Patent Abstract:
The system has, provided in a sending device, a generator generating transmission data including data, a data error detection code generated from the data and a safety flag indicating a degree of reliability, and transmission data; has, provided in a receiving device, a plurality of components of extracting transmission data, a safety flag, and a data error detection code from a received frame, and detecting a data error, a comparator comparing the matching of a plurality of received frames, and a selector selecting one received frame, from the frame error detection result, the safety flag, the data error detection result, and the matching comparison result; and determines the validity of transmitted data by the detection corresponding to the degree of reliability set with the safety flag.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This is a divisional of U.S. application Ser. No. 11/477,440, filed Jun. 30, 2006. This application relates to and claims priority from Japanese Patent Application Nos. 2005-190875, filed on Jun. 30, 2005; 2005-190881, filed on Jun. 30, 2005 and 2005-250495, filed on Aug. 31, 2005. The entirety of the contents and subject matter of all of the above is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a sending device, a receiving device, a communication control device, a communication system, and a communication control method. 
       BACKGROUND OF THE INVENTION 
       [0003]    In recent years, the demand for using, in process control systems, programmable electronically controlling devices which are not only limited to the control of primary plant functions (general functions) but also encompass control with respect to safety functions regarding human life and the environment has intensified. In the control of safety functions, safety is demanded, so for that reason, for one safety indicator with respect to data communication between devices, error detection matching is used and error correction is performed. 
         [0004]    However, there is demanded an improvement in the missed error detection rate, the probability of not detecting an error even with error detection, so in order to implement safety, technology has been devised in which two or more frames including data and error detection matching are received and a matching comparison of error detection codes is performed. This kind of technology is described e.g. in JP-A-2005-49967. 
         [0005]    Moreover, in the draft of Functional Safety Standard IEC 61508, there are mentioned, as primary factors obstructing safety, resending of the communication path, loss, insertion, erroneous order, delay, and masquerading (forgery), so countermeasures against these are demanded. For these, there is demanded a reduction in the missed error detection rate, the probability of not detecting an error even with error detection, so in order to implement safety, there has been devised the technology of carrying out a matching comparison of safety data having an important influence on the system. This kind of technology is described e.g. in JP-A-1986-134135. 
         [0006]    Also, with the advancement of technology in the electronics and information fields, the application range for programmable electronic devices is becoming wider, driven by the increased complication/compositeness of functions demanded of single devices, and at the same time, the reliability demanded of programmable electronic devices is increasing. 
         [0007]    In the midst of the progress in increasing scale and the integration of plants and the execution of highly automated plant operation, there are problems with the spread of international safety standards and a lack of experienced persons, and further improvements in safety, beyond the safety measures built up in the past, are in the process of becoming a necessary condition, so, as clearly defined in the functional safety standard IEC 61508-1 to -7, “Functional Safety of Electrical/Electronic/Programmable Electric Safety Related Systems”, Parts 1 to 7 (IEC 61508/61511, JIS C  0508 ), it is regarded as important to prevent and alleviate, in their respective layers, the occurrence of accidents and the extension of damage. 
         [0008]    As far as control devices are concerned, in case an anomaly is detected, the system is required, in order to satisfy the aforementioned functional safety standard, to operate with certainty, and even in the unlikely event of a breakdown, it is demanded to stop the processes on the safe side, so the functional safety system needs to have a special design with great importance attached to “safety” different from that of the control system. 
         [0009]    Also, in large-scale control systems, distributed control systems with process input/output devices having sensors installed in the vicinity of the process and controllers installed in a control room slightly separated from the process are becoming the mainstream, so it is becoming important, as far as functional safety is concerned, to find out how to prevent faulty operation of the process input/output device due to error in data communication between the controller and the process input output devices. 
         [0010]    As one of the most common error detection methods in data transmission, there is CRC (Cyclic Redundancy Check), as described in JP-A-1999-74869. 
       SUMMARY OF THE INVENTION 
       [0011]    Since the aforementioned prior art does not perform a matching comparison of the body of the data, there are limitations on improvements in safety. Specifically, the demand for high safety is not sufficiently addressed. Moreover, in general function control, availability is demanded. 
         [0012]    Since the aforementioned prior art does not carry out a matching comparison at the data sender, there are limitations on improvements in safety. Also, detection of masquerading (forgery) in data communication occurring in functional safety systems is required. 
         [0013]    In terms of the elements of reliability required of a programmable electronic device, there are availability and safety. For equipment control, availability is important, whereas for equipment protection, safety is important. Means of implementation of these two elements have many portions which are mutually exclusive. 
         [0014]    For this reason, it has in the past been considered to be common practice to split the system into a partial device assuming responsibility for availability and a partial device assuming responsibility for safety. Because of this, the device did not only increase in size, but the duplication and increased complication of the work of putting into operation and maintenance brought about a reduction in the reliability of the human element. 
         [0015]    It is an object of the present invention to provide a sending device, a receiving device, a communication control device and a communication control method capable of solving at least one of the aforementioned conventional problem areas, and, specifically, to provide a system which, together with having, with respect to the safety function, a high safety function for the reduction and so forth of the missed error correction rate and the like, is capable, with respect to the general function, of obtaining availability. 
         [0016]    Also, it is an object of the present invention to provide, together with reducing the missed error detection rate with respect to the safety function, a system which is capable of detecting masquerading. 
         [0017]    In addition, it is an object of the present invention to provide a system compatible with both high performance and safety. 
         [0018]    In order to attain the aforementioned object, in the present invention, a system has been configured to: receive a frame including data and safety flag information indicating the safety level; extract data and safety flag information from the aforementioned frame; and, in response to the aforementioned extracted safety level, carry out communication error detection of the aforementioned received data. Alternatively, a system has been configured to: receive the transfer of the data; receive the transfer of safety flag information indicating the safety level; generate a frame on the basis of the aforementioned data and safety flag information; and send the aforementioned frame as serial communication. 
         [0019]    More specifically, in a communication control device consisting of: a means of generating a packet including transmission data, and a frame including one frame error detection code generated from the aforementioned packet; a sending device having a means of sending the aforementioned frame and having a plurality of sending means; a plurality of transmitting means; a means of detecting a plurality of frame errors from a plurality of received frames received by means of a plurality of receiving means; a means of selecting one received frame from the aforementioned plurality of frames and adding validity flags extracting transmission data; the system being configured to provide, in the aforementioned sending device: a means of generating transmission data including data, a safety flag showing the reliability of the aforementioned data, and a data error detection code generated from the aforementioned data; and to provide, in the aforementioned receiving device: a plurality of means extracting, from the aforementioned received frame, data and safety flags and data error correction codes, and detecting data errors; a means of comparing the aforementioned plurality of received frames; a means of selecting one received frame from the aforementioned frame error detection result, the aforementioned safety flag, the aforementioned data error detection result, and the aforementioned matching comparison result; and a means of judging the validity of the transmission data, by means of the detection method corresponding to the degree of reliability set in the safety flag. 
         [0020]    Also, in order to attain the aforementioned object, the system has been configured to: send data to the sending destination communication control device through communication lines which at least in part have serial transmission; receive data sent through communication lines from the sending destination control device; compare the matching of the sent data and the received data; and, based on the matching comparison result, send output permission information showing output permission of previously sent data through communication lines to the sending destination communication control device. 
         [0021]    More specifically, in a communication system consisting of: a data sending side device, a data receiving side device, and communication lines making a connection in series between the aforementioned devices; the system has been configured so that the aforementioned data receiving side device sends the received data by echo back, the data and the echo back are compared in the aforementioned data sending side device, the result is sent, and the aforementioned data receiving side judges the validity of the data by means of the aforementioned matching comparison result. 
         [0022]    More specifically, in a communication control device consisting of a master communication control device and a slave communication control device connected to the output circuit, the system has been configured so that the aforementioned master communication control device sends the output data, the aforementioned slave communication control device sends the echo back of the aforementioned output data, the aforementioned master communication control device compares the matching of the aforementioned output data and the aforementioned echo back, the aforementioned master communication control device compares the matching of the aforementioned output data and the aforementioned echo back, and in case they coincide, permission is given for output to the aforementioned slave communication control device. 
         [0023]    Also, in a communication control device consisting of a master communication control device and a slave communication control device connected to the input circuit, the system has been configured so that the aforementioned slave communication control device sends the input data, the aforementioned master communication control device sends the echo back of the aforementioned input data, the aforementioned slave communication control device compares the matching of the aforementioned input data and the aforementioned echo back, and in case they coincide, permission is given for input to the aforementioned master communication control device. 
         [0024]    In addition, in order to attain the aforementioned object, the system has been configured to: receive data showing the relative level of safety; generate error codes regarding the respective plural data units; and generate data from the data showing the relative level of safety, the plural data units, and respective error codes added in case the data units have relatively high safety; and further to generate error codes regarding at least part of the generated data and add the generated data. Alternatively, the system has been configured to: receive data showing the relative level of safety; judge whether the received frame is in error from the received error code; and, in case the data unit has a relatively high level of safety, judge, for the respective unit data included in the received frame, whether the unit data are in error, from the corresponding plural error codes. 
         [0025]    In this way, concerning the safety function, it is possible to obtain high safety with a reduction in the missed error correction rate and the like, and further, availability with respect to e.g. general functions and the like can be obtained. 
         [0026]    Also, regarding the safety function, together with reducing the missed error detection rate, it is possible to implement detection of masquerading. 
         [0027]    By means of handshake communication, a check of the sending source and destination addresses of the frame, and a matching comparison of data and the echo back, it is possible to implement masquerading. 
         [0028]    Also, it becomes possible for high performance and safety to coexist. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  shows the system of an embodiment of the present invention. 
           [0030]      FIG. 2  shows a memory of the embodiment 
           [0031]      FIG. 3  shows a frame of the embodiment. 
           [0032]      FIG. 4  shows a reception judgment of the embodiment. 
           [0033]      FIG. 5  is a time chart of the embodiment. 
           [0034]      FIG. 6  shows the system of another embodiment of the present invention. 
           [0035]      FIG. 7  shows a communication control device (master communication control device) of the embodiment. 
           [0036]      FIG. 8  shows a communication control device (slave communication control device connected to the output circuit) of the embodiment. 
           [0037]      FIG. 9  shows a communication control device (slave communication control device connected to the input circuit) of the embodiment. 
           [0038]      FIG. 10  is a time chart of an output data communication procedure of the embodiment. 
           [0039]      FIG. 11  is a time chart of an input data communication procedure of the embodiment. 
           [0040]      FIG. 12  is a block diagram showing yet another embodiment. 
           [0041]      FIG. 13  is an explanatory diagram showing a data format with which sending and reception is carried out between the controller and the process input/output device. 
           [0042]      FIG. 14  is an explanatory diagram showing the format of a frame which is transferred between the communication devices. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0043]    Below, embodiments of the present invention will be explained. 
         [0044]    A system using a communication control device of an embodiment of the present invention is shown in  FIG. 1 . 
         [0045]    The inventive system consists of a sending device  1 , a first-type communication line  21 , a second-type communication line  22 , a receiving device  3 , an output circuit A  41 , an output circuit B  42 , and a control object  5 . 
         [0046]    Sending device  1  consists of a CPU (Central Processing Unit)  11 , a memory  12 , a DMAC (Direct Memory Access Controller)  13 , a first-type sending circuit  141 , a second-type sending circuit  142 , and a sending sequencer  15 . 
         [0047]    The details of memory  12  will be explained using  FIG. 2 . 
         [0048]    In memory  12 , there is allocated an output area A  121 , an area for carrying out control of output circuit A  41 . 
         [0049]    Output area A  121  consists of output data  1211 , a safety flag  1212  indicating whether the output data are a safety function, a data error detection code  1213 , and a validity flag  1214 . 
         [0050]    In the same way, an output circuit B area  122  is allocated. 
         [0051]    When output circuit A  41  is a general function, CPU  11  writes composite data  123  to output area A  121 . The validity flag is allocated  1 , the safety flag  0 , and data error detection code  1233  is allocated  0 . 
         [0052]    When output circuit B  42  is a safety function, CPU  11  writes composite data  124  to output area B  122 . The validity flag is allocated  1  and the safety flag  1 , and CPU  11  allocates a value computed from output data  1241  to a data error detection code  1243 . 
         [0053]    The control object consists of a plurality of control devices, and the system designer selects, depending of the degree of safety required in each of the control devices, whether a general function or a safety function is chosen. E.g., at a manufacturing site, a safety function is selected for emergency stop control devices related to human life, and a general function is selected for other devices. In this way, general functions and safety functions differ by object to be controlled, but the output data themselves are the same data. 
         [0054]    The details of frame  23  will be explained using  FIG. 3 . 
         [0055]    Frame  23  consists of a start flag  231 , a packet  232 , a frame error detection code  233 , and an end flag  234 . Packet  232  consists of a header  2321  and composite data  2322 . The address of memory  12  is allocated to header  2321 . 
         [0056]    The flow of data from memory  12  up to first-type communication line  21  and second-type communication line  22  will be explained using  FIG. 1 ,  FIG. 2 ,  FIG. 3 , and  FIG. 5 . 
         [0057]    A sending sequencer  15  instructs  17 , to DMAC (Direct Memory Access Controller)  13 , a transfer source address (address  1210  of output area A  121 ) and a transfer activation, and transfers, via a bus  16 , composite data  123 , a value read from output area A  121 , to a first-type sending circuit  141  and a second-type sending circuit  142 . The sending source address is transferred from DMAC  13  to first-type sending circuit  141  and second-type sending circuit  142 . The same holds true for output area B  122 . Next, a request to send  18  (t 1 ) is instructed from sending sequencer  15  to first-type communication line  141  and second-type sending circuit  142 . First-type sending circuit  141  generates a packet  232  from transfer source address  1210  and composite data  123 , computes a frame error detection code  233  from packet  232 , generates frame  23 , and sends it to a communication line  21  (t 11 ). Similarly, a frame  24  is sent from second-type sending circuit  142  to communication line  22  (t 12 ). Frame  23  and frame  24  have the same contents. Sending sequencer  15  generates frames from output area A  121  and output area B  122  and executes sending at regular intervals. 
         [0058]    The data flow from first-type communication line  21  and second-type communication line  22  up to memory  310  will be explained using  FIG. 1 ,  FIG. 3 ,  FIG. 4 , and  FIG. 5 . 
         [0059]    Receiving device  3  consists of a reception sequencer  301 , a first-type reception circuit  3021 , a second-type receiving circuit  3022 , a first-type reception buffer  3031 , a second-type reception buffer  3032 , a first-type frame error detector  3041 , a second-type frame error detector  3042 , a first-type data error detector  3051 , a second-type data error detector  3052 , a matching comparator  306 , a selector  307 , a flag adder  308 , a DMAC  309 , and a memory  310 . When first-type frame  23  received from first-type communication line  21  (t 13 ) has reception completed in first-type reception circuit  3021 , it is transferred  3111  to reception buffer  3031 , and when this is completed, it is reported with a first-type reception completion  3121  (t 2 ) report to reception sequencer  301 . In the same way, when second-type frame  24  is received (t 14 ), it is reported with a second-type reception completion  3122  report (t 3 ) to reception sequencer  301 . 
         [0060]    First-type frame error detector  3041  receives  3131  packet  232  and frame error detection code  233  from reception buffer  3031 , performs frame error detection, and reports a first-type frame error detection result  3141  (t 4 ). In the same way, second-type frame error detector  3042  reports a second-type frame error detection result  3142  (t 5 ). 
         [0061]    First-type data error detector  3051  receives  3151  output data  23221  and data error detection code  23223  from reception buffer  3031 , performs data error detection, and reports a first-type data error detection result  3161  (t 4 ). In the same way, second-type data error detector  3052  reports a second-type data error detection result  3162  (t 5 ). 
         [0062]    Matching comparator  306  receives  3171 ,  3172  output data  23221  from first-type reception buffer  3031  and second-type reception buffer  3032 , compares the matching of all the bits, and reports a data matching comparison result  318  (t 6 ). 
         [0063]    A first-type safety flag  3191  and a first-type validity flag  3201  are received from first-type reception buffer  3031 . A second-type safety flag  3192  and a second-type validity flag  3202  are received from second-type reception buffer  3032 . Reception sequencer  301  clears either a first-type timeout register  3011  or a second-type timeout register  3012 , based on a first-type reception completion  3121  report or a second-type reception completion  3122  report. After the first-type reception completion  3121  report, reception sequencer  301  sets second-type timeout register  3012  if there is no second-type reception completion  3122  report within a determined time. In the same way, if there is no first-type reception completion  3121  report, first-type timeout register  3011  is set. After two types of reception completion or timeouts, reception sequencer  301  makes a reception judgment  3013 , selects  321  a selector  307 , and reports safety flag addition  322  and validity flag addition  323  to flag adder  308 . Reception judgment  3013  is shown in  FIG. 4 . The judgment is performed in order starting from line number  1  of reception judgment  3013 . 
         [0064]    In the line of line number  1  shown in  FIG. 4 , first-type timeout register  3011  is shown as “0”, first-type frame error detection result  3141  as “0”, first-type data error detection result  3161  as “0”, first-type safety flag  3191  as “1”, and first-type validity flag  3201  as “1”, and further, second-type timeout register  3012  is shown as “0”, second-type frame error detection result  3142  as “0”, second-type data error detection result  3162  as “0”, second-type safety flag  3192  as “1”, second-type validity flag  3202  as “1”, and matching comparison result  306  as “1”, and when these conditions are satisfied, selection  321  is set to “first-type/second-type”, safety flag addition  322  is set to “1” and validity flag addition  323  is set to “1”. 
         [0065]    That is to say that, (1) regarding first-type timeout register  3011 , since the timeout is specified to be “1” in the legend of  FIG. 4 , it is “0”, indicating that that there is no timeout, (2) regarding first-type frame error detection result  3141 , since it is specified to be “1” in the legend of  FIG. 4  if an error is detected, it is “0”, indicating that that there is no error detected, (3) regarding first-type data error detection result  3161 , since it is specified to be “1” in the legend of  FIG. 4  if an error is detected, it is “0”, indicating that there is no error detected, (4) regarding first-type safety flag  3191 , since the safety function is specified to be “1” in the legend of  FIG. 4 , it is “1”, indicating that there is a safety function, (5) regarding first-type validity flag  3201 , since validity is specified to be “1” in the legend of  FIG. 4 , it is “1”, indicating that there is validity, and these inputs related to the first type are the same for the second type as well, so by reference to the legend of  FIG. 4 , second-type timeout register  3012  is “0”, second-type frame error detection result  3142  is “0”, second-type data error detection result  3162  is “0”, second-type safety flag  3192  is “1”, and second-type validity flag  3202  is “1”, (6) regarding matching comparison result  306 , since coincidence is specified in the legend of  FIG. 4  to be “1”, it is “1”, indicating coincidence. When the aforementioned conditions are satisfied, selection  321  is set to “first-type/second-type”, safety flag addition  322  is set to “1”, and validity flag addition  323  is set to “1”. 
         [0066]    In case the conditions of line number  1  are not satisfied, it is next judged whether the conditions of line number  2  are satisfied. Specifically, in the line of line  2  shown in  FIG. 4 , when the conditions are satisfied that first-type timeout register  3011  is “0”, first-type timeout error detection result  3141  is “0”, first-type data error detection result  3161  is “0”, first-type safety flag  3191  is “1”, and first-type validity flag  3201  is “0”, and further that second-type timeout register  3012  is “0”, second-type frame error detection result  3142  is “0”, second-type data error detection result  3162  is “0”, second-type safety flag  3192  is “1”, second-type validity flag  3202  is “0”, matching comparison result  306  is “1”, selection  321  is set to “first-type/second-type”, safety flag addition  322  is set to “1”, and validity flag addition  323  is set to “0”. 
         [0067]    Further, the items specified as “x” in the legend of  FIG. 4  indicate that they are excluded from the judgment conditions. E.g., in line number  3 , first-type data error detection result  3161  is specified as “x”, first-type safety flag  3191  as “x”, and first-type validity flag  3201  as “x”, so even if first-type data error detection result  3161 , first-type safety flag  3191 , and first-type validity flag  3201  are respectively “1”, or “0”, it signifies that this exerts no influence on the respective settings of selection  321  to “first-type/second-type” and of safety flag addition  322  and validity flag addition  323 . 
         [0068]    Reception judgment  3013  is judged as follows from the combination of the inputs. 
         [0069]    In line number  1 , it is judged that valid safety function data have been received without any anomaly being detected. 
         [0070]    In line number  2 , it is judged that pre-valid safety function data have been received without any anomaly being detected. 
         [0071]    In line number  3 , it is judged that general function data have been received from first-type communication line  21  and second-type communication line  22 . 
         [0072]    In line number  4 , it is judged that general function data have been received from second-type communication line  22 . 
         [0073]    In line number  5 , it is judged that general function data have been received from first-type communication line  21 . 
         [0074]    In line number  6 , it is judged that regular reception has not been possible. 
         [0075]    Selection  321  has three classes, “first type”, “second type”, and “first type/second type”, the first type being selected in “first type”, the second type being selected in “second type”, and the present type being switched in “first type/second type”. In case the first type was selected in the immediately preceding judgment, the second type is selected. In case the second type was selected in the immediately preceding judgment, the first type is selected. 
         [0076]    In selector  307 , based on selection  321 , either of a first-type received frame  3241  and a second-type received frame is selected. Selector  307  sends  325 , from the selected frame, a header  2321  including the write address of memory  310  to DMAC  309 . Also, it sends  326  composite data  2322  from the selected frame to flag adder  308 . 
         [0077]    Flag adder  308 , based on safety flag addition  322  and valid flag addition  323 , saves a safety flag  23222  and a valid flag  23224  of composite data  2322 . 
         [0078]    Reception sequencer  301  makes a write request  327  (t 7 ) to DMAC  309  and writes composite data  328  to be written to memory  310  via a bus  329 . 
         [0079]    The data flow from memory  310  up to control object  5  will be explained using  FIG. 1  and  FIG. 5 . 
         [0080]    DMAC  309  transfers (t 8 ) the corresponding composite data from memory  310  to output circuit A  41  and output circuit B  42  at regular intervals. 
         [0081]    When output circuit A  41  is a general function control and if validity flag  1214  is valid, it outputs  411  output data  1211 . If the flag is not valid, the circuit outputs a predetermined safety output value, or saves a previous value. 
         [0082]    When output circuit B  42  is a safety function control and validity flag  1214  is “valid” and safety flag  1212  is “safe”, and a data error is detected from output data  1211  and data error detection code  1213  but no error is detected, it outputs  421  output data  1211 . In cases other than that, it outputs a preset safety output value, or saves the previous value. 
         [0083]    In this way, the inventive system is applied to a process control system in which availability and safety coexist. 
         [0084]    A system using another example of communication control device is shown in  FIG. 6 . It consists of CPUs  4010 ,  4011 , communication control devices  4020 ,  4021 ,  4022 , and  4023 , a communication line  4003 , an output circuit  4042 , an input circuit  4043 , and a control object  4005 . Communication control devices  4020  and  4021  are master communication control devices MO and Ml. Communication control devices  4022  and  4023  are slave communication control devices S 2  and S 3 . Communication line  4003  is a multi-drop connection of a serial communication line, and when each communication control device itself is not sending, it normally carries out reception monitoring. 
         [0085]    The details of communication control device  4020  are shown in  FIG. 7 . Based on a master/slave selection  4201 , it is possible to select whether this communication control device is a master communication control device or a slave communication control device. A node number  4202  is the communication line ID (identifier) of this communication control device and must be set to a number which differs from the node numbers of other communication control devices connected to communication line  4003 . The connection with CPU  4010  goes through a memory  4209 . Memory  4209  is a two-port RAM (Random Access Memory). Since communication line  4003  is a serial communication line, a sending and reception circuit  4204  converts parallel data into serial data before sending to the communication line and, after reception from the communication line, converts the serial data into parallel data. Further, as for communication line  4003 , even if all of it is not a serial communication line, it is of course acceptable if only a part is a serial communication line. 
         [0086]    Communication control device  4021  is of the same type as communication control device  4020 . 
         [0087]    The details of communication control device  4022  are shown in  FIG. 8 . It is of the same type as communication control device  4020 , but it is connected to an output circuit  4042  via a memory  4229 . 
         [0088]    The details of communication device  4023  are shown in  FIG. 9 . It is of the same type as communication control device  4020 , but it is connected to an output circuit  4043  via a memory  4239 . 
         [0089]    The communication procedure of output data from CPU  4010  up to output circuit  4042  will be explained on the basis of the timechart of  FIG. 10 . 
         [0090]    CPU  4010  saves (t 1 ) the output data to memory  4209  at regular intervals. 
         [0091]    Communication control device  4020  on the sending side sends output data at regular intervals. A control circuit  4203  stores “2”, the node number of slave communication control device  4022 , in communication destination node number  6032  and, in order to generate frame OREQ 1 , instructs a DMAC  4208  to transfer the output data to a sending buffer  4205  and, after transfer, makes a request to send (t 2 ) to sending and receiving circuit  4204 . 
         [0092]    Communication control device  4020  sends frame OREQ 1  to communication line  4003  and, after sending completion, activates (t 3 ) a response timer  6031 . 
         [0093]    Communication control device  4022  on the reception side receives frame OREQ 1  and introduces it into a reception buffer  4227 . If the frame sending destination address is “2”, indicating that it is itself the destination, and the control field is OR 1 , control circuit  4223  stores destination address “0” in communication destination node number  6232 . The output data saved in reception buffer  4227  are transferred to a data buffer  6210 , and also, in order to generate frame OACK 1 , the output data saved in reception buffer  4227  are transferred (t 4 ) to a sending buffer  4225 . 
         [0094]    Communication control device  4022  sends frame OACK 1  to communication line  4003  and, after completion of sending, activates a response timer  6231 . Communication control device  4020  receives frame OACK 1  and introduces it in reception buffer  4207 . If, after completion of reception, the frame destination address is “0”, indicating that it is itself the destination, the source address coincides with communication destination address number  6032 , the control field is OA 1 , and the output data of sending buffer  4205  and the output data (echo back) of reception buffer  4207  coincide in a matching comparison by a matching comparator  4206 , response timer  6031  is halted (t 5 ). Control circuit  4203  saves (t 6 ) in frame OREQ 2  in sending buffer  4205 . 
         [0095]    Communication control device  4020  sends frame OREQ 2  to communication line  4003  and, after completion of sending, activates (t 7 ) response timer  6031 . 
         [0096]    Communication control device  4022  receives frame OREQ 2  and introduces it in reception buffer  4227 . If the frame destination address is “2”, indicating that it is itself the destination, the source address coincides with communication destination node number  6232 , and the control field is OR 2 , and response timer  6231  is halted. Control circuit  4223  instructs (t 8 ) a DMAC  4228  to save the output data saved in the data buffer in memory  4229 . It saves (t 9 ) frame OACK 2  in sending buffer  4225 . 
         [0097]    Communication control device  4022  sends frame OACK 2  to communication line  4003 . Communication control device  4020  receives frame OACK 2  and introduces it in reception buffer  4207 . If, after completion of reception, the frame destination address is “0”, indicating that it is itself the destination, the source address coincides with communication destination address number  6032 , the control field is OA 2 , and response timer  6031  is halted (t 10 ). Thereafter, the subsequent data communication is executed. 
         [0098]    Output circuit  4042  reads memory  4229  at regular intervals and outputs (t 11 ) the output data. 
         [0099]    According to the aforementioned operation, it is possible to output the transferred output data after checking that they are not erroneous. 
         [0100]    When, during the communication procedure, the master communication control device and the slave communication control device together find that the checked portions of the sending destination address, the source address, the control field, the data and so forth, of a received frame, do not have the expected values, they monitor the received frames and wait for received frames until the response timers have timed out and the expected values are received. 
         [0101]    In case the response timer in the master communication control device has timed out, the current data communication is terminated, and the subsequent data communication is executed. 
         [0102]    In case the response time in the slave communication control device has timed out, the current data communication is terminated, and the device waits for the subsequent data communication. 
         [0103]    Next, the input data communication procedure from input circuit  4043  up to CPU  4010  will be explained based on  FIG. 11 . 
         [0104]    The difference with  FIG. 10  is that, since the data transfer direction is the opposite, the order of the frames including data is different and the timing of the data matching comparison is different. Since the checking and timeout monitoring of addresses and control fields are the same as in  FIG. 10 , they will be omitted in the explanation below. 
         [0105]    Input circuit  43  saves (u 1 ) the input data in memory  4239  at regular intervals. 
         [0106]    Communication control device  4020  sends input request frames at regular intervals. The same processing as in  FIG. 10  is performed, but no data are included in frame IREQ 1  (u 2 , u 3 ). 
         [0107]    Communication control device  4023  includes input data in frame IACK 1  and sends it (u 4 , u 5 ). 
         [0108]    Communication control device  4020  includes input data (echo back) in frame IREQ 2  and sends it (u 6 , u 7 ). 
         [0109]    Communication control device  4023  sends frame IACK 2  (u 8 , u 9 ) if the input data of a reception buffer  4235  and the input data (echo back) of a reception buffer  4237  are found by comparison in a matching comparator  4236  to coincide. 
         [0110]    Communication control device  4020 , after receiving frame IACK 2 , saves the input data in memory  4209  (u 10 ). 
         [0111]    CPU  4010  reads memory  4209  at regular intervals (u 11 ). 
         [0112]    As explained above, it is possible, with respect to the communication of input data and output data related to the safety function, to implement detection of masquerading, together with a reduction in the missed error rate. 
         [0113]    Regarding another example, shown in  FIG. 12 , there will first be given a conceptual explanation. The example has a process input/output device  7004  and a controller  7001  controlling the input and output of the process, comprising an S-CRC generation/check circuit  7104  (S-CRC generation circuit  7406 ) as well as an operating mode control part  7105  ( 7404 ), and is configured to operate/halt S-CRC generation/check circuit  7104  (S-CRC generation circuit  7406 ) in response to the output of operating mode control part  7105  ( 7404 ). In case operating mode control part  7105  is set to a mode (hereinafter called the safe mode) making S-CRC generation/check circuit  7104  operate, the S-CRC generation circuit  7406  of process input/output device  7004  adds an S-CRC code to the data when data are sent from process input/output device  7004  to controller  7001 , and sends them to controller  7001  via a communication device, checks the data received by controller  7001  and the S-CRC code added in process input/output device  7004  and, in case there was an error, destroys them and simultaneously raises an error status item without using the corresponding received data. In case, on the contrary, data are sent from controller  7001  to process input/output device  7004 , an S-CRC code is added by the S-CRC generation/check circuit  7104  installed in controller  7001  to the data sent to process input/output device  7004  and sent to process input/output device  7004 , an S-CRC check circuit  7409  installed in process input/output device  7004  performs an S-CRC check with respect to received data from controller  7001  and, in case there was an error, destroys them and raises an error status flag. Further, by performing a check, in communication devices  7002  and  7003  carrying out sending and reception of data between controller  7001  and process input/output device  7004 , of the data and S-CRC code received from controller  7001  as well as of the data and the S-CRC code received from process input/output device  7004 , it is possible to raise the reliability of data communication between terminals from controller  7001  up to process input/output device  7004 . In case operating mode control part  7105  ( 7404 ) is set to a mode (hereinafter called the normal mode) halting S-CRC generation/check circuit  7104  (S-CRC generation circuit  7406 ), S-CRC generation and checking in controller  7001  and process input/output device  7004  are not carried out. 
         [0114]    As described above, not only between terminals of controller  7001  and input/output device  7004  but also in communication devices  7002  and  7003  relaying the communications of both, it is possible, by choosing a configuration in which a check is performed of S-CRC codes generated in both terminals, to prevent data in the normal mode, in which a S-CRC code is not added, from being mistakenly output to process input/output device  7004  in the safe mode, or to prevent input data of process input/output device  7004  in the normal mode from being mistakenly stored in data domains related to the safety function of controller  7001 , so it becomes possible to consolidate the conventional system which has been split into a partial device assuming responsibility for availability and a partial device assuming responsibility for safety. 
         [0115]    Also, the data format with which sending and reception is carried out between controller  7001  and process input/output device  7004  is constituted by the address and the input/output data (subsequently called the data) of process input/output device  7004 , the S-CRC code for the data, and status information indicating the operating mode and malfunction state of the device; an operating mode control part  7105  ( 7404 ) installed in controller  7001  and process input/output device  7004  reflects, during sending of data, the operating mode flag, a flag identifying whether the data sent and received are in the safe mode or in the normal mode, within the status information of the data format; and communication devices  7002  and  7003  relaying the sending and reception of data between controller  7001  and process input/output device  7004  have a means of checking the aforementioned operating mode flag and perform a CRC check only in the case that the operating mode flag is in the safe mode, and do not perform a CRC check in the case of the normal mode. 
         [0116]    Further, controller  7001  and process input/output device  7004  have means of checking whether the operating mode flag of the received data and their own operating modes coincide, check whether the operating modes on the data sending side and reception side coincide, and, in case the operating modes do not coincide, do not give permission on the side of process input/output device  7004  to output to the process, and operate so that, on the side of controller  7001 , output of the corresponding data, to a processor  7101  or a memory or the like inside controller  7001 , is forbidden. 
         [0117]    In addition, by providing registers reflecting an S-CRC error among the status information of the communication data format between controller  7001  and process input/output device  7004  separately in controller  7001 , relay communication devices  7002  and  7003 , and process input/output device  7004 , it becomes easy to designate the place of occurrence of the error, so it becomes possible to designate the place of malfunction during the occurrence of a malfunction and to shorten the time for analysis and repair. 
         [0118]    Although it is in part a repetition of the aforementioned explanation, the example will be explained in detail with reference to  FIG. 12 ,  FIG. 13 , and  FIG. 14 .  FIG. 12  is a block diagram showing an embodiment of the present invention.  FIG. 13  is an explanatory diagram the data format with which the transfer of data is performed between process input/output device  7004  and controller  7001 .  FIG. 14  is an explanatory diagram showing the frame format of the serial transmission of data communication of communication device  7002  and communication device  7003  shown in  FIG. 12 . 
         [0119]    First, an explanation of the outline of the general configuration and the operation of each part will be given with  FIG. 12 . 
         [0120]    In the present diagram, a programmable electronic control device is constituted internally by a controller  7001  having in its interior a processor memory or the like, a process input/output device  7004  which is the input/output interface with the plant process, and a communication device  7002  and a communication device  7003 , serving as relay communication devices carrying out the relaying of data communication between controller  7001  and process input/output device  7004 . 
         [0121]    First, an explanation will be given regarding the case where the output data to the process from controller  7001  to process input/output device  7004  are sent with the safe mode. 
         [0122]    The data output from processor  7101  are stored in a memory  7103  for the time being. These data are e.g. process control data computed on the basis of process state information from process input/output device  7004 . The data stored in this memory  7103  by instruction from processor  7101  have an S-CRC code added by S-CRC generation/check circuit  7104  and are saved in a register  7106 . Here, S-CRC is a CRC (Cyclic Redundancy Check) code added with respect to the safety data during the sending of the data, by controller  7001  or process input/output  7004 . Specifically, the data are delimited in a prescribed manner, a CRC code in the 16 to 32 bit range is generated based on these data, and when the data are sent, the data are sent together with this CRC code and it is checked on the reception side where the relationship between the data and the CRC code is correct, this being a detection of errors. This is to say that, based on the data, a calculation combining a shift called the CRC generating polynomial, addition, and the like, is performed, this being added to the data as a CRC code and sent, and upon reception, the received data is operated on with the CRC polynomial, this being a method of checking coincidence with the received CRC code. Further, the details will be described subsequently, but in the present embodiment, CRC with respect to the input/output data is called S-CRC and, moreover, CRC with respect to the frame shall simply be called CRC. 
         [0123]    The decision as to whether controller  7001  operates in the safe mode or in the normal mode is managed by operating mode control part  7105 . In the status portion of register  7106 , there are several registers indicating the device operating mode and malfunction state, and by instruction from operating mode control part  7105 , it is reflected in the status part of register  7106  whether controller  7001  is in the safe mode or in the normal mode. Further, the combination of the status information, the S-CRC code, and the input/output data are called unit data. The unit data, being the contents of register  7106 , are copied to a register  7208  by a bus interface control part  7107  of controller  7001  and a bus interface control part  7201  of communication device  7002 . 
         [0124]    In communication device  7002 , the status part of register  7208  is copied directly to a register  7204 , it being checked by an S-CRC check circuit  7205  whether there is any error in the input/output data on the basis of the S-CRC code, and the input/output data are copied to register  7204 . In case an error was verified in the input/output data with the S-CRC check in S-CRC check circuit  7205 , S-CRC check circuit  7205  reflects, to the status part of register  7204 , a flag indicating that an S-CRC error has occurred in communication device  7002 . The contents of register  7204  are stored in memory  7209  via a memory interface control part  7206 . If the unit data (status information, S-CRC code and input/output data combined) are stored in memory  7209 , the subsequent unit data are copied from register  7106  of controller  7001  to register  7208  of communication device  7002  and are stored, via memory interface control part  7206 , in memory  7209  by addition to the previously stored unit data. This operation is carried out repeatedly, so plural items of unit data are stored in memory  7209 . 
         [0125]    If a designated number of unit data items are stored in memory  7209 , the system moves to sending operation. As shown in  FIG. 14 , as for the contents stored in memory  7209 , several unit data  7612  and  7613  items are consolidated serially, and simultaneously with the configuration of a sending frame by the addition of a header  7611  in a CRC generation circuit  7202 , a frame  7601  is configured by adding a frame CRC code  7614 . In this way, the data error detection effect is improved by adding a dual error check with S-CRC codes added for each input/output unit data item and CRC codes added for each frame. The sent frame generated in CRC generation circuit  7202  is converted into serial data in a serial bus interface part  7207  and is sent to a serial bus interface part  7307  of communication device  7003  via a communication medium  7005 . Further, as shown in  FIG. 13 , in unit data  7612  constituting frame  7601 , as status information  7511 , if an error is detected in S-CRC check circuit  7205 , an S-CRC error  7522  is added, and if an error is detected in CRC check circuit  7203 , a CRC error  7523  is added. The explanation is in reversed order, but, in order to understand further in which circuit the error was detected, e.g., in case an error has been detected in the CPU, S-CRC error  7522  and CRC error  7523 , in order to be postscripted in CPU  7521 , are postscripted as in communication device  7002  ( 7532 ), communication device  7003  ( 7533 ), a PI/O  7534 , or as in communication device  7002  ( 7535 ) and communication device  7003  ( 7536 ). 
         [0126]    In communication device  7003 , serial bus interface part  7307  sends the received frame to CRC check circuit  7303 , and CRC check circuit  7303  performs a check of the CRC codes added for each frame, decomposes the information from the frame into individual data items and stores them in memory  7309 . The data stored in memory  7309  are sent via memory interface part  7306  to register  7308  and next, the status part of register  7308  is directly copied to the status part of a register  7304 , and the S-CRC code and the input/output data part are copied to register  7304  after implementation of a check of the S-CRC in an S-CRC check circuit  7305 . In case an error has detected in S-CRC check circuit  7305 , status information indicating that an S-CRC error has occurred in communication device  7003  is reflected in the status information of register  7304 . The contents of register  7304  are copied by a bus interface control part  7301  and a bus interface control part  7401  of process input/output device  7004  to a register  7403  of process input/output device  7004 . 
         [0127]    In process input/output device  7004 , as for the S-CRC code and the output data copied to register  7403 , an instruction of a timing control part  7402  is received and an S-CRC check is carried out in S-CRC check circuit  7409 . The status part is sent to an operating mode control part  7408  and, together with performing a check of whether the operating mode of the data output source reflected in the status part is the safe mode, it is checked with the flag of the status part whether the error did not occur in the process of transmission of the output data from controller  7001 , and only in the case where the operating mode is the safe mode and no error information is included in the status information is the output data part of register  7403  copied to a register  7410 , and a data output control part  7411  performs an output of an output signal  7413  to the process. 
         [0128]    Next, an explanation will be given regarding the case where data is sent with the safe mode from process input/output device  7004  to controller  7001 . 
         [0129]    In process input/output device  7004 , an input signal  7412  from the process is introduced into process input/output device  7004  by data input control part  7405 , the input data are sent simultaneously with being copied to the data part of a register  7407  to S-CRC generation circuit  7406 , and S-CRC circuit  7406  generates an S-CRC code with respect to the input data and stores the S-CRC code in the S-CRC part of register  7407 . In operating mode control part  7404 , before the communication of the input data, the information from controller  7001  as to whether the operating mode is the safe mode or the normal mode is sent via communication device  7002  and communication device  7003 . Operating mode control part  7404  reflects the operating mode status information indicating whether the operating mode of process input/output device  7004  is the safe mode or the normal mode in the status part of register  7407 . The contents of register  7407  are copied, by bus interface part  7401  and bus interface control part  7301  inside communication device  7003 , to register  7304  inside communication device  7003 . 
         [0130]    In communication device  7003 , the status part of register  7304  is directly copied to the status part of register  7308 , a check of the S-CRC code and the data part is performed in S-CRC check circuit  7305 , and they are respectively copied to the S-CRC and the input/output data part of register  7308  if there is no error. In case an error was detected in S-CRC check circuit  7305 , there is raised a flag in the status part of S-CRC check circuit  7308  to the effect that an S-CRC error occurred in communication device  7003 . The unit data copied to register  7308  are copied to memory  7309  by means of memory interface control part  7306 . A CRC generation circuit  7302  consolidates the plural data units copied to memory  7309  and, together with configuring the transmission frame, generates a CRC code with respect to the frame and sends it to serial bus interface part  7307 . Serial bus interface part  7307  converts the received frame to serial data and sends it through medium  7005  to serial bus interface part  7207  of communication device  7002 . 
         [0131]    In communication device  7002 , serial bus interface part  7207  sends the received frame to CRC check circuit  7203 , CRC check circuit  7203  checks the presence of a CRC error with respect to the received frame, decomposes the frame into individual data items, and stores them in memory  7209 . The data of memory  7209  are copied to register  7204  by memory interface control part  7206 , the status part of register  7204  is directly copied to register  7208 , an S-CRC check is carried out on the S-CRC and the input/output data parts with S-CRC check circuit  7205  and, if there is no error, they are respectively copied to the S-CRC part and the input/output data part of register  7208 . In case an error was found with S-CRC check circuit  7205 , S-CRC check circuit  7205  raises a flag in the status part of register  7208  to the effect that an S-CRC error has occurred in communication device  7002 . The data of register  7208  are copied to register  7106  by bus interface control part  7201  and bus interface control part  7107  of controller  7001 . 
         [0132]    In controller  7001 , operating mode control part  7105  checks, by the operating mode flag of the data sending source of the status part of register  7106 , whether the sending source is in the safe mode, and if it is not in the safe mode, it sends error information to processor  7101  and discards the data of register  7106 . In case it is verified that the sending source is in the safe mode, the S-CRC part and the data part of register  7106  are sent to S-CRC generation/check circuit  7104 , and in case there is no error found as a result of the S-CRC check, the input/output data are sent to processor  7101 . 
         [0133]    In the communication of data in the normal mode between controller  7001  and input/output device  7004 , data sending and reception are performed by a setting of the status or by the operating mode control parts  7105  and  7404 , without operation of S-CRC generation/check circuit  7104 , S-CRC check circuits  7205  and  7305 , S-CRC generation circuit  7406 , or S-CRC check circuit  7409 , and for the other parts, are carried out in the same way as in the safe mode. As a result of this, in the sending and reception of data from controller  7001  up to process input/output device  7004 , it becomes possible, without changing the data format or the frame configuration for transmission between communication device  7002  and communication device  7003 , to implement both the safe mode and the normal mode with the same devices, including relaying communication device  7002  and communication device  7003 . 
         [0134]    An explanation will be given regarding the case where output data to a process is sent with the normal mode from controller  7001  to process input/output device  7004 . In particular, the explanation will mainly be given for points which differ from the safe mode, so regarding portions which are the same as for the safe mode, the explanation will be omitted in part. 
         [0135]    Data which are output from processor  7101  are stored in memory  7103  for the time being. The data stored in this memory  7103  are stored, in a way differing from the safe mode, without operation of S-CRC generation/check circuit  7104  and without any item being added to the S-CRC domain, in register  7106 . 
         [0136]    The decision as to whether controller  7001  operates in the safe mode or in the normal mode is managed by operating mode control part  7105 . It is reflected in the status part of register  7106  whether controller  7001  operates in the safe mode or the normal mode. The unit data, being the contents of register  7106 , are copied to register  7208  by bus interface control part  7107  of controller  7001  and bus interface control part  7201  of communication device  7002 . 
         [0137]    In communication device  7002 , the status part of register  7208  is directly copied to register  7204 . In a way differing from the safe mode, S-CRC check circuit  7205  does not operate, so without performing an error check of the input/output data based on S-CRC, the data are copied to register  7204 . The contents of register  7204  are stored in memory  7209  via memory interface control part  7206 . If unit data (status information and input/output data combined) are stored in memory  7209 , the subsequent unit data are copied from register  7106  of controller  7001  to register  7208  of communication device  7002  and, via memory interface control part  7206 , are stored in memory  7209  by addition to the previously stored unit data. This operation is carried out repeatedly to store a plurality of unit data items in memory  7209 . Further, nothing is stored in the S-CRC domain. 
         [0138]    If a designated number of unit data items are stored in memory  7209 , the system moves to sending operation. As shown in  FIG. 14 , as for the contents stored in memory  7209 , several unit data  7612  and  7613  items are consolidated serially, and simultaneously with the configuration of a sending frame by the addition of a header  7611  in a CRC generation circuit  7202 , a frame  7601  is configured by adding a frame CRC code  7614 . In the safe mode, an S-CRC code is added for each input/output unit data item and a CRC code is added for each frame, but in the normal mode, the check is limited to a CRC error check. The frame for sending, generated in CRC generation circuit  7202 , is converted to serial data in serial bus interface part  7207  and sent, via communication medium  7005 , to serial bus interface part  7307  of communication device  7003 . 
         [0139]    In communication device  7003 , serial bus interface part  7307  sends the received frame to CRC check circuit  7303 , and CRC check circuit  7303  performs a check of the CRC codes added for each frame, decomposes the information from the frame into individual data items and stores them in memory  7309 . The data stored in memory  7309  are sent via memory interface part  7306  to register  7308  and next, the status part of register  7308  is directly copied to the status part of a register  7304 , and the S-CRC (in which nothing is stored) and the input/output data parts are copied to register  7204  without the S-CRC check based on S-CRC check circuit  7305  being performed, since they are in the normal mode. The contents of register  7304  are copied to register  7403  of process input/output device  7004  by means of bus interface control part  7301  and bus interface control part  7401  of process input/output device  7004 . 
         [0140]    In process input/output device  7004 , regarding the S-CRC (in which nothing is stored) copied to register  7403  and the output data, since the system is in the normal mode, no S-CRC check is carried out by S-CRC check circuit  7409 . The status part is sent to operating mode control part  7408  and, together with performing a check of whether the operating mode of the data output source reflected in the status part is the normal mode, it is checked with a flag of the status part whether an error did not occur in the output data in the transmission process from controller  7001 , and in case no error information is included, the output data part of register  7403  is copied to register  7410 , and data output control part  7411  performs an output of output signal  7413  to the process. 
         [0141]    Next, an explanation will be given regarding the case where data are sent in the normal mode from process input/output device  7004  to controller  7001 . 
         [0142]    In process input/output device  7004 , input signal  7412  from a process is introduced by data input control part  7405  into process input/output device  7004 , and the input data are copied to the data part of register  7407 . Since the system is in the normal mode, S-CRC circuit  7406  does not operate. Nothing is stored in the S-CRC domain. In operating mode control part  7404 , before the communication of the input data, information on whether the operating mode is the safe mode or the normal mode is sent from controller  7001  via communication device  7002  and communication device  7003 . Operating mode control part  7404  reflects the operating mode status, indicating whether the operating mode of process input/output device  7004  is the safe mode or the normal mode, to the status part of register  7407 . The contents of register  7407  are copied to register  7304  inside communication device  7003  by means of bus interface part  7401  and bus interface control part  7301  inside communication device  7003 . 
         [0143]    In communication device  7003 , the status part of register  7304  is directly copied to the status part of register  7308 . Since the system is in the normal mode, the data are copied to the input data part, without carrying out a check in S-CRC check circuit  7305 . At this point, nothing is stored in the S-CRC domain. The unit data copied to register  7308  are copied to memory  7309  by means of memory interface control part  7306 . CRC generation circuit  7302  consolidates the plural data units copied to memory  7309  and, together with configuring the transmission frame, generates a CRC code with respect to the frame, and sends it to serial bus interface part  7307 . Serial bus interface part  7307  converts the received frame to serial data and sends them via medium  7005  to serial bus interface part  7207  of communication device  7002 . 
         [0144]    In communication device  7002 , serial bus interface part  7207  sends the received frame to CRC check circuit  7203  and CRC check circuit  7203  checks for the presence of a CRC error with respect to the frame and decomposes the frame into individual data units and stores them in memory  7209 . The data of memory  7209  are copied to register  7204  by memory interface control part  7206  and the status part of register  7204  is directly copied to register  7208 , and, since the operating mode is the normal mode, the data are respectively copied to the input/output data part, without performing the S-CRC check in S-CRC check circuit  7205 . The data of register  7208  are copied to register  7106  by bus interface control part  7201  and bus interface control part  7107  of controller  7001 . Nothing is stored in the S-CRC domain. 
         [0145]    In controller  7001 , operating mode control part  7105  checks the sending source with operating mode flag of the data source of the status part of register  7106  and sends the input/output data to processor  7101 . 
         [0146]    It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.

Technology Classification (CPC): 7