Patent Publication Number: US-2003231727-A1

Title: Communication method, electronic equipment, and communication program storage medium

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a communication method of transmitting and/or receiving both data and a synchronizing signal for data receiving, electronic equipment for transmitting and/or receiving both data and a synchronizing signal for data receiving, and a communication program storage medium storing a communication program, which is executed in electronic equipment having a hardware for data communications and also having a function of execution of a program to cause the electronic equipment to perform the data communications.  
       [0003] 2. Description of the Related Art  
       [0004] Hitherto, there are known two types of data transmission between electronic equipment and electronic equipment, that is, a synchronous transmission system and an asynchronous transmission system. The synchronous transmission system is concerned with a system in which a transmission side transmits a synchronizing signal together with data, and a receiving side receives the data in synchronism with the transmitted synchronizing signal. In the event that the data is not properly received, in other words, there is an error in data transmission, it may happen that retransmission of the data is performed. Japanese Patent Application Laid Open Gazette Hei. 8-221335 proposes a technique in which checking a period of a synchronizing signal enhances a success rate of retransmission at the time of transmission errors. Also as to the asynchronous transmission system, as a technology disclosed in Japanese Patent Application Laid Open Gazette Hei. 9-6725, there is known a technology of using a synchronous transmission system to enhance detection accuracy of transmission errors.  
       [0005] By the way, as a method of detecting data transmission errors between electronic equipment and electronic equipment, there are proposed many technologies. For example, Japanese Patent Application Laid Open Gazette Sho. 63-275074 proposes a technology in which when a series of data is sequentially transmitted, discrepancy of timing between a synchronizing signal and a reference clock signal of electronic equipment managing timings of data transmission is exactly detected, so that omission of individual data and overlapping are detected. However, use of only the technology disclosed in the above-referenced Japanese Patent Application Laid Open Gazette Sho. 63-275074 would make it difficult to detect that contents of data are changed owing to noises or the like. As a typical solution of detecting that contents of data are changed owing to noises or the like, there are known parity check and a method referred to as CRC (Cyclic Redundancy Checking) using constant called generating polynomial. According to any of those parity check and CRC, the transmission side adds redundancy bits after data to be transmitted and then transmits, and the receiving side decides whether contents of the data are exactly transmitted using both the transmitted data and redundancy bits. With respect to the parity check, there are two types of schemes of an even parity and an odd parity. With respect to the CRC, the number of bits of the redundancy bits is varied in accordance with a bit length of the constant used.  
       [0006] Thus, in the event that the parity check is performed, a difference of the adopted schemes between the receiving side and the transmission side would involve erroneous detection of the transmission errors. Also in the event that the CRC is performed, a difference of the used constant between the receiving side and the transmission side would involve erroneous detection of the transmission errors, too.  
       [0007] Further, there is an interface adopting no parity check and CRC.  
       SUMMARY OF THE INVENTION  
       [0008] In view of the foregoing, it is an object of the present invention to provide a communication method, electronic equipment, and a communication program storage medium, which are capable of detecting changes of contents of data due to noises and the like, independently of the parity check and the CRC.  
       [0009] To achieve the above-mentioned object, the present invention provides a communication method comprising:  
       [0010] a data communication step that transmits and/or receiving both data and a synchronizing signal for data receiving, and  
       [0011] a synchronizing signal monitor step that monitors whether a time width of a predetermined section of a signal waveform of the synchronizing signal satisfies a predetermined reference.  
       [0012] The communication method of the present invention includes three methods of transmitting both data and a synchronizing signal for data receiving, receiving both data and a synchronizing signal for data receiving, and transmitting and receiving both data and a synchronizing signal for data receiving.  
       [0013] To achieve the above-mentioned object, the present invention provides electronic equipment comprising a data communication section that transmits and/or receiving both data and a synchronizing signal for data receiving, and  
       [0014] a synchronizing signal monitor section that monitors whether a time width of a predetermined section of a signal waveform of the synchronizing signal satisfies a predetermined reference. The electronic equipment of the present invention includes three types of electronic equipment of the transmission side transmitting both data and a synchronizing signal for data receiving, electronic equipment of the receiving side receiving both data and a synchronizing signal for data receiving, and electronic equipment transmitting and receiving both data and a synchronizing signal for data receiving.  
       [0015] In the receiving method having the synchronizing signal monitor step and the electronic equipment of the receiving side having the synchronizing signal monitor section, it is presumed that occurrence of distortion and ringing on the transmitted synchronizing signal brings about degradation of reliability that contents of data received in synchronism with the synchronizing signal are accurate. Accordingly, monitoring the synchronizing signal makes it possible to evaluate the reliability that contents of the data received are accurate, without performing the parity check and CRC. Even in the event that the parity check and CRC are performed, it possible to evaluate the reliability that contents of the data are accurate, before performing the parity check and CRC.  
       [0016] In the transmission method having the synchronizing signal monitor step and the electronic equipment of the transmission side having the synchronizing signal monitor section, it is presumed that satisfaction of the signal waveform of the transmitted synchronizing signal with a predetermined reference may increase reliability that contents of data transmitted in synchronism with the synchronizing signal are accurate. Accordingly, the synchronizing signal is monitored to decide whether the signal waveform of the synchronizing signal satisfies a predetermined reference. As a result, if the synchronizing signal transmitted together with the data satisfies the predetermined reference, it is possible to ensure that contents of data are accurate on the transmitted data at the transmitted time point immediately after the data is transmitted.  
       [0017] In the communication method of the present invention, it is preferable that the synchronizing signal monitor step monitors whether a time width of a predetermined section of the synchronizing signal is between a predetermined permissible minimum time width and a predetermined permissible maximum time width. In the electronic equipment of the present invention, it is preferable that the electronic equipment further comprises a reference storage section that stores reference information representative of a permissible minimum time width and a permissible maximum time width of the predetermined section, and said synchronizing signal monitor section monitors whether a time width of a predetermined section of the synchronizing signal is between the permissible minimum time width and the permissible maximum time width represented by the reference information stored in said reference storage section.  
       [0018] In the communication method of the present invention and the electronic equipment of the present invention, it is preferable that said synchronizing signal is a clock signal, and said synchronizing signal monitor step monitors, as the time width of the predetermined section, one or more selected from among a rise time, a fall time, a time width of an H-level, a time width of an L-level, and a predetermined transmission period, of the clock signal.  
       [0019] With respect to the selection of items (rise time of the clock signal, and the like) to be monitored in form of time width of the predetermined section, it is effective that the item is decided in view of the balance between a degree of reliability of data contents and a processing load of the synchronizing signal monitor section.  
       [0020] In the communication method of the present invention, it is preferable that said communication method further comprises a receipt result report step that reports a monitored result by said synchronizing signal monitor step to a party of communications. In the electronic equipment of the present invention, said electronic equipment further comprises a communication result report section that reports a monitored result by said synchronizing signal monitor section to a party of communications.  
       [0021] Performing such a report makes it possible for the party of communications to know reliability of data. And in the event that reliability of data is low, it is possible to perform necessary processing such as retransmission processing for data and processing of stopping processing of received data.  
       [0022] To achieve the above-mentioned object, the present invention provides a communication program storage medium storing a communication program to be executed by electronic equipment having hardware for data communications and functions of executing programs, wherein said communication program causes said electronic equipment to perform the data communications, said electronic equipment comprising:  
       [0023] a data communication section that transmits and/or receiving both data and a synchronizing signal for data receiving, and  
       [0024] a synchronizing signal monitor section that monitors whether a time width of a predetermined section of a signal waveform of the synchronizing signal satisfies a predetermined reference.  
       [0025] When the communication program stored in the communication program storage medium of the present invention is installed in the electronic equipment having function of executing a program and is executed, the electronic equipment can be operated as the electronic equipment.  
       [0026] In the communication program storage medium according to the present invention as mentioned above, it is preferable that said electronic equipment further comprises a reference storage section that stores reference information representative of a permissible minimum time width and a permissible maximum time width of the predetermined section, and  
       [0027] wherein said synchronizing signal monitor section monitors whether a time width of a predetermined section of the synchronizing signal is between the permissible minimum time width and the permissible maximum time width represented by the reference information stored in said reference storage section. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0028]FIG. 1 is a perspective view of a personal computer according to an embodiment of electronic equipment of the present invention, to which a magneto-optical disk (MO) also according to an embodiment of electronic equipment of the present invention is connected.  
     [0029]FIG. 2 shows hardware construction views of the personal computer and the magneto-optical disk shown in FIG. 1.  
     [0030]FIG. 3 is a view showing an embodiment of a communication program stored in a communication program storage medium of the present invention.  
     [0031]FIG. 4 is a functional block diagram of an embodiment of electronic equipment of the present invention.  
     [0032]FIG. 5 is a flowchart useful for understanding processes of data communications to be performed in the electronic equipment shown in FIG. 4.  
     [0033]FIG. 6 is a circuit diagram of a portion for performing an error detection in data transmission, of the SCSI controller provided on the personal computer shown in FIG. 2.  
     [0034]FIG. 7( a ) and FIG. 7( b ) are a view showing a transition of data in a data line wherein a series of data are sequentially transmitted, and a view showing a data strobe signal, respectively.  
     [0035]FIG. 8 is a flowchart useful for understanding set up processing for the magneto-optical disk shown in FIG. 2, of the personal computer shown in FIG. 2 connected to the magneto-optical disk.  
     [0036]FIG. 9 is a flowchart useful for understanding read command processing of the magneto-optical disk upon receipt of read command from the host.  
     [0037]FIG. 10 is a view showing an outline of a flow of processing from the set up processing explained referring to FIG. 8 to the read command processing explained referring to FIG. 9.  
     [0038]FIG. 11 is a view showing an example of a signal waveform of a data strobe signal.  
     [0039]FIG. 12 is a view showing another example of a signal waveform of a data strobe signal.  
     [0040]FIG. 13 is a view showing an outline of a flow of processing subsequent to the flow of the processing explained referring to FIG. 10.  
     [0041]FIG. 14 is a flowchart useful for understanding write command processing of the magneto-optical disk upon receipt of write command from the host. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
     [0042] Embodiments of the present invention will be described with reference to the accompanying drawings.  
     [0043]FIG. 1 is a perspective view of a personal computer according to an embodiment of electronic equipment of the present invention, to which a magneto-optical disk (MO) unit also according to an embodiment of electronic equipment of the present invention is connected.  
     [0044] A personal computer  100  comprises: a main frame  101  incorporating therein a CPU (Central Processing Unit), a RAM (Random Access Memory), and a hard disk; a display unit  102  for displaying images and strings of characters on a display screen  102   a  in accordance with instructions from the main frame  101 ; a keyboard  103  for inputting user&#39;s instructions and character information to the personal computer; and a mouse  104  for inputting orders associated with icons or the like displayed on positions on the display screen  102   a  when the positions are designated.  
     [0045] The main frame  101  of the personal computer  100  comprises, on the outside appearance, a flexible disk (FD), a flexible disk mounting slot  101   a  onto which CD-ROM is loaded, and a CD-ROM mounting slot  101   b.  Inside the main frame  101 , there are incorporated a flexible disk drive for driving the flexible disk loaded through the flexible disk mounting slot  101   a,  and a CD-ROM drive for driving the CD-ROM loaded through the CD-ROM mounting slot  101   b.    
     [0046] The personal computer  100  is provided with a SCSI (Small Computer System Interface) connector and an RS-232C (Recommended Standard 232C) connector.  
     [0047] A magneto-optical disk (MO) unit  200  comprises an F-ROM (flash memory) as well as the CPU and the RAM (random access memory). The magneto-optical disk (MO) unit  200  further comprises, on the outside appearance, an MO mounting slot  201   a  onto which a magneto-optical disk is loaded, and incorporates therein an MO drive for driving and accessing the loaded magneto-optical disk. The F-ROM stores therein a program for performing read and write of information for the magneto-optical disk. The CPU executes the program. The RAM is used as a working area for the program. The magneto-optical disk unit  200  is provided with a SCSI (Small Computer System Interface) connector and an RS-232C (Recommended Standard 232C) connector, in a similar fashion to that of the personal computer  100  shown in FIG. 1.  
     [0048] The SCSI connector of the personal computer  100  shown in FIG. 1 is connected to the SCSI connector of the magneto-optical disk unit  200  shown in FIG. 1 via a SCSI cable  300 .  
     [0049]FIG. 2 shows hardware construction views of the personal computer and the magneto-optical disk unit shown in FIG. 1.  
     [0050] The hardware construction view of the personal computer  100  shows a central processing unit (CPU)  111 , a RAM  112 , a hard disk controller  113 , a flexible disk (FD) drive  114 , a CD-ROM drive  115 , a mouse controller  116 , a keyboard controller  117 , a display controller  118 , an SCSI controller  119 , and an RS-232 controller  120 . Those are connected to one another through a bus  110 .  
     [0051] The hard disk controller  113  accesses a hard disk  130  of a hard disk drive incorporated in the main frame of the personal computer  100 . The flexible disk drive  114  and the CD-ROM drive  115  access, as described referring to FIG. 1, a flexible disk  140  and a CD-ROM  150 , which are loaded through the flexible disk mounting slot  101   a  and the CD-ROM mounting slot  101   b,  respectively.  
     [0052] The hardware construction view of the magneto-optical disk unit  200  shown in FIG. 1 shows a CPU  211 , an F-ROM  212 , a RAM  213 , an ODC (optical magnetic disk controller)  214 , a DSP (digital signal control circuit)  215 , an SCSI controller  216 , and an RS-232 controller  217 . Those are connected to one another through a bus  210 .  
     [0053] The SCSI controller  119  of the personal computer  100  is connected to the SCSI controller  216  of the magneto-optical disk unit  200  via a SCSI cable  300 . Data transmission is performed between the personal computer  100  and the magneto-optical disk unit  200  via the SCSI cable  300 . Those SCSI controllers  119  and  216  perform data transmission in accordance with a standard of SCSI, and also perform an error detection of the data transmission. Details of such an error detection of the data transmission will be described later. In a similar fashion to that of those SCSI controllers  119  and  216 , the RS-232 controller  120  and  217 , which are provided on the personal computer  100  and the magneto-optical disk unit  200 , respectively, control data transmission in accordance with a standard of RS-232.  
     [0054] The ODC (optical magnetic disk controller)  214  provided on the magneto-optical disk unit  200  controls read and write of information for the magneto-optical disk. The ODC  214  receives a command transmitted to the SCSI controller  216  of the magneto-optical disk unit  200 , decodes the received command, and executes the operation indicated by the command. The ODC  214  performs the parity check for writing data, a CRC (cyclic redundancy checking) and the like. The CPU  211  and the DSP  215 , which are provided on the magneto-optical disk unit  200 , control basic operations of the magneto-optical disk unit  200 , such as rotary driving, taking-in and sending of a magneto-optical disk, and tracking and focusing for the magneto-optical disk.  
     [0055]FIG. 3 is a view showing an embodiment of a communication program stored in a communication program storage medium of the present invention.  
     [0056] A communication program  400  is stored in the CD-ROM  150 . The communication program  400  comprises a data communication section  410 , a reference storage section  420 , a synchronizing signal monitor section  430 , and a communication result report section  440 . Functions of the sections constituting the communication program  400  will be explained in conjunction with functions of the sections constituting the electronic equipment  500  shown in FIG. 4.  
     [0057] The communication program  400  shown in FIG. 3 is stored in the CD-ROM  150 , and is up loaded onto the personal computer  100  shown in FIG. 1 when the CD-ROM  150  is loaded through the CD-ROM mounting slot  101   b  of the personal computer  100  and is accessed by the CD-ROM drive  115  shown in FIG. 2. The communication program  400 , which is up loaded onto the personal computer  100 , is stored in the hard disk  130  of the personal computer  100 . To execute the communication program  400 , the communication program  400  stored in the hard disk  130  is read and developed in RAM  112  so as to be executed by the CPU  111 .  
     [0058] The communication program  400  is not always up loaded on the personal computer  100  from a state that it is stored in the CD-ROM  150 , and it is acceptable that the communication program  400  is up loaded on the personal computer  100  from a state that it is stored in another portable type of storage medium (for example, FD  140  shown in FIG. 2), or it is also acceptable that the personal computer  100  shown in FIG. 1 and FIG. 2 is connected to a communication network such as internet, and the communication program  400  is loaded on the personal computer  100  via the communication network, further or alternatively it is acceptable that the communication program  400  is stored in the hard disk  130  of the personal computer  100  beforehand. In effect, anyone is acceptable, as the communication program  400 , which is executed in the personal computer  100 .  
     [0059]FIG. 4 is a functional block diagram of an embodiment of electronic equipment of the present invention.  
     [0060] Electronic equipment  500  shown in FIG. 4 is implemented in the personal computer  100  shown in FIG. 1 and FIG. 2 when the communication program  400  in FIG. 3 is executed in the personal computer  100 .  
     [0061] The electronic equipment  500  shown in FIG. 4 comprises a data communication section  510 , a reference storage section  520 , a synchronizing signal monitor section  530 , and a communication result report section  540 . The data communication section  510 , the reference storage section  520 , the synchronizing signal monitor section  530 , and the communication result report section  540  correspond to the data communication section  410 , the reference storage section  420 , the synchronizing signal monitor section  430 , and the communication result report section  440 , respectively, which are shown in FIG. 3. The respective sections constituting the electronic equipment  500  shown in FIG. 4 are constituted of compounds of a hard ware of the personal computer  100  shown in FIG. 1 and FIG.  2 , an operating system (OS) operating in the personal computer  100 , and the communication program  400  shown in FIG. 3 as the application program to be executed on the OS. To the contrary, the respective sections  410  to  440  constituting the communication program  400  shown in FIG. 3 are constituted of only the application program of the compounds. The functions of the sections  410  to  440  constituting the communication program  400  shown in FIG. 3, when the communication program  400  is executed in the personal computer, are the same as those of the functions of the sections  510  to  540  constituting the electronic equipment  500  shown in FIG. 4, respectively. Accordingly, the explanation of the respective functions of the sections  510  to  540  constituting the electronic equipment  500  shown in FIG. 4 serves as the explanation of the respective functions of the sections  410  to  440  constituting the communication program  400  shown in FIG. 3.  
     [0062] The data communication section  510  constituting the electronic equipment  500  shown in FIG. 4 transmits and/or receives both data and a synchronizing signal (here a clock signal) for receiving of the data. That is, the data communication section  510  corresponds to a data receiving section when data receiving is performed, and the data communication section  510  corresponds to a data transmission section when data transmission is performed. The reference storage section  520  shown in FIG. 4 stores reference information representative of permissible minimum time width and permissible maximum time width of a predetermined section of a synchronizing signal for data receiving. The synchronizing signal monitor section  530  shown in FIG. 4 monitors whether a time width of a predetermined section of a synchronizing signal for data receiving is between the permissible minimum time width and the permissible maximum time width represented by the reference information stored in the reference storage section  520 . That is, the synchronizing signal monitor section  530  monitors a time width of a predetermined section of a clock signal or a synchronizing signal for data receiving. Monitoring objects are one or ones selected from among a rise time, a fall time, a time width of an H-level, a time width of an L-level, and a predetermined transmission period, of the clock signal. The communication result report section  540  shown in FIG. 4 reports a monitored result by the synchronizing signal monitor section  530  to the party of the communication through the data communication section  510 .  
     [0063]FIG. 5 is a flowchart useful for understanding processes of data communications to be performed in the electronic equipment shown in FIG. 4.  
     [0064] As shown in FIG. 5, the data communication performed in the electronic equipment  500  shown in FIG. 4 comprises three steps of a data communication step  61 , a synchronizing signal monitor step  62 , and a receipt result report step  63 . The data communication step  61  transmits and/or receives both data and a synchronizing signal (here a clock signal) for receiving of the data. That is, the data communication step  61  corresponds to a data receiving step when data receiving is performed, and the data communication step  61  corresponds to a data transmission step when data transmission is performed. The synchronizing signal monitor step  62  monitors whether a time width of a predetermined section of a synchronizing signal for data receiving is between the permissible minimum time width and the permissible maximum time width represented by the reference information stored in the reference storage section  520  shown in FIG. 5. That is, the synchronizing signal monitor step  62  monitors a time width of a predetermined section of a clock signal or a synchronizing signal for data receiving. Monitoring objects are one or ones selected from among a rise time, a fall time, a time width of an H-level, a time width of an L-level, and a predetermined transmission period, of the clock signal. Incidentally, it is acceptable that while the data communication step  61  is executed, the synchronizing signal monitor step  62  is simultaneously executed. The communication result report step  63  reports a monitored result by the synchronizing signal monitor step  62  to the party of the communication.  
     [0065] Next, there will be explained in detail the SCSI controller  119  provided on the personal computer  100  shown in FIG. 2.  
     [0066]FIG. 6 is a circuit diagram of a portion for performing an error detection in data transmission, of the SCSI controller provided on the personal computer shown in FIG. 2.  
     [0067] The SCSI controller  119  provided on the personal computer  100  shown in FIG. 2 is provided with a data strobe line  1190 . The SCSI controller  119  is further provided with a data line (not illustrated) for transmitting data in addition to the data strobe line  1190 . A portion of performing an error detection of data transmission, of the SCSI controller  119  comprises a rise detection circuit  1191 , a fall detection circuit  1192 , a “High” period detection circuit  1193 , a “Low” period detection circuit  1194 , and an operating frequency detection circuit  1195 .  
     [0068] When the personal computer  100  shown in FIG. 2 reads data stored in the magneto-optical disk loaded on the magneto-optical disk unit  200  shown in FIG. 2, the data stored in the magneto-optical disk is transmitted together with the data strobe signal from the magneto-optical disk unit  200  via the SCSI cable  300 . The data strobe signal is the clock signal generated in the magneto-optical disk unit  200 . A portion of performing of data transmission, of the SCSI controller  119  provided on the personal computer  100  receives the data stored in the magneto-optical disk in synchronism with the data strobe signal transmitted together with the data. The received data is fed to the data line (not illustrated), while the data strobe signal is fed to the data strobe line  1190 . On the other hand, when data of the personal computer  100  shown in FIG. 2 is written into the magneto-optical disk loaded on the magneto-optical disk unit  200  shown in FIG. 2, data to be written into the magneto-optical disk is transmitted together with the data strobe signal from the personal computer  100 . The SCSI controller  119  of the personal computer  100  further comprises a clock signal generator (not illustrated), that generates the data strobe signal. The data strobe signal thus generated is transmitted via the data strobe line  1190  to the portion of performing the data transmission, of the SCSI controller  119 . Data to be written into the magneto-optical disk is transmitted via the data line (not illustrated) to the portion of performing the data transmission. The portion of performing the data transmission, of the SCSI controller  119  provided on the personal computer  100  transmits the data to be written into the magneto-optical disk to the SCSI controller  216  of the magneto-optical disk unit  200  together with the data strobe signal.  
     [0069]FIG. 7( a ) is a view showing a transition of data in a data line wherein a series of data are sequentially transmitted, and FIG. 7( b ) is a view showing a data strobe signal.  
     [0070] In FIG. 7( a ) and FIG. 7( b ), horizontal directions of the figures are denoted as a time axis, and the time axis of FIG. 7( a ) is harmonized with the time axis of FIG.  7 ( b ). In FIG. 7( b ), a vertical direction of the figure is denoted as an axis representative of a voltage value.  
     [0071] In FIG. 7( a ), a parallel line indicates a section D, wherein individual data of a series of data in the data line is decided. In the event that the personal computer  100  shown in FIG. 2 is of the receiving side, the portion of performing the data transmission, of the SCSI controller  119  provided on the personal computer  100  triggers a rise of the data strobe signal shown in FIG. 7( b ) to receive individual data. On the other hand, in the event that the personal computer  100  is of the transmission side, the portion of performing the data transmission transmits the data together with the data strobe signal in such a manner that the rise of the data strobe signal is in synchronism with the decided section of the data.  
     [0072] Next, referring to FIG. 7( b ) there will be explained the detection circuits  1191  to  1195  shown in FIG. 6. The detection circuits  1191  to  1195  each detect a predetermined section of the data strobe signal in accordance with decisions of H-level and L-level of the data strobe signal by thresholds. The hard disk  130  of the personal computer  100  stores therein a threshold for deciding H-level and a threshold for deciding L-level of the data strobe signal. While it is acceptable that those thresholds are different in value from one another on each detection circuit, FIG. 7( b ) exemplarily shows that a threshold for H-level is 4.5V and a threshold for L-level is 1.5V on any detection circuits. The detection circuits  1191  to  1195  each determine a time width of a detected predetermined section using a clock signal higher in speed than the data strobe signal. The hard disk  130  of the personal computer  100  stores therein information for designating a detection circuit to be operated at the time of the data transmission. At the time of the data transmission, of those five detection circuits  1191  to  1195 , only the detection circuit designated by the information is operated. According to the present embodiment, it is assumed that at the time of the data transmission all the detection circuits are operated. The rise detection circuit  1191  shown in FIG. 6 receives from the hard disk  130  two thresholds of an H-level of threshold and an L-level of threshold, and measures a time width (a rise time Tr) since a value of the data strobe signal reaches the L-level of threshold in a rise section of a signal until the value reaches the H-level of threshold. The fall detection circuit  1192  also receives the two thresholds, and measures a time width (a fall time Tf) since a value of the data strobe signal lowers to the H-level of threshold in a fall section of the signal until the value lowers to the L-level of threshold. The “High” period detection circuit  1193  receives only the H-level of threshold of the two thresholds, and measures a time width (a time width Th of the H-level) since a value of the data strobe signal reaches the H-level of threshold in the rise section of the signal until the value lowers to the H-level of threshold in the fall section. The “Low” period detection circuit  1194  receives only the L-level of threshold of the two thresholds, and measures a time width (a time width Tl of the L-level) since a value of the data strobe signal lowers to the L-level of threshold in the fall section of the signal until the value reaches the H-level of threshold in the rise section. The operating frequency detection circuit  1195  receives only the L-level of threshold, and measures a time width Fh since a value of the data strobe signal reaches the L-level of threshold in the rise section of the signal until the value reaches again the L-level of threshold in the next rise section, that is, measures a period of the data strobe signal. Incidentally, any one is acceptable, as the operating frequency detection circuit  1195 , which measures a predetermined transmission period of the data strobe signal, for example, a period, and it is acceptable that any section of a signal wave of the data strobe signal is utilized for measurement. As the detection circuit, it is not restricted to the detection circuits  1191  to  1195 , any one is acceptable, as the detection circuit, which measures a time width of a predetermined section of the signal wave of the data strobe signal, and for example, it is acceptable that the detection circuit measures a time width Fl since a value of the data strobe signal reaches the L-level of threshold in the rise section of the signal until the value reaches the H-level of threshold in the next rise section.  
     [0073] From a standpoint that the more the time widths (Tr, etc.) measured by the detection circuits  1191  to  1195  are out of the time widths computed from the clock frequency of the data strobe signal, the more a reliability that contents of the data synchronized with the data strobe signal is exact is lowered, the hard disk  130  of the personal computer  100  records permissible limits on the time widths Tr, Tf, Th, Tl, and Fh measured by the detection circuits using the permissible minimum time width and the permissible maximum time width. The selected detection circuits derive from the hard disk  130  the permissible minimum time width and the permissible maximum time width on the time widths to be measured, and monitor whether the measured time widths are between the permissible maximum time width and the permissible maximum time width.  
     [0074] The detection circuits  1191  to  1195  can output their associated monitor results in form of detection signals, respectively. The hard disk  130  of the personal computer  100  stores therein information indicative of whether it causes the detection circuits to output the detection signals. The detection circuits  1191  to  1195  output or do not output the detection signals in accordance with the information. Here, it is assumed that the detection circuits  1191  to  1195  output the detection signals. In the event that the personal computer  100  is of the receiving side, the detection signal is transmitted to the transmission source of the received data. And in the event that the personal computer  100  is of the transmission side, the detection signal is transmitted to the transmission destination of the transmitted data. Thus, this way makes it possible for the party received the detection signal to decide whether data transmission is performed normally. That is, when the party received the detection signal indicative of that the time width is between the permissible minimum time width and the permissible maximum time width, it can be considered that the data transmission is performed normally. On the other hand, when the party received the detection signal indicative of that the time width is out of between the permissible minimum time width and the permissible maximum time width, it can be considered that the data transmission is not performed normally. Saving of the monitor result based on the detection signal into the hard disk  130  of the personal computer  100  makes it possible to confirm statistics information as to whether there is a possibility that transmission errors occurred in the past, and thereby confirming a quality of the transmission system.  
     [0075] Incidentally, while the hard disk  130  of the personal computer  100  records at the stage of forwarding of a factory thresholds of the detection circuits, values of the permissible minimum time width and the permissible maximum time width, information designating detection circuits to be operated, and information indicative of whether it causes the detection circuits to output the detection signals, it is permitted to alter those values and the contents of the information by operation of keyboard  103  and the mouse  104 .  
     [0076] The circuit of the portion of performing an error detection of data transmission shown in FIG. 6, of the SCSI controller  119  provided on the personal computer  100 , as mentioned above, is also provided on the portion of performing an error detection of data transmission, of the SCSI controller  216  provided on the magneto-optical disk unit  200 , shown in FIG. 2. In a similar fashion to that of the hard disk  130  of the hard disk drive of the personal computer  100  shown in FIG. 2, it is acceptable that the F-ROM  212  of the magneto-optical disk unit  200  also records various types of values and information beforehand. However, here, it is assumed that the F-ROM  212  does not record various types of values and information beforehand.  
     [0077] First, there will be explained a set up processing of recording those various types of values and information into the F-ROM  212  referring to FIG. 8.  
     [0078]FIG. 8 is a flowchart useful for understanding set up processing for the magneto-optical disk shown in FIG. 2, of the personal computer shown in FIG. 2 connected to the magneto-optical disk.  
     [0079] A set up processing program for executing a set up processing routine shown in FIG. 8 is installed in the hard disk  130  of the host equipment (here the personal computer  100  shown in FIG. 2), which is connected to the magneto-optical disk unit  200 . The set up processing routine shown in FIG. 8 is initiated when the set up processing program starts. The set up processing program is supplied via a portable type of disk or Internet and is installed in the hard disk.  
     [0080] First, a user designates on the personal computer  100  detection circuits to be operated at the time of data transmission from among the five detection circuits provided on the magneto-optical disk unit  200 . With respect to the designated detection circuit, the user designates on the personal computer  100  thresholds of the H-level and the L-level, and values of the permissible minimum time width and the permissible maximum time width. Further, the user selects on the personal computer  100  as to whether the detection circuit outputs the monitor result in form of a detection signal.  
     [0081] When the set up for those various types of values is performed, the personal computer  100  performs the set up processing for the magneto-optical disk unit  200  in accordance with the results of the set up for those various types of values.  
     [0082] Step S 51  performs set up of thresholds of H-level and L-level, and values of the permissible minimum time width and the permissible maximum time width. That is, the thresholds of H-level and L-level, and the values of the permissible minimum time width and the permissible maximum time width, which are set up on the personal computer  100 , are transmitted from the SCSI controller  119  of the personal computer  100  via the SCSI cable  300  to the SCSI controller  216  of the magneto-optical disk unit  200 .  
     [0083] Next, step S 51  sets up one or more detection circuits to be operated at the time of data transmission from among the five detection circuits provided on the magneto-optical disk unit  200 . That is, information representative of the designated detection circuits on the personal computer  100  is transmitted from the SCSI controller  119  of the personal computer  100  via the SCSI cable  300  to the SCSI controller  216  of the magneto-optical disk unit  200 , in a similar fashion to that of the above-mentioned values.  
     [0084] Next, step S 53  performs set up as to whether the detection circuit outputs the monitor result in form of a detection signal. That is, information indicative of whether the detection circuit outputs the monitor result in form of a detection signal is also transmitted utilizing the SCSI interface, in a similar fashion to that of the step S 52 .  
     [0085] The values and information transmitted in the above-mentioned steps are recorded onto the F-ROM  212  of the magneto-optical disk unit  200 .  
     [0086] When the set up of the step S 53  is completed, the set up processing routine is terminated.  
     [0087] With respect to transmissions of the various types of values and information from the personal computer  100  to the magneto-optical disk unit  200 , it is acceptable to utilize RS-232 interface as well as the SCSI interface. Or alternatively, in the event that the personal computer  100  and the magneto-optical disk unit  200  are each provided with an interface such as ATAPI (ATA Packet Interface), USB (Universal Serial Bus), and IEEE 1394, it is acceptable to utilize those interfaces.  
     [0088] Next, there will be explained data transmission in the magneto-optical disk unit  200  subjected to such a set up.  
     [0089] First, in conjunction with FIG. 9, there will be explained a case where the personal computer  100  (host) shown in FIG. 2 reads data recorded on the magneto-optical disk loaded onto the magneto-optical disk unit  200  shown in FIG. 2, that is, a case where the magneto-optical disk unit  200  receives a read command from the host. In this case, the magneto-optical disk unit  200  is of the transmission side.  
     [0090]FIG. 9 is a flowchart useful for understanding read command processing of the magneto-optical disk upon receipt of read command from the host.  
     [0091] The read command is transmitted from the personal computer  100  via the SCSI cable  300  to the SCSI controller  216  of the magneto-optical disk unit  200 . A read command processing routine shown in FIG. 9 starts whenever the magneto-optical disk unit  200  receives the read command.  
     [0092] In the read command processing, first, the ODC  214  shown in FIG. 2 reads data from the magneto-optical disk loaded on the MO mounting slot  201   a  shown in FIG. 1 in accordance with the transmitted read command (step S 61 ). The data read from the magneto-optical disk is transmitted from the ODC  214  to the portion of performing data transmission, of the SCSI controller  216  of the magneto-optical disk unit  200 . The SCSI controller  216  of the magneto-optical disk unit  200  is also provided with a clock signal generator in a similar fashion to that of the SCSI controller  119  of the personal computer  100  shown in FIG. 2. The clock signal generator generates the data strobe signal. The data strobe signal thus generated is also transmitted to the portion of performing the data transmission. Of the detection circuits of the magneto-optical disk unit  200 , the detection circuit designated to be operated at the time of data transmission derives various types of values from the F-ROM  212 , and measures time width of a predetermined section of a signal wave of a data strobe signal, just before the data strobe signal is fed to the portion of performing data transmission of the SCSI controller  216 , and decides whether the measured time width is between the derived permissible minimum time width and permissible maximum time width (step S 62 ). The F-ROM  212  of the magneto-optical disk unit  200  records information indicating that the detection circuits output their associated monitor results in form of detection signals. When the decision is made in the step S 62 , the detection circuit outputs the detection signal representative of the decision result. The outputted detection signal is transmitted to the personal computer  100  as well as the CPU  211  of the magneto-optical disk unit  200 . In the event that there is detected the detection signal indicating that the time width is within the permissible limit, it can be considered that a reliability of the data transmitted in synchronism with the data strobe signal is high, and thus the read command processing is normally terminated. On the other hand, in the event that there is detected the detection signal indicating that the time width is out of the permissible limit, the monitor result based on the detection signal is saved into the F-ROM  212  of the magneto-optical disk unit  200  (step S 63 ), and the read command processing is terminated. In this case, it is considered that a reliability of the data transmitted in synchronism with the data strobe signal is low, and thus it is preferable that the CPU  211  provided on the magneto-optical disk unit  200  causes ODC  214  to execute again the data read processing in the step S 61 , or alternatively it is preferable that the personal computer  100 , which received the detection signal, transmits again to the magneto-optical disk unit  200  the same content of read command as that of the read command previously transmitted.  
     [0093] Here, with respect to a case where the set up processing, which has been explained in conjunction with FIG. 8, is executed in form of an initial set up, and thereafter the read command processing, which has been explained in conjunction with FIG. 9, is executed in accordance with the initial set up, it will be more concretely explained.  
     [0094]FIG. 10 is a view showing an outline of a flow of processing from the set up processing explained referring to FIG. 8 to the read command processing explained referring to FIG. 9.  
     [0095] On the personal computer  100  shown in FIG. 2, as the circuit to be operated at the time of data transmission, of the five detection circuits provided on the magneto-optical disk unit  200 , only the rise detection circuit  1191  for measuring the rise time Tr is designated. As the threshold of H-level for the rise detection circuit  1191 , 4.5V is set up. And as the threshold of L-level, 1.25V is set up. Further, there are set up values of the permissible minimum time width and the permissible maximum time width for the time width measured by the rise detection circuit  1191 . Furthermore, it is selected that the monitor result by the detection circuit is outputted in form of a detection signal.  
     [0096] First, the personal computer  100  (“HOST” in FIG. 10) executes the set up processing shown in FIG. 8 for the magneto-optical disk unit  200  (“Drive” in FIG. 10). The F-ROM  212  of the magneto-optical disk unit  200  is in a state that various types of values and information as to the detection circuit are not yet recorded, and thus the set up processing offers the initial set up. The initial set up causes the F-ROM  212  of the magneto-optical disk unit  200  to record 4.5V as the threshold of H-level and 1.25V as the threshold of L-level, for the rise detection circuit  1191 . Further it is recorded that the values of the permissible minimum time width and the permissible maximum time width for the time width measured by the rise detection circuit  1191 , and the monitor result by the detection circuit are output in form of a detection signal.  
     [0097] Thus, after the initial set up is made, upon receipt of the read command from the personal computer  100 , the magneto-optical disk unit  200  executes the read command processing shown in FIG. 9. Here, there will be described in detail the detection processing for the rise time Tr of the read command processing in conjunction with FIG. 11 and FIG. 12.  
     [0098]FIG. 11 is a view showing an example of a signal waveform of a data strobe signal.  
     [0099] Upper FIG. 11, there is shown a data strobe signal. Two-dot chain line shows a waveform of the data strobe signal on a design. A solid line shows a distorted waveform. Here, there will be explained by way of example the distorted waveform shown by the solid line. In FIG. 11, below the data strobe signal, there is shown a reference clock signal, which is used when the rise time Tr of the data strobe signal. In FIG. 11, the horizontal direction of the figure denotes the time axis, and the vertical direction of the figure denotes the axis representative of voltage values. In FIG. 11, the time axis of the data strobe signal is harmonized with the time axis of the reference clock signal.  
     [0100] The rise detection circuit  1191  first decides whether the value of the data strobe signal reaches 1.25V whenever the reference clock signal shown in FIG. 11 rises. When it is decided that the value of the data strobe signal reaches 1.25V, the rise detection circuit  1191  starts the count of the reference clock signal. Subsequently, the rise detection circuit  1191  decides whether the value of the data strobe signal reaches 4.5V whenever the reference clock signal rises. Simultaneously, the rise detection circuit  1191  monitors whether the value of the data strobe signal goes down to 1.25V.  
     [0101] When it is decided that the value of the data strobe signal reaches 4.5V, the rise detection circuit  1191  terminates the count of the reference clock signal. As soon as the rise detection circuit  1191  terminates the count of the reference clock signal, the rise detection circuit  1191  computes the rise time Tr from the counted value of the reference clock signal, and decides whether the computed rise time Tr is between the permissible minimum time width and the permissible maximum time width. As to the distorted data strobe signal, which is indicated by the solid line, the rise time Tr measured by the rise detection circuit  1191  is longer than the permissible maximum time width. And thus, the rise detection circuit  1191  immediately outputs the detection signal indicative of that matter.  
     [0102] On the other hand, when the value of the data strobe signal goes down to 1.25V, the rise detection circuit  1191  clears the counted value of the reference clock signal without computing the rise time Tr, and immediately outputs the detection signal indicative of such a matter that the rise time is out of between the permissible minimum time width and the permissible maximum time width.  
     [0103]FIG. 12 is a view showing another example of a signal waveform of a data strobe signal.  
     [0104] The data strobe signal shown in FIG. 12 goes down to 1.25V before reaching 4.5V after reaching 1.25V once wing to an influence of reflection and the like. For this reason, the rise detection circuit  1191  outputs the detection signal indicative of such a matter that the rise time is out of between the permissible minimum time width and the permissible maximum time width, at the time when the value of the data strobe signal goes down to 1.25V (cf. the arrow in the figure).  
     [0105] Now returning to FIG. 10, the detection signal outputted from the rise detection circuit  1191  is transmitted to the personal computer  100 . When the personal computer  100  detects from the transmitted detection signal such a matter that the rise time Tr is out of the permissible range, the personal computer  100  executes a retry processing in which read command of the same content as that of the read command transmitted previously is transmitted again to the magneto-optical disk unit  200 .  
     [0106] In order to enhance the accuracy of detection of change of data contents owing to noises or the like, a user designates on the personal computer  100  one or more detection circuits from among four detection circuits excepting the already designated rising detection circuit  1191 , of the five detection circuits provided on the magneto-optical disk unit  200 . This designation makes it possible to perform a measurement of the time width by a newly designated detection circuit as well as the measurement of the rise time Tr by the already designated rising detection circuit  1191 . Incidentally, it is possible to designate another detection circuit instead of the already designated rising detection circuit  1191 .  
     [0107] Here, in conjunction with FIG. 13, there will be described a case where a user designates on the personal computer  100  the “High” period detection circuit  1193  for measuring the H-level of time width Th as well as the already designated rising detection circuit  1191 , and the user sets up the value of 4.75V as H-level of threshold for the “High” period detection circuit  1193  and also sets up values of the permissible minimum time width and the permissible maximum time width for the H-level of time width Th.  
     [0108]FIG. 13 is a view showing an outline of a flow of processing subsequent to the flow of the processing explained referring to FIG. 10.  
     [0109] When a designation of the new detection circuit is performed, the set up processing shown in FIG. 8 is executed again as processing for adding the new set up condition to the set up condition for the initial set up. Here, onto the F-ROM  212  of the magneto-optical disk unit  200 , the value of 4.75V as H-level of threshold for the “High” period detection circuit  1193  is added, and values of the permissible minimum time width and the permissible maximum time width for the “High” period detection circuit  1193  are added, too.  
     [0110] Thus, after the new set up condition is added to the set up condition for the initial set up, transmission of the read command from the personal computer  100  causes the magneto-optical disk unit  200  to execute the read command processing shown in FIG. 10, so that both the detection signal representative of the monitor result by the rise detection circuit  1191  and the detection signal representative of the monitor result by the “High” period detection circuit  1193  are transmitted to the personal computer  100 .  
     [0111] It is effective that a combination of the selected detection circuit is decided in view of the balance between a degree of reliability of data contents and a processing load. For example, it is acceptable that the rise detection circuit  1191  and the operating frequency detection circuit  1195  are used alternately, or alternatively those two circuits are simultaneously used.  
     [0112] Next, in conjunction with FIG. 14, there will be explained a case where data of the personal computer  100  (host) shown in FIG. 2 is written into the magneto-optical disk loaded onto the magneto-optical disk unit  200  shown in FIG. 2, that is, a case where the magneto-optical disk unit  200  receives a write command from the host. In this case, the magneto-optical disk unit  200  is of the receiving side.  
     [0113]FIG. 14 is a flowchart useful for understanding write command processing of the magneto-optical disk upon receipt of the write command from the host.  
     [0114] In a similar fashion to that of the read command, the write command is transmitted from the personal computer  100  via the SCSI cable  300  to the portion of executing data transmission of the SCSI controller  216  of the magneto-optical disk unit  200 . Write data into the magneto-optical disk and the data strobe signal are also transmitted together with the write command via the SCSI cable  300  to the portion of executing data transmission of the SCSI controller  216 . The transmitted write data is fed to a data line (not illustrated) and is transmitted via the data line to the ODC  214  shown in FIG. 2. On the other hand, the data strobe signal, which is transmitted together with the write data, is fed to the data strobe line  1190 . Of the detection circuits of the SCSI controller  216  of the magneto-optical disk unit  200 , the detection circuit designated to be operated at the time of data transmission derives various types of values from the F-ROM  212 , and measures time width of a predetermined section of a signal wave of a data strobe signal, just after the data strobe signal is fed to the data strobe line  1190 , and decides whether the measured time width is between the derived permissible minimum time width and permissible maximum time width (step S 111 ). As an execution timing of the step S 111  is compared with execution timing of the parity check and CRC by the ODC  214  for the write data received in synchronism with the data strobe signal subjected to the decision in the step S 111 , the execution timing of the step S 111  is faster. The F-ROM  212  of the magneto-optical disk unit  200  records information indicating that the detection circuits should output their associated monitor results in form of detection signals, respectively. When the decision is made in the step S 111 , the detection circuits output the detection signals each representative of the associated decision result. The outputted detection signals are transmitted to the CPU  211  of the magneto-optical disk unit  200  and the personal computer  100  as well. In the event that there is outputted the detection signal indicative of such a matter that the time width is within the permissible range, it is regarded that reliability of the received write data is high, and the ODC  214  shown in FIG. 2 writes the write data into the magneto-optical disk loaded onto the MO mounting slot  201   a  shown in FIG. 1 in accordance with the transmitted write command (step S 112 ), and the write command processing is normally terminated. On the other hand, in the event that there is outputted the detection signal indicative of such a matter that the time width is out of the permissible range, the monitor result based on the detection signal is saved into the F-ROM  212  of the magneto-optical disk unit  200  (step S 113 ), and the write command processing is terminated. In this case, reliability of the received write data is regarded low, and it is preferable that the CPU  211  of the magneto-optical disk unit  200  executes a host retry processing of requesting retransmission of the write data to the personal computer  100 . It is acceptable that the above-mentioned statistics information is stored in a non-volatile storage of the magneto-optical disk and is utilized for confirmation of quality of transmission.  
     [0115] While the above-mentioned embodiments are concerned with a combination of the personal computer and the magneto-optical disk unit, the present invention can be widely adopted, not restricted to the storage such as the disk units, in electronic equipment provided with a parallel interface different from SCSI, for example, a computer system, an external storage, a communication apparatus, a transmission apparatus, a receiving apparatus, a transfer apparatus, an interface apparatus, transmission and receiving apparatus, etc., and also in electronic equipment provided with a serial interface.  
     [0116] As mentioned above, according to the present invention, it is possible to detect changes of contents of data due to noises and the like, independently of the parity check and the CRC, and request retransmission of the data promptly by reporting it to the data transmission source, and thereby preventing processing of erroneous data from being performed at the receiving end. Thus, according to the present invention, it is possible to possible to improve reliability of data transmission.  
     [0117] Although the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by those embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and sprit of the present invention.