed bottlenecks with external interfaces.

  In the case of having a dedicated line memory, the capacity becomes finite, and an upper limit can be set on the processable image main scanning width. The main scanning width of the image here refers to the data capacity, and if it is binary data, it matches the number of pixels, but if it is multi-value data, the amount of data increases even with the same number of pixels. There is no problem if the system has a line memory exceeding the image main scanning width handled by the system, but there is a case where a sufficient amount of line memory cannot be provided due to the limitation of the number of gates (cost) of the ASIC. On the other hand, there is a case where the main scanning width of the processed image is smaller than the line memory capacity. If the compression / decompression unit is configured to perform compression / decompression processing only in units of line memory capacity, it is necessary to add dummy data in advance so that the main scanning width of the processed image matches the line memory capacity. Further, even if the main scanning width data is equal to or smaller than the line memory, a processing unit that minimizes dummy data can be selected as long as the processing unit can be specified and processed.

  In order to cope with the limitation on the main scanning width, it is necessary to add a redundant image to the processed image in advance by software or to divide the processed image into a plurality of images. That is, the following processing is required by software.

Processing at the time of compression is as follows.
(1) The run memory capacity of the compression / decompression unit is compared with the amount of processed image data.
(2) Process the data as follows.
(A) If “run memory capacity of compression / decompressor = processed image data amount”, processing of the processed image is unnecessary.
(B) If “run memory capacity of compression / decompressor> processed image data amount”, dummy data is added to the processed image.
(C) If “run memory capacity of compression / decompression device <processed image data amount”, the processed image is divided and input to the compression / decompression device. However,
(C-1) If the “processed image data amount is an integral multiple of the run memory capacity of the compression / decompression unit”, it is not necessary to add dummy data.
(C-2) If the “processed image data amount is not an integer multiple of the run memory capacity of the compression / decompression unit”, dummy data is added to the last line.
(3) The processing information is stored in the memory in association with the processed image.
(4) The processed image data is input to the compression / decompression unit.

Processing at the time of decompression is as follows.
(1) Obtaining decompressed image data as an output of a compression / decompression machine (2) Obtain processing information associated with a processed image from a memory.
(3) The image data is restored based on the processing information.

  The operation of the image DMAC and the compression / decompression unit when there is no interface circuit between the image DMAC and the compression / decompression unit will be described. For simplicity, description of the operation of the code DMAC is omitted. At the time of compression, the image DMAC accepts a CPU activation command, reads image data in a predetermined area of the RAM, and transfers it to the compression / decompression unit. The data stored in the RAM is two-dimensional image data, and the line length is stored in advance in the IWIDTH register in the image DMAC. The image DMAC transmits a plurality of lines while indicating the end of the line by sending an EOL (End Of Line) signal to the compression / decompression unit for each line length in accordance with the value of IWIDTH. When the compression / decompression unit (or the compression unit) receives one line of data from the image DMAC, the compression / decompression unit (or the compression unit) temporarily stores the data in the line memory and then performs compression processing. Further, the compressed code data is sequentially transferred to the code DMAC.

  At the time of decompression, the image DMAC receives a CPU activation command and requests data from the compression / decompression unit. The compression / decompression unit that has been requested for data from the image DMAC receives the code data from the code DMAC, and stores the code data in the line memory while expanding the data. Further, when the line memory becomes full, the image data is transferred to the image DMAC. The image DMAC stores the transferred data in a predetermined area of the RAM. This is because (1) the line length (IWIDTH set value) of the processed image does not exceed the line memory capacity of the compression / decompression machine, and (2) the compression / decompression machine does not receive the line memory capacity from the image DMAC. This operation is established under the condition that the line length of the processed image is detected by EOL.

  For data division and dummy data addition processing, the capacity of the line memory (= the maximum set value of the processing unit in the main scanning direction of the compression / decompression unit) and the main scanning width of the processed image (not the number of pixels but the data capacity) are indicated. There is an interface device that automatically processes and restores data based on hardware based on the same information). There is also an interface device that can arbitrarily set a set value of a line length, which is a processing unit of the compression / decompression unit, by software.

The operation of the interface circuit between the image DMAC and the compression / decompression unit will be described. The operation of the interface circuit differs depending on the relationship between the main scanning width of the processed image and the line memory capacity. The classification is shown in FIG. The main scanning width of the processed image is notified from the image DMAC as a signal line as IWIDTH. The line memory capacity is stored in the register in the interface circuit as XWIDTH, and is notified to the compression / decompression unit via a signal line.
(1) If “compressor / decompressor line memory capacity> processed image data amount”, dummy data is added to the processed image.
(2) If “line memory capacity of compression / decompression device = processed image data amount”, processing of the processed image is unnecessary.
(3) If “compressor / decompressor line memory capacity <processed image data amount”, the main scan of the processed image is divided. If the “processed image data amount is an integral multiple of the line memory capacity of the compression / decompression unit”, it is not necessary to add dummy data. If the “processed image data amount is not an integral multiple of the line memory capacity of the compression / decompression unit”, dummy data is added to the last line.

A specific division method is as follows.
(A) If “compressor / decompressor line memory capacity <processed image data amount ≦ compressor / decompressor line memory capacity × 2”, the main scan of the processed image is divided into two. If it cannot be divided into two, dummy data is added to the last line so that it can be divided into two.
(B) If “compression decompressor line memory capacity × 2 <processed image data amount ≦ compress decompressor line memory capacity × 3”, the main scan of the processed image is divided into three. If it cannot be divided into three, dummy data is added to the last line so that it can be divided into three.
(C) If “compressor / decompressor line memory capacity × (k−1) <processed image data amount ≦ compressor / decompressor line memory capacity × k”, the main scan of the processed image is divided into k. If k division is not possible, dummy data is added to the last line so that k division is possible.

  The following is a conventional example of a compression / decompression device. The “image forming apparatus” disclosed in Patent Document 1 uses a fixed-capacity storage area to convert the format of image data stored in the primary storage unit, regardless of the data conversion format. This is an apparatus that can efficiently transfer image data to the secondary storage unit. The memory control unit secures a compressed image storage area (converted image storage area) on the image memory (primary storage unit). The image data written in the normal image storage area in the image memory by the input / output image DMAC is divided into predetermined size (1 byte) by the image transfer DMAC and read sequentially and transferred to the compression / decompressor. To do. Therefore, code data (converted image data) that is compressed (converted into another data format) is written in the compressed image storage area by the code transfer DMAC. The code data is transferred to the HDD (secondary storage unit) by the HDD controller.

The “image processing device” disclosed in Patent Document 2 is a device that enables compression / decompression processing of image data without using a large-capacity buffer memory. The division processing unit stores the image data input from the image reading unit as image data of a predetermined size in one of the compression buffer memories. The next image data is stored in the other compression buffer memory. At the same time, the image data stored in one compression buffer memory is output to the compression processing unit. The compression processing unit generates code data for each block from the image data input while being divided for each block of a predetermined size, and outputs the code data to the temporary storage unit. Thereby, the code data based on the image data can be generated without using a buffer memory for storing the image data for one page.
JP 2003-018336 A Japanese Patent Laid-Open No. 2003-051952

  However, the conventional compression / decompression apparatus has the following problems. In order for a compressor using a line memory to process data with a line length larger than the line memory capacity, it is necessary to divide the processing data into a plurality of times. When the compressed code data is decompressed and output by the decompressor, it is necessary to connect the plurality of output line data and transfer them to the DMA controller as one line. In the method in which these processes are performed by software, the degree of freedom of setting is increased, but calculation by software is required, so that the control becomes complicated and the processing speed is reduced. A method of implementing this software processing as hardware has also been proposed, but the hardware configuration becomes complicated and is not practical. The method of simply adding dummy data to the processed image has a problem that overhead due to dummy data transfer cannot be ignored.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems, and to efficiently transfer image data with a simple configuration in an interface device between a DMA controller and a compression / decompression module.

  In order to solve the above-described problems, the present invention has a configuration in which the setting value of the line length, which is the processing unit of the compression / decompression unit, is calculated and determined by the hardware of the interface device. That is, the image data of a predetermined unit length in the image memory is received via the DMA controller, and transferred to the compressor that performs compression processing in the setting processing unit using the line memory. Means for calculating the data length of the setting unit of the compressor based on the predetermined unit length and the capacity of the line memory, and compressing the image data of the predetermined unit length so as to divide the image data into the capacity of the line memory or less And a means for transferring the data to the compressor by dividing the data length into unit setting processing units.

  In addition, an interface device for a compression / decompression device that receives output data from a decompressor that performs decompression processing in units of setting processing using a line memory and transfers image data of a predetermined unit length to the image memory via a DMA controller. Since one or more pieces of image data in the setting unit of the decompressor are connected to form image data of a predetermined unit length, the data length of the setting unit of the decompressor is close to the capacity of the line memory, and dummy data is also reduced. As described above, the unit for calculating the setting processing unit based on the predetermined unit length and the capacity of the line memory, and one or a plurality of setting processing unit image data output from the decompressor are connected to form the image data of the predetermined unit length. And means for transferring to the image memory via the DMA controller.

  Also, for image compression / decompression device that transmits / receives image data of specified unit length in image memory to / from compression / decompression device that performs compression / decompression processing by setting processing unit using line memory Means for calculating the data length of the setting processing unit of the compression / decompressor based on the predetermined unit length and the capacity of the line memory so that the interface device divides the image data of the predetermined unit length to be equal to or less than the capacity of the line memory; A unit that divides image data of a predetermined unit length into data lengths of setting processing units of the compression / decompression unit and transfers them to the compression / decompression unit, and one or a plurality of setting processing unit image data output from the compression / decompression unit are connected. And means for transferring the image data of a predetermined unit length to the image memory via the DMA controller.

  In the present invention, the configuration as described above allows data having a line length larger than the line memory capacity to be input to the compressor without changing the DMA controller and the compressor. Furthermore, since it is not necessary to calculate and determine the set value of the line length, which is the processing unit of the compressor, by software, the control becomes simple and the processing can be speeded up.

  In addition, data having a line length larger than the line memory capacity can be obtained as the decompressed output without changing the DMA controller and the decompressor. Furthermore, since it is not necessary to calculate and determine the setting value of the line length, which is the processing unit of the decompressor, by software, the control is simplified and the processing is speeded up.

  In addition, data having a line length larger than the line memory capacity can be input to the compressor expander and obtained as a decompressed output without any change between the compression / decompressor and the DMA controller. Further, since it is not necessary to calculate and determine the set value of the line length, which is the processing unit of the compression / decompression unit, by software, the control is simplified and the processing is speeded up.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to FIGS.

  The first embodiment of the present invention calculates the set value of the line length, which is the processing unit of the compressor, based on the line length information of the data transferred from the DMA controller and the line memory capacity of the compressor, When the amount of data to be transferred is larger than the line memory capacity of the compressor, this is an interface device for a compression module that divides one line of data so that it is less than the line memory capacity and transfers it to the compressor in multiple times. .

  FIG. 1 is a system configuration diagram using an ASIC incorporating an interface circuit according to the first embodiment of the present invention. This system is an example applied to a printer or MFP. In FIG. 1, a printer controller 100 is a printer control board mounted on a printer or MPF. The CPU 101 is the main CPU of the printer controller. The ASIC 102 is an LSI incorporating a compression / decompression unit. Details are shown in FIG. The ROM 103 is a ROM incorporating a program. The RAM 104 is a main memory. The HDD 105 is a hard disk. The expansion slot 106 is a slot into which an option board can be mounted for expansion of RAM / ROM. The operation unit interface 107 is an interface for connecting an operation panel. The engine interface 108 is an interface for connecting a plotter or a scanner. The network interface 109 is an interface for connecting a LAN. The engine 110 is a main body of a plotter or a scanner. The host PC 111 is a computer that uses a plotter or a scanner.

  FIG. 2 is a configuration diagram of the ASIC 102 incorporating the interface circuit according to the first embodiment of the present invention. This ASIC 102 shows a configuration in which image data stored in the RAM 104 is compressed (encoded) by the compression / decompression device and stored in the HDD 105, and the code stored in the HDD 105 is expanded by the compression / decompression device and expanded in the RAM 104. Yes. The image or code storage device may be other than the RAM 104 and the HDD 105. In FIG. 2, a CPU 101 is a main CPU of the printer controller. The ASIC 102 is an ASIC with a built-in compression / decompression unit. The HDD 103 is a hard disk capable of storing images and codes. The RAM 104 is a memory that can store images and codes. The system control unit 113 is a circuit that controls each module in the ASIC 102 and controls access to the RAM 104 and the HDD 105 in accordance with a command from the CPU 101.

  The HDD interface 114 is a circuit that performs interface control with the HDD 105. The code DMAC 115 is a DMA controller for code transfer. This circuit transfers the code output from the compression / decompression unit 116 to the HDD 105 during compression, and inputs the code stored in the HDD 105 to the compression / decompression unit 116 during expansion. The compression / decompression unit 116 is a hardware module that compresses and decompresses an image. It may be separated into a compressor and an expander. The image DMAC 117 is a DMA controller for image transfer. The image is treated as a two-dimensional image and transferred in main scanning units. At the time of compression, the image data on the RAM 104 is input to the compression / expansion unit 116, and at the time of expansion, the image data output from the compression / expansion unit 116 is transferred to the RAM 104. The RAM interface 118 is a circuit that performs interface control with the RAM 104. The interface circuit 112 is a hardware module for transferring data between the image DMAC 117 and the compression / decompression unit 116. The line memory 119 is a buffer memory that holds data for one line.

  FIG. 3 is a diagram illustrating a configuration of the compression / decompression unit and the surroundings. The interface circuit 112 is located between the compression / decompression unit 116 and the image DMAC 117. In this circuit block, 64-bit data is exchanged by exchanging the REQ signal and the ACK signal. In FIG. 3, a compression / decompression unit 116 is a hardware module incorporating a compression / decompression algorithm executing means. The interface circuit 112 is a hardware module for transferring data between the image DMAC and the compression / decompression unit. The image DMAC 107 is a hardware module that performs DMA transfer from the memory to the compression / decompression unit (compression unit) and DMA transfer from the compression / decompression unit (decompression unit) to the memory. The interface circuit 112 has an XWIDTH register and can be set by software. The interface circuit 112 includes an arithmetic circuit, and can calculate XWIDTH based on XWIDTH_MAX (the maximum setting value of XWIDTH, that is, the line memory capacity) and IWIDTH (main scanning width of the processed image).

  FIG. 4 is a diagram illustrating case classification of operations different in the relationship between the main scanning width of the processed image and the line memory capacity in the interface circuit according to the first embodiment. FIG. 5 is a functional block diagram of a circuit for obtaining the main scanning width of the compression / decompression unit. FIG. 6 is a diagram illustrating the flow of data during compression.

  The operation of the interface circuit according to the first embodiment of the present invention configured as described above will be described. The operation of the interface circuit differs depending on the relationship between the main scanning width of the processed image and the line memory capacity. The classification is shown in FIG. The main scanning width of the processed image is notified from the image DMAC as a signal line as IWIDTH. The line memory capacity (XWIDTH_MAX) is notified from the compression / decompression unit to the interface device through a signal line. A method of setting the register of the interface device by software may be used. The interface circuit calculates based on information of XWIDTH_MAX and IWIDTH, and sets a value in the IWIDTH register inside the interface circuit. XWIDTH is notified to the compression / decompression unit via a signal line.

A method for calculating XWIDTH with an algorithm that minimizes the addition of dummy data will be described. Although the dummy data is useless data, it is encoded together with the processed image, so it should be the data with the best compression rate. In general, data corresponding to white pixels (ALL0 or ALL1) is desirable.
(1) If “compressor / decompressor line memory capacity ≧ processed image data amount”, IWIDTH is substituted into XWIDTH. If “compressor / decompressor line memory capacity = processed image data amount”, processing of the processed image is unnecessary.

(2) If “compressor / decompressor line memory capacity <processed image data amount”, the main scan of the processed image is divided. The division method is as follows.
(A) If “compressor / decompressor line memory capacity <processed image data amount ≦ compressor / decompressor line memory capacity × 2”, the main scan of the processed image is divided into two. If the processed image can be divided into two, select the value as XWIDTH. If it cannot be divided into two, dummy data is added and divided into two. The size of the dummy data is (processed image data amount mod2) and is 0 or 1.

(B) If “compression decompressor line memory capacity × 2 <processed image data amount ≦ compress decompressor line memory capacity × 3”, the main scan of the processed image is divided into three. If the processed image can be exactly divided into three, the value is selected as XWIDTH. If it cannot be divided into three, dummy data is added and divided into three. The size of the dummy data is (−processed image data amount mod3) and is 0, 1 or 2.

(C) If “compressor / decompressor line memory capacity × (k−1) <processed image data amount ≦ compressor / decompressor line memory capacity × k”, the main scan of the processed image is divided into k. If the processed image can be divided into k, the value is selected as XWIDTH. If k division is not possible, dummy data is added and k division is performed. The size of the dummy data is (−processed image data amount modk) and is any one of 0 to (k−1).

  In this way, if there is no XWIDTH that can divide the processed image into integers, XWIDTH is automatically calculated by the arithmetic circuit of the interface circuit by the method of selecting XWIDTH that minimizes the number of divisions and the amount of dummy data. . An arithmetic circuit for calculating XWIDTH will be described with reference to FIG. In the circuit of FIG. 5A, the processed image data amount M is divided by the line memory capacity NN of the compression / decompression unit, and the quotient (M / NN) is rounded up to obtain the division number k. The dummy data amount is obtained by the remainder (−M modk) obtained by dividing the negative number of the processed image data amount M by the division number k. The main scanning width N of the compression / decompression unit is obtained by adding the dummy data amount to the processed image data amount M and dividing by the division number k. FIG. 5B is another circuit example of the same function. When the division number k is 1, the amount of processed image data is the main scanning width of the compression / decompression unit. When the division number k is 2 or more, the dummy data amount is 0 to (k−1). The numerical values in parentheses shown in FIG. 5 are calculation examples.

  The operation flow of the interface circuit will be described. At the time of compression, the line memory capacity of the compression / decompression device is compared with the main scanning width of the processed image. According to the case classification of FIG. 4, the image data is input to the compression / decompression unit while processing the data. The data flow during compression is shown in FIG. The main scan width of the processed image is held as IWIDTH [13: 3] in the image DMAC. The signal is transmitted to the interface circuit through a signal line. The line memory capacity of the compression / decompression unit is held as XWIDTH [10: 3] in the interface circuit. In the example of FIG. 6, IWIDHT is 10 and XWIDTH is 3.

Therefore, the interface circuit performs the following operation.
(1) One line of image data inputted from the image DMAC is divided into four times and inputted to the compression / decompression unit.
(2) In the fourth transfer of one line, the missing data is added with dummy data and input to the compression / decompression unit.
(3) When the compression / decompression unit requires an EOL (End Of Line) signal indicating the final data of one line, EOL is generated for each line memory capacity.
(4) After the completion of one line, the image data is transferred by the same operation for the second and subsequent lines.

  The internal operation of the interface circuit during compression will be described with reference to FIGS. 64-bit data is exchanged by handshaking. Data is exchanged by burst transfer, which is an interface in which the burst is not interrupted for one line. The interface circuit has one internal buffer, and data is output at the next clock after data input. When the interface circuit is ready for transfer, it outputs REQ_D to the image DMAC and requests data. The image DMAC that has received REQ_D outputs DATA_D simultaneously with ACK_D. The interface circuit that has detected ACK_D continues to latch data every clock from the next clock. This operation is basically the same as the known burst mode DMA. The only difference is that the dummy data is prepared prior to the DMA transfer.

The following two counters are used for DMA transfer control.
(1) X counter: a counter for counting XWIDTH. The setting value of XWIDTH is loaded at the start of transfer, and counts down each time data is input from the image DMAC. When the counter value is 1, XWIDTH is loaded again.
(2) I counter: A counter that counts IWIDTH. The setting value of IWIDTH is loaded at the start of transfer, and counts down each time data is input from the image DMAC. When the counter value becomes 1, the countdown is stopped and 1 is held. When IWIDTH is an integral multiple of XWIDTH (including the case of the same value), the two counters become 1 simultaneously. In this case, there is no need to add dummy data.

The interface circuit performs the following operation while referring to the two counter values.
(1) When the data input from the image DMAC is output to the compression / decompression unit when the X counter is 1, EOL_U is asserted.
(2) When the I counter reaches 1, REQ_D is immediately negated. Further, dummy data generated internally is output to the subsequent compression / decompression unit. When the value is other than 1, input data from the image DMAC is output to the compression / decompression unit.
(3) When the two counters are both 1, one line of the processed image is completed, so the two counters are reloaded with initial values to prepare for the transfer of the next line.

  As described above, in the first embodiment of the present invention, the interface device of the compression module is a processing unit of the compressor based on the line length information of the data transferred from the DMA controller and the line memory capacity of the compressor. When the line length setting value is calculated and the amount of data transferred from the DMA controller is larger than the line memory capacity of the compressor, the data for one line is divided so that it is less than the line memory capacity and divided into multiple times. Since the data is transferred to the compressor, data having a line length larger than the line memory capacity can be input to the compressor without changing the DMA controller and the compressor.

  The second embodiment of the present invention calculates the set value of the line length, which is the processing unit of the decompressor, based on the line length information of the data transferred from the DMAC and the line memory capacity of the decompressor, and the processing data amount is When it is larger than the line memory capacity of the decompressor, it is an interface device of the decompression module that connects a plurality of line data output from the decompressor as one line and transfers them to the DMA controller.

  The configuration of the interface device according to the second embodiment of the present invention is the same as that of the first embodiment. The difference is that the setting value of the line length, which is the processing unit of the decompressor, is calculated. Since this calculation circuit and the like are the same as those in the first embodiment, description thereof will be omitted. At the time of decompression, the decompressed image data is obtained as the output of the compression / decompression unit. According to the case of FIG. 4, the image data is transferred to the memory / HDD while restoring the data.

FIG. 7 shows the data flow during decompression. Since the data compressed under the conditions of FIG. 6 is expanded, the interface circuit performs the following operation.
(1) Transfer four times of image data input from the compression / decompression device as one line and input to the image DMAC.
(2) In the fourth transfer of one line, the added dummy data is deleted and input to the image DMAC.
(3) Since the image DMAC knows the main scan width of the processed image (holds the IWIDTH data), the EOL signal is unnecessary.
(4) After the completion of one line, the image data is transferred by the same operation for the second and subsequent lines.

  The internal operation of the interface circuit during expansion will be described with reference to FIGS. This is basically the same as the well-known burst mode DMA. 64-bit data is exchanged by handshaking. Data is exchanged by burst transfer, which is an interface in which the burst is not interrupted for one line. The interface circuit has one internal buffer, and data is output at the next clock after data input. When the interface circuit receives REQ_U from the compression / decompression unit, it latches DATA_U and asserts ACK_U at the same time. The interface circuit continues to latch data every clock from the next clock.

The following two counters are used for DMA transfer control.
(1) X counter: a counter for counting XWIDTH. The setting value of XWIDTH is loaded at the start of transfer, and counts down each time data is input from the image DMAC. When the counter value is 1, XWIDTH is loaded again.
(2) I counter: A counter that counts IWIDTH. The setting value of IWIDTH is loaded at the start of transfer, and counts down each time data is input from the image DMAC. When the counter value becomes 1, the countdown is stopped, and 1 is held until the X counter becomes 1. When IWIDTH is an integral multiple of XWIDTH (including the case of the same value), the two counters become 1 simultaneously. In this case, dummy data is not added to the decompressed image, and therefore no data discarding operation occurs.

The interface circuit performs the following operation while referring to the two counter values.
(1) When the I counter reaches 1, thereafter, the data input from the compression / decompression unit is read and discarded. When the value is other than 1, input data from the compression / decompression unit is output to the image DMAC.
(2) When both counters are 1, one line of the processed image is completed, so the two counters are reloaded with initial values to prepare for the transfer of the next line.

  In the second embodiment, there is no EOL signal at the time of decompression. However, in a system that requires EOL, the following processing is performed. EOL is transferred from the compressor / decompressor every XWIDTH, but EOL is asserted to the image DMAC only when IWIDTH expires. When the data input from the compression / decompression unit is output to the image DMAC when the I counter is 1, the EOL signal is asserted.

  As described above, in the second embodiment of the present invention, the interface device of the decompression module is the processing unit of the decompressor based on the line length information of the data transferred from the DMA controller and the line memory capacity of the decompressor. When the setting value of the line length is calculated and the processing data amount is larger than the line memory capacity of the decompressor, the multiple line data output from the decompressor are connected as one line and transferred to the DMA controller. Data with a line length larger than the line memory capacity can be input to the compressor without changing the DMA controller and compressor.

  The third embodiment of the present invention calculates the set value of the line length, which is the processing unit of the compression / decompression unit, based on the line length information of the data transferred from the DMA controller and the line memory capacity of the compression / decompression unit, Sometimes, if the amount of data transferred from the DMA controller is larger than the line memory capacity of the compressor, the data for one line is divided so that it is less than the line memory capacity, transferred to the compressor in multiple times, and decompressed. Sometimes, when the processing data amount is larger than the line memory capacity of the decompressor, the interface device of the compression / decompression module connects the plurality of line data output from the decompressor as one line and transfers them to the DMA controller.

  The configuration of the interface device in the third embodiment of the present invention is the same as in the first and second embodiments. The configurations of the first and second embodiments are applied in both the compression and decompression directions. Since the configuration and operation of each are the same as those in the first and second embodiments, the description thereof is omitted.

  The interface device of the compression / decompression module according to the present invention is most suitable as an interface device between an image compression / decompression module built in an ASIC and a general-purpose DMAC in a copying machine, a printer, or an MFP. The present invention can also be applied to a processing device other than the image compression / decompression device, such as an image correction device or a digital watermark adding device.

1 is a system configuration diagram using an ASIC incorporating an interface circuit in Embodiment 1 of the present invention. It is a block diagram of ASIC which incorporates the interface circuit in Example 1 of this invention. It is a figure which shows the connection relation of the interface circuit in Example 1 of this invention, a compression / expansion device, and image DMAC. FIG. 6 is a diagram illustrating a case of different operations in the interface circuit according to the first exemplary embodiment of the present invention depending on the relationship between the main scanning width of a processed image and the line memory capacity. It is a functional block diagram of a circuit for obtaining a main scanning width of a compression / decompression device in the interface circuit according to the first embodiment of the present invention. It is a figure which shows the flow of the data at the time of compression by the interface circuit in Example 1 of this invention. It is a figure which shows the data flow at the time of expansion | extension by the interface circuit in Example 2 of this invention. It is a figure which shows the case division | segmentation of the operation | movement which is different in the conventional interface circuit by the relationship between the main scanning width | variety of a process image, and line memory capacity.

Explanation of symbols

100 ... Printer controller, 101 ... CPU, 102 ... ASIC, 103 ... ROM, 104 ... RAM, 105 ... HDD, 106 ... Expansion slot, 107 ... Operation unit Interface: 108 ... Engine interface, 109 ... Network interface, 110 ... Engine, 111 ... Host PC, 112 ... Interface circuit, 113 ... System control unit, 114 ... HDD interface , 115: Code DMAC, 116: Compression / decompression unit, 117: Image DMAC, 118: RAM interface, 119: Line memory.

Claims (3)

  An interface device for a compression / decompression device that receives image data of a predetermined unit length in an image memory via a DMA controller and transfers the image data to a compressor that performs compression processing in a set processing unit using a line memory, wherein the predetermined unit Means for calculating a data length of a set processing unit of the compressor based on the predetermined unit length and the capacity of the line memory, so as to divide the long image data into the capacity of the line memory or less, and the predetermined unit An interface device for a compression / decompression device, comprising: means for dividing long image data into data lengths of setting processing units of the compressor and transferring the data to the compressor.   An interface device for a compression / decompression device that receives output data from a decompressor that decompresses a set processing unit using a line memory and transfers image data of a predetermined unit length to the image memory via a DMA controller. In order to concatenate one or a plurality of image data of the setting unit of the decompressor into the image data of the predetermined unit length, the data length of the setting processing unit of the decompressor is a dummy close to the capacity of the line memory. A unit for calculating the setting processing unit based on the predetermined unit length and the capacity of the line memory and one or a plurality of setting processing unit image data output from the decompressor so as to reduce data And a means for transferring the image data of the predetermined unit length to the image memory via the DMA controller. Use interface device.   An interface device for a compression / decompression device that transmits / receives image data of a predetermined unit length in an image memory to / from a compression / decompression device that performs compression / decompression processing in units of setting processing using a line memory while transmitting / receiving the image data via a DMA controller And setting the data length of the setting processing unit of the compression / decompression unit based on the predetermined unit length and the capacity of the line memory so as to divide the image data of the predetermined unit length below the capacity of the line memory. Means for calculating, means for dividing the image data of the predetermined unit length into data lengths of setting processing units of the compression / decompression unit and transferring them to the compression / decompression unit, and setting processing units output from the compression / decompression unit Means for concatenating one or a plurality of image data and transferring the image data as the predetermined unit length to the image memory via the DMA controller. Decompression dexterity interface device, characterized in that.

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