JP2010193225A - Serial transfer device, serial transfer system and image forming apparatus with serial transfer system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent data, which are made abnormal by noise or the like, from being output from an output port during serial communication in which the number of harnesses between substrates is reduced. <P>SOLUTION: A microcomputer executes a program including the steps of: when data communication is started and serial data are received (YES in S1000 and S1010), converting the received serial data into parallel data (S1020); processing the parallel data (S1030), and when a combination of data is not a non-existent combination (NO in S1040), outputting data from the port and holding latest data (S1050, S1060); and, when the combination of data is the non-existent combination (YES in S1040), using the held data without outputting the data from the port. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a serial transfer device that serially transfers parallel data and outputs the parallel data, and more particularly to a serial transfer device that detects an abnormality occurring during transfer. The present invention also relates to a serial transfer system including such a serial transfer device. Furthermore, the present invention relates to an image forming apparatus provided with such a serial transfer system.

  In recent image forming apparatuses, not only a copy function but also a model called a so-called multifunction machine having a printer function, a scanner mechanism, and a FAX function has been developed. Although not limited to such a multi-function device, control becomes more complex with the increase in functionality, and the control structure is hierarchized to control multiple lower controllers from a single upper controller, Distributed control by unit. In such communication between controllers, communication between control units, or communication between a control unit and a control driver (for example, a motor driver), a large number of communication lines (harnesses) are connected to communicate data in parallel. (Parallel communication).

  In view of the fact that such parallel data communication requires many communication lines and increases costs, an SPI (Serial Peripheral Interface) capable of high-speed data communication with few communication lines has been developed. This SPI is a comparatively simple serial communication, and has a configuration in which two shift registers are connected in a ring shape to communicate serially between the shift registers. In this serial communication, transmission and reception are performed simultaneously.

  As the principle of the SPI, the principle of the shift register itself is used. The transmission output unit includes a parallel-to-serial conversion type shift register, and parallel data is converted into a serial signal by a shift clock generated by the master (transmission side). At this time, a signal for one bit is output by one clock. The receiving unit is composed of a serial-to-parallel conversion type shift register, and samples the serial signal sent from the transmission side with a shift clock generated by the master and converts it into parallel data.

  The shift clock is generated by the master (transmission side), and this clock is shared with the slave (reception side) as an SCK signal. The transmission operation and the reception operation are simultaneously generated by this clock. That is, when 1 bit is output (shifted), 1 bit is input simultaneously. In such an example, 8 bits (1 byte) of data is input / output in 8 clocks (actually more bit data is transferred). This can be considered that the data of each other is transferred when the 8-bit data of the master (sending side) and the slave (receiving side) are switched. The master (transmission side) outputs its own clock, and inputs / outputs data bits in synchronization with the clock, while the slave (reception side) outputs data bits in synchronization with the clock output by the master (transmission side). I / O is in progress.

  Japanese Laid-Open Patent Publication No. 2-239728 (Patent Document 1) discloses a serial transfer circuit that detects such an abnormality in serial communication. This serial transfer circuit includes a parallel / serial conversion means for serially outputting parallel input data, a first set of serial / parallel conversion means for inputting serial data output by the parallel / serial conversion means by serial shift and outputting the parallel data, parallel A first set of serial / parallel conversion in a serial transfer circuit comprising: data output control means for controlling data input / output of the serial conversion means; and a plurality of signal lines for supplying a plurality of bits of data to the data output control means A second set of serial / parallel conversion means serially connected to the serial output terminal of the means, and a parallel data output means for outputting the parallel output of the second set of serial / parallel conversion means to a plurality of signal lines, The data output control means converts the test data into parallel / serial The first set of serial / parallel conversion means is serially transferred to the second set of serial / parallel conversion means, and the output data of the parallel data output means is sent via a plurality of signal lines. And a means for detecting a serial transfer error by detecting pass / fail of the read data and the test data.

  According to this serial transfer circuit, the data output control means outputs the test data to the parallel / serial conversion means, and serially passes through the first set of serial / parallel conversion means to the second set of serial / parallel conversion means. If the serial transfer line from the parallel / serial conversion means to the second set of serial / parallel conversion means is normal, test data is output in parallel by the second set of conversion means. If the serial transfer line has a connection abnormality such as disconnection or short circuit, the second set of conversion means does not output test data. Thus, the parallel data output means outputs the parallel output data of the second set of conversion means to the signal line, the data output control means reads this data via the signal line, and the read data and the test data A pass / fail is detected and a serial transfer error is detected. That is, when the parallel output data of the serial / parallel conversion means matches the test data, the serial transfer line is detected as having no abnormality, and when the parallel output data does not match, the serial transfer line is detected as having an abnormality. Thus, since the data output control means automatically performs this detection, it is possible to automatically detect abnormality of the serial transfer line.

JP-A-2-239728

  The serial transfer circuit disclosed in Patent Document 1 connects a plurality of serial / parallel conversion means, outputs test data, and detects disconnection or the like based on whether or not parallel data is output by the conversion means. . In this serial transfer circuit, test data is transferred and the combination is returned to the control side as parallel data to detect whether or not an error has occurred.

  However, such a configuration is not preferable in that a plurality of signal lines are required, and the number of harnesses is required for the amount of parallel data.

  Accordingly, an object of the present invention is to monitor data transmitted by a serial signal in serial communication that reduces the number of necessary harnesses so that data that becomes abnormal due to noise or static electricity is not output from an output port. A serial transfer device, a serial transfer system, and an image forming apparatus including the serial transfer system are provided.

  A serial transfer device according to an aspect of the present invention is a serial transfer device that serially transfers parallel data. The serial transfer device includes a connection means for connecting a signal line connected to another serial transfer device, an input / output means for outputting a signal to an external device or inputting a signal from the external device, and an external Conversion to convert parallel data to be sent from the device and sent to another serial transfer device into serial data, or to convert serial data received from another serial transfer device to parallel data to the external device Means, transfer means for transferring the parallel data obtained by converting the serial data received from the other serial transfer device to the external device via the input / output means, and serial data received from the other serial transfer device. Determination means for determining whether or not the received data is abnormal based on the parallel data converted by the conversion means Including the.

  According to this serial transfer device, parallel data to be transmitted to another serial transfer device is converted into serial data, or serial data received from another serial transfer device is converted into parallel data. Transfer data. At this time, the determination unit determines whether or not the received data is abnormal based on the parallel data obtained by converting the serial data received from another serial transfer device by the conversion unit. If it is determined to be abnormal, for example, the data (control data) is not transferred to the external device. For this reason, it is possible to prevent the motor (control target) connected to the input / output means as an external device from running away or malfunctioning. Even if such a system is constructed, the number of harnesses (signal lines) does not increase. As a result, in serial communication that reduces the number of required harnesses, serial data that monitors data transmitted with serial signals and prevents abnormal data due to noise or static electricity from being output from input / output means to external devices A transfer device can be provided.

  The serial transfer device further includes a control unit for controlling the transfer unit so that the parallel data converted from the received serial data is not transferred to the external device when it is determined that the received data is abnormal. Can be configured.

  If the received data is abnormal, the data is not transferred to the motor (control target) connected to the input / output means as an external device. For this reason, it can avoid that the motor which is a control object runs away or breaks down.

  The serial transfer device includes a holding unit for holding data transferred to an external device via the input / output unit, and parallel data converted from the received serial data when it is determined that the received data is abnormal. And means for transferring the held data to the external device.

  If the received data is abnormal, the received data is not transferred to the motor (control target) connected to the input / output means as an external device. Is done. Since the data before the occurrence of the abnormality is transferred to the external device, the motor is not controlled by the abnormal data. For this reason, it can avoid that the motor which is a control object runs away or breaks down.

  Here, the determining means can be configured to include means for determining whether or not the received data is abnormal based on the parallel data pattern converted by the converting means.

  For example, for a 2-phase excitation stepping motor or a DC motor controlled by an H-bridge circuit, a 4-bit parallel data pattern is predetermined. If the data pattern obtained by converting the received serial data into parallel data is other than this predetermined pattern, it can be determined that the received data is abnormal.

  Further, the determination means can be configured to include means for determining that the received data is abnormal based on the fact that the parallel data converted by the conversion means does not change for a predetermined time or more.

  If the signal line is disconnected, the signal line is short-circuited, or the connector as an example of the connecting means is disconnected, the data obtained by converting the received serial data into parallel data does not change. If such a state continues for a predetermined time or longer, it can be determined that the received data is abnormal. The received serial data itself has not changed.

  In addition, this serial transfer device, when it is determined that the received data is abnormal, means for transferring to the external device data that does not cause the external device to be in an abnormal state, instead of parallel data converted from the received serial data Can be further included.

  If it is determined that the received data is abnormal, data that does not cause the external device to be in an abnormal state is transferred to the external device. For this reason, it is possible to avoid the runaway or failure of the motor or motor driver to be controlled.

  The data that does not cause the external device to be in an abnormal state can be configured to be data that does not cause the external device to operate.

  If it is determined that the received data is abnormal, data that the external device does not operate (all non-excited in the case of a two-phase excitation stepping motor) is transferred to the external device. For this reason, since the motor to be controlled is stopped, it is possible to avoid runaway or failure.

  The serial transfer device can be configured to further include notification means for notifying other serial transfer devices of the occurrence of an abnormality when it is determined that the received data is abnormal.

  In the case where such a serial transfer system connected to the serial transfer device is constructed, when an abnormality is detected by one serial transfer device, the occurrence of the abnormality is notified to the other serial transfer device. When the other serial transfer device is connected to the host controller, the other serial transfer device notifies the host controller of the occurrence of an abnormality, and the host controller detects that the device on which the serial transfer device is mounted (image formation described later). The entire apparatus etc. can be controlled.

  Here, the notification means can be configured to include means for notifying the occurrence of a transfer abnormality to another serial transfer device using a signal line.

  Since the occurrence of transfer abnormality is notified to other serial transfer devices using a communication line for transferring serial data, a harness for abnormal communication is not required.

  A serial transfer system according to another aspect of the present invention includes any of the two serial transfer devices (transmitting side and receiving side) described above and a signal line connecting the two serial transfer devices.

  Since the serial transfer device in the serial transfer system configured as described above operates as described above, if the data changes due to noise or the like during the transfer of serial data, the serial data is transferred to the serial transfer device on the receiving side. It is possible to determine whether or not there is a communication abnormality using the data after conversion into parallel data. When the received data is abnormal, it is possible to prevent the abnormal signal from being output to the external device via the input / output means, so that the motor to be controlled can run away or fail without increasing the harness. Can be avoided.

  An image forming apparatus according to still another aspect of the present invention is an image forming apparatus including any of the serial transfer systems described above.

  In an image forming apparatus, for example, when a hierarchical distributed control system is applied to perform data communication between a host controller and a lower controller using a serial transfer system, or data communication is performed between a main board and a sub board using a serial transfer system. There is a case. In such a case, it is possible to determine whether or not there is a communication abnormality using the data after converting the serial data into parallel data. When the received data is abnormal, it is possible to prevent an abnormal signal from being output to an external device via the input / output means. Therefore, a motor or lift-up motor that drives the sheet conveying roller to be controlled without increasing the harness, etc. Can avoid runaway or breakdown.

  According to the serial transfer device of the present invention, when data changes during serial transfer, the receiving serial transfer device can determine whether the data is abnormal data by using the parallel data after parallel conversion of the serial data. . When the received data is abnormal, no abnormal signal is output to the external device. For this reason, it can avoid that the motor which is a control object runs away or breaks down. In this way, in serial communication that reduces the number of necessary harnesses, the data transmitted by the serial signal is monitored so that data that becomes abnormal due to noise or static electricity is not output from the output port to the external device. A serial transfer device, a serial transfer system, and an image forming apparatus including the serial transfer system can be provided.

1 is a cross-sectional view showing an internal structure of an image forming apparatus including a serial transfer system (transmission / reception unit) according to a first embodiment of the present invention. FIG. 2 is a control block diagram of the image forming apparatus in FIG. 1. It is a figure which shows the structure of the transmission / reception unit in FIG. It is a control block diagram of the transmission / reception unit in FIG. It is a timing chart which shows an example of the signal in a transmission / reception unit. It is a figure which shows an example of the signal in a transmission / reception unit. It is a flowchart which shows the control structure of the program performed with the microcomputer of the transmission / reception unit which concerns on the 1st Embodiment of this invention. It is a figure which shows the state of the signal in a transmission / reception unit. It is a figure which shows the generation | occurrence | production state of the abnormal data in FIG. It is a timing chart which shows the transmission / reception timing of the serial data in a serial transfer system. It is a control block diagram of the transmission / reception unit which concerns on the 2nd Embodiment of this invention. It is a control block diagram of the transmission / reception unit which concerns on the 3rd Embodiment of this invention. It is a control block diagram of the transmission / reception unit which concerns on the 4th Embodiment of this invention.

<First Embodiment>
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same parts are denoted by the same reference numerals. Their functions and names are also the same. Therefore, detailed description thereof will not be repeated. In the following description, the apparatus provided with the serial transfer system (transmission / reception unit) according to the embodiment of the present invention is not limited, but will be described as an image forming apparatus (multifunction machine).

[Configuration of Image Forming Apparatus]
FIG. 1 is a cross-sectional view showing an internal structure of an image forming apparatus 100 including a serial transfer system according to the first embodiment of the present invention.

  The image forming apparatus 100 forms a multicolor image or a single color image on a predetermined sheet (recording paper) in accordance with image data transmitted from the outside. In general, the image forming apparatus 100 is an image forming apparatus. 100 main body units 110 and an automatic document processing apparatus 120. The main body 110 includes an optical scanning device 150, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit 6, a fixing unit 7, a paper feed cassette 81, a paper discharge tray 91, and the like. Configured.

  A document placing table 92 made of transparent glass on which a document is placed is provided on the upper part of the main body 110, and an automatic document processing device 120 is attached to the upper side of the document placing table 92. The automatic document processing device 120 automatically conveys the document on the document placing table 92. Further, the automatic document processing device 120 is configured to be rotatable in the direction of arrow M, and the document can be placed manually by opening the document table 92.

  Image data handled in the image forming apparatus 100 is data corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, four developing devices 2, photosensitive drums 3, chargers 5, and cleaner units 4 are provided so as to form four types of latent images corresponding to the respective colors, and four of black, cyan, magenta, and yellow are provided. One image station is configured.

  The charger 5 functions to uniformly charge the surface of the photosensitive drum 3 to a predetermined potential. The optical scanning device 150 is configured as a unit including a laser emitting unit and a reflection mirror. The optical scanning device 150 includes a polygon mirror that scans a laser beam and optical elements such as a lens and a mirror for guiding the laser beam reflected by the polygon mirror to the photosensitive drum 3.

  The optical scanning device 150 has a function of forming an electrostatic latent image corresponding to the image data on the surface thereof by exposing the charged photosensitive drum 3 according to the input image data. The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toners of four colors (Y, M, C, K). The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt unit 6 disposed above the photosensitive drum 3 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and an intermediate transfer belt cleaning unit 65. I have. Four intermediate transfer rollers 64 are provided corresponding to the respective colors Y, M, C, and K. The intermediate transfer belt driving roller 62, the intermediate transfer belt driven roller 63, and the intermediate transfer roller 64 are driven to rotate while the intermediate transfer belt 61 is stretched. The intermediate transfer roller 64 provides a transfer bias for transferring the toner image on the photosensitive drum 3 onto the intermediate transfer belt 61.

  The intermediate transfer belt 61 is provided so as to be in contact with the four photosensitive drums 3, and each color toner image formed on the photosensitive drum 3 is sequentially superimposed and transferred onto the intermediate transfer belt 61. Thus, a color toner image (multicolor toner image) is formed on the intermediate transfer belt 61. The intermediate transfer belt 61 is formed in an endless shape using, for example, a film having a thickness of about 100 μm to 150 μm.

  The toner image is transferred from the photosensitive drum 3 to the intermediate transfer belt 61 by an intermediate transfer roller 64 that is in contact with the back side of the intermediate transfer belt 61. A high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 64 in order to transfer the toner image. The intermediate transfer roller 64 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 mm to 10 mm and whose surface is covered with a conductive elastic material (for example, ethylene-propylene-diene rubber, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt 61. In this embodiment, a roller-shaped electrode is used as the transfer electrode, but a brush-shaped electrode or the like can be used in addition to that.

  As described above, the electrostatic latent images visualized according to the respective colors on the respective photosensitive drums 3 are stacked on the intermediate transfer belt 61. In this way, the laminated image information is transferred onto the recording sheet by the transfer roller 10 disposed at the contact position between the recording sheet and the intermediate transfer belt 61 described later by the rotation of the intermediate transfer belt 61.

  At this time, the intermediate transfer belt 61 and the transfer roller 10 are pressed against each other at a predetermined nip, and a voltage for transferring the toner to the recording paper is applied to the transfer roller 10 (opposite to the toner charging polarity (−)). Polarity (+) high voltage). Further, in order to obtain the above nip constantly, the transfer roller 10 uses either the transfer roller 10 or the intermediate transfer belt drive roller 62 as a hard material (metal or the like) and the other as a soft material such as an elastic roller (an elastic rubber roller). Or a foamed resin roller or the like).

  Further, as described above, the toner adhering to the intermediate transfer belt 61 by contacting the photosensitive drum 3 or the toner remaining on the intermediate transfer belt 61 without being transferred onto the recording paper by the transfer roller 10 is used in the next step. Therefore, the intermediate transfer belt cleaning unit 65 is configured to remove and collect the toner. The intermediate transfer belt cleaning unit 65 is provided with, for example, a cleaning blade as a cleaning member that comes into contact with the intermediate transfer belt 61. The intermediate transfer belt 61 that comes into contact with the cleaning blade is driven by an intermediate transfer belt driven roller 63 from the back side. It is supported.

  The paper feed cassette 81 is a tray for storing sheets (recording paper) used for image formation, and is provided below the optical scanning device 150 of the main body 110. A sheet used for image formation can also be placed on the manual paper feed cassette 82. A paper discharge tray 91 provided above the main body 110 is a tray for collecting printed sheets face down.

  The main body 110 is provided with a substantially vertical sheet conveyance path S for sending the sheets of the sheet feeding cassette 81 and the manual sheet feeding cassette 82 to the sheet discharge tray 91 via the transfer roller 10 and the fixing unit 7. It has been. In the vicinity of the paper transport path S from the paper feed cassette 81 or the manual paper feed cassette 82 to the paper discharge tray 91, there are a pickup roller 11a, a pickup roller 11b, a plurality of transport rollers 12a to 12d, a registration roller 13, and a transfer roller. 10, a fixing unit 7 and the like are arranged. Such a roller for conveying a sheet is driven by, for example, a two-phase excitation stepping motor.

  The conveyance rollers 12a to 12d are small rollers for promoting and assisting conveyance of the sheet, and a plurality of the conveyance rollers 12a to 12d are provided along the sheet conveyance path S. The pickup roller 11 a is provided near the end of the paper feed cassette 81, picks up sheets one by one from the paper feed cassette 81, and supplies them to the paper transport path S. Similarly, the pickup roller 11b is provided near the end of the manual paper feed cassette 82, picks up one sheet at a time from the manual paper feed cassette 82, and supplies it to the paper transport path S.

  The registration roller 13 temporarily holds the sheet being conveyed on the sheet conveyance path S. The sheet has a function of conveying the sheet to the transfer roller 10 at the timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the sheet are aligned.

  The fixing unit 7 includes a heat roller 71 and a pressure roller 72, and the heat roller 71 and the pressure roller 72 rotate with the sheet interposed therebetween. The heat roller 71 is set to have a predetermined fixing temperature by a control unit based on a signal from a temperature detector (not shown), and the pressure roller 72 and the toner are thermocompression-bonded to the sheet. The multicolor toner image transferred onto the sheet is melted, mixed and pressed, and thermally fixed to the sheet.

  Next, the sheet conveyance path will be described in detail. As described above, the image forming apparatus 100 is provided with the paper feed cassette 81 and the manual paper feed cassette 82 for storing sheets in advance. In order to feed sheets from these sheet feeding cassettes 81 or manual sheet feeding cassettes 82, pickup rollers 11a or pickup rollers 11b are arranged to guide the sheets one by one to the sheet conveyance path S.

  The sheet conveyed from the sheet feeding cassette 81 or the manual sheet feeding cassette 82 is conveyed to the registration roller 13 by the conveying roller 12a in the sheet conveying path S, and aligns the leading edge of the sheet with the leading edge of the image information on the intermediate transfer belt 61. It is conveyed to the transfer roller 10 at a timing, and image information is written on the sheet. Thereafter, the sheet passes through the fixing unit 7 so that the unfixed toner on the sheet is melted and fixed by heat, and is discharged onto the sheet discharge tray 91 through the conveyance roller 12b disposed thereafter.

  The above-mentioned transport path is for a single-sided printing request for a sheet. On the other hand, when a double-sided printing request is made, the single-sided printing is completed and the trailing edge of the sheet that has passed through the fixing unit 7 is When the sheet is held by the final conveying roller 12b, the conveying roller 12b rotates backward to guide the sheet to the conveying roller 12c and the conveying roller 12d. Thereafter, after printing is performed on the back surface of the sheet through the registration roller 13, the sheet is discharged to the discharge tray 91.

[Control block of image forming apparatus]
FIG. 2 shows a control block diagram of the image forming apparatus 100. As shown in FIG. 2, the image forming apparatus 100 is controlled by a hierarchical distributed system.

  The main controller 200 is the highest control unit, and the scan unit controller 210, the printer unit controller 220, the FAX unit controller 230, the interface controller 240, and the power supply controller 250 are connected to each other by communication lines. Yes. The main controller 200 comprehensively controls these controllers connected at the lower level.

  The scan unit controller 210 mainly controls the scanner function in the image forming apparatus 100. The printer unit controller 220 mainly controls a printer function (image forming function) in the image forming apparatus 100. The FAX unit controller 230 mainly controls the facsimile communication function in the image forming apparatus 100.

  The interface controller 240 receives, for example, print data transmitted from a personal computer (hereinafter referred to as “personal computer”) to the image forming apparatus, receives facsimile data from another image forming apparatus, and forms other images. When transmitting facsimile data to the apparatus, it communicates with other devices according to a prescribed communication procedure. The power controller 250 controls the main power of the image forming apparatus 100 and the power supplied to various units.

  Furthermore, the serial transfer system (transmission / reception unit) according to the present embodiment will be described with reference to FIG. In the following, a transmission / reception unit configured below the printer unit controller 220 will be described, but a transmission / reception unit in another unit controller may be used.

  The transmission / reception unit 1000 is connected to a mechanical control main board A1100 connected to the printer unit controller 220 and controlled by the printer unit controller 220, and a mechanical control main board A1100 (hereinafter referred to as “board A1100”) via a serial communication line 1010. Mechanical control sub-substrate B1200 (hereinafter referred to as “substrate B1200”). The substrate B1200 is connected to a motor 1210, a motor 1212, a motor 1214,... Via a motor driver, and a sensor 1220, a sensor 1222, a sensor 1224,.

  As described above, the substrate B1200 controls a motor to be controlled (for example, a two-phase excitation stepping motor that drives a roller for conveying a sheet) via a motor driver, or is detachable from an electromagnetic clutch (for example, the image forming apparatus 100). Or a clutch provided between the photosensitive drum 3 provided in the photosensitive unit and a motor mounted on the image forming apparatus 100. A signal is input from the sensor to the substrate B1200. When the distance between the board A1100 and the motor, electromagnetic clutch, or sensor is long, the harness becomes longer if the board A1100 is directly connected to the motor, electromagnetic clutch, or sensor, so the board is divided into the main (board A1100) and sub (board) B1200), and data communication is performed between these boards by the serial communication line 1010. This data communication may be serial communication and is not limited to the above-described SPI.

[Serial transfer system]
With reference to FIG. 3, the structure of the transmission / reception unit 1000 in FIG. 2 will be described in more detail. A circuit board A 1100 is connected to a printer unit controller 220 and controls a paper transport function in the printer unit. A CPU (Central Processing Unit) 1102 and a serial / parallel converter 1104 with a data determination function connected to the CPU 1102 (hereinafter referred to as “serial / parallel”). Converter 1104 ”), a microcomputer (hereinafter referred to as“ microcomputer ”) 1106 that implements a data determination function and executes an abnormality process in the serial / parallel converter 1104, and a serial / parallel converter. A communication connector 1108 for connecting 1104 and the serial communication line 1010 is mounted.

  The substrate B1200 implements a serial / parallel converter 1204 with a data determination function (hereinafter referred to as “serial / parallel converter 1204”), a data determination function in the serial / parallel converter 1204, and executes an abnormality process. And a communication connector 1208 for connecting the serial / parallel converter 1204 and the serial communication line 1010 are mounted. Further, the board B1200 is connected to a serial / parallel converter 1204, and a motor driver 1300 having an excitation circuit and a drive circuit, and a motor driver 1300, a motor 1210, a motor 1212, and a motor 1214 are connected to the board B1200. An input / output connector 1302 for connecting the converter 1204 and the sensors 1220, 1222, and 1224 is mounted.

  As described above, the present invention is characterized by a transfer abnormality process in a serial transfer system (transmission / reception unit) using SPI in which the substrate A1100 and the substrate B1200 are connected by the serial communication line 1010 to transfer serial data. Such a feature is realized by a program executed by the microcomputer in FIG. The serial / parallel converter 1104 or the serial / parallel converter 1204 may have the function of this microcomputer. In the following, this feature is realized by a program executed in the microcomputer 1106 or the microcomputer 1206 by combining the serial / parallel converter 1104 and the microcomputer 1106 and combining the serial / parallel converter 1204 and the microcomputer 1206. It will be described as being done.

  As described above, the serial transfer system using the SPI is advantageous in that the number of serial communication lines 1010 can be reduced as compared with the parallel communication. This merit increases as the number of motors or electromagnetic clutches to be controlled or the number of sensors increases. Normally, in SPI, about 40 bits of data are transferred per process. The feature of the present invention is not related to the amount of data in one process. For this reason, in the following description, it is assumed that 8-bit data is transferred in one process. This data is, for example, an output for controlling the motor 1210, which is a stepping motor of two-phase excitation, from the substrate B1200 (this is serially transferred from the substrate A1100.) 4 bits, four on / off sensors to the substrate B1200 Input (This is serially transferred to the board A1100.) 4 bits, 4 bits in total.

[Serial transfer data]
FIG. 4 shows a control block diagram of the transmission / reception unit when such 8 bits (4 bits × 2) are transferred. FIG. 4 is a control block diagram in which the configuration diagram of FIG. 3 is replaced when 8 bits (4 bits × 2) are transferred.

  In the substrate A1100, a serial / parallel converter 1104, a microcomputer 1106, a communication connector 1108, and an input / output port 1109 constitute a communication unit 1101 (serial transfer device). The communication unit 1101 and the CPU 1102 constitute a substrate A1100 shown in FIG. 4, which is equivalent to the substrate A1100 shown in FIG.

  In the board B1200, a serial / parallel converter 1204, a microcomputer 1206, a communication connector 1208, and an input / output port 1209 constitute a communication unit 1201 (serial transfer device). The communication unit 1201, the motor driver 1300, and the input / output connector 1302 constitute the board B1200 shown in FIG. 4, which is equivalent to the board B1200 shown in FIG.

  Since the communication unit 1101 of the board A1100 and the communication unit 1201 of the board B1200 shown in FIG. 4 are equivalent, the communication unit (serial transfer device) according to the present invention has the same configuration on the transmission side and the reception side. Even if the implementation is different due to differences in the functions of individual devices, data is transferred by serial communication between the transmission side and the reception side and converted to parallel data on the reception side. If it detects, it will not be limited to the aspect of FIG.3 and FIG.4.

  A substrate B1200 is connected to an I / O connector 1302 through a motor 1210 that is a two-phase excitation stepping motor (hereinafter, the motor 1210 is a two-phase excitation stepping motor), four on / off sensors 1220, 1222, Sensors 1224 and 1226 are connected. An output signal from the board B1200 to the motor 1210 (motor output signal as an output on the board B side) and an input signal of the sensor 1220, sensor 1222, sensor 1224, and sensor 1226 to the board B1200 (sensor input as an input on the board B side) Signal) will be described.

  FIG. 5 shows a timing chart of these motor output signals and sensor input signals, and FIG. 6 shows the contents of these motor output signals and sensor input signals.

  As shown in FIGS. 5 and 6, the motor output signal An (1) to the motor output signal An (4) (n = 1, 2,...) Excite one stepping motor in two phases. This is control data (4 bits) to the motor 1210. Sensor input signal Bn (1) to sensor input signal Bn (4) (n = 1, 2,...) Are detected data from four on / off sensors 1220, 1222, 1222 and 1226 (see FIG. 4 bits).

  The time t shown in FIG. 5 is assumed to be the timing of n = 8 in FIG. This n increases by 1 over time when serial communication is performed between the substrate A1100 and the substrate B1200. When n increases by 1, serial transfer is performed once. At this time (when n = 8), the parallel data “A8 (1) = 1, A8 (2) = 0, A8 (3) = 0, A8 (4) = 1” is transferred from the substrate A1100 to the substrate B1200. A transmission data set A8 composed of corresponding serial data (transmission data set A8 on the board A1100 side and reception data set A8 on the board B1200 side) is transmitted from the board B1200 to the board A1100 with “B8 (1) = 1, B8. (2) = 1, B8 (3) = 0, B8 (4) = 0 ”is a transmission data set B8 (transmission data set B8 on the board B1200 side and board A1100 side) composed of serial data. A reception data set B8) is being transmitted. In this way, 4 bits of the motor output signal and 4 bits of the sensor input signal are serially communicated in one process.

  For the 4 bits of the motor output signal, only 2 adjacent bits of the 4 bits are “1 (indicating on and energized)” or all 4 bits are “0 (indicating off and de-energized)”. Is either Here, being adjacent means the Nth bit (An (N)) and the (N + 1) th bit (An (N + 1)). Note that An (4) and An (1) are adjacent to each other. There is no motor output signal in which 2 bits of other patterns are on (1 bit skipped on), only 1 bit is on, 3 bits are on, or all 4 bits are on. For this reason, the normal 4-bit motor control data (parallel data) is used on the board A1100. However, when noise is superimposed or data changes due to static electricity during serial communication (in the following, the noise is reduced). An abnormality can be determined as follows. During serial communication, if noise is superimposed on one off bit in the serial data and turned on, three bits are turned on as a result of serial / parallel conversion in the board B1200. The microcomputer 1206 of the board B1200 detects this state and determines that the data is abnormal.

  As described above, in the present invention, a program for executing abnormality processing in a serial transfer system (transmission / reception unit) using an SPI that transfers serial data by connecting the substrate A1100 and the substrate B1200 with the serial communication line 1010. It is realized by. The control structure of the program executed by the microcomputer will be described below. As described with reference to FIG. 4, the communication unit 1101 of the board A1100 and the communication unit 1201 of the board B1200 are equivalent (that is, data is transmitted to and received from the other board on both boards). The microcomputer 1106 mounted on the communication unit 1101 and the microcomputer 1206 mounted on the communication unit 1201 have the same configuration and execute the same abnormality determination program. Hereinafter, a program executed by the microcomputer 1206 installed in the communication unit 1201 will be described. The microcomputer 1106 on the substrate A1100 also executes the same program as the microcomputer 1206 at the same timing.

Software configuration
FIG. 7 is a flowchart showing a control structure of a program executed by the microcomputer 1206. Note that the microcomputer 1206 also executes other programs in parallel with the programs related to abnormality determination and abnormality processing of data received through serial communication. However, the other programs are not directly related to the essential parts of the present invention, and the details thereof will not be described here.

  In step (hereinafter, step is referred to as S) 1000, microcomputer 1206 determines whether or not data communication is started. At this time, the microcomputer 1206 determines that data communication has started, for example, by receiving a specific signal according to the communication procedure. If it is determined that data communication has started (YES in S1000), the process proceeds to S1010. Otherwise (NO in S1000), this process ends.

  In step S1010, the microcomputer 1206 determines whether serial data has been received from the substrate A1100. At this time, in the above-described SPI, transmission and reception are performed simultaneously. If it is determined that serial data has been received from substrate A 1100 (YES in S 1100), the process proceeds to S 1020. If not (NO in S1100), the process returns to S1010 and waits until serial data is received from the board A1100.

  In S1020, microcomputer 1206 controls serial / parallel converter 1204 to convert the received serial data into parallel data.

  In S1030, microcomputer 1206 processes the converted parallel data. At this time, 4 bits (An (1), An (2), An (3), An (4)) of the motor output signal transmitted from the substrate A1100 to the substrate B1200 and converted into parallel data are adjacent to each other. Whether the bit is “1 (ON indicates excitation state)”, whether all 4 bits are “0 (OFF indicates non-excitation state)”, and other 2 bits of the other patterns are ON ( Whether or not 1 bit is skipped is ON), or only 1 bit is ON, 3 bits are ON, or all 4 bits are ON.

  In S1040, microcomputer 1206 determines whether or not the received data is abnormal. When the adjacent 2 bits of the 4 bits (An (1), An (2), An (3), An (4)) of the motor output signal described above are “1 (indicating ON and excited state)” When all of the 4 bits are “0 (indicating off and de-energized)”, it is not determined to be abnormal. If 2 bits of other patterns are on (1 bit skipped on), or if only 1 bit is on, 3 bits are on, or all 4 bits are on, it is determined to be abnormal The If it is determined that the received data is abnormal (YES in S1040), the process proceeds to S1050. If not (NO in S1050), the process proceeds to S1070.

  In step S1050, the microcomputer 1206 outputs a motor output signal represented by parallel data obtained by converting the received serial data to the output port of the input / output port 1209. In step S1060, the microcomputer 1206 holds the latest data output from the port.

  In S1070, microcomputer 1206 determines whether or not the data communication is terminated. At this time, the microcomputer 1206 determines that the data communication is completed, for example, by receiving a specific signal according to the communication procedure. If it is determined that the data communication has ended (YES in S1070), this process ends. Otherwise (NO at S1070), the process returns to S1010.

[Serial transfer operation]
The operation of the serial transfer system in image forming apparatus 100 according to the present embodiment based on the structure and flowchart as described above will be described. In the following description, the operation on the substrate B1200 will be described, but the same operation is performed on the substrate A1100.

  When serial data communication using the SPI starts between the board A 1100 and the board B 1200 (YES in S1000) and the board B 1200 receives serial data from the board A 1100 (YES in S1010), the microcomputer 1206 of the board B 1200 is serial. Data is converted into parallel data (S1020).

  As shown in FIG. 8, when the serial data communication is started, the input A1 (1) to the input A1 (4) on the board A1100 side (the transmission data set A1 on the board A1100 side and the reception data set on the board B1200 side). A1) and the input B1 (1) to the input B1 (4) on the board B1200 side (the transmission data set B1 on the board B1200 side and the reception data set B1 on the board A1100 side) are simultaneously transmitted and received. At this time, in the board A1100, the input A1 (1) to the input A1 (4) that are parallel data (output signals to the motor) are transmitted from the board A1100 to the board B1200 as a transmission data set A1 that is serial data. In response to this, the board B1200 receives the transmission data set A1 that is serial data as the reception data set A1, and the output A1 (1) to the output A1 (4) in which the reception data set A1 is parallel data. Converted. At the same timing, in the board B1200, the input B1 (1) to the input B1 (4) that are parallel data (input signals from the sensor) are transmitted from the board B1200 to the board A1100 as a transmission data set B1 that is serial data. . In response to this, the substrate A1100 receives the transmission data set B1 that is serial data as the reception data set B1, and the output B1 (1) to the output B1 (4) in which the reception data set B1 is parallel data. Converted.

  The transmission data set A3 is serial data “1001” corresponding to parallel data “A3 (1) = 1, A3 (2) = 0, A3 (3) = 0, A3 (4) = 1”. To do. If serial transfer can be performed normally, the output A3 (1) to output A3 (4) are converted to “A3 (1) = 1, A3 (2) = 0, which is a serial conversion of the serial data“ 1001 ”as the reception data set A3. A3 (3) = 0, A3 (4) = 1 ”. This data is determined to be correct data because the adjacent 2 bits are on (NO in S1040). Therefore, the output A3 (1) to output A3 (4) as they are are output to the input / output port 1209 (S1050). Thereafter, the latest data is held (S1060).

  A case where noise is superimposed on the transmission data set A4 transmitted from the board A1100 to the board B1200 at the next timing after the transmission data set A3 is serially transferred will be described.

  The transmission data set A4 is assumed to be serial data “1001” corresponding to “A4 (1) = 1, A4 (2) = 0, A4 (3) = 0, A4 (4) = 1”. Assuming that noise is superimposed during serial transfer to change to serial data “1011”, output A4 (1) to output A4 (4) are obtained by converting serial data “1011” as reception data set A4 into parallel “ A4 (1) = 1, A4 (2) = 0, A4 (3) = 1, A4 (4) = 1 ”. However, since there is no control signal for motor 1210 in which 3 bits are turned on, it is determined that the received data is abnormal (YES in S1040). At this time, the outputs A4 (1) to A4 (4) are not output to the input / output port 1209. In this case, since the previous outputs A3 (1) to A3 (4) are held, the motor output signal is used to control the motor 1210. This state is a state in which the retained data is output to the port as shown in FIG.

  This state will be described with reference to FIG. As shown in FIG. 9, when abnormal data is detected in the received serial data, it is not output to the input / output port. Since the signal output to the input / output port before one process (one cycle time) is held, abnormal data is not output to the motor driver 1300.

  At this time, serial data (transmission data set and reception data set in FIG. 8) is transmitted and received at sufficiently short intervals with respect to changes in transmission / reception signals (motor output signal and sensor input signal). This is shown in FIG. As shown in FIG. 10, although the reception signal is delayed with respect to the transmission signal, serial data is transmitted and received at a sampling time (triangle mark in FIG. 10) sufficiently shorter than the change of the transmission / reception signal.

  For this reason, even if the motor output signal and the sensor input signal change once per second, serial data is transferred with a shorter sampling time. By using (holding) the signal transferred one sampling time before), it can be output to the motor driver 1300 to prevent the motor 1210 from running out of control, or the motor driver 1300 circuit can be prevented from being destroyed. Or

  As described above, according to the serial transfer system mounted on the image forming apparatus 100 according to the present embodiment, when data changes during serial transfer, the parallel data after the receiving microcomputer converts the serial data into parallel data. Is used to determine abnormal data. At this time, no abnormal signal is output to the input / output port. For this reason, it can avoid that the motor which is a control object runs away or breaks down.

<Second Embodiment>
Hereinafter, a second embodiment of the present invention will be described.

  The serial transfer system (transmission / reception unit) according to the present embodiment includes a substrate A2100 and a substrate B2200.

  FIG. 11 is a diagram showing the configuration of the transmission / reception unit according to the present embodiment, and corresponds to FIG.

  As shown in FIG. 11, the substrate A2100 includes a circuit 2102 for pulling down a connection line (serial data line) between the serial / parallel converter 1104 and the communication connector 1108. The circuit 2102 has a configuration in which a grounded resistor is connected to the serial data line. Furthermore, the microcomputer 2106 which performs the process different from the microcomputer 1206 in 1st Embodiment is provided.

  The board B 2200 includes a circuit 2202 that pulls down a connection line (serial data line) between the serial / parallel converter 1204 and the communication connector 1208. The circuit 2202 has a configuration in which a grounded resistor is connected to the serial data line. Further, the microcomputer 2206 is a process different from the microcomputer 2206 in the first embodiment, and executes the same process as the microcomputer 2106.

  In the configuration shown in FIG. 11, a circuit 2102 and a circuit 2202 for pulling down the serial data line are provided. By configuring the circuit in this way, the serial signal is disconnected when the serial communication line 1010 is disconnected or the connector is disconnected. Is fixed to Low. The microcomputer 2106 and the microcomputer 2206 detect this state (signal is low for a predetermined time or more) and determine that an abnormality has occurred in the serial transfer system.

  Note that instead of the circuit 2102 and the circuit 2202 illustrated in FIG. 11, a resistor connected to a positive potential (Vcc) may be connected to the serial data line. In this case, the serial signal is fixed to High when the serial communication line 1010 is disconnected or the connector is disconnected. The microcomputer 2106 and the microcomputer 2206 detect this state (signal is high for a predetermined time or more) and determine that an abnormality has occurred in the serial transfer system.

  When the disconnection of the serial communication line 1010 or the disconnection of the connector is detected as described above, the microcomputer 2206 of the board B 2200 outputs a signal that the control target does not operate. For example, the signal is such that all 4 bits of output to the motor 1210 are off. Thereby, the motor 1210 can be prevented from operating.

  As described above, according to the serial transfer system according to the present embodiment, as a circuit configuration for pulling up or pulling down the serial data line, an abnormality is detected based on a signal fixed to High or Low when the serial communication line is disconnected. it can.

<Third Embodiment>
Hereinafter, a third embodiment of the present invention will be described.

  The serial transfer system (transmission / reception unit) according to the present embodiment includes a substrate A3100 and a substrate B3200.

  FIG. 12 is a diagram showing the configuration of the transmission / reception unit according to the present embodiment, and corresponds to FIG. As shown in FIG. 12, as described in the second embodiment, the substrate A3100 and the substrate B3200 are provided with the circuit 2102 and the circuit 2202 for pulling down the serial data line.

  In addition to this, as shown in FIG. 12, the substrate A3100 includes a microcomputer 3106 that executes processing different from the microcomputer 1106 in the first embodiment and the microcomputer 2106 in the second embodiment. The board B 3200 includes a microcomputer 3206 that executes processing different from the microcomputer 1206 in the first embodiment and the microcomputer 2206 in the second embodiment.

  The microcomputer 3106 or the microcomputer 3206 shown in FIG. 12 monitors a signal string composed of the converted parallel signals after converting the received serial signals into parallel signals. When the signal sequence does not change, the microcomputer 3106 or the microcomputer 3206 determines that an abnormality has occurred in the serial transfer system.

  At this time, an abnormality determination time (this time has passed) based on the type of the control target device (for example, a motor) connected to the substrate A3100 or the substrate B3200 or the detection device (for example, a sensor) connected to the substrate A3100 or the substrate B3200. Even if the signal sequence does not change, it may be determined that the abnormality is determined). This is because, for example, when a sensor with a low detection frequency of the detection target is connected, if a time equal to or lower than the detection frequency is set, an abnormality cannot be correctly determined, so it is necessary to set a time longer than the detection frequency. Due to that.

  As described above, in the serial transfer system according to the present embodiment, the received signal train can be monitored to detect that an abnormality has occurred in parallel communication.

<Fourth embodiment>
Hereinafter, a fourth embodiment of the present invention will be described.

  The serial transfer system (transmission / reception unit) according to the present embodiment includes a substrate A4100 and a substrate B4200.

  FIG. 13 is a diagram showing the configuration of the transmission / reception unit according to the present embodiment, and corresponds to FIG. As illustrated in FIG. 13, as described in the second embodiment, the substrate A4100 and the substrate B4200 are provided with the circuit 2102 and the circuit 2202 that pull down the serial data line.

  In addition to this, as shown in FIG. 13, the substrate A4100 performs processing different from that of the microcomputer 1106 in the first embodiment, the microcomputer 2106 in the second embodiment, and the microcomputer 3106 in the third embodiment. A microcomputer 4106 is provided. The board B 3200 includes a microcomputer 1206 that executes processing different from the microcomputer 1206 in the first embodiment, the microcomputer 2206 in the second embodiment, and the microcomputer 3206 in the third embodiment.

  When the microcomputer 4106 or the microcomputer 4206 shown in FIG. 13 determines that an abnormality has occurred in the serial transfer system, the microcomputer 4106 notifies the other board of the occurrence of the abnormality. Here, a case will be described in which the communication line from the board A to B of the serial communication line 1010 (consisting of a transmission side communication line and a reception side communication line in SPI communication) is disconnected.

  For example, when the serial signal is fixed to Low (in the case of a pull-down circuit) or High (in the case of a pull-up circuit) as in the second embodiment described above, the serial communication line 1010 (harness) is disconnected. It is determined that an abnormality has occurred in serial communication. If it is determined that such an abnormality has occurred, the substrate B 4200 fixes the parallel data transmitted from the substrate B 4200 to the substrate A 4100 in a specific pattern (eg, “0000”, “1111”, etc.). When such a signal is transmitted from the substrate B4200 to the substrate A4100, the abnormality of the serial transfer system detected by the substrate B4200 can be detected in the substrate A4100.

  The board A 4100 notifies the upper printer unit controller 220 and / or the main controller 200 of the abnormality of the serial transfer system. The main controller 200 that has received such an abnormality notification controls the power supply controller 250 to stop the entire image forming apparatus 100, or the printer unit controller 220 temporarily activates the print function of the image forming apparatus 100. Can be stopped automatically. As described above, when a serious abnormality in serial communication (a serious abnormality with respect to an abnormality in which about one bit changes for one cycle due to static electricity or the like) is detected, all or some functions of the image forming apparatus 100 are detected. Can be controlled to stop.

  Since the microcomputer 4106 of the board A4100 has the same function as the microcomputer 4206 of the board B4200, it is determined that the serial transfer system is abnormal in the board A4100 when the communication line from the board B to A is disconnected. Then, a notification process to the substrate B4200) is executed.

  As described above, according to the serial transfer system according to the present embodiment, it is possible to notify the abnormality from the board detecting the abnormality of the serial transfer system to the other board without providing a dedicated communication line at the time of abnormality. it can.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the above-described embodiment. The scope of the present invention is indicated by each claim in the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are intended. Including.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 200 Main controller 210 Scan unit controller 220 Printer unit controller 230 FAX unit controller 240 Interface controller 250 Power supply controller 1000 Transmission / reception unit (serial transfer system)
1010 Serial communication line 1100, 2100, 3100, 4100 Mechanical control main board A (board A)
1200, 2200, 3200, 4200 Mechanical control main board B (board B)
1101, 1201 Communication unit (serial transfer device)
1104, 1204 Serial / parallel converter with data judgment function (serial / parallel converter)
1106, 1206, 2106, 2206, 3106, 3206, 4106, 4206 Microcomputer 1108, 1208 Communication connector 1109, 1209 Input / output port 1210, 1212, 1214 Motor 1220, 1222, 1224, 1226 Sensor 1300 Motor driver 1302 Input / output connector

Claims (11)

A serial transfer device for serially transferring parallel data,
Connection means for connecting a signal line connected to another serial transfer device;
Input / output means for outputting signals to external devices or inputting signals from external devices;
Converts parallel data to be transmitted to the other serial transfer device from the external device into serial data, or converts serial data received from the other serial transfer device to parallel data. Conversion means for converting;
Transfer means for transferring parallel data obtained by converting the serial data received from the other serial transfer device by the conversion means to the external device via the input / output means;
A serial transfer device comprising: determination means for determining whether the received data is abnormal based on parallel data obtained by converting the serial data received from the other serial transfer device by the conversion means;   The serial transfer device further includes control means for controlling the transfer means so that the parallel data converted from the received serial data is not transferred to the external device when it is determined that the received data is abnormal. The serial transfer device according to claim 1, further comprising: The serial transfer device
Holding means for holding data transferred to the external device via the input / output means;
The method according to claim 2, further comprising means for transferring the held data to the external device instead of the parallel data converted from the received serial data when it is determined that the received data is abnormal. Serial transfer device.   The said determination means contains the means for determining whether the received data are abnormal based on the pattern of the parallel data converted by the said conversion means. Serial transfer device.   The determination means includes means for determining that the received data is abnormal based on the fact that the parallel data converted by the conversion means does not change for a predetermined time or more. The serial transfer device according to any one of the above.   The serial transfer device, when it is determined that the received data is abnormal, means for transferring to the external device data that does not cause the external device to be in an abnormal state instead of parallel data converted from the received serial data The serial transfer device according to claim 1, further comprising:   The serial transfer device according to claim 6, wherein the data that does not cause the external device to be in an abnormal state is data that the external device does not operate.   8. The serial transfer device according to claim 1, further comprising notification means for notifying the other serial transfer device of the occurrence of an abnormality when it is determined that the received data is abnormal. 9. The serial transfer device described in 1.   9. The serial transfer device according to claim 8, wherein the notification means includes means for notifying the other serial transfer device of occurrence of a transfer abnormality using the signal line.   A serial transfer system comprising two serial transfer devices according to claim 1 and a signal line connecting the two serial transfer devices. An image forming apparatus comprising the serial transfer device system according to claim 10.

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