Patent Publication Number: US-6339477-B2

Title: Data communication system for high-speed data transmission and reception operations and method for doing the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority from Japanese Patent Application No. Hei-8-276718 filed on Oct. 18, 1996, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a data communication system that has a first information processing unit such as a computer and the like, and a second information processing unit such as a facsimile device with a printing function and the like. The present invention also relates to a data communication control method for such a data communication system. In particular, the present invention relates to the data communication system and the data communication control method wherein the second information processing unit transmits facsimile data and the like in response to transmission requests from the first information processing unit. 
     2. Description of Related Art 
     Multifunction peripheral devices, which have a plurality of functions and which act as peripheral equipment for computers, are now being developed. An example of such a multifunction peripheral device is a facsimile device that has a printing function. The facsimile device that has the printing function is configured to print data received from external devices such as a computer, a word processor and the like using its printer unit that usually prints facsimile data. 
     After receiving the facsimile data received from other facsimile devices and the like via a communication line, the facsimile device with the printing function prints facsimile data. In addition, the facsimile device with the printing function receives data transmitted by the computer and prints such data received from the computer. 
     Another type of multifunction peripheral device is the multifunction peripheral device that has expanded the functions of the facsimile device with the printing function. This type of multifunction peripheral device can send data received from a facsimile device or data read through a scanner to a computer and send facsimiles based on data transmitted by the computer. In this way, the computer can centrally control facsimile data receipt and transmission operations. The multifunction peripheral device is very useful in that it can transmit data read by a scanner to the computer, which can then edit the data, and subsequently receive edited data from the computer for facsimile transmission. In this way, with the multifunction peripheral device, facsimile data can be checked without the need for printing by displaying the data on the display of the computer and previously received facsimile data can be stored for subsequent usage. 
     The computer has main control over its communication operations with the multifunction peripheral device, which may be the facsimile device with the printing function. The computer transmits transmission requests to the multifunction peripheral device at predetermined time intervals. The computer subsequently receives data transmitted by the facsimile device in response to the transmission requests. 
     In addition, the computer checks for the existence of data to be transmitted to the multifunction peripheral device at predetermined intervals. When there is data that needs to be transmitted, the computer transmits the data to the multifunction peripheral device. 
     Meanwhile, for conventional data communication systems, the time interval at which the computer transmits the transmission requests is fixed regardless of the existence of data transmitted from the multifunction peripheral device. This does not pose a problem when the data to be transmitted from the multifunction peripheral device is, for example, status information data of the multifunction peripheral device which is small in size and whose content does not change very often. On the other hand, when a large amount of data such as facsimile data has been received by the multifunction peripheral device and needs to be transmitted to the computer, it takes a long time until the computer receives all the data and thus, high-speed operations cannot be performed. 
     The above problem is also holds true when transmitting data from the computer. That is, the interval for verifying the presence of data to be transmitted to the multifunction peripheral device is fixed regardless of the existence of the data to be transmitted. Therefore, the above setup hampers the high-speed transmission of data to the multifunction peripheral device. 
     Meanwhile, in parallel with performing data transmission and reception operations with the multifunction peripheral device, the computer also executes other operations and thus, transmission requests are transmitted at comparatively long intervals when there is no data to be received from the multifunction peripheral device. In the same way, when there is no data to be transmitted, the verification of the presence of data to be transmitted is preferably performed at comparatively long intervals. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing problems in the prior art, it is a primary object of the present invention to provide a data communication system and a data communication control method for executing high-speed data reception operations. It is another object of the present invention to provide the data communication system and the data communication method for executing high-speed data transmission operations. 
     To achieve the aforementioned objects, one aspect of the present invention provides a data communication system that has a first information processing unit and a second information processing unit. The first information processing unit provides a transmission request to the second information processing unit. The second information processing unit receives the transmission request from the first information processing unit and sends response data to the first information processing unit in response to the transmission request. The first information processing unit provides a subsequent transmission request to the second information processing unit at a first time interval unless the second information processing unit sends the response data, and provides the subsequent transmission request to the second information processing unit at a second time interval shorter than the first time interval when the second information processing unit sends the response data. 
     In this way, the time needed for receiving data from the second information processing unit can be shortened when data is previously received. In this way, data reception operations can be performed at high-speed. 
     Preferably, the first information processing unit is further for determining if there is transmission data for the second information processing unit. The first information processing unit determines if there is transmission data at a third time interval when there is no transmission data during a previous determination operation and determines if there is transmission data at a fourth time interval shorter than the third time interval when there is transmission data during a previous determination operation. 
     In this way, the data transmission operations within the data communication system can be performed at high-speed. 
     Another aspect of the present invention provides a data communication method for facilitating communication between the first information processing unit and the second information processing unit. This method involves sending a transmission request from the first information processing unit to the second information processing unit, determining if the second information processing unit sends response data in response to the transmission request from the first information processing unit, sending a subsequent transmission request from the first information processing unit to the second information processing unit at a first time interval unless the second information processing unit sends the response data, and sending the subsequent transmission request from the first information processing unit to the second information processing unit at a second time interval shorter than the first time interval when the second information processing unit sends the response data. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments thereof when taken together with the accompanying drawings in which: 
     FIG. 1 is a perspective view illustrating a computer and a multifunction peripheral device of a data communication system according to a preferred embodiment of the present invention; 
     FIG. 2 is a schematic cross-sectional view of the multifunction peripheral device according to the preferred embodiment of the present invention; 
     FIG. 3 is a block diagram illustrating the construction of hardware of the data communication system according to the preferred embodiment of the present invention; 
     FIG. 4 is a block diagram illustrating the construction of software of the data communication system according to the preferred embodiment of the present invention; 
     FIG. 5 is a flowchart of a main process executed by a resource manager program of the computer according to the preferred embodiment of the present invention; 
     FIGS. 6A and 6B are flowcharts of data reception and transmission processes executed by the resource manager program according to the preferred embodiment of the present invention; 
     FIGS. 7A and 7B are timing charts illustrating data reception operations executed of the resource manager program according to the preferred embodiment of the present invention; and 
     FIGS. 8A,  8 B,  9 A and  9 B are timing charts illustrating data reception and data transmission operations of the resource manager program according to the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PRESENTLY PREFERRED EXEMPLARY EMBODIMENT 
     A preferred embodiment of the present invention is described hereinafter with reference to FIGS. 1 through 9B. As shown in FIG. 1, a data communication system of the present invention includes a computer  50  (also referred to as a first information processing unit), which may be a personal computer (PC) or the like, and a multifunction peripheral device  1  (also referred to as a second information processing unit). The multifunction peripheral device  1  has a scanner unit, a printer unit and a facsimile unit. As shown in FIGS. 1 to  3 , the multifunction peripheral device  1  and the computer  50  are connected to each other via a parallel interface (I/F)  3 , a cable  4  and a parallel I/F  55  so that they can communicate with each other. 
     The multifunction peripheral device  1  mainly includes a facsimile unit that performs facsimile operations, a printer unit  18  that prints data transmitted by the facsimile unit or the computer  50 , and a scanner unit  16  that scans images and transmits the scanned image to the facsimile unit or the computer  50 . The computer  50  generates operation command signals for controlling each unit of the multifunction peripheral device  1 . The multifunction peripheral device  1  transmits facsimile data or scanned data to the computer  50 . Moreover, the computer  50  transmits facsimile data to another facsimile device via the facsimile unit of the multifunction peripheral device  1 . 
     The construction of each unit of the multifunction peripheral device  1  and the construction of the computer  50  are explained in detail hereinafter. 
     As shown in FIG. 3, the multifunction peripheral device  1  has an NCU (network controller unit)  5 , a CPU  10 , a modem  11 , a buffer memory unit  12 , a ROM unit  13 , an EEPROM unit  14 , a RAM unit  15 , a scanner unit  16 , an encoder  17 , a printer unit  18 , an image memory unit  19  and a decoder  20 . 
     The NCU  5 , which is a part of the facsimile unit, executes communication line control operations. The multifunction peripheral device  1  is connected to a telephone line via the NCU  5 . The CPU  10  is connected via a bus line to the other various units of the multifunction peripheral device  1  and controls such various units to perform facsimile operations, that is, data communication operations following a predetermined communication control procedure. 
     The modem  11 , which is a part of the facsimile unit, converts digital image signals into analog signals and transmits the analog signals to the outside via the telephone line and the NCU  5 . The modem  11  also converts the analog image data signals transmitted from the outside via the telephone line and the NCU  5  into digital signals, and performs transmission and reception of various communication control signals. 
     The buffer memory unit  12  includes a plurality of regions such as a transmission buffer region  12   a  and a reception buffer region which are for temporarily storing encoded image data that are transmitted to and received from the outside via the telephone line. 
     The ROM unit  13  stores a control program for controlling the printer unit  18 , the scanner unit  16  and the facsimile unit. The EEPROM unit  14  stores various data such as preset dial numbers, name of parties to be called and one-touch dial numbers. The contents of the EEPROM unit  14  remain intact even if the multifunction peripheral device  1  is deactuated. The RAM unit  15  temporarily stores data for various operations. 
     As shown in FIG. 2, the scanner unit  16  is an apparatus for reading images from a set of documents  32 . The construction and operation of the scanner unit  16  is explained hereinafter. The documents  32  are placed on a document table  31  disposed at an upper side of the body la of the multifunction peripheral device  1 . A separator  33  and a first carrier roller  34  separate each sheet of the document  32  and transport each sheet towards a pair of second carrier rollers  35 . When one sheet of document  32  (which is set facing downwards in the present embodiment) is being transported from the pair of the second carrier rollers  35  towards a paper release roller  36 , a light source  38  of a reading member  37  disposed between the rollers  35  and  36  irradiates the sheet of document  32 . The resulting reflection light from the sheet of document  32  enters a reading head  39  (which may be a line image sensor and the like) via lenses and reflectors. In this way, the reading head  39  generates the image data of every sheet of document  32 . 
     The encoder  17  shown in FIG. 3 encodes the image data read by the scanner unit  16 . The facsimile unit externally transmits the encoded image data in sequence via the transmission region  12   a  of the buffer memory unit  12 . The facsimile unit may also transmit the encoded image data immediately or at a designated time after the image data is temporarily stored in the image memory unit  19 . This transmission function of the facsimile unit using the image memory unit  19  is very convenient in case the facsimile device that will receive the image data is busy or data is to be transmitted to a plurality of devices. 
     The facsimile unit transmits not only the image data read by the scanner unit  16  but also the data transmitted by and received from the computer  50 . Image data read by the scanner unit  16  and processed by the computer  50 , and text file generated by the computer  50  and converted to facsimile data are examples of data that are transmitted to the outside by the facsimile unit. 
     During normal data reception operations in which the facsimile unit stores data in real time, the facsimile unit receives image data transmitted from another facsimile device via the telephone line after executing a predetermined communication control operation with such facsimile device. The facsimile unit subsequently stores the received image data in the reception buffer region  12   b  of the buffer memory unit  12 . Thereafter, the decoder  20  decodes (that is, expands) the image data, converts the image data into a dot image for printing page by page and stores the dot image in a bit image storage region of the image memory  19 . The image data are expanded according to a predetermined resolution, and the resulting image data are transmitted to the printer unit  18  for printing page by page. 
     As shown in FIG. 1, an operation unit  21  of the facsimile unit has a display  43  (which may be a liquid crystal display or the like for displaying the operating condition of the facsimile unit and characters used for storing the names of the parties to be called), numeric keys  44 , function keys  45 , one-touch memory keys  46 , abbreviation keys  47  and the like. 
     Here, the facsimile unit sends the received facsimile data to the computer  50  which may store the data as files. Furthermore, in the data communication system according to the present embodiment, the image data read by the scanner unit  16  could be transmitted by the facsimile unit to the computer  50  which may store the scanned data in a file. In turn, the computer  50  can process the stored image data and send the processed image data to the multifunction peripheral device  1  for printing or facsimile transmission image to other facsimile devices. 
     Next, the printer unit  18  which acts as an image generator is explained hereinafter. The printer unit  18  records data (e.g., image stored in the image memory  19 , data received by the facsimile unit, data transmitted by the computer  50  and stored in the image memory unit  19 , etc.) as hard copy on recording paper. 
     In other words, the image data received from the computer  50  is temporarily stored in the image memory unit  19 . The image data may then be printed by the printer unit  18  with the CPU  10  controlling these data input/output and storage processes. 
     Details of the construction of the printer unit  18  are explained hereinafter with reference to FIG. 2. A paper supply cassette  22  is provided at a rear portion of the body la of the multifunction peripheral device  1 . Recording paper  23  in the paper supply cassette  22  is supplied toward a photoreceptor drum  25 . Next, a light scanning unit  26  projects laser light scanning rays on the photoreceptor drum  25  to generate a latent image on the same drum  25 . The latent image is developed by using toner provided by a toner cartridge  27  and a developing unit  28  and is then copied on the recording paper  23 . The recording paper  23  subsequently passes through a fixing unit  29 , which includes a heating roller and pressure roller and which fixes the image. The recording paper  23  then goes to a delivery tray  30 . In this way, the printer unit  18  of the present embodiment is an electrostatic electronic image recording type printer. It must be noted that a thermal-type printer and the like that prints images on heat sensitive paper may also be used as the printer unit  18 . 
     Meanwhile, as shown in FIG. 3, the computer  50 , which is the first information processing unit, includes a CPU  51 , a ROM unit  52 , a RAM unit  53 , an input/output I/F  54  and a two-way parallel I/F  55 . The CPU  51  includes a microprocessor and the like. The ROM unit  52  is for storing control programs and the like. The RAM unit  53  is for storing various data including image data read by the scanner unit  16  of the multifunction peripheral device  1 . The input/output I/F  54  has input/output ports while the two-way parallel I/F  55  also has input/output ports for communicating with the multifunction peripheral device  1 . 
     The computer  50  further includes a hard disk drive (HDD)  56 , a floppy disk drive (FDD)  57 , a display (which may be a CRT)  58 , a keyboard  59  and a mouse  60 , all of which are connected to the input/output I/F  54 . The hard disk drive  56 , the floppy disk drive  57  and the display  58  are connected to the input/output I/F  54  via a hard disk drive controller (HDC)  61 , a floppy disk drive controller (FDC)  62  and a display controller (DISPC) 63 , respectively. 
     The parallel I/F  3  and the parallel I/F  55  are two-way communication I/F that facilitate communication between the computer  50  and the multifunction peripheral device  1 . Through the parallel I/F  3  and the parallel I/F  55 , the computer  50  controls the scanner unit  16  to read data, the printer unit  18  to generate the image and the facsimile unit to receive and transmit data via the NCU  5  and the like. 
     With the hardware construction of the data communication system of the present invention explained in the above, the software of the data communication system will be explained hereinafter with reference to FIG.  4 . In the present embodiment, as shown in FIG.  4 , the operating system  70  of the computer  50  is the WINDOWS operating system. A FAX application program  71  for implementing the scanning, printing and facsimile functions of the multifunction peripheral device  1  and general application programs  72  such as word processing software run on the OS  70 . These application programs and other programs such as drivers and the like are installed (stored) in the HDD  56  and the like beforehand with the CPU  51  executing these programs to implement the various operations. 
     The FAX application program  71  is an application program of the multifunction peripheral device  1  that enables the computer  50  to operate the multifunction peripheral device  1  as a facsimile device. 
     When the FAX application program  71  is in operation, buttons such as a log button  81 , a scan fax button  82  and the like for implementing the various operations of the multifunction peripheral device  1  are displayed on the display  58 . These operations are executed by clicking the respective buttons displayed on the display  58 . For example, when the log button  81  is clicked, a log manager program is actuated. The log manager program manages transmission and reception record of the facsimile data and displays such transmission and reception record on the display  58 . When the transmission and reception record is displayed on the display  58 , a user can designate a specified transmission file and the like and click a “send” command icon displayed on the display  58  to transmit such file again. 
     When the “send” command is selected, the log manager program provides the name of the selected transmission file and a facsimile transmission command to a facsimile driver program  75 . After receiving the facsimile transmission command, the facsimile driver program  75  transmits the data for facsimile transmission to the multifunction peripheral device  1  via a resource manager program  77 . The facsimile driver program  75  transmits the data for facsimile transmission together with other various control signals (that is, control signals for implementing the facsimile transmission) that include a start signal for the facsimile transmission operation. 
     When the log manager program is in operation and a “print” command is selected, the transmission and reception record is printed by the multifunction peripheral device  1 . In this case, the log manager program provides the name of the file to be printed and the print command to a printer driver program  76 . The printer driver program  76  transmits various control signals (that is, control signals necessary for print operations) including print data and a print start signal to the multifunction peripheral device  1  via the resource manager program  77 . 
     Furthermore, the log manager program may be actuated automatically when, for example, the facsimile driver program  75  indicates the storage of newly-received data with the log manager program displaying the data reception record and the like on the display  58 . 
     When the scan fax button  82  is clicked, the facsimile driver program  75  sends a document scan command to the scanner unit  16  of the multifunction peripheral device  1  via the resource manager program  77 . Accordingly, the document  32  provided on the document table  31  of the multifunction peripheral device  1  is carried by the carrier rollers  34  and  35  and is scanned by the reading head  39 . The multifunction peripheral device  1  then sends the scanned data to the facsimile driver program  75  via the resource manager program  77 . Thereafter, the facsimile driver program  75  provides the transmission record information to the log manager program and then sends the scanned data to the facsimile unit  95  of the multifunction peripheral device  1  via the resource manager program  77 . In this way, the facsimile unit  95  of the multifunction peripheral device  1  performs the facsimile transmission of the scanned data. 
     The FAX application program  71  also facilitates the facsimile transmission of revised image data that is displayed on the display  58  of the computer  50  and scanned through the scanner unit  16  and the facsimile transmission of files stored in the HDD  56  and the like of the computer  50 . A view editor program  83  for implementing the above-described functions is provided in the FAX application program  71 . Aside from the FAX application program  71 , the view editor program  83  can also be activated by other application programs. Furthermore, the view editor program  83  activates when a file (that is, a file that stores data received via the facsimile unit  95  or data read by the scanner unit  16 ) having specified file extension is opened. 
     In this way, the view editor program  83  is for storing data received by the facsimile unit  95  or data scanned by the scanner unit  16  in the computer  50  and for displaying such data on the display  58 . After displaying the data, the view editor program  83  can be used to edit the image data by deleting parts of the image data, adding text, and the like. 
     Aside from opening a file that has the predetermined file extension, the view editor program  83  may also be activated by placing a document  32  on the document table  31  of the multifunction peripheral device  1 . Furthermore, the view editor program  83  can also be activated by clicking a view editor program icon displayed on the display  58 . At any rate, when the view editor program  83  is activated, a menu is displayed on the display  58  from which a user can select a command from among those displayed. For example, the menu includes a FAX button and when this FAX button is clicked, a scan setting window is displayed. The scan setting window enables the setting of scanning condition such as resolution, scanning size and the like. 
     Therefore, after setting the suitable scanning conditions on the scan setting window, the user may click a start button in the scan setting window to make the view editor program  83  send scanning condition information and a transmission request for the scan start command to the facsimile driver program  75 . Then, the facsimile driver program  75  transmits the scanning condition and the scan start command to the multifunction peripheral device  1  via the resource manager program  77 . 
     After the multifunction peripheral device  1  receives the scanning conditions and the scan start command, its scanner unit  16  performs the scanning operation based on designated scanning conditions and the multifunction peripheral device  1  sends the scanned data to the facsimile driver program  75  via the resource manager program  77 . Thereafter, the facsimile driver program  75  stores the data in the RAM  53 . Thereafter, the facsimile driver program  75  informs the view editor program  83  of the receipt of the read data (scanned data) and hands over control of the data to the view editor program  83  before terminating its own operations. In response, the view editor program  83  displays the scan data stored in the RAM  53  on the display  58  and superimposes a display of the setting conditions of the facsimile transmission on such display of the scan data. In this way, the user may designate where to send the facsimile transmission on the setting screen. When the user clicks the start button, the view editor program  83  provides the scan data as facsimile transmission data and the transmission request for starting facsimile transmission to the facsimile driver program  75 . After providing the transmission status information to the log manager program, the facsimile driver program  75  sends the aforementioned scan data to the facsimile unit  95  of the multifunction peripheral device  1  via the resource manager program  77 . Thereafter, the facsimile unit  95  of the multifunction peripheral device  1  executes the facsimile transmission of the scanned data. 
     While the facsimile driver program  75  sends signals for scanning a document and for requesting the transmission of scan data when the FAX button or the scan FAX button  82  is clicked, these functions may also be executed by other programs. For example, the scanner driver program  74  may also send signals for scanning a document and for requesting the transmission of the scanned data. 
     When the scan button is selected from the menu of the view editor program  83 , the scanner unit  16  of the multifunction peripheral device  1  performs the scanning operation based on the command from the scanner driver program  74 . The scanned data are displayed on the window screen of the view editor program  83  in the same way as in the case of the facsimile transmission. When the user selects, for example, the storage of data in the HDD  56 , the view editor program  83  retrieves the scan data stored in the RAM  53  and stored the scan data in the HDD  56  under a suitable filename. 
     The printer driver program  76  is activated when the print button is selected from among the menu of the view editor program  83 . The printer driver program  76  controls the printer unit  18  of the multifunction peripheral device  1  to print the image data on recording paper. 
     Meanwhile, when a general application program  72  such as word processing software and the like is activated, selection of a command such as print and the like in such application program  72  results in the activation of the printer driver program  76  with the display of a screen for setting resolution, paper size, contrast and the like and for executing the start command of the printing operation. That is, by selecting a print command in the application program  72 , the printing operation is performed via the printer driver program  76 . 
     In general, the method of access of the computer  50  with respect to the scanner unit  16 , the printer unit  18  or the facsimile unit  95  varies depending on the hardware construction of the scanner unit  16 , the printer unit  18 , the facsimile unit  95  or the computer  50  itself. In this way, it will be troublesome to adjust access methods of the application programs  71  and  72  to suit various hardware. Accordingly, the respective driver programs  74 ,  75  and  76  are disposed between the application programs  71  and  72  and the multifunction peripheral device  1  and the access methods from the application programs  71  and  72  are standardized. At the same time, the driver programs  74 ,  75  and  76  are set to deal with changes in hardware, operating systems and the like. 
     Similarly, a display driver program  78  for controlling the display  58 , a keyboard driver program  79  for controlling the keyboard  59  and a mouse driver program  80  for controlling the mouse  60  work on the OS  70 . 
     In the present embodiment, the resource manager program  77  is provided for supervising two-way data communication between the above-described driving programs  74 ,  75  and  76  and the multifunction peripheral device  1 . The resource manager program  77  activates when the OS  70  is activated. If the resource manager program  77  is inactive (that is, closed) at the time the driver programs  74 - 76  is activated, the driver programs  74 - 76  automatically activate the resource manager program  77 . After the activation of the resource manager program  77 , an icon  84  indicating the resource manager program  77  is displayed on the display  58 . When the operation of the resource manager program  77  needs to be stopped temporarily, a user may click the icon  84  to terminate the operation of the resource manager. 
     Meanwhile, both the scanner driver program  74  and the printer driver program  76  may be activated even if the FAX application program  71  is inactive. For example, the respective driver programs are activated when “print” and “scan” commands are generated from the view editor program  83  or an application  72  such as a word processing application or the like. In case the resource manager program  77  is inactive, the respective driver programs activate the resource manager program  77  and secure transmission and reception buffers for facilitating data communication with the multifunction peripheral device  1 . The FAX application program  71  and the facsimile driver program  75  are usually active and thus, the resource manager program  77  is also usually active. That is, the resource manager program  77  needs to remain ready to receive data at any time because it is impossible to know when the multifunction peripheral device  1  will transmit the facsimile data received from other facsimile devices and the like to the computer  50 . 
     The scanner driver program  74 , the facsimile driver program  75  and the printer driver program  76  may access the resource manager program  77 . The resource manager program  77  receives control data or the like from the respective driver programs  74 - 76  and sends such data in data packets to the multifunction peripheral device  1  to identify the driver program from which the data is coming from. In addition, the resource manager program  77  also delivers the data packet transmitted from the multifunction peripheral device  1  to the respective driver. In this way, control operations based on the transmitted and received data are performed by the respective driver programs and the multifunction peripheral device. 
     Through its execution of the resource manager program  77 , the CPU  51  of the computer  50  acts as a reception and transmission controller for principally controlling communication operations between the computer  50  and the multifunction peripheral device  1 . Accordingly, the CPU  51  transmits transmission requests from the computer  50  to the multifunction peripheral device  1  at a predetermined interval. In addition, the CPU  51  receives data sent by the CPU  10 , which acts as the transmission controller of the multifunction peripheral device  1 , to the computer  50  in response to the transmission requests. 
     Regarding the transmission of data from the computer  50 , each driver program generates the transmission data and sends the transmission request to the resource manager program  77 . When there is data that needs to be transmitted, the resource manager program  77  transmits such data to the multifunction peripheral device  1 . 
     If the interval for transmitting the transmission requests is set to be constant regardless of the existence of data to be received from the multifunction peripheral device  1 , the computer  50  will not be able to perform high-speed operations when there is a large amount of data such as facsimile data to be received. 
     Moreover, regarding the transmission of data from the computer  50 , if the interval for verifying the existence of data to be transmitted is set to be constant regardless of the existence of such transmission data, the computer  50  will not be able to perform high-speed operations when transmitting print data to the multifunction peripheral device  1 . 
     Because the computer  50  executes processes other than the aforementioned data transmission and reception processes, the interval for transmitting the transmission requests is preferably long enough when there is no data to be received from the multifunction peripheral device  1 . In the same way, when there is no data to be transmitted, the interval for verifying the existence of data to be transmitted is preferably set long enough to allocate time for executing the other processes. 
     Accordingly, the data communication system according to the present invention intends to solve the aforementioned problems by shortening the transmission interval of the transmission requests to receive data within a short period of time and by shortening the interval for verifying the existence of transmission data when there is data to be transmitted to transmit data within a short period of time. 
     Hereinafter, the transmission and the reception processes as performed by the resource manager program  77  are explained with reference to flowcharts shown in FIGS. 5,  6 A and  6 B and timing charts shown in FIGS. 7A to  9 B. 
     After the resource manager program  77  is activated, step S 1  activates a timer (which may be based on an internal clock of the computer  50 ) and sets the initial value of the timer to “A”. The timer counts down from its initially set value and is controlled by the OS  70  for switching tasks between the resource manager program  77  and other programs being executed. 
     That is, after the resource manager program  77  sets the timer to a predetermined value, the OS  70  temporarily stops the execution of the resource manager program  77  and executes other programs that are being run in parallel with the resource manager program  77 . Then, when the timer value becomes zero, the OS  70  again executes the resource manager program  77 . 
     To put it more concretely, the resource manager program  77  does not resume its operations until the timer value becomes zero; that is, the operations of the resource manager program  77  remain suspended while step S 2  is still giving a negative output. When the value of the timer becomes zero, that is, when step S 2  gives a positive output, step S 3  transmits the transmission request to the multifunction peripheral device  1  in order to determine whether or not there is reception data to be received from the multifunction peripheral device  1 . When step S 3  gives a negative output, that is, when step S 3  determines that there is no reception data from the multifunction peripheral device  1  in response to the transmission request, control goes to step S 4  which sets the timer value to “A” again. In order for the computer  50  to determine the existence of the reception data, the multifunction peripheral device  1  may transmit a message to the computer  50  that indicates that there is no data with the computer  50  being set to determine such message. It may also be that the computer  50  is arranged to wait for a response from the multifunction peripheral device  1  for a predetermined time period. In this arrangement, the computer  50  determines that there is no data from the multifunction peripheral device  1  when it does not receive any data within the predetermined time period. Here, in the present embodiment, the computer  50  determines the existence of reception data by checking port signals of the parallel I/F  55 . 
     Next, when step S 7  checks for the presence of transmission data from any of the driver programs  74 - 76  and determines that there is no such transmission data (that is, step S 7  gives a negative output), control goes back to step S 2  with the value of the timer set to “A”. The execution of this process will remain suspended until the timer value becomes zero. Therefore, when there is no reception data and no transmission data, the resource manager program  77  performs transmission of the transmission requests to the multifunction peripheral device  1  and the determination of the existence of transmission data from the driver programs  74 - 76  at every time interval “A”. It must be noted that the determination of the existence of transmission data from the driver programs  74 - 76  may be executed using messages. 
     Meanwhile, when there is reception data from the multifunction peripheral device  1 , that is, when step S 3  gives a positive output, control goes to step S 5  which executes a data reception process. As shown in the flowchart of FIG. 6A, in this data reception process, step S 10  receives data, step S 11  determines to which driver program the data is intended for based on identification information contained in the data received and step S 12  sends the data received to the corresponding driver. 
     After the completion of the data reception process, control goes to step S 6  that sets the value of the timer to “B”. It must be noted that the timer value “B” is smaller than the timer value “A”. That is, for example, the timer value “A” may indicate a time period of 0.5 to 1 second while the timer value “B” may indicate a time period of 0.1 to 0.2 seconds. Step S 7  determines if there is any data to be transmitted from any of the driver programs  74 - 76 . When there is no transmission data, that is, when step S 7  gives a negative output, control returns to step S 2  which suspends the execution of this process of the resource manager program  77  until the timer, whose timer value of “B” is set in step S 6 , becomes zero. 
     Therefore, when reception data exists and there is no transmission data, the time interval for transmitting the transmission requests to the multifunction peripheral device  1  is set to “B”. Because the timer value “B” is set to be smaller than the timer value of “A”, the interval for transmitting transmission request to the multifunction peripheral device  1  when there is data received from the same peripheral device  1  is shorter than the interval when there is no data received. 
     When there is transmission data from a driver program, that is, when step S 7  gives a positive output, control goes to step S 8  which executes a data transmission process. As shown in FIG. 6B, in this data transmission process, step S 13  receives the data from the corresponding driver program, step S 14  executes a packeting process for processing the data into packets by adding identification information to the data and the like, and step S 15  transmits the data packet to the multifunction peripheral device  1 . Print data, data for facsimile transmission or the like are examples of transmission data from the drivers  74 - 76 . 
     After the execution of the above-described transmission process, step S 9  sets the value of the timer to “B” and control then goes to step S 2  which suspends this process of the resource manager program  77  until the value of the timer becomes zero. That is, when no reception data exists and there is transmission data, the time interval for determining the existence of the transmission data is set to be shorter than the case when there is no transmission data. In this way, overall processing speed of the computer  50  becomes faster. 
     Next, concrete examples of the data communication control process of the data communication system according to the present embodiment of the present invention are explained with reference to the timing charts of FIGS. 7A through 9B. It must be noted here that the resource manager program&#39;s transmission of the data received from the multifunction peripheral device  1  to the respective drivers  74 - 76  has been omitted and is not shown in FIGS. 7A,  8 A and  9 A. FIG. 7A illustrates the timing in which the resource manager program  77  transmits the transmission request to the multifunction peripheral device  1  and determines if there is any data to be received (corresponding to step S 3 ) and the timing for sending transmission checks (corresponding to step S 7 ) in which the resource manager program  77  determines the existence of transmission data from the driver programs  74 - 76 . FIG. 7B illustrates the time intervals for performing the transmission request/data reception determination operation of the resource manager program  77  which is for determining the presence of data to be received from the multifunction peripheral device  1 . In this example, for purposes of simplicity, transmission data to be sent from the computer  50  (more concretely, driver programs  74 - 76 ) to the multifunction peripheral device  1  are not shown in FIGS. 7A and 7B, and the transmission check operations are not illustrated in FIG.  7 B. 
     When the timer value of the aforementioned timer becomes zero, the resource manager program  77  performs the transmission request/data reception determination and the transmission determination at timings {circle around (1)} through {circle around (3)}. Here, because there is no data received and there is no data to be transmitted, the time interval until the execution of the subsequent data reception determination operation and the subsequent transmission determination operation will be “A”. In FIG. 7B, the timing at which the reception/determination operation is executed (that is, the timing at which the timer value becomes zero) are indicated as black spots. As shown in FIG. 7B, the intervals between data reception determination operations {circle around (1)} through {circle around (3)} are longer than the intervals between data reception determination operations {circle around (4)} through {circle around (7)}. 
     Because of the reception of data from the multifunction peripheral device  1  in {circle around (4)} through {circle around (7)}, the timer is set to “B” and thus, the time interval up to a subsequent reception determination operation becomes the sum of the time period necessary for performing the data reception process and the time period indicated by timer value “B”. In this way, the time interval between subsequent data reception determination operations when there is data received from the multifunction peripheral device  1  becomes shorter than the time interval when there is no data received from the multifunction peripheral device. The slanted lines in FIG. 7B indicate the time period in which the resource manager program  77  performs the data reception operation. 
     Meanwhile, the interval between the timing {circle around (7)} and the timing {circle around (8)} is short because of the reception of data during the data reception determination operation at the timing {circle around (7)}. On the other hand, no reception data is received in the data reception determination operation at the timing {circle around (8)}, and thus, the interval between the timing {circle around (8)} to a subsequent timing {circle around (9)} is longer than the time interval between the timing {circle around (7)} and the timing {circle around (8)}. 
     Next, FIGS. 8A and 8B illustrate a case in which there is reception data from the multifunction peripheral device  1  and there is transmission data from the driver. 
     Because the resource manager program  77  receives data from the multifunction peripheral device  1  at the timing {circle around (1)}, the timer value is set to “B”. Thereafter, because there is transmission data from the driver program at the timing {circle around (2)}, the resource manager program  77  receives transmission data from the driver program and the timer value is again set to “B”. In this way, the time interval between the completion of the transmission process of the timing {circle around (2)} and the timing {circle around (3)} will be “B” which is shorter than the time interval “A”. It must be noted that the time interval “B” is shown to be larger in FIG. 8B than in FIG. 7B to clearly indicate the time interval “B”. 
     At the timing {circle around (3)} and the timing {circle around (4)}, because both the reception data from the multifunction peripheral device  1  and the transmission data from the computer  50  (that is, the driver) exist, the time interval from the completion of the data transmission process of the timing {circle around (4)} to the data determination process of the timing {circle around (5)} is time interval “B”. 
     In the data reception determination process at the timing {circle around (5)}, because there is no reception data from the multifunction peripheral device  1 , the resource manager  77  temporarily sets the timer value to “A”. However, because there is transmission data from the computer  50  at the timing {circle around (6)}, the timer value is set to “B” and thus, the interval from the completion of the transmission process of the timing {circle around (6)} to the data reception determination operation of the timing {circle around (7)} is set to “B”f. 
     In this way, when there is data to be transmitted, the time interval up to the next determination process is shortened, and thus, the computer  50  can perform transmission operations faster. 
     FIG. 9 illustrates another example in which there is reception data from the multifunction peripheral device  1  and there is transmission data from the driver program. In the same way as in the previous examples, the data transmission process and data reception process can both be executed at shortened time intervals. 
     As explained above, when there is no reception data and no transmission data, the transmission of the transmission requests and the reception determination are set to a reasonably long time interval “A”. Also, the execution of the process of the resource manager program  77  is suspended until the timer value becomes zero and thus, with the process of the resource manager program  77  being suspended during such time interval, the other processes of the computer  50  can avail of enough CPU time. 
     On the other hand, when the reception data or the transmission data exists, the process of sending transmission requests and the data reception process are executed at shorter time intervals. In the same way, the verification of the presence of transmission data and the data transmission process are also executed at shorter time intervals. In this way, the data communication system of the present invention can perform high-speed data reception and data transmission operations. 
     The present invention having been described should not be limited to the disclosed embodiment, but it may be modified in many other ways without departing from the scope and the spirit of the invention. 
     For example, although the same timer is used for the data reception process and the data transmission process of the resource manager program  77 , different timers may also be used for these processes. In this way, while the time values “A” and “B” are used for both transmission of transmission requests and the transmission checks, with the use of separate timers, the time interval for sending the transmission requests and the time interval for sending the transmission checks may be set to different values. Moreover, while the above embodiment is explained with reference to the multifunction peripheral device provided with a scanner function, a printer function and a facsimile function, the present invention is not limited to such peripheral device and may be applied to other data communication devices that execute digital data communication. 
     Furthermore, although the parallel I/F is used for data communication in the aforementioned data communication system, a serial I/F may also be employed. 
     Such changes and modifications are to be understood as being included with the scope of the present invention as defined by the appended claims.