Abstract:
An image formation apparatus has a controller which performs monitoring and control over a directly connected option apparatus by communicating with a controller of the directly connected option apparatus. Monitoring and control over another option apparatus that itself has a controller is performed not by the controller of the image formation apparatus but by the controller of the option apparatus close to the image formation apparatus. The image formation apparatus can keep track of the situation of a far-off option apparatus without performing direct monitoring or control thereof, by the controller of the option apparatus sending to the controller of the image formation apparatus a notice indicating the situation of the option apparatus sent from the controller of yet another option apparatus.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an image formation apparatus connectable with a plurality of option apparatuses and the option apparatuses. 
     BACKGROUND OF THE INVENTION 
     A variety of option apparatuses connectable to an image formation apparatus are conventionally provided to expand the function of the image formation apparatus according to the user&#39;s desire and operating environment. Such option apparatuses include a paper feed option apparatus to allow volume feeding of paper, sorter, duplex printing unit, etc. each having a structure allowing communication with the image formation apparatus. 
     For example, when a plurality of paper feed option apparatuses is placed and connected downstream from the image formation apparatus, the image formation apparatus and the plurality of paper feed option apparatuses transport recording media (hereinafter referred to as “sheets”) such as paper from a desired paper feed option apparatus to another image formation apparatus located downstream on the transport path while communicating with each other. 
     Conventionally, when an image formation apparatus is connected to a paper feed option apparatus that supplies recording media to perform media transport control, a controller in the image formation apparatus monitors transport control of sheets in all the paper feed option apparatuses and sends control data to the option apparatuses if necessary, thus carrying out all sheet transport control and monitoring processing. And also for a paper ejection option apparatus that performs a post-processing on sheets ejected from the image formation apparatus, a controller in the image formation apparatus performs the sheet transport control and monitoring processings for all the paper ejection option apparatuses. 
     Furthermore, as another example, it is provided that the sheet transport control and monitoring processings of the paper feed and paper ejection option apparatuses are separated from the controller in the image formation apparatus, and an option controller performs the sheet transport control and monitoring processings of all the option apparatuses. 
     However, such a conventional image formation apparatus has such problems as shown below: 
     If the number of paper feed option apparatuses is one or the sheet transport speed is not high, when the controller in the image formation apparatus or the option controller performs sheet transport control and monitoring processing of the paper feed option apparatus, an increase in the processing load of the controller would not be significant. However, when a plurality of option apparatuses is connected or the sheet transport speed is high, processing of the controller becomes more complicated, higher processing is required, the load of control and monitoring processing increases, which will require a high-speed and expensive processing unit such as a CPU to be used as the controller. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide an image formation apparatus, option apparatuses of the image formation apparatus and an image formation system made up of these image formation apparatus and option apparatuses capable of suppressing the increase of processing load on the controller of the image formation apparatus or the option controller when a plurality of option apparatuses is connected. 
     That is, a subject of the present invention is to provide an option apparatus for an image formation apparatus connectable directly or via another option apparatus to the image formation apparatus, capable of connecting a further option apparatus while being connected to the image formation apparatus, comprising directly connected communication means for communicating with the image formation apparatus or other option apparatuses and option apparatus controlling means for controlling the own operation based on an instruction received from an image formation apparatus directly connected on the image formation apparatus side or other option apparatuses via the communication means, characterized in that the option apparatus controlling means controls and/or monitors the operation of the other option apparatus directly connected away from the image formation apparatus and sends the state of the other option apparatuses to be controlled and/or monitored to the image formation apparatus directly connected on the image formation apparatus side or a further option apparatus using the communication means. 
     It is another subject of the present invention to provide an image formation apparatus that allows connection of a single and/or multiple option apparatuses of the image formation apparatus of the present invention, comprising image formation controlling means for controlling image formation processing using an option apparatus, characterized in that the image formation controlling means monitors and/or controls the operation of the option apparatus directly connected and monitors the states of the option apparatuses connected after the directly connected option apparatus through a communication with the directly connected option apparatus. 
     Furthermore, it is another subject of the present invention to provide an image formation system comprising an image formation apparatus and an option apparatus connectable directly or via another option apparatus to the image formation apparatus, capable of connecting a further option apparatus while being connected to the image formation apparatus, characterized in that the option apparatus comprises directly connected communication means for communicating with the image formation apparatus or another option apparatus and option apparatus controlling means for controlling the own operation based on an instruction received from an image formation apparatus directly connected on the image formation apparatus side or another option apparatus via the communication means, controls and/or monitors the operation of the other option apparatus directly connected away from the image formation apparatus and sends the state of the other option apparatus to be controlled and/or monitored to an image formation apparatus directly connected on the image formation apparatus side or a further option apparatus using the communication means, and the image formation apparatus comprises image formation controlling means for controlling image formation processing using an option apparatus and monitoring and/or controlling the operation of the option apparatus directly connected through a communication with the option apparatus controlling means of the option apparatus, characterized in that the image formation controlling means monitors the states of the option apparatuses connected after the directly connected option apparatus through a communication with the option apparatus controlling means owned by the directly connected option apparatus. 
     Furthermore, it is another subject of the present invention to provide a recording medium that stores a program that can be executed by a computer apparatus, characterized in that the apparatus that executes the program is allowed to function as an option apparatus of the image formation apparatus of the present invention. 
     Furthermore, it is another subject of the present invention to provide a recording medium that stores a program that can be executed by a computer apparatus, characterized in that the apparatus that executes the program is allowed to function as the image formation apparatus of the present invention. 
     Furthermore, it is another subject of the present invention to provide a recording medium that stores a program that can be executed by a computer apparatus, characterized in that the apparatus that executes the program is allowed to function as the image formation apparatus or option apparatus in the image formation system of the present invention. 
     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
     FIG. 1 illustrates a configuration of an image formation apparatus and option apparatuses according to an embodiment of the present invention; 
     FIG. 2 is a block diagram showing an outlined configuration of the image formation apparatus and controllers in the option apparatuses according to the embodiment of the present invention; 
     FIGS. 3A to  3 C are flow charts showing a powering-on and connection state setting procedure of the image formation apparatus and option apparatuses according to the embodiment of the present invention; 
     FIGS. 4A to  4 D are flow charts showing a sheet transport processing procedure of an image formation apparatus and option apparatuses according to a first embodiment of the present invention; 
     FIGS. 5A to  5 C are flow charts showing a sheet transport processing procedure of the image formation apparatus and option apparatuses according to the first embodiment of the present invention; 
     FIGS. 6A to  6 C are flow charts showing sheet transport processing procedure of the image formation apparatus and option apparatuses according to the first embodiment of the present invention; 
     FIGS. 7A to  7 C are flow charts showing sheet transport processing procedure of the image formation apparatus and option apparatuses according to the first embodiment of the present invention; 
     FIGS. 8A to  8 C are flow charts showing a sheet transport processing procedure of an image formation apparatus and option apparatuses according to a second embodiment of the present invention; 
     FIGS. 9A to  9 C are flow charts showing sheet transport processing procedure of the image formation apparatus and option apparatuses according to the second embodiment of the present invention; and 
     FIGS. 10A to  10 C is a flow chart showing a sheet transport processing procedure of an image formation apparatus and option apparatuses according to a third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. 
     First Embodiment 
     (Configuration of Image Formation Apparatus) 
     FIG. 1 illustrates a configuration example of an image formation system made up of an image formation apparatus and option apparatuses according to an embodiment of the present invention. In this embodiment, the image formation apparatus forms toner images on a sheet through electrophotographic process. 
     In the figure, reference numeral  100  denotes an image formation apparatus, reference numerals  101  and  102  denote paper feed option apparatuses and reference numerals  133  and  134  denote paper ejection option apparatuses. The image formation apparatus  100  is placed above the option apparatus  101  and the option apparatus  101  is placed above the option apparatus  102 . 
     Reference numerals  104  to  107  denote sheets to which images are transferred by the image formation apparatus and a plurality of sheets is loaded. Sheets  104  and  105  are placed in a paper feed apparatus built in the image formation apparatus. Reference numerals  108  to  111  denote pickup rollers that send sheets and groups of rollers  112  to  120  transport sheets to an electrophotographic process section  103 . 
     A roller pair  117  is placed downstream on the transport path from the position where a sheet transported in the image formation apparatus  100  joins a sheet transported from the option apparatus  101 . When the image formation apparatus  100  is already transporting a sheet, a sheet from the option apparatus  101  is temporarily stopped at the position just before the roller pair  117 . 
     A roller pair  119  is placed downstream from the position where a sheet transported in the option apparatus  101  joins a sheet transported by the option apparatus  102 . When the option apparatus  101  is already transporting a sheet, a sheet from the option apparatus  102  is temporarily stopped at the position just before the roller pair  119 . 
     Reference numeral  121  denotes a connector that connects the image formation apparatus  100  and option apparatus  101  enabling communication with each other and relays a communication line  130   a  used to communicate a controller  127  in the image formation apparatus  100 , a controller  128  in the option apparatus  101  and a controller  129  in the option apparatus  102 , and a power supply control signal line  130   b . As in the case of reference numeral  121 , reference numeral  122  denotes a connector that connects the option apparatus  101  and the option apparatus  102  and relays the communication line  130   c  and the power supply control signal line  130   d.    
     Reference numeral  123  denotes a tray to hold sheets with images formed by the electrophotographic process section  103  in the image formation apparatus and sheets are transported by a roller pair  124  with the side on which images are formed face down. 
     Reference numeral  125  denotes an ejection port for sheets with images formed by the electrophotographic process section  103  in the image formation apparatus and sheets are transported by a roller pair  126  with the side on which images are formed face up. 
     The plurality of sheets  104  to  107  is transported by the roller groups along the transport path indicated by dotted lines and arrows in FIG.  1  and ejected onto the tray  123  or through the ejection port  125  with images formed on their surfaces. 
     Reference numeral  131  denotes a confluence (1) of sheet transport paths in the image formation apparatus  100  and is located just before (upstream) the roller pair  117 . The confluence (1)  131  indicates the position at which a sheet  105  transported in the image formation apparatus  100  joins a sheet  106  transported from the option apparatus  101 . 
     Reference numeral  132  denotes a confluence (2) of sheet transport paths in the option apparatus  101  and is located just before the roller pair  119 . The confluence (2)  132  indicates the position at which a sheet  106  transported in the option apparatus  101  joins a sheet  107  transported from the option apparatus  102 . 
     Reference numeral  133  denotes an option apparatus connected downstream from the image formation apparatus  100  and ejects a sheet ejected from the image formation apparatus onto a tray provided for the option apparatus  133  or to an option apparatus  134  downstream. 
     Reference numeral  134  denotes an option apparatus installed below the option apparatus  133  and transports and ejects sheets transported from the option apparatus  133 . 
     Reference numerals  135  and  136  denote trays to hold sheets transported by the option apparatuses  133  and  134  and reference numerals  137  to  142  denote roller pairs to transport sheets ejected from the image formation apparatus  100 . For simplicity of explanations, FIG. 1 shows only roller pairs  138  and  142  to transport sheets out to the trays  135  and  136 , but roller pairs to transport sheets out to other trays are also provided in the actual system. 
     Reference numerals  143  and  144  denote controllers of the option apparatuses  133  and  134  and are connected via a signal line  145   c  and power supply control line  145   d . A signal line  145   a  and power supply control line  145   b  connect the controller  127  in the image formation apparatus  100  and the controller  143 . Reference numerals  149  and  150  denote connectors between the image formation apparatus  100  and the option apparatus  133  and between the option apparatuses  133  and  134 , respectively and relay the signal lines  145   a  and  145   c  and power supply control signal lines  145   b  and  145   d.    
     However, the connectors  121 ,  122 ,  149  and  150  can also be replaced by cables or other communication means connectable in the order of transport paths. 
     (Controller Configuration) 
     FIG. 2 is a block diagram showing configurations and connection relationships of the controller  127  in the image formation apparatus  100 , the controller  128  in the option apparatus  101  and the controller  129  in the option apparatus  102 . However, the controllers  143  and  144  in the option apparatuses  133  and  134  have the same configurations as those of the controllers  128  and  129 , and therefore these are not shown. 
     Reference numeral  200  denotes a CPU that is located inside the controller  127  and controls the image formation apparatus to control image formation and sheet transport. The CPU  200  incorporates a ROM  200   a , a RAM  200   b  and a timer  200   c . However, the ROM  200   a , RAM  200   b  and timer  200   c  can also be installed outside the CPU  200 . 
     The ROM  200   a  stores the processing content to be executed by the CPU  200  all the time and software regarding the image formation processing, sheet transport processing and communication processing is written therein. 
     The RAM  200   b  stores data temporarily required to execute image formation processing, sheet transport processing and communication processing by the CPU  200 . 
     The timer  200   c  generates various timings to execute image formation processing, sheet transport processing and communication processing. 
     Reference numeral  201  denotes an image formation circuit and is a circuit to carry out electrophotographic process when an image is formed on a sheet by the image formation apparatus. 
     Reference numeral  202  denotes a circuit to control various actuators (not shown) driven when sheet transport and image formation processing are carried out by the image formation apparatus. 
     Reference numeral  203  denotes a circuit to input output signals from various sensors (not shown) to the CPU  200  when sheet transport and image formation processing are carried out by the image formation apparatus. 
     Reference numeral  204  denotes a circuit to carry out processing of turning ON/OFF power from the image formation apparatus to the option apparatuses and controls the power supply circuit of the option apparatus  101  via a power supply control signal line  205 . 
     Reference numeral  206  denotes a circuit to carry out communication processing between the image formation apparatus and option apparatuses and is bus-connected to the option apparatus via a communication line  130   d . However, the connection mode is not limited to a particular mode. 
     Reference numerals  207  and  214  denote CPUs that are located in the controller  128  and  129  and control the option apparatuses  101  and  102 , respectively to control sheet transport to the image formation apparatus  100 . The CPUs  207  and  214  contain ROMs  207   a  and  214   a , RAMs  207   b  and  214   b  and timers  207   c  and  214   c . However, the ROMs  207   a  and  214   a , RAMs  207   b  and  214   b  and timers  207   c  and  214   c  can also be installed outside the CPUs  207  and  214 . 
     The ROMs  207   a  and  214   a  store the processing content to be executed by the CPUs  207  and  214  all the time and software regarding the sheet transport processing and communication processing is written therein. 
     The RAMs  207   b  and  214   b  store data temporarily required to execute sheet transport processing and communication processing by the CPUs  207  and  214 . 
     The timers  207   c  and  214   c  generate various timings to execute sheet transport processing and communication processing. 
     Reference numerals  212  and  218  denote circuits to control various actuators (not shown) driven when sheet transport is carried out by the option apparatuses  101  and  102 . 
     Reference numerals  213  and  219  denote circuits to input output signals from various sensors (not shown) to the CPUs  207  and  214  when sheet transport is carried out by the option apparatuses  101  and  102 . 
     Reference numerals  209  and  216  denote circuits to carry out processing of turning ON/OFF power from one option apparatus to the other option apparatus and the circuit  209  controls the power supply circuit of the option apparatus via a power supply control signal line  130   d.    
     Reference numerals  211  and  217  denote circuits to carry out communication processing between the image formation apparatus  100  and option apparatuses  101  and  102  and are connected to the option apparatuses via a communication line  130   c . However, the connection mode is not particularly limited. 
     (Operation When Power is Turned On) 
     FIGS. 3A to  3 C are flow charts showing the processing procedure after the power to the image formation apparatus  100 , option apparatuses  101 ,  102 ,  133  and  134  is turned on. FIG. 3A, FIG.  3 B and FIG. 3C show the operations of the image formation apparatus  100 , option apparatuses  101  and  133 , and option apparatuses  102  and  134 , respectively. 
     In step S 100 , immediately after the power to the image formation apparatus  100  is turned on, the CPU  200  is initialized. In the next step S 101 , the timer  200   c  is started to measure the time until the power to the option apparatus  101  connected is turned on. This is intended to prevent a voltage fluctuation in a surrounding AC line (not shown) caused by turning on power to all apparatuses simultaneously by providing starting time differences and to recognize option apparatuses connected upstream or downstream one by one starting with the option apparatus closest to the image formation apparatus  100 . 
     In step S 102 , i t is checked with the timer  200   c  start ed in step S 101  whether a predetermined time has elapsed or not and if the predetermined time has elapsed, a signal to turn on the power to the option apparatus  101  is output in the next step S 103 . 
     On the other hand, in step S 200  (FIG.  3 B), the option apparatus  101  turns on power by a signal output to the option apparatus  101  and initializes the CPU  207  in the option apparatus  101  in step S 201 . 
     In step S 202 , the timer  207   c  is started to turn on the power to the option apparatus  102  connected upstream from the option apparatus  101 . 
     In step S 203 , it is checked through the timer  207   c  started in step S 200  whether a predetermined time has elapsed or not and if it is confirmed that the predetermined time has elapsed, a signal for turning on the power to the option apparatus  102  located further upstream is output in step S 204 . 
     In step S 205 , the information of the option apparatus  101  is sent to the image formation apparatus  100  through communication processing a predetermined time after the power to the option apparatus  101  is turned on. This transmission content is the information concerning the function and state of the option apparatus  101 . 
     The data sent in step S 205  is received by the image formation apparatus  100  (step S 104 ) and the image formation apparatus  100  recognizes in step S 105  that the option apparatus  100  is connected one step upstream on the sheet transport path and sets the state of connection with the option apparatus  101  on the RAM  207   b.    
     On the other hand, in step S 300  (FIG.  3 C), the option apparatus  102  receives the power-on signal output by option apparatus  101  in step S 204  and turns on the power to the option apparatus  102  and then initializes the CPU  214  in the option apparatus  102  in step S 301 . 
     In step S 303 , the option apparatus performs processing of turning on the power to the option apparatus connected further upstream. Although in this embodiment, no option apparatus is connected further upstream from the option apparatus  102 , signals for turning on the power are output also in the configuration having three or more option apparatuses in which further paper feed option apparatuses are connected upstream from the option apparatus  102  . 
     Then, in step S 305 , the information of the option apparatus  102  is sent to the downstream option apparatus  101 . The option apparatus  101  that has received the information of the option apparatus  102  in step S 206  (FIG. 3B) recognizes in step S 207  that the option apparatus  102  is connected one step upstream from the option apparatus  101 , sets the state of connection with the option apparatus  102  in the RAM  200   b  and transfers the apparatus information of the option apparatus  102  to image formation apparatus  100 . 
     In step S 305 , it is also possible to configure the option apparatus  102  to directly send the own information to the image formation apparatus  100 . 
     In step S 107 , the image formation apparatus  100  recognizes that the option apparatus  102  is connected two steps upstream on the sheet transport path and sets the state of connection with the option apparatus  102  in the RAM  200   b.    
     Also in the configuration having three or more option apparatuses in which a plurality of paper feed option apparatuses are further connected upstream from the option apparatus  102 , the apparatus information is sequentially transmitted to a downstream option apparatus, and the receiving downstream option apparatus retains the apparatus information of the option apparatus connected upstream from it. And, the image formation apparatus  100  sets the apparatus information and the connection states of all the option apparatuses connected upstream from it in the RAM  200   b.    
     However, as the processing for setting the state of connection between the option apparatuses  101  and  102 , it is also possible to configure the option apparatus  102  to send the information of the own apparatus only to the image formation apparatus  100  without sending it to the option apparatus  101  and configure the image formation apparatus  100  to send the information of the option apparatus  102  to the option apparatus  101 . 
     According to the flow charts shown in FIGS. 3A to  3 C, the image formation apparatus  100  can turn on the power to the option apparatus  101  installed one step upstream and the option apparatus  101  can turn on the power to the option apparatus  102  installed one step upstream. Furthermore, the image formation apparatus  100  can recognize the information and connection state of the upstream option apparatuses  101  and  102  and the option apparatus  101  can recognize the information and connection state of the option apparatus  102  one step upstream. 
     In this embodiment, the option apparatuses  133  and  134  connected downstream from the image formation apparatus  100  operate in the same way as the option apparatuses  101  and  102  except that the powering-on sequence changes from upstream to downstream. That is, by replacing the processing of sequentially turning on power from the image formation apparatus  100  in an upstream direction and sequentially receiving option apparatus information by the processing of sequentially turning on power in a downstream direction and sequentially receiving option apparatus information, it is possible to turn on power to all option apparatuses and recognize the information and connection states. 
     Furthermore, in the configuration in which a plurality of option apparatuses other than the paper feed option apparatuses  101 ,  102  and the paper ejection option apparatuses  133 ,  134  are connected upstream or downstream, the operation is the same. 
     In this case, it is optional to decide whether to recognize all option apparatuses connected upstream from the image formation apparatus  100  and then recognize option apparatuses connected downstream or vice versa. Furthermore, if the image formation apparatus  100  can receive apparatus information from an upstream option apparatus and apparatus information from a downstream option apparatus independently, it is also possible to turn on power to both apparatuses simultaneously. 
     (Sheet Transport (Supply) Processing) 
     FIGS. 4A to  4 D and FIGS. 5A to  5 C are flow charts that show sheet transport processing of the image formation apparatus  100 , option apparatuses  101  and  102 , and option apparatus upstream from the option apparatus  102  (not shown in FIG.  1 ). 
     FIG.  4 A and FIG. 5A show the operation of the image formation apparatus  100 , FIG.  4 B and FIG. 5B show the operation of the option apparatus  101 , FIG.  4 C and FIG. 5C show the operation of the option apparatus  102 , and FIG. 4D shows the operation of the option apparatus upstream from the option apparatus  102 . 
     Followings are the description of operations in the case when sheet  1  (sheet  106  in FIG. 1) is fed from the option apparatus  101 , sheet  2  (sheet  107  in the same figure) is fed by the option apparatus  102  via the option apparatus  101  to the image formation apparatus  100 , and sheet  3  (not shown) is fed by the option apparatus upstream from the option apparatus  102  via the option apparatus  102  and option apparatus  101  to the image formation apparatus  100 . 
     First, in step S 400 , the image formation apparatus  100  sends sheet transport information to the option apparatuses  101  and  102  and the option apparatus upstream from the option apparatus  102 . 
     Sheet transport information specifies any one of the option apparatuses  101  and  102  and option apparatus upstream from the option apparatus  102  and instructs the specified apparatus to feed sheets, and also instructs the downstream apparatus to transport the sheets. If the option apparatus is instructed to feed a plurality of sheets, each of the option apparatuses is controlled so that the each sheet will be fed to the image formation apparatus  100  in the instructed order. 
     The option apparatus  101  receives and recognizes the transport information of sheets  1 ,  2 , and  3  from the image formation apparatus  100  in step S 500 . The option apparatus  101  also stores the received transport information of sheets  1 ,  2 , and  3  in the RAM  207   b . Since the option apparatus  101  transports sheet  2  from the option apparatus  102 , it receives the transport information of sheet  2 . In addition, since the option apparatus  101  transports sheet  3  from the option apparatus upstream from the option apparatus  102 , it receives the transport information of sheet  3 . The option apparatus  101  then starts to transport sheet  1  (step S 501 ). In addition, the option apparatus  101  starts the timer  207   c . In the following, the timers in the respective apparatuses are set for determining the timing of transport of sheets in transporting the respective sheets, and are used for transport control. 
     On the other hand, the option apparatus  102  receives and recognizes the transport information of sheet  2  from the image formation apparatus  100  in step S 600 , and since the option apparatus  102  transports sheet  3  from the option apparatus upstream from it, it receives the transport information of sheet  3 . The option apparatus  102  also stores the received transport information of sheets  2  and  3  in the RAM  214   b . The option apparatus  102  then starts to transport sheet  2  (step S 601 ). In addition, the option apparatus  102  starts the timer  214   c.    
     When the option apparatus  101  starts to transport sheet  1  in step S 501 , the image formation apparatus  100  checks the transport of sheet  1  according to the sensor information input from the sensor input circuit  203  when sheet  1  is transported to the image formation apparatus  100  and starts transport control (step S 401 ). Alternatively, the image formation apparatus  100  may have been driven the roller pair  118  so as to transport sheet  1  without detection of the sensor signal. 
     In step S 502 , the option apparatus  101  determines with the timer  207   c  whether sheet  1  has reached the confluence (1)  131  just before the roller pair  117  or not and if sheet  1  has reached the confluence, the option apparatus  101  stops the transport of sheet  1  in step S 503 . However, if no other sheet exists at the confluence (1)  131 , it is possible to continue to transport sheet  1  without stopping. 
     Then, in step S 504 , the option apparatus  101  sends data to notify the image formation apparatus  100  of the stoppage of transport of sheet  1  and in step S 402 , the image formation apparatus  100  receives and recognizes the data indicating that the transport of sheet  1  has been stopped. The image formation apparatus  100  also stops the transport of sheet  1  in the image formation apparatus  100 . 
     The option apparatus  102  that started the transport of sheet  2  in step S 601  determines with the timer  214   c  in step S 602  whether sheet  2  has reached the confluence (2)  132  just before the roller pair  119  or not and if sheet  2  has reached the confluence, the option apparatus  102  stops the transport of sheet  2  in step S 603 . However, if no other sheet exists at the confluence (2)  132 , it is possible to continue to transport sheet  2  without stopping. 
     Then, the option apparatus  102  sends the data to notify the stoppage of transport of sheet  2  to the option apparatus  101  in step S 604 . This data is received by the option apparatus  101  (step S 505 ) and the option apparatus  101  recognizes that the transport of sheet  2  has been stopped. 
     In step S 403 , the image formation apparatus  100  determines whether sheet  1  can pass through the confluence (1)  131  in the image formation apparatus  100  or not and if sheet  1  can pass through the confluence, the image formation apparatus  100  moves on to step S 404  and sends to the option apparatus  101  the data to indicate that it is possible to transport sheet  1 . 
     In step S 506  and step S 507 , the option apparatus  101  monitors communication data, and when it is determined that the data output by the image formation apparatus  100  in step S 404  shows that sheet  1  can pass through the confluence (1)  131 , the option apparatus  101  moves on to step S 508 . 
     In step S 508 , the processing of transporting sheet  1  in the option apparatus  101  restarts, and in step S 405 , the processing of transporting sheet  1  in the image formation apparatus  100  restarts. 
     When sheet  2  is allowed to pass through the confluence (2)  132  just before the roller pair  119 , the option apparatus  101  sends the data indicating that sheet  2  can pass through the confluence to the option apparatus  102  (step S 509 ). The option apparatus  102  monitors the communication in order to detect whether sheet  2  whose transport has been stopped in step S 604  is allowed to pass through the confluence (2)  132  or not (steps S 606 , S 607 ), and after confirming the reception of the data indicating that sheet  2  is allowed to pass through the confluence (2)  132  from the option apparatus  101 , the option apparatus  102  restarts to transport sheet  2  in step S 608 . 
     When sheet  1  is ejected from the option apparatus  101 , data indicating the completion of ejection of sheet  1  is sent to the image formation apparatus  100  (step S 510 ) and the image formation apparatus  100  receives and recognizes sheet  1  ejection completion data in step S 406 . 
     Then, the image formation apparatus  100  performs image formation processing on sheet  1  transported into the image formation processing  100  in step S 407 . 
     On the other hand, the option apparatus  101  that has completed the ejection of sheet  1  starts to transport sheet  2  transported from the option apparatus  102  to the option apparatus  101  (step S 511 ). 
     When the ejection of sheet  2  is completed, the option apparatus  102  sends the data indicating the completion of ejection of sheet  2  to the option apparatus  101  in step S 610  and the option apparatus  101  receives the data indicating the completion of ejection of sheet  2  in step S 512 . 
     In step S 408 , when the image formation apparatus  100  detects through a signal from the sensor input circuit  203  that sheet  2  has been transported to the image formation apparatus  100 , the image formation apparatus  100  starts to transport sheet  2 . Alternatively, the image formation apparatus  100  may have been driven the roller pair  118  so as to transport sheet  2  without detection of the sensor signal. 
     In step S 513 , the option apparatus  101  determines whether sheet  2  has reached the confluence (1)  131  just before the roller pair  117  and if sheet  2  has reached the confluence, the option apparatus  101  stops the transport of sheet  2  in step S 514  (FIG.  5 B). However, if there is no other sheet at the confluence (1)  131 , the option apparatus  101  can also continue to transport sheet  2  without stopping. 
     In step S 515 , the option apparatus  101  sends data to notify the image formation apparatus  100  of the stoppage of transport of sheet  2  and the image formation apparatus  100  receives and recognizes this data indicating the stoppage of transport of sheet  2 . Then, the image formation apparatus  100  stops transporting sheet  2  in the image formation apparatus  100  (step S 409 ). 
     In step S 410 , the image formation apparatus  100  determines whether sheet  2  can pass through the confluence (1)  131  in the image formation apparatus  100  or not and if sheet  2  can pass through the confluence, the image formation apparatus  100  moves on to step S 411  and sends to the option apparatus  101  data indicating that it is possible to transport sheet  2 . 
     In step S 517 , the option apparatus  101  monitors communication data, and when it is determined in step S 518  that sheet  2  can pass through the confluence (1)  131 , the option apparatus  101  moves on to step S 519 . 
     In step S 519 , the option apparatus  101  restarts the processing of transporting sheet  2  in the option apparatus  101 , and in step S 412 , the image formation apparatus  100  also restarts the processing of transporting sheet  2 . 
     In step S 521 , when the option apparatus  101  ejects sheet  2 , the data indicating the completion of ejection of sheet  2  is sent to the image formation apparatus  100  through communication processing. 
     The image formation apparatus  100  that has received this data in step S 413  performs image formation processing on sheet  2  in step S 414 . 
     The transport control for sheets  1  and  2  has been explained in the above description. As with sheet  2 , sheet  3  is sequentially transported from the option apparatus located upstream from the option apparatus  102  to the option apparatus  102  one step downstream from the option apparatus, to the option apparatus  101  further downstream, and then to the image formation apparatus  100 , as shown in steps S 620  to S 628 . Eventually, in steps up to steps S 419 , S 529 , and S 619 , sheet  1 ,  2 , and  3  are transported to the image formation apparatus  100  in this order, and image formation is conducted. 
     According to sheet transport and monitoring processing shown in the flow charts in FIGS. 4A to  4 D and FIGS. 5A to  5 C, the image formation apparatus  100  first sends sheet transport information to all of the connected option apparatuses  101  and  102  and option apparatus upstream from the option apparatus  102 , and performs sheet transport control and monitoring of only the option apparatus  101  one step upstream after sheet transport processing is started, the option apparatus  101  performs sheet transport control and monitoring of only the option apparatus  102  one step upstream, and the option apparatus  102  performs sheet transport control and monitoring of only the option apparatus one step upstream, and in this way it is possible to carry out image formation processing and transport processing on all sheets. 
     Furthermore, also in the configuration in which a plurality of paper feed option apparatuses are further connected upstream, each apparatus performs sheet transport control and monitoring of the option apparatus one step upstream from itself, thus making it possible to carry out image formation processing and transport processing on all sheets. 
     (Sheet Transport (Ejection) Processing) 
     FIGS. 6A to  6 C and FIGS. 7A to  7 C are flow charts to show sheet transport processing of the image formation apparatus  100 , option apparatuses  133  and  134 . 
     FIG.  6 A and FIG. 7A show the operation of the image formation apparatus  100 , FIG.  6 B and FIG. 7B show the operation of the option apparatus  133  and FIG.  6 C and FIG. 7C show the operation of the option apparatus  134 . 
     Followings are the description of the operation in case when the sheets  1  and  2  are transported from the image formation apparatus  100  through the option apparatus  133  to the option apparatus  134  at which the sheets  1  and  2  are ejected and loaded. 
     First, in step S 700 , the image formation apparatus  100  sends sheet transport information to the option apparatuses  133  and  134 . Sheet transport information instructs sheet ejection and load by specifying the option apparatus to which the sheet(s) is(are) to be loaded, and also instructs the downstream apparatus to transport the sheets. 
     The sheet transport information is received by the option apparatuses  133  and  134  in step S 800  and step S 900 , respectively. 
     In step S 701 , data is sent to inquire whether it is possible to eject sheet  1  to the option apparatus  133  connected right downstream from the image formation apparatus  100 . The option apparatus  133  receives this inquiry data in step S 801  and determines whether it is possible to transport sheet  1  in step S 802 . If it is impossible to transport the sheet, the option apparatus  133  notifies this to the image formation apparatus  100  in step S 803  and if it is determined that it is possible to transport the sheet, the option apparatus  133  notifies this to the image formation apparatus  100  in step S 804 . These notifications are both received by the image formation apparatus  100 , which is monitoring the communication (step S 702 ). 
     Based on the notification received in step S 702 , the image formation apparatus  100  determines in step S 703  whether sheet  1  can pass through the ejection port  125  of the image formation apparatus  100  or not and if sheet  1  can pass through the ejection port  125 , the image formation apparatus  100  moves on to step S 704 . On the other hand, if sheet  1  cannot pass through the ejection port  125 , the image formation apparatus  100  continues communication monitoring processing in step S 702  until the option apparatus  133  notifies that it is possible to transport the sheet. 
     In step S 704 , the image formation apparatus  100  sends an advance notice that sheet  1  will be ejected to the option apparatus  133 , and then in step S 705 , the image formation apparatus  100  starts to eject sheet  1 . The option apparatus  133  receives the advance notice of ejection of sheet  1  in step S 805  and then starts to transport sheet  1  in step S 806 . 
     Then, in step S 807 , the option apparatus  133  inquires the option apparatus  134  located downstream about whether sheet  1  being transported in the option apparatus  133  can be ejected or not. 
     This inquiry data is received by the option apparatus  134  in step S 901 , and it is determined in step S 902  whether sheet  1  can be transported or not. If sheet  1  cannot be transported, the option apparatus  134  notifies this to the option apparatus  133  in step S 903 . If sheet  1  can be transported, the option apparatus  134  notifies that sheet  1  can be transported in step S 904 . 
     The option apparatus  133  monitors the communication in step S 808  and determines in step S 809  whether sheet  1  can be ejected or not based on the notification received from the option apparatus  134 . If sheet  1  can be ejected, the option apparatus  133  moves on to the next step S 810 , notifies the image formation apparatus  100  of the start of the ejection of sheet  1 . Then, in the following step S 811 , the option apparatus  133  sends the option apparatus  134  an advance notice of ejection before sheet  1  is ejected from the option apparatus  133 . 
     Upon reception of the advance notice of ejection from the option apparatus  133  in step S 905 , the option apparatus  134  starts to transport sheet  1  transported to the option apparatus  134  (step S 906 ). 
     When the ejection of sheet  1  is completed, for example, the image formation apparatus  100  inquires the option apparatus  133  whether it is possible to eject sheet  2  or not (step S 707 ). 
     The option apparatus  133  receives this inquiry in step S 812  and determines in step S 813  whether the option apparatus  133  can transport sheet  2  or not. If sheet  2  cannot be transported for such a reason that the processing of sheet  1  is in progress, the option apparatus  133  notifies this to the image formation apparatus  100  in step S 814 . If sheet  2  can be transported, the option apparatus  133  notifies that sheet  2  can be transported to the image formation apparatus  100  in step S 815 . This determination result of the option apparatus  133  is received by the image formation apparatus  100  in step S 708  and the image formation apparatus  100  determines whether sheet  2  can pass through the ejection port  125  or not based on the received determination result (step S 709 ). If it is determined that sheet  2  cannot pass through the ejection port  125 , the image formation apparatus  100  waits until it is determined that sheet  2  is allowed to pass through the ejection port  125 . On the other band, if the image formation apparatus  100  is notified from the option apparatus  133  that sheet  2  can pass through the ejection port  125 , the image formation apparatus  100  sends an advance notice of sheet ejection to the option apparatus  133  in step S 710 . This notice is received by the option apparatus  133  in step S 816  and the option apparatus  133  recognizes the advance notice of the ejection of sheet  2 . 
     Following the advance notice of the ejection of sheet  2 , the image formation apparatus  100  starts to eject sheet  2  in step S 711  and the option apparatus  133  also starts to transport sheet  2  in step S 817 . 
     In step S 818 , the completion of ejection of sheet  1  in the option apparatus  133  is notified to the image formation apparatus  100  and received and recognized by the image formation apparatus  100  in step S 712 . Then, the option apparatus  133  inquires the option apparatus  134  in step S 819  about whether sheet  2  can be ejected or not. 
     This inquiry is received by the option apparatus  134  in step S 907  and the option apparatus  134  determines in step S 908  whether sheet  2  can be transported or not. The determination result is notified to the option apparatus  133  in step S 909  if sheet  2  cannot be transported or in step S 910  if sheet  2  can be transported. 
     In step S 820 , the option apparatus  133  receives from the option apparatus  134  the determination result of whether it is possible to transport sheet  2  or not. Then, in step S 821 , the option apparatus  133  determines whether the option apparatus  134  has notified as to whether sheet  2  can be ejected or not and waits until the notification is received. 
     When the preceding sheet  1  is ejected from the option apparatus  134 , the option apparatus  134  notifies this to the option apparatus  133  (step S 911 ). In step S 822 , upon reception of a notice that the option apparatus  134  has completed the transport of sheet  1 , the option apparatus  133  notifies the image formation apparatus  100  in step S 823  that sheet  1  has been ejected from the option apparatus  134  and sends an advance notice of ejection of sheet  2  to the option apparatus  134  in step S 824 . 
     The option apparatus  134  receives and recognizes the advance notice of ejection of sheet  2  from the option apparatus  133  in step S 912 . Then, in step S 913 , the option apparatus  134  starts to transport sheet  2  based on the advance notice of ejection received in step S 912 . 
     On the other hand, in step S 825 , the option apparatus  133  starts to eject sheet  2  following the advance notice of the ejection output in step S 824 . When the transport of sheet  2  in the option apparatus  133  is completed, the option apparatus  133  notifies this to the image formation apparatus  100  in step S 826 . The image formation apparatus  100  receives and recognizes this notice in step S 714 . 
     When the ejection of sheet  2  is completed, the option apparatus  134  notifies this to the option apparatus  133  and completes the processing in step S 914 . Upon reception of the notice of the completion of ejection of sheet  2  by the option apparatus  134  in step S 827 , the option apparatus  133  notifies the image formation apparatus  100  that the option apparatus  134  has ejected sheet  2  in step S 828 . Then, the image formation apparatus  100  receives and recognizes the completion of ejection of sheet  2  by the option apparatus  134  in step S 715  and a series of ejection processing is completed. 
     According to sheet transport control and monitoring processing shown in the flow charts in FIGS. 6A to  6 C and FIGS. 7A to  7 C, the image formation apparatus  100  first sends sheet transport information to all the connected option apparatuses  133  and  134 , performs sheet transport control and monitoring of only the option apparatus  133  one step downstream after sheet transport processing is started and the option apparatus  133  performs sheet transport control and monitoring of only the option apparatus  134  one step downstream, thus making it possible to carry out image formation processing and transport processing on all sheets. 
     Furthermore, also in the configuration in which a plurality of paper ejection option apparatuses other than the paper ejection apparatuses  133 ,  134  are connected downstream, each apparatus performs sheet transport control and monitoring of the option apparatus one step downstream from itself, thus making it possible to carry out transport processing on all sheets, on which images are formed. 
     Second Embodiment 
     Then, the sheet transport processing operation of the image formation apparatus and option apparatuses according to a second embodiment of the present invention will be explained using the flow charts shown in FIGS. 8A to  8 C and FIGS. 9A to  9 C. FIGS. 8A to  8 C and FIGS. 9A to  9 C are the flow charts that show sheet transport processing in the image formation apparatus  100  and the option apparatuses  133  and  134 . FIG.  8 A and FIG. 9A show the operation of the image formation apparatus  100 , FIG.  8 B and FIG. 9B show the operation of the option apparatus  133  and FIG.  8 C and FIG. 9C show the operation of the option apparatus  134 . 
     In this embodiment, the configuration of the image formation apparatus itself is the same as that of the first embodiment, and therefore explanations thereof will be omitted. Furthermore, in sheet transport processing, which will be explained below, suppose sheet  1  and sheet  2  are ejected from the option apparatus  134  via the option apparatus  133  as in the case of the first embodiment. 
     First, in step S 716 , the transport information of sheet  1  and sheet  2  is sent from the image formation apparatus  100  to the option apparatuses  133  and  134 . This transport information is received by the option apparatuses  133  and  134  in step S 829  and step S 915 , respectively. Upon reception of the transport information, the option apparatuses  133  and  134  send information on the time required until the own apparatus is allowed to transport sheet  1  and sheet  2  to the corresponding apparatus connected upstream in steps S 830  and S 916 , respectively. 
     The option apparatus  133  receives the sheet  1 ,  2  transport wait time data from the option apparatus  134  in step S 831  and sends this data together with the wait time of the option apparatus  133  to the image formation apparatus  100  in step S 832 . 
     The image formation apparatus  100  receives the sheet  1 ,  2  transport wait time of the option apparatus  133  in step S 717  and receives the wait time of the option apparatus  134  in step S 718 . 
     In step S 719 , it is determined whether sheet  1  can pass through the ejection port  125  or not. Based on the transport wait time for sheet  1  and sheet  2  received in step S 717 , it is determined that sheet  1  can pass through the ejection port  125  after the timer  200   c  in the image formation apparatus  100  counts the time corresponding to the transport wait time. 
     Here, the method of calculating the transport wait time will be explained. The time after a certain sheet (called a “preceding sheet”) is transported and carried into the option apparatus  133  or the option apparatus  134  until the option apparatus  133  or  134  can accept the next sheet (called the “following sheet”) (the time during which the transport or post-processing of the preceding sheet is not affected and the following sheet does not catch up the preceding sheet), that is, the transport wait time can be determined according to the transport distance up to the sheet ejection port in the option apparatus, length of the sheet transported, transport speed and post-processing operation time. 
     Therefore, it is possible to calculate the transport wait time by storing the transport wait time determined by a combination of these elements in a non-volatile storage medium such as ROM in the option apparatus beforehand or referencing or calculating this stored transport wait time in real time using these values. 
     This embodiment will be explained assuming that upon reception of the sheet transport information, the option apparatuses  133  and  134  will calculate the sheet transport wait time of their own sheets. When two option apparatuses  133  and  134  are connected to the image formation apparatus  100  as in the case of this embodiment, the ejection wait time at the image formation apparatus  100  can be calculated as follows. 
     That is, suppose the transport wait time calculated by the option apparatus  133  is T 1 [S], the transport wait time calculated by the option apparatus  134  is T 2 [S], then when the option apparatus  134  sends the own transport wait time T 2 [S] to the image formation apparatus  100  via the option apparatus  133 , the option apparatus  133  sends the transport wait time to the image formation apparatus  100  assuming that: 
     When T 1 ≧T 2 , the transport wait time of the image formation apparatus  100  is T 1   
     When T 1 &lt;T 2 , the transport wait time of the image formation apparatus  100  is T 2   
     Of course, it is also possible to configure the system unlike that shown in FIGS. 8A to  8 C, so that each option apparatus  133 ,  134  directly sends T 1 [S] or T 2 [S] to the image formation apparatus  100  individually and the image formation apparatus  100  makes the above decision (calculation). 
     Furthermore, when three or more option apparatuses are connected, it is possible to determine the transport wait time of the image formation apparatus  100  in the like manner based on the option apparatus with the longest transport wait time. 
     The time required for a communication between the apparatuses should be normally short enough compared to the transport wait time, so even if an upstream apparatus calculates the transport wait time step by step, the number of option apparatuses does not affect the time required to calculate this transport wait time. However, in the case where an option apparatus with extremely low calculation performance is mixed in, it is also possible to configure the system so that when the image formation apparatus  100  recognizes that option apparatus, the transport wait time is directly sent to the image formation apparatus  100 . 
     When the transport wait time has elapsed, the image formation apparatus  100  starts to eject sheet  1  in step S 720  and at the same time sends an advance notice of transport to the option apparatus  133 . 
     In step S 833 , when the option apparatus  133  receives the advance notice of transport that the image formation apparatus  100  sent in step S 720 , the option apparatus  133  starts to transport sheet  1 . In step S 834 , a sensor, which is not shown in the figure, detects whether sheet  1  has reached a predetermined position near the ejection port or not by detecting the position of the end of the sheet, and when the sensor detects that sheet  1  has reached the predetermined position, the option apparatus  133  starts to eject sheet  1  (step S 835 ). Furthermore, simultaneously with the start of ejection of sheet  1 , the option apparatus  133  sends an advance notice of ejection to the option apparatus  134 . 
     Upon reception of the advance notice of ejection that the option apparatus  133  sends in step S 835 , the option apparatus  134  starts to transport sheet  1  in step S 917 . 
     When the ejection of sheet  1  is completed, the option apparatus  133  sends this information to the image formation apparatus  100  in step S 836  and the image formation apparatus  100  receives this notice in step S 721  and recognizes that sheet  1  has been ejected from the option apparatus  133 . Then, in step S 722 , the image formation apparatus  100  determines whether following sheet  2  can pass through the ejection port  125  or not. Based on the transport wait time of sheet  2  received in step S 718 , after the timer  200   c  in the image formation apparatus  100  counts, it is determined that following sheet  2  can pass through the ejection port  125 . Once it is determined that following sheet  2  can pass through the ejection port  125 , the image formation apparatus  100  starts to eject sheet  2  in step S 723  and at the same time sends an advance notice of transport to the option apparatus  133 . 
     In step S 837 , upon reception of the advance notice of transport that the image formation apparatus  100  sent in step S 723 , the option apparatus  133  starts to transport sheet  2 . Then, in step S 838 , a sensor, which is not shown in the figure, detects whether sheet  2  has reached a predetermined position near the ejection port and when the sensor detects that sheet  2  has reached the predetermined position, the option apparatus  133  starts to eject sheet  2  (step S 839 ). Furthermore, simultaneously with the start of ejection of sheet  2 , the option apparatus  133  sends an advance notice of ejection to the option apparatus  134 . 
     On the other hand in step S 918 , upon reception of the advance notice of ejection that the option apparatus  133  sent in step S 839 , the option apparatus  134  starts to transport sheet  2 . Furthermore, in step S 919 , when sheet  1  is ejected from the option apparatus  134 , the option apparatus  134  notifies this to the option apparatus  133 , the upstream apparatus. 
     The option apparatus  133  receives the notice of the ejection of sheet  1  at the option apparatus  134  in step S 840  and notifies the image formation apparatus  100  of the ejection of sheet  1  from the option apparatus  134  in step S 841 . The image formation apparatus  100  recognizes in step S 724  that sheet  1  has been ejected from the option apparatus  134 . 
     Then, in step S 842 , the option apparatus  133  notifies the image formation apparatus  100  that sheet  2  has been ejected from the option apparatus  133  and the image formation apparatus  100  recognizes this in step S 725 . 
     When sheet  2  has been ejected last, the option apparatus  134  notifies this to the option apparatus  133  in step S 920 . This notification is received by the option apparatus  133  in step S 843  and then transmitted to the image formation apparatus  100  in step S 844 . Then, the image formation apparatus  100  recognizes in step S 726  that the ejection of sheet  2  from the option apparatus  134  has been completed. 
     As described in this embodiment, it is possible to reduce the processing load by the image formation apparatus receiving the information of the time required until it is possible to sequentially eject sheets from a plurality of option apparatuses connected downstream and by the option apparatuses connected downstream from the image formation apparatus performing sheet transport control and monitoring processing. 
     Similarly, it is possible to reduce the processing load also in the configuration in which in addition to the paper ejection apparatuses  133 ,  134 , a plurality of paper ejection option apparatuses are connected downstream. 
     Third Embodiment 
     Next, the sheet transport operations of the image formation apparatus and option apparatuses according to a third embodiment of the present invention will be explained. In this embodiment, with regard to the processing in step S 104  and step S 106  explained using the flow charts in FIG. 3A to  3 C, the image formation apparatus  100  acquires the apparatus information from the option apparatuses  101  and  102  as to whether it is possible to perform sheet transport control and monitoring processing of other option apparatuses connected upstream as communication data, and in step S 105  and step S 107 , the image formation apparatus  100  determines the processing capacities of the option apparatuses  101  and  102  and directly performs sheet transport control and monitoring processing of the option apparatus  102  upstream from the option apparatus  101  without the intermediary of the option apparatus  101 , which cannot control or monitor the option apparatus  102 . 
     Furthermore, with regard to the option apparatuses  133  and  134  connected downstream from the image formation apparatus  100 , though not shown in the figure, the image formation apparatus  100  also directly perform sheet transport control and monitoring processing. 
     The processing in that case will be explained using the flow charts shown in FIGS. 10A to  10 C. FIGS. 10A to  10 C are modifications of the sheet transport (feeding) processing explained using the flow charts shown in FIGS. 4A to  4 D in the first embodiment and shows the processing after the image formation apparatus  100  determines that the option apparatus  101  cannot perform sheet transport control and monitoring processing of the upstream option apparatus  102 . In FIGS. 10A to  10 C, the same processes as those in FIGS. 4A to  4 D will be assigned the same step numbers and detailed explanations thereof will be omitted. 
     In step S 409 , the image formation apparatus  100  performs processing equivalent to step S 505  in FIG.  4 B and directly controls the sheet transport state of the option apparatus  102 . Likewise, in step S 411 , the image formation apparatus  100  performs the processing in step S 509  in FIG.  4 B and instructs the option apparatus  102  to restart to transport sheet  2  while monitoring sheet  1 . 
     Furthermore, in step S 413 , the image formation apparatus  100  performs processing equivalent to that in step S 512  in FIG. 4B, that is, the image formation apparatus  100  recognizes that sheet  2  has been ejected from the option apparatus  102  and recognizes that the option apparatus  101  will continue to transport sheet  2 . 
     Hereafter, the image formation apparatus  100  performs transport control and monitoring processing of sheet  2  in the option apparatus  101 . 
     This embodiment only describes the processing of the sheet supply option apparatuses, but with regard to the sheet ejection option apparatuses connected downstream from the image formation apparatus  100 , the image formation apparatus  100  can also perform similar processing by directly controlling without the intermediary of an option apparatus with low processing performance. 
     As described above, according to this embodiment, the image formation apparatus acquires the processing performance of each option apparatus connected by the communication means after power is turned on and when it is determined that an option apparatus connected upstream or downstream cannot perform control or monitoring of other option apparatuses, the image formation apparatus can directly control the option apparatus connected one step upstream (or downstream) from the option apparatus. 
     Other Embodiment 
     The first to third embodiments above describe the cases where two option apparatuses are installed upstream from the image formation apparatus  100 , two option apparatuses are installed downstream and two sheets are transported, but the configuration is not limited to this and the number of option apparatuses connected, the number of sheets transported and timings of image formation processing or ejection completion processing, etc. can all be set arbitrarily. 
     Moreover, the method of communications between the image formation apparatus and the option apparatuses is not limited to a particular method, but any protocol can be used. 
     Furthermore, the above embodiments only describe option apparatuses involved in sheet transport, but the effects of the present invention can be implemented with any option apparatuses serially connected from the image formation apparatus even if they are not sheet transport option apparatuses. 
     Furthermore, FIGS. 3A to  3 C illustrate the case where a timer is started when power is turned on and power to the downstream option apparatuses is turned on when the timer times out, but it is also possible to configure the system so that power to the downstream option apparatuses is turned on upon completion of predetermined processing such as initialization processing carried out after powering-on is completed, for example. 
     The present invention can also be applied to a system configured by a plurality of devices (for example, host computer, interface device, reader, printer, etc.) or to a standalone apparatus (for example, copier, facsimile apparatus, etc.). 
     Furthermore, it goes without saying that the object of the present invention can be attained by supplying a storage medium (or recording medium) that records program codes of software implementing the functions of the aforementioned embodiments to a system or apparatus and allowing a computer (or CPU or MPU) of the system or apparatus to read and execute the program codes stored in the storage medium. In this case, the program codes read from the storage medium themselves implement the functions of the aforementioned embodiments and the storage medium that stores the program codes make up the present invention. Furthermore, it goes without saying that the present invention includes not only the case where the functions of the aforementioned embodiments are implemented by executing the program codes read by the computer but also the case where the operating system (OS), etc. operating on the computer performs part or the whole of actual processing and the functions of the aforementioned embodiments are implemented through this processing. 
     Furthermore, it goes without saying that the present invention also includes the case where after the program codes read from the storage medium are written in memory provided on a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function expansion card or the CPU, etc. provided on the function expansion unit performs part or the whole of actual processing and the functions of the aforementioned embodiments are implemented through this processing. 
     When the present invention is applied to the above storage medium, the program codes corresponding to the flow charts explained above (shown in at least one of FIG. 3A to FIG. 10) are stored in the storage medium. 
     As explained above, according to the image formation apparatus and option apparatuses of the present invention, it is possible to distribute control of the entire apparatus by allowing each apparatus to perform monitoring or control of the operation of an option apparatus immediately upstream and/or immediately downstream, thus reducing the processing load of the image processing apparatus or option controller, preventing the processing load of the image processing apparatus from drastically increasing even if the number of option apparatuses connected changes, and thereby having the effect of making it possible to configure the image processing apparatus without using expensive circuit parts with high-speed processing capability. 
     The present invention has been described above based on the preferred embodiments. However, these embodiments are intended to contribute to a better understanding of the present invention and it goes without saying that the present invention is not limited to the scope disclosed in the above described embodiments. The present invention is intended to include any variations made possible by those skilled in the art without departing from the spirit of the present invention specified in the following claims.