JP7558728B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus that forms an image on a recording medium based on an image read by an image reading device that reads an image of a document.

Multifunction devices and multifunction printers handle a variety of image data, including image data read by an image reading device that reads images from documents, image data that has been converted from the read image data for printing, image data to be sent to an external device, and image data that has been expanded from PDL data sent from a PC.

JP 2001-238038 A

Patent document 1 describes a configuration in which this image data is transferred to various image processing units of the device via a common image data bus, where the necessary processing is performed, and then transferred to an external device or printer. Patent document 1 also describes that image data obtained by the image reading device and image data for printing are transferred alternately on a line-by-line basis on the common image data bus. As a result, it describes that the operation of transferring image data obtained by the image reading device to an external computer and the printing operation of transferring image data for printing from the external device to a printer can be performed simultaneously using the common image data bus.

However, in the above-mentioned Patent Document 1, the bandwidth usage of the image data bus may reach the upper limit of the bandwidth of the image data bus. When this happens, the processing cannot keep up, and an error occurs, causing the device to stop, or other malfunctions.

In view of the above problem, the present invention aims to prevent the bandwidth usage of the data bus from reaching its upper limit.

In order to solve the above problems, an image forming apparatus according to the present invention comprises:
In an image forming apparatus including an image forming unit that forms an image on a recording medium,
an image reading unit that reads an image of a document based on an instruction to start reading the image of the document and outputs pixel data corresponding to the read result;
a control unit that executes a first process of transferring pixel data output from the image reading unit to the image forming unit via a data bus, and a second process of converting data input from an external device of the image forming apparatus into pixel data for forming an image on the recording medium, and transferring the converted pixel data to the image forming unit via the data bus;
having
the image forming unit forms an image on the recording medium based on pixel data transferred via the data bus;
the image reading unit outputs pixel data corresponding to the reading result in a first cycle if the control unit is not executing the second process when the instruction is input, and outputs pixel data corresponding to the reading result in a second cycle longer than the first cycle if the control unit is executing the second process when the instruction is input ;
The image reading unit is characterized in that, when outputting in the first cycle, after outputting pixel data obtained by reading the image of the original document, it does not add an empty data section in which no pixel data is output, and when outputting in the second cycle, after outputting pixel data obtained by reading the image of the original document, it adds an empty data section in which no pixel data is output, thereby resulting in output data for one cycle .

This invention makes it possible to prevent data bus bandwidth usage from reaching its upper limit.

1 is a cross-sectional view of an image forming apparatus according to a first embodiment. FIG. 1 is a block diagram according to a first embodiment. FIG. 2 is a block diagram relating to an image data output control unit 105. FIG. 4 is a diagram illustrating a control flow according to the first embodiment. 4 is a time chart showing a period of a horizontal synchronization signal HSYNC and a pixel configuration of read image data.

First Embodiment
Preferred embodiments of the present invention will be described below with reference to the drawings. However, the shapes of the components and their relative positions described in the embodiments may be changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions, and the scope of the present invention is not intended to be limited to the following embodiments.

Figure 1 is a cross-sectional view showing the configuration of a monochrome electrophotographic copying machine (hereinafter referred to as an image forming apparatus) 1 used in this embodiment. Note that the image forming apparatus may be, for example, a facsimile machine, a printing machine, a printer, etc. Also, the recording method is not limited to the electrophotographic method, and may be, for example, an inkjet method. Furthermore, the type of the image forming apparatus may be either monochrome or color.

The configuration and functions of the image forming device 1 will be described below with reference to FIG. 1. As shown in FIG. 1, the image forming device 1 has an image reading device 100 and an image printing device 301.

The documents P loaded on the document stacking section 2 are fed one by one by the pickup roller 3, and then transported further downstream by the feed roller 4. Opposite the feed roller 4 is a separation roller 5 that is pressed against the feed roller 4. The separation roller 5 is configured to rotate when a load torque equal to or greater than a predetermined torque is applied to the separation roller 5, and has the function of separating documents that are fed in a two-sheet stack.

The pickup roller 3 and the feed roller 4 are connected by a swing arm 12. The swing arm 12 is supported by the rotation shaft of the feed roller 4 so that it can rotate around the rotation shaft of the feed roller 4.

The document P is transported by various transport rollers such as the feed roller 4 and the transport roller 6, and is discharged onto the discharge tray 10 by the discharge roller 11.

Pixel data representing an image read by the document reading unit 16, which reads the image on the first side of the document being transported, is output to the image reading control unit 101, which will be described later. Note that the image read by the document reading unit 16 is represented by multiple pixels, and the pixel data corresponds to data for one pixel. Note that, hereinafter, the pixel data is also referred to as image data.

In addition, image data representing the image read by the document reading unit 17, which reads the image on the second side of the document being transported, is output to the image reading control unit 101 in the same manner as described for the document reading unit 16.

The manuscript is read as described above.

There are two document reading modes: a first reading mode and a second reading mode. The first reading mode is a mode in which an image of a document transported by the method described above is read. The second reading mode is a mode in which an image of a document placed on the document glass 214 (transparent member) is read by the document reading unit 16, which moves at a constant speed. Normally, images of sheet-like documents are read in the first reading mode, and images of bound documents such as books and pamphlets are read in the second reading mode.

Inside the image printing device 301, sheet storage trays 302 and 304 are provided. Different types of recording media can be stored in the sheet storage trays 302 and 304. For example, A4 size plain paper is stored in the sheet storage tray 302, and A4 size thick paper is stored in the sheet storage tray 304. Note that a recording medium is something on which an image is formed by the image forming device, and examples of recording media include paper, resin sheets, cloth, overhead projector sheets, labels, etc.

The recording medium stored in the sheet storage tray 302 is fed by the pickup roller 303 and sent to the registration roller 308 by the transport roller 306. The recording medium stored in the sheet storage tray 304 is fed by the pickup roller 305 and sent to the registration roller 308 by the transport rollers 307 and 306.

The image signal output from the image reading device 100 is input to an optical scanning device 311 including a semiconductor laser and a polygon mirror. The outer peripheral surface of the photosensitive drum 309 is charged by a charger 310. After the outer peripheral surface of the photosensitive drum 309 is charged, a laser beam corresponding to the image signal input from the document reading device 200 to the optical scanning device 311 is irradiated onto the outer peripheral surface of the photosensitive drum 309 from the optical scanning device 311 via the polygon mirror and mirrors 312 and 313. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 309.

The electrostatic latent image is then developed by toner in the developer 314, forming a toner image on the outer peripheral surface of the photosensitive drum 309. The toner image formed on the photosensitive drum 309 is transferred to the recording medium by a transfer charger 315 provided at a position (transfer position) opposite the photosensitive drum 309. The registration roller 308 feeds the recording medium to the transfer position in accordance with the transfer timing at which the image is transferred to the recording medium by the transfer charger 315.

As described above, the recording medium onto which the toner image has been transferred is sent to the fixing device 318 by the conveyor belt 317, where it is heated and pressurized to fix the toner image onto the recording medium.

When an image is formed in single-sided printing mode, the recording medium that has passed through the fixing unit 318 is discharged to a discharge tray (not shown) by discharge rollers 319 and 324. When an image is formed in double-sided printing mode, the recording medium is conveyed to a reversal path 325 by discharge rollers 319, conveyance rollers 320, and reversal rollers 321 after a fixing process is performed on the first side of the recording medium by the fixing unit 318. The recording medium is then conveyed again to the registration rollers 308 by conveyance rollers 322 and 323, and an image is formed on the second side of the recording medium by the method described above. The recording medium is then discharged to a discharge tray (not shown) by discharge rollers 319 and 324.

Figure 2 is a block diagram of the image forming device 1 according to this embodiment. Note that the image reading control unit 101 and the main controller unit 107 are configured with at least one ASIC, and execute the functions described below.

The image reading control unit 101 is provided in the image reading device 100, and processes the image data sent from the document reading units 16 and 17, and controls the image reading device 100. The read image data receiving unit 102 receives the image data output from the document reading units 16 and 17. The shading correction unit 103 performs shading correction on the image data.

The buffer memory 104 holds the image data after shading correction. The scanner image data output control unit 105 controls the output of image data to the main controller unit 107. The scanner image data output control unit 105 reads out and outputs the image data stored in the buffer memory 104 one line at a time. The data rate (frequency) of the image data read out from the buffer memory 104 can be set to any value, and the number of image data pixels in one line can also be set to any value. The buffer memory 104 may be a page memory that holds multiple pages of scanned image data, or may be configured as a line memory that holds multiple lines of image data.

The CPU 106 controls each component of the image reading device 100 and the image reading control unit 101.

The main controller unit 107 processes the image data received from the image reading control unit 101 and the PDL data received from the outside. The scanner image data receiving unit 108 receives the image data output by the scanner image data output control unit 105. The scanner image processing unit 109 processes the image data received by the scanner image data receiving unit 108 (such as color conversion processing) so that the image printing device 301 can form (print) an image corresponding to the image data. The image data bus 110 is a data bus capable of transferring image data, is connected to various control units, and serves as a bus for exchanging image data throughout the device.

The image data processed by the scanner image processing unit 109 is sent via the output unit 118 to a print control unit 400 that controls the image printing device 301. The print control unit 400 is provided in the image printing device 301. Note that the main controller unit may be provided in the image reading device 100 or in the image printing device 301.

The printer image processing unit 111 converts the PDL data sent from an external computer into bitmap data, and generates image data for the image printing device 301 to form (print) an image corresponding to the image data. The generated image data is sent via the output unit 118 to the print control unit 400 that controls the image printing device 301.

The image compression unit 112 compresses the image data sent from the scanner image processing unit 109 via the image data bus 110 into a format such as JPEG. The RAM 113 functions as a buffer for the image data flowing on the image data bus 110, and inputs and outputs image data as necessary. When the bandwidth usage of the image data bus 110 reaches its upper limit, the image data is temporarily saved in the RAM 113 before the upper limit is reached in order to secure the data bandwidth, and the amount of image data flowing on the image data bus 110 is reduced.

The system bus 114 is a control bus through which data for controlling the main controller unit 107 flows. The image data bus I/F 115 is a bus bridge that connects the system bus 114 and the image data bus 110 and converts the data structure.

The network I/F 116 is a circuit that exchanges data with external network devices such as a LAN. For example, when an original image read by the image reading device 100 is sent to an external device, the image data from the scanner image processing unit 109 is sent to the image compression unit 112 via the image data bus 110 and compressed into JPEG format. The compressed image data is then sent from the network I/F 116 to the external device via the image data bus I/F 115 and the system bus 114. The network I/F 116 also receives data from the external device. The received PDL data for printing is sent to the image data bus 110 via the system bus 114 and the image data bus I/F 115, sent to the printer image processing unit 111, and then output to the print control unit 400. The system bus 114 is also connected to a fax modem and an operation unit 120 via an operation unit I/F for user operation.

The CPU 117 controls the entire main controller unit 107. The CPU 117 can communicate with the CPU 106 of the image reading control unit 101, and controls the image reading control unit 101. The CPU 117 sets the image clock frequency VCLK corresponding to the frequency (period) at which the scanner image data output control unit 105 outputs image data, and sets the period of the image data line synchronization signal HSYNC, via the CPU 106 of the image reading control unit 101. The scanner image data output control unit 105 outputs image data in synchronization with the image clock frequency VCLK.

Figure 3 is a block diagram showing the details of the scanner image data output control unit 105.

The scanner image data output control unit 105 has a clock generator 201 and a control signal generation unit 202 inside. The reference clock source 200 is a crystal oscillator or the like, and generates the reference clock. The clock generator 201 has a built-in frequency synthesizer circuit that uses a PLL, and can generate a clock signal of any frequency from the reference clock signal.

The control signal generating unit 202 uses the clock signal generated by the clock generator 201 to generate a read control signal that controls the timing of reading out the image data held in the buffer memory 104, and an image clock signal VCLK. Therefore, by changing the frequency of the clock signal generated by the clock generator 201, it is possible to control the frequency of the image clock signal VCLK and the timing of reading out the image data from the buffer memory 104.

The control signal generating unit 202 also generates a horizontal synchronization signal HSYNC to be output to the scanner image data receiving unit 108. The control signal generating unit 202 has a counter circuit (not shown) that operates at the same clock frequency as the image clock VCLK. By setting a count value in this counter that is the basis for the period of the horizontal synchronization signal HSYNC, it is possible to generate a horizontal synchronization signal HSYNC of any period synchronized with the image clock VCLK. In other words, by changing the value of the counter that the control signal generating unit 202 has, it is possible to change the number of image clock signals VCLK included in one period of the horizontal synchronization signal.

Register 203 holds the setting value of the frequency of the clock signal generated by clock generator 201 and the setting value (count value) of the cycle of the horizontal synchronization signal HSYNC of control signal generating unit 202. Based on instructions from CPU 117, CPU 106 changes or sets the setting value of the frequency of the clock signal held in register 203 and the setting value of the cycle of the horizontal synchronization signal HSYNC. CPU 117 calculates the bandwidth usage of image data bus 110 and instructs CPU 106 to change each setting value based on the calculation results.

Figure 4 is a diagram explaining the control flow. The processing of the flowchart shown in Figure 4 is executed by the CPU 117.

The CPU 117 receives an instruction from the user via the operation unit 120 to start a job using the image reading device 100, such as copying or image transmission (S300).

S301 is a step for calculating the bandwidth used on the image data bus 110. The CPU 117 calculates the total bandwidth of the image data bus 110 that will be used by the submitted reading job and the bandwidth used by jobs such as printing that are currently being processed.

The CPU 117 determines whether the total bandwidth value calculated in S301 exceeds a first predetermined value (S302). If the total bandwidth value calculated exceeds the first predetermined value, the CPU 117 advances the process to S303. Note that the first predetermined value is a value smaller than the upper limit of the bandwidth of the image data bus 110.

If the calculated total bandwidth does not exceed the first predetermined value, the CPU 117 instructs the CPU 106 to execute the reading job (S307). As a result, the image reading device 100 reads the document.

S303 is the first bandwidth usage fee reduction process.

In S303, a process is performed to reduce the frequency of the image clock signal VCLK output by the control signal generating unit 202. The CPU 117 instructs the CPU 106 to reduce the frequency of the image clock signal VCLK. The CPU 106 changes the frequency of the image clock signal VCLK in response to the instruction from the CPU 117. For example, if the normal frequency is 50 MHz and the frequency after frequency switching is set to 42.5 MHz, the bandwidth usage of the image data by the reading job on the image data bus 110 is reduced by 15%.

In S302, if the total bandwidth value calculated in S301 exceeds a second predetermined value that is greater than the first predetermined value, the process proceeds to S304. S304 is a second bandwidth usage reduction process. The second predetermined value is a value smaller than the upper limit of the bandwidth of the image data bus 110.

In S304, a process is performed to extend the period of the horizontal synchronization signal HSYNC. The CPU 117 instructs the CPU 106 to extend the period of the horizontal synchronization signal HSYNC, and the CPU 106, upon receiving this, rewrites the value of the register 203 to switch the period of the horizontal synchronization signal HSYNC. For example, the normal period setting is count value = 7048, period = 140.96 us, and after period switching, the count value = 10070, period = 201.4 us.

Figure 5 shows the horizontal synchronization signal period, count value, and pixel configuration of image data under normal conditions and after the horizontal synchronization signal period is expanded. Figure 4 (a) shows an example under normal conditions, where the count number is 7048 within one period of the horizontal synchronization signal. From the start timing of the horizontal synchronization signal period, 16 pixels of invalid pixel data are added, and then the number of valid image pixels is 7016 pixels (corresponding to the longitudinal size of an A4 document of 297 mm), and then the pixel configuration is such that 16 pixels of invalid pixel data are added. In this embodiment, in the portion of the 16 pixels of invalid pixel data, the control signal generating unit 202 outputs the image clock VCLK to the scanner image data receiving unit 108, but does not output a read control signal for reading image data from the buffer memory 104. In other words, during the 16 pixels of image data that are indicated as invalid pixel data, the image data is not actually output to the scanner image data receiving unit 108.

Figure 4(b) is an example when the cycle of the horizontal synchronization signal is switched. The count number is 10070 within one cycle of the horizontal synchronization signal. From the start timing of the cycle of the horizontal synchronization signal, 16 pixels of invalid pixel data are added, then there are 7016 valid image pixels (corresponding to the longitudinal size of an A4 document, 297 mm), then there are 3022 pixels of null data, and then 16 pixels of invalid pixel data are added, resulting in a pixel configuration. The processing of the null data is the same as that of the invalid pixel data in Figure 4(a). In other words, during the null data section, the image clock VCLK is output to the scanner image data receiving unit 108, but image data is not output. Therefore, during the null data section and the invalid pixel data section, image data does not flow on the image data bus 110.

In S302, if the total bandwidth value calculated in S301 exceeds a third predetermined value that is greater than the second predetermined value, the process proceeds to S305. S305 and S306 are a third bandwidth usage reduction process. The third bandwidth usage reduction process implements both the first and second bandwidth usage reduction processes, and the first bandwidth usage reduction process is implemented in S305, followed by the second bandwidth usage reduction process in S306. The third predetermined value is a value smaller than the upper limit of the bandwidth of the image data bus 110.

After performing any of the bandwidth usage reduction processes from S303 to S306, the process proceeds to S307, and scanning of the document begins.

S308 is a step for determining whether or not there is a next document to be read. If there is a next document, the process returns to S307 and continues reading the document. If there is no next document, the process proceeds to S309. S309 is a step for returning the frequency of the image clock VCLK and the cycle of the horizontal synchronization signal HSYNC, which were set in the bandwidth usage reduction process, to their normal settings. Once the settings have been returned to their normal values, the reading job ends.

As described above, in this embodiment, when a reading job using the image reading device 100 is submitted, the total value of the bandwidth of the image data bus 110 used by that job and the bandwidth used by a job such as printing currently being processed is calculated. Then, based on the calculated total value, the image clock frequency VCLK and the period of the horizontal synchronization signal are changed. As a result, it is possible to prevent the usage of the data bus bandwidth from reaching the upper limit.

When performing the bandwidth usage reduction process, if necessary, the document transport speed of the image reading device 100 may be reduced in conjunction with the bandwidth usage reduction process, or control may be implemented to increase the distance between documents.

In addition, in this embodiment, the frequency of the image clock signal VCLK and the period of the horizontal synchronization signal HSYNC output by the control signal generating unit 202 are switched between two stages, normal and reduced bandwidth usage, in response to an instruction from the CPU 117, but this is not limited to two stages. Also, the CPU 117 may notify the CPU 106 of specific numerical values for the frequency of the image clock signal VCLK and the period of the horizontal synchronization signal HSYNC.

In addition, in this embodiment, the frequency of the image clock signal VCLK and the period of the horizontal synchronization signal HSYNC are switched on a job-by-job basis in the image reading device 100, but they may also be switched on a page-by-page basis in the read image data.

The functions of CPU 106 may be performed by CPU 117, or the functions of CPU 117 may be performed by CPU 106.

The image printing device 301 and the print control unit 400 are included in the image forming unit. The document reading units 16 and 17 are included in the image reading unit.

The reading job using the image reading device 100 is included in the first process. Specifically, the process of transferring the image data output from the scanner image data output control unit 105 to the print control unit 400 via the image data bus 110 is included in the first process.

The print job in which the image printing device 301 forms an image based on the PDL data sent from the external device is included in the second process. Specifically, the second process includes the process of converting the PDL data sent from the external device into bitmap data, generating image data for printing by the image printing device 301, and transferring the generated image data to the print control unit 400 via the image data bus 110.

Second Embodiment
Description of parts having the same configuration as the first embodiment will be omitted.

In the first embodiment, the frequency of the image clock frequency VCLK and the period of the horizontal synchronization signal are changed based on the total value of the bandwidth of the image data bus 110 used by the input reading job and the bandwidth used by a job such as printing currently being processed. In this embodiment, when a reading job using the image reading device 100 is input, the frequency of the image clock signal VCLK is changed based on whether a print job in which the image printing device 301 forms an image based on PDL data sent from an external device is being executed. Specifically, when a reading job is input, if a print job in which the image printing device 301 forms an image based on PDL data sent from an external device is being executed, the CPU 117 instructs the CPU 106 to reduce the frequency of the image clock signal VCLK. On the other hand, when a reading job is input, if a print job in which the image printing device 301 forms an image based on PDL data sent from an external device is not being executed, the CPU 117 does not switch the frequency of the image clock signal VCLK. That is, in this embodiment, if the second process is being executed when a reading job is submitted, the CPU 117 instructs the CPU 106 to reduce the frequency of the image clock signal VCLK. On the other hand, if the second process is not being executed when a reading job is submitted, the CPU 117 does not switch the frequency of the image clock signal VCLK.

As described above, in this embodiment, when a reading job using the image reading device 100 is submitted, the frequency of the image clock signal VCLK is changed based on whether a print job is being executed in which the image printing device 301 forms an image based on PDL data sent from an external device. As a result, it is possible to prevent the bandwidth usage of the data bus from reaching the upper limit.

The following configuration may also be applied. Specifically, when a reading job is submitted, if a print job in which the resolution of the image to be formed is set to a first resolution is in progress, CPU 117 instructs CPU 106 to reduce the frequency of the image clock signal VCLK. On the other hand, when a reading job is submitted, if a print job in which the resolution of the image to be formed is set to a second resolution lower than the first resolution is in progress, CPU 117 does not switch the frequency of the image clock signal VCLK. This is because the higher the resolution of the image to be formed, the greater the bandwidth usage of image data bus 110.

In this embodiment, the frequency of the image clock signal VCLK is changed, but this is not the only option. For example, the period of the horizontal synchronization signal HSYNC may be changed.

Reference Signs List 16, 17 Document reading unit 101 Image reading control unit 104 Buffer memory 105 Scanner image data output control unit 107 Main controller unit 301 Image printing device 400 Print control unit

Claims (6)

In an image forming apparatus including an image forming unit that forms an image on a recording medium,
an image reading unit that reads an image of a document based on an instruction to start reading the image of the document and outputs pixel data corresponding to the read result;
a control unit that executes a first process of transferring pixel data output from the image reading unit to the image forming unit via a data bus, and a second process of converting data input from an external device of the image forming apparatus into pixel data for forming an image on the recording medium, and transferring the converted pixel data to the image forming unit via the data bus;
having
the image forming unit forms an image on the recording medium based on pixel data transferred via the data bus;
the image reading unit outputs pixel data corresponding to the reading result in a first cycle if the control unit is not executing the second process when the instruction is input, and outputs pixel data corresponding to the reading result in a second cycle longer than the first cycle if the control unit is executing the second process when the instruction is input ;
The image forming apparatus is characterized in that, when outputting in the first cycle, the image reading unit does not add an empty data section in which no pixel data is output after outputting pixel data obtained by reading the image of the original document, and, when outputting in the second cycle, adds an empty data section in which no pixel data is output, thereby resulting in output data for one cycle . the image forming apparatus includes a generating unit that generates a clock signal;
the image reading unit outputs pixel data corresponding to the reading result in synchronization with the clock signal;
2. The image forming apparatus according to claim 1, wherein the generation unit generates the clock signal by setting the frequency of the clock signal to a first value and the period of the clock signal to the first period when the control unit is not executing the second process when the instruction is input, and generates the clock signal by setting the frequency of the clock signal to the first value and the period of the clock signal to the second period when the control unit is executing the second process when the instruction is input. The image forming apparatus includes:
A counter unit that counts the number of pulses of the clock signal;
an output section that outputs a predetermined signal when the count of the counter section reaches a predetermined count;
having
a period during which the predetermined signal is output is longer than the second period;
3. The image forming apparatus according to claim 2, wherein the image reading section outputs a predetermined number of pixel data within one period of the predetermined signal. In an image forming apparatus including an image forming unit that forms an image on a recording medium,
an output unit that outputs a synchronization signal;
an image reading unit that reads an image of a document based on an instruction to start reading the image of the document and outputs pixel data corresponding to the read result based on the synchronization signal, the image reading unit outputting a predetermined number of pixel data corresponding to the read result within one cycle of the synchronization signal;
a control unit that executes a first process of transferring pixel data output from the image reading unit to the image forming unit via a data bus, and a second process of converting data input from an external device of the image forming apparatus into pixel data for forming an image on the recording medium, and transferring the converted pixel data to the image forming unit via the data bus;
having
the image forming unit forms an image on the recording medium based on pixel data transferred via the data bus;
the output unit outputs the synchronization signal in a first cycle if the control unit is not executing the second process when the instruction is input, and outputs the synchronization signal in a second cycle longer than the first cycle if the control unit is executing the second process when the instruction is input ;
The image forming apparatus is characterized in that, when outputting in the first cycle, the image reading unit does not add empty data in which no pixel data is output after outputting the pixel data obtained by reading the image of the original document, and when outputting in the second cycle, the image reading unit adds an empty data section in which no pixel data is output after outputting the pixel data obtained by reading the image of the original document, thereby resulting in output data for one cycle . In an image forming apparatus including an image forming unit that forms an image on a recording medium,
an image reading unit that reads an image of a document based on an instruction to start reading the document and outputs pixel data corresponding to the read result;
a control unit that executes a first process of transferring pixel data output from the image reading unit to the image forming unit via a data bus, and a second process of converting data input from an external device of the image forming apparatus into pixel data for forming an image on the recording medium, and transferring the converted pixel data to the image forming unit via the data bus;
having
the image forming unit forms an image on the recording medium based on pixel data transferred via the data bus;
when the control unit is executing the second process and a resolution of the image to be formed by the image forming unit is a first resolution when the instruction is input, the image reading unit outputs pixel data corresponding to the reading result in a first cycle;
when the control unit is executing the second process when the instruction is input and a resolution of an image to be formed by the image forming unit is a second resolution higher than the first resolution, the image reading unit outputs pixel data corresponding to the reading result in a second cycle longer than the first cycle ;
The image forming apparatus is characterized in that, when outputting in the first cycle, the image reading unit does not add empty data in which no pixel data is output after outputting the pixel data obtained by reading the image of the original document, and when outputting in the second cycle, the image reading unit adds an empty data section in which no pixel data is output after outputting the pixel data obtained by reading the image of the original document, thereby resulting in output data for one cycle . In an image forming apparatus including an image forming unit that forms an image on a recording medium,
an output unit that outputs a synchronization signal;
an image reading unit that reads an image of an original document based on an instruction to start reading the original document and outputs pixel data corresponding to the read result based on the synchronization signal, the image reading unit outputting a predetermined number of pixel data within one cycle of the synchronization signal;
a control unit that executes a first process of transferring pixel data output from the image reading unit to the image forming unit via a data bus, and a second process of converting data input from an external device of the image forming apparatus into pixel data for forming an image on the recording medium, and transferring the converted pixel data to the image forming unit via the data bus;
the image forming unit forms an image on the recording medium based on the pixel data transferred via the data bus;
the output unit outputs the synchronization signal at a first cycle when the control unit is not executing the second process and a resolution of the image to be formed by the image forming unit is a first resolution when the instruction is input;
when the control unit is not executing the second process and a resolution of an image to be formed by the image forming unit is a second resolution higher than the first resolution when the instruction is input, the output unit outputs the synchronization signal at a second period longer than the first period ;
The image forming apparatus is characterized in that, when outputting in the first cycle, the image reading unit does not add empty data in which no pixel data is output after outputting the pixel data obtained by reading the image of the original document, and when outputting in the second cycle, the image reading unit adds an empty data section in which no pixel data is output after outputting the pixel data obtained by reading the image of the original document, thereby resulting in output data for one cycle .

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