Abstract:
An image forming device includes a processor configured to process image data, an image forming unit configured to perform image formation based on the image data processed by the processor, a cover configured to, when being opened, allow an external access to the image forming unit therethrough, a detector configured to detect whether the cover is opened, and an interrupting unit configured to, when determining with the detector that the cover is kept opened for a first time period, interrupt the processing of the image data by the processor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119 from Japanese Patent Application No. 2008-245873 filed on Sep. 25, 2008. The entire subject matter of the application is incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The following description relates to one or more image forming devices, more particularly to one or more techniques to protect the image forming devices from electrostatically-caused errors. 
     2. Related Art 
     A technique has been known which is adapted to reset an application specific integrated circuit (ASIC) to avoid electrostatically-caused malfunction when a cover is opened such that a user can access the inside of a printer (an image forming device). 
     SUMMARY 
     However, according to the aforementioned technique, the ASIC is reset even when the cover is opened in such a manner that the user can hardly touch the inside of the device, such as when the cover is opened just for a moment and then soon closed. Therefore, in such a case, an unnecessary time period might be required for restoring the ASIC from the reset state, and thus it result in lower printing efficiency. 
     Aspects of the present invention are advantageous to provide one or more improved image forming devices that make it possible to improve efficiency of image formation. 
     According to aspects of the present invention, an image forming device is provided, which includes a processor configured to process image data, an image forming unit configured to perform image formation based on the image data processed by the processor, a cover configured to, when being opened, allow an external access to the image forming unit therethrough, a detector configured to detect whether the cover is opened, and an interrupting unit configured to, when determining with the detector that the cover is kept opened for a first time period, interrupt the processing of the image data by the processor. 
     According to aspects of the present invention, further provided is an image forming device, which includes a processor configured to process image data, an image forming unit configured to perform image formation based on the image data processed by the processor, a cover configured to, when being opened, allow an external access to the image forming unit therethrough, a detector configured to detect whether the cover is opened, and a maintaining unit configured to, when determining with the detector that the cover is kept opened for less than a first time period, maintain the processing of the image data by the processor. 
    
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         FIG. 1  is a cross-sectional view schematically showing an overall configuration of a color printer in an embodiment according to one or more aspects of the present invention. 
         FIG. 2  is a block diagram schematically showing an electrical configuration for light emission control illumination, in which a main ASIC, a sub ASIC, and LED units are connected in the embodiment according to one or more aspects of the present invention. 
         FIG. 3  schematically shows positional states of the LED units when an upper cover is closed in the embodiment according to one or more aspects of the present invention. 
         FIG. 4  schematically shows positional states of the LED units when the upper cover is opened in the embodiment according to one or more aspects of the present invention. 
         FIG. 5  is a perspective view schematically showing an LED unit in the embodiment according to one or more aspects of the present invention. 
         FIG. 6  is a time chart showing a relationship between an open-close detection signal Sd issued in response to an operation of opening/closing the upper cover and a reset signal Reset in a ready state of the printer in the embodiment according to one or more aspects of the present invention. 
         FIG. 7  is a time chart showing a relationship between the open-close detection signal Sd and the reset signal Reset during a printing operation by the printer in the embodiment according to one or more aspects of the present invention. 
         FIG. 8  is a time chart showing a relationship between the open-close detection signal Sd and the reset signal Reset corresponding to each block in the ready state of the printer in the embodiment according to one or more aspects of the present invention. 
         FIG. 9  is another time chart showing a relationship between the open-close detection signal Sd and the reset signal Reset corresponding to each block in the ready state of the printer in the embodiment according to one or more aspects of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     It is noted that various connections are set forth between elements in the following description. It is noted that these connections in general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. 
     Embodiment 
     1. Overall Configuration of Printer 
     Hereinafter, an embodiment according to aspects of the present invention will be described with reference to  FIGS. 1 to 9 .  FIG. 1  is a cross-sectional view schematically showing an overall configuration of a color printer  1  as an image forming device in an embodiment according to aspects of the present invention. The image forming device of the embodiment is not limited to a color printer. For instance, the image forming device may be a Multi-Function Peripheral (MFP) provided with various functions such as a copy function and a facsimile function. 
     In  FIG. 1 , the left side and the right side on the figure are defined as a front side and a rear side of the printer  1 , respectively. Further, the near side and the far side in the direction perpendicular to the figure are defined as a right side and a left side of the printer  1 , respectively. Moreover, the upside and the downside on the figure are defined as an upside and a downside of the printer  1 , respectively. Here, the color printer  1  is configured to form a color image with four colors (black K, yellow Y, magenta M, and cyan C) of developers. 
     As illustrated in  FIG. 1 , the color printer  1  (hereinafter, simply referred to as a printer  1 ) includes, in a main body  10 , a feeding unit  20  configured to feed a sheet P, an image forming unit  30  configured to form an image on the sheet P fed, an ejecting unit  90  configured to eject the sheet P with the image formed thereon, and a main control board  100  configured to control each of the aforementioned units when forming the image. 
     At an upper side of the main body  10 , an upper cover  11  is attached rotatably in the vertical direction around a rotation shaft  12  which is provided at a rear end of the printer  1 . The upper cover  11  is provided with an LED control board  110  configured to control an LED unit ( 40 K,  40 Y,  40 M, or  40 C) corresponding to each color. It is noted that, in the following description, respective components corresponding to the colors that have the same configuration may be identified with only an element number. Specifically, for instance, each of the LED units ( 40 K,  40 Y,  40 M, and  40 C) may be identified as the LED unit  40 . 
     When a front end of the upper cover  11  is lifted and opened around the rotation shaft  12 , an opening  11 A is formed sequentially from the front side of the main body  10 . Through the opening  11 A, a user can access the image forming unit  30 . 
     Further, to a portion of the main body  10  that faces a front end of the upper cover  11 , a cover switch  13  is provided which is configured to detect an opened/closed state of the upper cover  11  with it being set ON/OFF depending on the opened/closed state of the upper cover  11 . The cover switch  13  generates an open-close detection signal Sd based on the ON/OFF state thereof. 
     The upper cover  11  is configured with an upper surface thereof onto which the sheet P is ejected from the main body  10 , and a lower surface thereof at which four holding members ( 14 K,  14 Y,  14 M, and  14 C) for holding the respective LED units ( 40 K,  40 Y,  40 M, and  40 C) is provided. 
     The feeding unit  20 , disposed at a lower side within the main body  10 , includes a feed tray  21  detachably attached to the main body  10 , and a sheet feeding mechanism  22  configured to feed the sheet P from the feed tray  21  to the image forming unit  30 . The sheets P stacked in the feed tray  21  are sequentially conveyed up by the sheet feeding mechanism  22  in a manner separated on a sheet-by-sheet basis. After that, the sheet P is fed to the image forming unit  30  via a registration roller  29  that performs positional correction for the sheet P. 
     The image forming unit  30  includes the four LED units ( 40 K,  40 Y,  40 M, and  40 C) respectively corresponding to the four colors and four process cartridges ( 50 K,  50 Y,  50 M, and  50 C) respectively corresponding to the four colors, a transfer unit  70 , and a fixing unit  80 . Each of the LED units  40 , placed above a corresponding one of photoconductive drums  53 , has an LED head  41  disposed to face the photoconductive drum  53 , and a back plate  42 . 
     The LED head  41  has a plurality of light-emitting diodes (LEDs) aligned in the right-to-left direction on a surface of the LED head  41  that faces the photoconductive drum  53  (see  FIG. 5 ). Each of the LEDs emits light in accordance with a signal input thereinto from the below-mentioned LED control board  110  based on image data of an image to be formed, and exposes the surface of the photoconductive drum  53  with the emitted light. Namely, each of the LEDs is driven by a sub ASIC  114  of the LED control board  110  in accordance with a lighting pattern based on the image data (see  FIG. 2 ). 
     The back plate  42 , which is a member supporting the LED head  41 , is attached swingably to the upper cover  11  via the holding member  14 . Thereby, when the upper cover  11  is turned up, each LED unit  40  (LED head  41 ) is moved from an exposure position where the LED unit  40  faces the photoconductive drum  53  to an upper evacuation position (see  FIG. 4 ). 
     As illustrated in  FIG. 1 , the process cartridges ( 50 K,  50 Y,  50 M, and  50 C) are aligned in the front-to-rear direction between the upper cover  11  and the feed unit  20 . Further, each process cartridge  50  has a drum unit  51  and a development unit  61  detachably attached to the drum unit  51 . The development unit  61  has a development roller  63  and a toner container  66 . It is noted that the process cartridges  50  have the same configuration with just difference among the colors of toners respectively stored in the toner containers  66  of the development units  61 . 
     The drum unit  51  is provided with the photoconductive drum  53  and a charger  54 . When the development unit  61  is attached to the drum unit  51 , the drum unit  51  has an exposure hole formed such that the photoconductive drum  53  is externally viewed therethrough. The LED unit  40  (LED head  41 ) is inserted into the exposure hole  55  to face an upper surface of the photoconductive drum  53 . 
     The transfer unit  70 , provided between the feed unit  20  and the process cartridges  50 , includes a driving roller  71 , a driven roller  72 , a feeding belt  73 , and a transfer roller  74 . 
     The feeding belt  73  is wound around the driving roller  71  and the driven roller  72 . Inside the feeding belt  73 , four transfer rollers  74  are disposed to face the respective photoconductive drums  53  across the feeding belt  73 . In other words, the feeding belt  73  is pinched between each transfer roller  74  and the photoconductive drum  53  facing the transfer roller  74 . The fixing unit  80  is disposed behind the process cartridges  50  and the transfer units  70 . 
     In the image forming unit  30  configured as above, first, the surface of each photoconductive drum  53  is evenly charged by the corresponding charger  54 , and then exposed with LED light emitted by the corresponding LED head  41 . Thereby, an electrical potential of the exposed portion drops, and an electrostatic latent image based on the image data is formed on the surface of each photoconductive drum  53 . 
     Subsequently, the toner stored in the toner container  66  is supplied to the development roller  63 . The toner held on the development roller  63  is supplied to the electrostatic latent image formed on the photoconductive drum  53 . Thereby, the toner is selectively held on the photoconductive drum  53  and the electrostatic latent image is developed into a visible image. Thus, a toner image is formed through inversion development. 
     Then, while the sheet P supplied onto the feeding belt  73  is passing between the photoconductive drums  53  and the transfer rollers  74 , the toner images respectively formed on the photoconductive drums  53  are sequentially transferred onto the sheet P. When the sheet P passes through the fixing unit  80 , the toner images transferred onto the sheet P are thermally fixed. Thereafter, the sheet P with the toner images thermally fixed thereon is ejected onto the upper cover  11 . 
     2. Electrical Configuration for Light Emission Control 
     Next, an electrical configuration for light emission control in the embodiment will be described with reference to  FIGS. 2 to 5 .  FIG. 2  is a block diagram schematically showing an electrical configuration for light emission control, in which the main control board  100 , the LED control board  110 , and the LED units  40  are electrically connected.  FIG. 3  shows a positional state of each LED unit  40  when the upper cover  11  is closed.  FIG. 4  shows a positional state of each LED unit  40  when the upper cover  11  is opened.  FIG. 5  is a perspective view schematically showing the LED head  41 . 
     The main control board  100  includes a main application specific integrated circuit (ASIC)  102 , a memory unit  103 , and a timer unit  104 . The main ASIC  102  is configured to control each element included in the printer  1  when the printer  1  performs image formation. The memory unit  103  includes a ROM and a RAM. Further, the timer unit  104  includes one or more timers for measuring time periods taken for processes by the main ASIC  102 . 
     Specifically, the main ASIC  102  controls rotational speeds of the photoconductive drum  53  and the driving roller  71 , a speed at which the sheet P is fed at the feed unit  20  or the fixing unit  80 , and timing for exposure directly or indirectly via another control board such as the LED control board  110 . Especially, in control for illumination of the light emitted by each LED unit  40 , the main ASIC  102  supplies print data, reset signals (Reset), control signals (containing setting data and correction data), and a clock signal (clock) to the LED control board  110 . 
     In the meantime, the LED control board  110  provided to the upper cover  11  includes a sub ASIC  114 . The main ASIC  102  and the sub ASIC  114  are linked via a flat cable  140 . The sub ASIC  114  is configured to transmit control signals (CONT) and drive signals (DRIV) to the LED heads  41  based on the image data of the image to be formed and to control emission of each LED head  41  in accordance with the lighting pattern based on the image data. 
     More specifically, the sub ASIC  114  includes four blocks ( 115 K,  115 Y,  115 M, and  115 C) that correspond to the four LED units ( 40 K,  40 Y,  40 M, and  40 C), respectively. Each of the blocks  115  receives the print data, the control signals (containing setting data and correction data), and the reset signal Reset from the main ASIC  102  via the flat cable  140 . Each of the blocks  115  is individually brought into a reset state where an operation thereof is reset, by the reset signal Reset. In the reset state, a process performed by each block  115  for the image formation, such as generation and output of the control signal CONT and the drive signal DRIV, is stopped. 
     In addition, the LED units  40  (the LED heads  41 ) are electrically connected with the blocks  115  of the sub ASIC  114  via flat cables ( 130 K,  130 Y,  130 M, and  130 C), respectively. An earth cable  84  of each LED unit  40  is linked with a shield plate  81 . Further, as illustrated in  FIGS. 3 and 4 , the shield plate  81  is linked, via an earth cable  83 , with a conductive chassis  10 A connected to ground. Namely, each earth cable  84  is connected to ground. It is noted that, as illustrated in  FIG. 5 , the earth cables  84  is provided at both sides of each LED head  41  in the right-to-left direction. 
     In addition, each LED unit  40  has earth contact points  82 . As illustrated in  FIG. 5 , the earth contact points  82  are respectively provided at both the sides of the LED head  41  in the right-to-left direction. Each of the earth contact points  82  establishes contact with the conductive chassis  10 A only when the upper cover  11  is closed (see  FIG. 3 ). In other words, as shown in  FIG. 4 , when the upper cover  11  is opened, each of the earth contact points  82  is away from the conductive chassis  10 A. Therefore, when the upper cover  11  is opened, the LED control board  110  is connected to the ground at the side of the LED control board  110  via the earth cable  83 . 
     Further, as illustrated in  FIG. 2 , the printer  1  includes a low-voltage power source board  150 . The low-voltage power source board  150  generates, e.g., a low voltage of 3.3 V and supplies the low voltage to the main control board  100  via a power source cable  151  and to the LED control board  110  via a power source cable  152 . 
     3. Reset Control of Sub ASIC 
     Subsequently, referring to  FIGS. 6 to 9 , reset control for the sub ASIC  114  to be taken along with operations of opening and closing the upper cover  11  will be set forth. 
     3-1. Reset Control in Ready State 
     Practical Example 1 
     Referring to  FIG. 6 , reset control for the sub ASIC  114  will be described which is taken when the upper cover  11  is opened in a ready state where the printer  1  performs no printing operation.  FIG. 6  is a time chart showing a relationship between the open-close detection signal Sd issued in response to an operation of opening/closing the upper cover  11  and the reset signal Reset, in the ready state of the printer  1 . 
     It is assumed that the user opens the upper cover  11  at a time t 1  shown in  FIG. 6 , for an operation such as replacing a process cartridge  50 . At this time, the cover switch  13  generates an open-close detection signal Sd which drops from a logic high level (H) to a logic low level (L) in response to the upper cover  11  being opened, and supplies the open-close detection signal Sd to the main ASIC  102 . 
     Then, at a time t 2  after lapse of a predetermined time period K 1  since the time t 1 , the main ASIC  102  generates a reset signal Reset which drops from a logic high level (H) to a logic low level (L). The predetermined time period K 1  is, for instance, measured by a timer of the timer unit  104 . It is noted that the predetermined time period K 1  is, for instance, set to a time period until the user may touch the image forming unit  30  such as the process cartridge  50  after opening the upper cover  11 . 
     The reset signal Reset is supplied to the sub ASIC  114 . Specifically, for example, the reset signal Reset is concurrently supplied to each of the blocks ( 115 K,  115 Y,  115 M, and  115 C) of the sub ASIC  114  to concurrently set each of the blocks  115  to the reset state. The reason why each of the blocks  115  is set to the reset state here is to avoid malfunction of each block  115  electrostatically caused when the user touches an earth contact point  82  of an LED unit  40  during the operation. 
     Subsequently, it is assumed that the user completes the operation and closes the upper cover  11  at a time t 3  shown in  FIG. 6 . At this time, the cover switch  13  generates an open-close detection signal Sd that rises from the logic low level (L) to the logic high level (H) in response to the upper cover  11  being closed, and supplies the open-close detection signal Sd to the main ASIC  102 . 
     Then, at a time t 4  after lapse of a predetermined time period K 2  since the time t 3 , the main AISC  102  changes the reset signal Reset from the logic low level (L) to the logic high level (H). The predetermined time period K 2  is, for example, measured by a timer of the timer unit  104 . 
     By the reset signal Reset of the logic high level (H), the reset state of each block  115  of the sub ASIC  114  is concurrently released, and an initialization process is carried out in each block  115 . After the initialization process is completed, each block  115  keeps waiting in a ready state. 
     The reason why the reset state of each block  115  is released after lapse of the predetermined time period K 2  since the upper cover  11  has been closed is as follows. For example, when the upper cover  11  is not completely closed, the open-close detection signal Sd may wiggle between the logic high level (H) and the logic low level (L). Even in such a situation, when the reset state of each block  115  is released, it is possible to prevent the operations of setting and releasing the reset state of each block  115  from being unnecessarily repeated by the open-close detection signal Sd wiggling. In other words, it is possible to render invalid fluctuation of the open-close detection signal Sd within the predetermined time period K 2 . 
     In addition, as shown in  FIG. 6 , when the upper cover  11  is opened at a time t 5  and closed at a time t 6 , and a cover-opened time period Topen between the time t 5  and the time t 6  is shorter than the predetermined time period K 1 , the main ASIC  102  does not render valid the reset signal Reset (namely, does not set the reset signal Reset to the logic low level) or reset each block  115 . 
     In other words, when the user opens the upper cover  11  for a short while such that the user does not touch the inside of the main body  10  (e.g., for just taking a look at the inside of the main body  10 ) and soon closes the upper cover  11 , each block  115  is not reset. This is to reduce unnecessary stop operations for the sub ASIC  114  and improve efficiency of the image formation by the printer  1 . 
     3-2. Reset Control in Printing Operation 
     Practical Example 2 
     Next, referring to  FIG. 7 , reset control for the sub ASIC  114  will be set forth which is taken when the upper cover  11  is opened during a printing operation by the printer  1 .  FIG. 7  is a time chart showing a relationship between the open-close detection signal Sd and the reset signal Reset during the printing operation by the printer  1 . It is noted that the “printing operation” by the printer  1  includes operations until the printer  1  prints out a predetermined number of pages of sheets P after receiving a command to print the predetermined number of pages of sheets P. 
     For example, it is assumed that a sheet P becomes jammed at a time t 1  shown in  FIG. 7  and the user opens the upper cover  11  to remove the jammed sheet P. At this time, in response to the upper cover  11  being opened, the cover switch  13  generates the open-close detection signal Sd which drops from the logic high level (H) to the logic low level (L) and supplies the open-close detection signal Sd to the main ASIC  102 . 
     At this time, the main ASIC  102  changes the reset signal Reset from the logic high level (H) to the logic low level (L) to set each block  115  of the sub ASIC  114  to the reset state. Namely, when the upper cover  11  is opened during the printing operation, each block  115  is reset at the same time when the upper cover  11  is opened, as illustrated in  FIG. 7 . When the upper cover  11  is opened during the printing operation by the printer  1 , the user is, in general, likely to access the image forming unit  30  to perform paper jam settlement or cartridge replacement. In such a case, a long cover-opened time period Topen is required. Therefore, by stopping (resetting) the sub ASIC  114  promptly, it is possible to avoid malfunction of the sub ASIC  114  electrostatically caused when the user touches an earth contact point  82  of an LED head  41  in an operation. 
     It is noted that, in the same manner as the practical example 1, the reset state of each block  115  is not released at the same time when the upper cover  11  is closed. Hence, it is possible to reduce unnecessary stop operations for the sub ASIC  114 . 
     3-3. Reset Control for Each Block 
     Practical Example 3 
     Subsequently, referring to  FIGS. 8 and 9 , reset control will be set forth which is taken to individually reset the blocks  115  of the sub ASIC  114 .  FIGS. 8 and 9  are time charts showing relationships between the open-close detection signal Sd and a reset signal (Reset_K, Reset_Y, Reset_M, or Reset_C) corresponding to each of the blocks  115 . In the practical examples 1 and 2, each of the blocks  115  is concurrently reset by the reset signal Reset. Meanwhile, in the practical example 3, a predetermined time period K 1  after the upper cover  11  is opened is set for each of the blocks  115 , and the blocks  115  are reset at respective different moments. 
     Specifically, in the case where the upper cover  11  is opened at a time t 1  shown in  FIG. 8  when the printer  1  is in the ready state, the main ASIC  102  first changes the reset signal Reset_K for the block  115 K from the logic high level (H) to the logic low level (L) at a time t 2  after lapse of a predetermined time period (K 1 - 1 ) since the time t 1 . Then, the main ASIC  102  supplies the reset signal Reset_K of the logic low level (L) to the block  115 K and sets the block  115 K to the reset state. 
     Subsequently, the main ASIC  102  changes the reset signal Reset_K for the block  115 Y from the logic high level (H) to the logic low level (L) at a time t 3  after lapse of a predetermined time period (K 1 - 2 ) since the time t 1 . Then, the main ASIC  102  supplies the reset signal Reset_Y of the logic low level (L) to the block  115 Y and sets the block  115 Y to the reset state. 
     In the same manner, at a time t 4  after lapse of a predetermined time period (K 1 - 3 ) since the time t 1 , the main ASIC  102  supplies the reset signal Reset_M of the logic low level (L) to the block  115 M and sets the block  115 M to the reset state. Further, at a time t 5  after lapse of a predetermined time period (K 1 - 4 ) since the time t 1 , the main ASIC  102  supplies the reset signal Reset_C of the logic low level (L) to the block  115 C and sets the block  115 C to the reset state. It is noted that, here, the predetermined time period (K 1 - 1 ), which corresponds to the LED unit  40 K provided the closest to an open end (a front end opposite to the rotation shaft  12 ) of the upper cover  11 , is set to be the shortest among the predetermined time periods K 1  (K 1 - 1 , K 1 - 2 , K 1 - 3 , and K 1 - 4 ). 
     The reason why the different predetermined time periods K 1  after the upper cover  11  is opened are respectively set for the blocks  115 , and the blocks  115  are reset at respective different moments is given as follow. For example, as illustrated in  FIG. 9 , the cover-opened time period Topen during which the upper cover  11  is opened is longer than the predetermined time period (K 1 - 1 ) and shorter than the predetermined time period (K 1 - 2 ), the block  115 K is only reset. In other words, when the cover-opened time period Topen is short, the number of blocks  115  reset can be reduced. Therefore, an initialization time period for initializing the blocks  115  after the reset states of the blocks  115  are released can drastically be reduced in comparison with the case where all the blocks  115  are initialized (see  FIGS. 8 and 9 ). Thus, it leads to improved efficiency of the image formation by the printer  1  to reduce unnecessary stop operations for the blocks  115  depending on the cover-opened time period Topen and shorten the initialization time period for the blocks  115 . 
     Further, the reason why the blocks  115  are reset depending on the cover-opened time period Topen sequentially in the order of block arrangement from the open end (the front end opposite to the rotation shaft  12 ) of the upper cover  11  to the rotation shaft  12 , i.e., from the front side to the rear side of the printer  1  is as follows. In general, in the case of the upper cover  11  turning around the rotation shaft  12  as a supporting axis, the LED unit  40 K provided at the open end of the upper cover  11  is likely to be first touched by the user (see  FIG. 4 ). Therefore, by setting the predetermined time period (K 1 - 1 ) for the LED unit  40 K provided at the open end of the upper cover  11  to be the shortest and resetting the block  115 K first, it is possible to avoid electrostatically caused malfunction in a preferable manner. 
     4. Effects of Embodiment 
     When the cover-opened time period Topen is shorter than the predetermined time period K 1 , the main ASIC  102  does not render valid the reset signal Reset or reset the blocks  115 . Therefore, for instance, when the cover-opened time period Topen is too short for the user to touch the inside of the main body  10 , the blocks  115  are not reset. Thereby, it is possible to reduce unnecessary stop operations for the sub ASIC  114  and improve efficiency of the image formation by the printer  1 . 
     In addition, after lapse of the predetermined time period K 1 , each of the blocks  115  is set to the reset state. Therefore, it is possible to avoid malfunction of the blocks  115  electrostatically caused when the user touches an earth contact point  82  of an LED head  41  in an operation. 
     Further, the reset state of each of the blocks  115  is released after lapse of the predetermined time period K 2  since the upper cover  11  has been closed. Therefore, it is possible to prevent the operations of setting and releasing the reset states of the block  115  from being unnecessarily repeated by the main ASIC  102 . 
     Further, when the user opens the upper cover  11  during the printing operation by the printer  1 , the sub ASIC  114  is concurrently stopped (reset). Hence, even when the user touches an earth contact point  82  of an LED head  41 , for example, during an operation of settling a paper jam, it is possible to avoid electrostatically caused malfunction of the sub ASIC  114 . 
     Moreover, by setting the predetermined time period K 1  defined from the moment when the upper cover  11  is opened individually for each of the blocks  115  and resetting the blocks  115  at respective different moments, it is possible to reduce unnecessary stop operations for the blocks  115  depending on the cover-opened time period Topen during which the upper cover  11  is opened. Thereby, it is possible to shorten the initialization time period, and thus it leads to improved efficiency of the image formation by the printer  1 . 
     Further, when the predetermined time period K 1  is set individually for each of the blocks  115 , by first resetting the block  115 K which corresponds to the LED unit  40 K located the closest to the open end of the upper cover  11 , it is possible to avoid electrostatically caused malfunction in a preferable manner. 
     Hereinabove, the embodiment according to aspects of the present invention has been described. The present invention can be practiced by employing conventional materials, methodology and equipment. Accordingly, the details of such materials, equipment and methodology are not set forth herein in detail. In the previous descriptions, numerous specific details are set forth, such as specific materials, structures, chemicals, processes, etc., in order to provide a thorough understanding of the present invention. However, it should be recognized that the present invention can be practiced without reapportioning to the details specifically set forth. In other instances, well known processing structures have not been described in detail, in order not to unnecessarily obscure the present invention. 
     Only an exemplary embodiment of the present invention and but a few examples of its versatility are shown and described in the present disclosure. It is to be understood that the present invention is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein. For example, the following modifications are possible. 
     [Modifications] 
     (1) In the aforementioned embodiment, a control system is configured with the sub ASIC  114  provided to the upper cover  11  and the main ASIC  102  provided to the main body  10 , and the main ASIC  102  is adapted to interrupt the operations of the sub ASIC  114  and to release the interrupted state. However, for example, a control circuit configured to process image data for forming an image, an interrupting unit configured to interrupt the image data processing of the control circuit when a time period during which the upper cover  11  is kept opened reaches a predetermined time period, and a releasing unit configured to release the interrupted state of the image data processing by the control unit may separately be provided. 
     (2) In the aforementioned embodiment, the main ASIC  102  interrupts the operations of the sub ASIC  114  by supplying the reset signals to the sub ASIC  114 . However, for example, a function for interrupting the operations of the sub ASIC  114  and a function for releasing the termination of the operations may be achieved by a power source supply unit. Specifically, the power source supply unit may be configured to, in response to the upper cover  11  being opened/closed, interrupt/resume the operations of the sub ASIC  114  through ON/OFF control of power supply to the sub ASIC  114 . 
     (3) The aforementioned practical example 3 of the embodiment has exemplified that the block  115 K is first reset. However, the block  115 C may first be reset. In other words, the main ASIC  102  may be configured to first reset a predetermined one of the plural blocks  115 . In such a configuration, even when an initialization process is required after the termination of the operations of the sub ASIC  114  is released, as the operations of all the blocks are not necessarily required to be terminated, the initialization process can promptly be achieved. Hence, it is possible to improve efficiency of the image formation by the printer  1 . Additionally, a block  115 , which is likely to be electrostatically influenced when the upper cover  11  is opened, may be selected appropriately depending on a situation as a block to be first reset. 
     (4) In the aforementioned embodiment, the LED head  41  using the LEDs is employed to expose the surface of the photoconductive drum  53  with light emitted thereby. However, as substitute for the LEDs, light emitting elements such as electroluminescence (EL) devices, fluorescent substances, and laser emitting devices may be employed. Further, as substitute for the LED head  41 , a unit may be employed which has multiple light shutters aligned (e.g., liquid crystal devices, PLZT devices, etc.) and selectively controls respective open/close time periods of the multiple light shutters based on the image data.