JP3770247B2 - Data transmission / reception method, data receiving apparatus, and asynchronous communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data transmission / reception method. , De Data receiver Asynchronous communication system In particular, Packet data containing multiple bytes is sent Data transmission / reception method , De Data receiver Asynchronous communication system About.
[0002]
[Prior art]
In transmitting and receiving data between a plurality of computers (a plurality of control circuits), the asynchronous communication system does not need to define a communication procedure, and can be said to be a communication system that is easier to communicate than a synchronous communication system.
[0003]
However, in the conventional asynchronous communication system, when communication is interrupted, communication fails, and it is necessary to reset the transmission side and reception side computers.
[0004]
Regarding data transmission / reception between a plurality of computers in an asynchronous communication system, for example, Patent Document 1 discloses a technique for performing error check such as parity check on received data one byte at a time. Document 2 discloses a technique for dividing packet data into n-bit words, adding data called transmission data length for each word, and determining whether received data is normal based on the transmission data length. Has been.
[0005]
[Patent Document 1]
JP-A-9-102777
[0006]
[Patent Document 2]
JP-A-6-95901
[0007]
[Problems to be solved by the invention]
As described above, in the past, although it was possible to determine whether or not data was received normally, there was a communication failure that occurred when all data that should have been received due to interruption could not be received. It was difficult to avoid.
[0008]
The present invention has been conceived in view of such a situation, and an object of the present invention is to provide a data transmission / reception method capable of avoiding communication failure due to interruption in an asynchronous communication system. , De Data receiver Asynchronous communication system Is to provide.
[0009]
[Means for Solving the Problems]
A data transmission / reception method according to an aspect of the present invention is directed to a data transmission / reception method for transmission / reception of packet data including a plurality of bytes from a transmission unit to a reception unit in an asynchronous communication system. In the data transmission / reception method, a plurality of bytes constituting the same packet data are transmitted to the transmission unit, and transmission of the next byte is finished before a predetermined time elapses after transmission of the previous byte. Let's send The second The time from the end of transmission of the last byte of the first packet data to the end of transmission of the header byte of the second packet data to be transmitted next to the first packet data is equal to or longer than the predetermined time. To transmit the header byte of the second packet data, When the transmission of the first packet data is interrupted and the transmission of the second packet data is started, the second packet is transmitted after the transmission of the bytes included in the first packet data is finished. The header bytes of the second packet data are transmitted so that the time until transmission of the header bytes of data is equal to or longer than the predetermined time, The receiving unit is in a state where the receiving unit is receiving a header byte of certain packet data, has not yet received the final byte of the certain packet data, and the certain packet If reception of a byte next to the certain byte cannot be performed before the predetermined time has elapsed since the reception of a certain byte constituting the data, the certain packet data received so far is configured. Byte data to be discarded is discarded, the reception of the certain packet data is terminated, and the reception of the next packet data is waited. The predetermined time is set to 10 milliseconds or more and 100 milliseconds or less. It is characterized by that.
[0010]
A data transmission / reception method according to another aspect of the present invention is directed to a data transmission / reception method for transmission / reception of packet data including a plurality of bytes from a transmission unit to a reception unit in an asynchronous communication system. In the data transmission / reception method, a plurality of bytes constituting the same packet data are transmitted to the transmission unit so that transmission of the next byte is completed before a predetermined time elapses after transmission of the previous byte is completed. To send The second The time from the end of transmission of the last byte of the first packet data to the end of transmission of the header byte of the second packet data to be transmitted next to the first packet data is equal to or longer than the predetermined time. To transmit the header byte of the second packet data, When the transmission of the first packet data is interrupted and the transmission of the second packet data is started, the second packet is transmitted after the transmission of the bytes included in the first packet data is finished. The header bytes of the second packet data are transmitted so that the time until transmission of the header bytes of data is equal to or longer than the predetermined time, The receiving unit is in a state where the receiving unit is receiving a header byte of certain packet data, has not yet received the final byte of the certain packet data, and the certain packet If reception of the next byte of the certain byte cannot be performed before the predetermined time has elapsed since the reception of a certain byte constituting the data, the reception of the certain packet data is terminated. And waiting for reception of the next packet data.
[0011]
In the data transmission / reception method of the present invention, it is preferable that when the reception unit terminates reception of the certain packet data, byte data constituting the certain packet data received so far is discarded.
[0012]
In the data transmitting / receiving method of the present invention, it is preferable that the predetermined time is 10 milliseconds or more and 100 milliseconds or less.
[0014]
The data receiving apparatus according to the present invention is intended for a data receiving apparatus that receives packet data including a plurality of bytes transmitted from a predetermined transmission unit in an asynchronous communication system. The predetermined transmission unit transmits a plurality of bytes constituting the same packet data so that the transmission of the next byte is completed before a predetermined time elapses after the transmission of the previous byte is completed. The second The time from the end of transmission of the last byte of the first packet data to the end of transmission of the header byte of the second packet data to be transmitted next to the first packet data is equal to or longer than the predetermined time. To the header byte of the second packet data, When the transmission of the first packet data is interrupted and the transmission of the second packet data is started, the second packet is transmitted after the transmission of the bytes included in the first packet data is finished. Transmitting the header byte of the second packet data so that the time until transmission of the header byte of data is equal to or longer than the predetermined time, The data receiving apparatus is in a state where the data receiving apparatus is receiving a header byte of a certain packet data and has not yet received a final byte of the certain packet data. The first determination means and the first determination means are in a state in which the data receiving apparatus is receiving a header byte of a certain packet data, and the last byte of the certain packet data. Is determined to be in a state in which reception of a certain byte constituting the certain packet data is not completed and reception of the next byte after the certain byte is not completed. The second determination means for determining whether or not the above has continued and the state where the second determination means has not finished receiving the next byte of the certain byte has continued for the predetermined time or more. A reception end control means for ending the reception of the certain packet data when the determination is made, and the reception end control means It is characterized by waiting for reception of packet data.
The data receiving apparatus according to the present invention further includes a buffer memory for temporarily storing data received from the predetermined transmission unit, and the reception end control means ends the reception of the certain packet data. It is preferable that the certain packet data stored in the buffer memory is discarded.
An asynchronous communication system according to the present invention is directed to an asynchronous communication system including a transmission unit and a reception unit, and packet data including a plurality of bytes is transmitted from the transmission unit to the reception unit. In the asynchronous communication system, a plurality of bytes constituting the same packet data are transmitted to the transmission unit, and transmission of the next byte ends before a predetermined time elapses after transmission of the previous byte ends. A first transmission control unit, and a second packet data header to be transmitted next to the first packet data after the transmission of the last byte of the first packet data to the transmission unit is completed. A second transmission control unit that causes the header bytes of the second packet data to be transmitted so that the time until the transmission of bytes is equal to or longer than the predetermined time; When the transmission unit suspends transmission of the first packet data and starts transmission of the second packet data, the second packet data is transmitted after the transmission of bytes included in the first packet data ends. A third transmission control unit that causes the header bytes of the second packet data to be transmitted so that the time until the transmission of the header bytes of the packet data is equal to or longer than the predetermined time; The receiving unit is in a state where the receiving unit is receiving a header byte of certain packet data, has not yet received the final byte of the certain packet data, and the certain packet If reception of the next byte of the certain byte cannot be performed before the predetermined time has elapsed since the reception of a certain byte constituting the data, the reception of the certain packet data is terminated. And a reception control unit for waiting for reception of the next packet data.
In the asynchronous communication system according to the present invention, the reception unit includes a buffer memory that temporarily stores data received from a predetermined transmission unit, and the reception control unit receives the packet data. It is preferable to discard the certain packet data stored in the buffer memory when it is terminated.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 is a block diagram showing a DVD (Digital Versatile Disk) reproducing apparatus according to an embodiment of the present invention. Referring to FIG. 1, a DVD playback apparatus 1 includes motors 3 to 5, a motor driver 6, an optical unit 7, a head amplifier 8, a front end 9, a back end 10, an audio converter 31, a video driver 32, and a front panel key 33. A receiver 34 and a remote controller (hereinafter abbreviated as a remote controller) 35.
[0017]
The motors 3 to 5 are various motors for driving the disk 2 in order to reproduce information from the disk 2. The motor driver 6 controls the operation of the motors 3 to 5. The optical unit 7 includes a reproducing head that scans the disk 2 to read information (audio information or video information) and outputs a signal. The head amplifier 8 amplifies the signal read from the optical unit 7. The front end 9 controls the motor driver 6 and digitally processes the signal output from the head amplifier 8. The back end 10 decodes the signal output from the front end 9. The audio converter 31 receives an audio signal decoded and output from the back end 10, converts the audio signal into an analog signal for driving an audio output system such as a speaker, and outputs the analog signal. The video driver 32 receives a video signal based on video information decoded and output from the back end 10 and outputs the video signal to an image of a monitor such as a CRT (Cathode Ray Tube) display or LCD (Liquid Crystal Display). Convert to a signal for screen display on the system and output. The front panel key 33, the receiver 34, and the remote controller 35 are operated by the user in order to give information to the DVD playback apparatus 1 from the outside.
[0018]
The types of the disc 2 include a disc (for example, a CD (Compact Disc)) in which information to be reproduced (and recorded) is only audio information, and information to be reproduced (and recorded) is audio information and video information. A certain disk (for example, DVD) is included.
[0019]
When operated by the user, the remote controller 35 transfers an operation instruction signal as an infrared signal, and the receiver 34 receives the infrared signal. The receiver 34 converts the received infrared signal into a signal format that can be processed by the back end 10 and outputs the signal format.
[0020]
The front end 9 is output by a serial communication processing unit 11 that performs processing such as channel selection during communication with the back end 10, an amplifier 13 that amplifies and outputs a signal output from the head amplifier 8, and an amplifier 13. The signal processing unit 14 for performing predetermined digital signal processing and error correction processing, the transmission data buffer memory 16 for temporarily storing data to be sent to the back end 10, and the back end 10 are transmitted. A transmission data counter 17 for counting the number of data is included. The front end 9 includes a CPU (Central Processing Unit) 15 that controls the operation of various elements included in the front end 9. Further, the front end 9 includes a RAM (Random Access Memory) 15A and a ROM (Read Only Memory) 15B used for control processing of the CPU 15.
[0021]
The back end 10 receives the signal processed by the signal processing unit 14, decodes and outputs the AV (Audio Visual) decoder 18, the control unit 20 that controls the output of the signal to the video driver 32, the front end 9, A serial communication processing unit 21 that performs processing such as channel selection during communication, a timer 22 that measures time T1, which will be described later, a received data buffer memory 23 that temporarily stores data received from the front end 9, and The reception data number counter 24 counts the number of data received from the front end 9. Further, the back end 10 includes a CPU 19 that controls operations of various elements included in the back end 10. Further, the back end 10 includes a RAM 19A and a ROM 19B used for the control process of the CPU 19. Further, the control unit 20 has an OSD (On Screen Display) for outputting digital information to a screen, which is not shown.
[0022]
When the disc 2 is a DVD, in the DVD reproducing apparatus 1, a signal read from the DVD by the optical unit 7 is digital signal processed by the front end 9 via the head amplifier 8 and output to the back end 10. At this time, the back end 10 decodes the audio signal and the video signal in the given digital signal by the AV decoder 18 in a predetermined procedure. The decoded audio signal is converted through the audio converter 31 and output through an audio output system such as a speaker (not shown). The decoded video signal passes through the control unit 20 and is then supplied to the video driver. The screen is output as an image on a monitor (not shown) 32.
[0023]
On the other hand, when the disc 2 is a CD, in the DVD playback apparatus 1, the audio signal read by the optical unit 7 and amplified by the head amplifier 8 is digital-signal processed by the front end 9 and back end 10 And is output from a speaker or the like via the audio converter 31.
[0024]
FIG. 2 is a timing chart of data transmission in the front end 9 when data communication is performed between the front end 9 and the back end 10. FIG. 2A shows a state in which data of packet A is normally transmitted, and then data of packet B is transmitted. FIG. 2B shows a state in which data of packet D is transmitted after transmission of data of packet C is interrupted.
[0025]
First, referring to FIG. 2A, packet data of packet A is composed of header byte 100, bytes 101 to 104, and last byte 105, and is transmitted in order. Thereafter, the header byte 200 and the byte 201 of the packet B are transmitted in order.
[0026]
Next, referring to FIG. 2B, the header byte 300 of the packet C is transmitted, and after the bytes 301 and 302 of the packet C are sequentially transmitted, the packet C is transmitted without transmitting the final byte. Then, the header byte 400, bytes 401 to 403, and the last byte 404 are sequentially transmitted as data of the packet D.
[0027]
In the same packet, the front end 9 transmits data so that the transmission of the next byte is completed in less than time T1 after the previous byte is transmitted. That is, for example, the time from the end of transmission of the header byte 100 to the end of transmission of the byte 101, the time from the end of transmission of the byte 101 to the end of transmission of the byte 102, and the header byte 300 The time from the end of the transmission of the byte 301 to the end of the transmission of the byte 301 is less than the time T1.
[0028]
Further, when the front end 9 transmits the data of the next packet after transmitting the data of a certain packet, the front end 9 completes the transmission of the last byte of the certain packet and then the header byte of the next packet. The data is transmitted so that the time until the end of transmission is equal to or greater than time T1. That is, for example, the time from the end of transmission of the last byte 105 to the end of transmission of the header byte 200 and the time from the end of transmission of the byte 302 to the end of transmission of the header byte 400 are: It is set as time T1 or more.
[0029]
Next, the reception process executed by the CPU 19 of the back end 10 will be described with reference to FIG. 3 which is a flowchart of the reception process.
[0030]
Referring to FIG. 3, when data is transmitted from front end 9, CPU 19 first receives the first byte (header byte) of the transmitted data in step (hereinafter, step is omitted) S1. To do.
[0031]
Next, in S2, the CPU 19 determines whether or not the back end 10 is receiving packet data. Note that the state in which the back end 10 is receiving packet data refers to the state from the reception of the header byte for the packet data from the front end 9 to the reception of the final byte, which will be described in detail later. This is a state in which the setting indicating that the reception is being performed is made in S7, and the reception completion state is not set in S11 described later. In addition, the state where the back end 10 is not receiving packet data is a state where the setting indicating that the packet is being received is not set in S7 which will be described later, or the setting indicating that the packet is being received in S7 which will be described later. This is a state in which the reception completion state is set in S11 described later.
[0032]
If the CPU 19 determines in S2 that the packet data is being received, the process proceeds to S4. If the CPU 19 determines that the packet data is not being received, the process proceeds to S3.
[0033]
In S3, the CPU 19 stops the timing operation of the timer 22, and advances the process to S5.
[0034]
In S4, after resetting the timer 22, the CPU 19 causes the timer 22 to start a time measuring operation, and advances the process to S5.
[0035]
In S <b> 5, the CPU 19 determines whether or not reception of the currently received byte (header byte 100, bytes 101 to 104, last byte 105, etc.) has been completed. If it is determined that the reception has been completed, the process proceeds to S6. If it is determined that the reception has not been completed, the process proceeds to S9.
[0036]
In S6, the CPU 19 stores the byte data determined to have been received in S5 in the received data buffer memory 23, and in S7, sets that the back end 10 is receiving packet data. , The process proceeds to S8. As a specific process for setting that packet data is being received, for example, a process of setting a flag can be cited.
[0037]
In S8, the CPU 19 determines whether or not reception of one packet has been completed for the currently received packet data. If it is determined that the reception has been completed, the process proceeds to S11. If it is determined that the reception has not been completed, the process returns to S2. A specific example of the process for determining whether or not the reception is completed includes a process for determining whether or not the last byte (EDC (Error Detecting Code) byte) has been received.
[0038]
On the other hand, in S9, the CPU 19 determines whether or not the timer 22 has timed out. If it is determined that the timer 22 has not yet occurred, the process returns to S5, and if it is determined that it has occurred, the process proceeds to S10. In S10, the CPU 19 discards the data recorded in the received data buffer memory 23 and returns the process to S1.
[0039]
In S11, the reception completion state of packet data is set, and the process proceeds to S12. A specific example of the process for setting the reception completion state includes a process of resetting the flag when the flag is set in S7.
[0040]
In S12, the CPU 19 moves the data recorded in the received data buffer memory 23 to the RAM 19A and saves it.
[0041]
In S <b> 13, the CPU 19 executes a process according to the received data, and then enters a standby state waiting for transmission of data from the front end 9. If data is transmitted from the front end after entering this standby state, the process is executed again from S1.
[0042]
In the reception process described above, the timer 22 is reset every time one byte is received by executing the processes of S2 and S4 through the processes of S5 to S8. If the timer 22 times out before receiving 1 byte (YES in S9), the data being received is discarded (S10), and the process returns to S1 to wait for the next data transmission. It becomes a state. Here, the characteristics of the reception processing of this embodiment will be described with reference to FIG. FIG. 4 is a timing chart of data reception corresponding to the data transmission shown in FIG. FIG. 4 shows a state in which the back end 10 receives the header byte 300, the bytes 301 and 302, the header byte 400, the bytes 401 to 403, and the final byte 404 transmitted from the front end 9 in order.
[0043]
In the reception processing of the present embodiment, as shown in FIG. 4, after the byte 302 transmitted from the front end 9 is received, the back end 10 detects completion of reception of the next byte for a time T1 or more. If not, the data stored in the received data buffer memory 23 at that time is discarded, and the back end 10 is ready to receive the next packet data.
[0044]
The time T1 in the present embodiment described above is, for example, 10 to 100 msec (milliseconds) so that the back end 10 can reliably recognize the interruption of communication and does not unnecessarily increase the communication time. Is preferred. In an actual system, it can be considered that there is no problem even if the measurement performance of the timer 22 and the processing capability of the front end 9 are taken into account, or 10 msec.
[0045]
Further, the data transmission mode in the front end 9 as described with reference to FIG. 2 in the present embodiment is achieved by the control of each element of the front end 9 that is executed by the CPU 15 according to the program recorded in the ROM 15B. . In addition, the reception process in the back end 10 as described with reference to FIG. 3 is executed by the CPU 19 according to the program recorded in the ROM 19B.
[0046]
In the present embodiment described above, the data reproducing apparatus of the present invention is configured by the DVD reproducing apparatus 1 including the front end 9. Further, in the present embodiment described above, the data receiving apparatus of the present invention is configured by the DVD reproducing apparatus 1 including the back end 10. Note that examples of the data transmission device and the data reception device are not limited thereto. For example, when the DVD playback device 1 is tested using an external device such as a personal computer, the present invention can be applied with the personal computer as the data transmission device of the present invention and the DVD playback device 1 as the data reception device. it can.
[0047]
Further, the program as recorded in the ROMs 15B and 19B as described above may be recorded on a recording medium integrally formed with the data transmitting device or the data receiving device, or the data transmitting device or the data receiving device. May be recorded on a recording medium configured to be detachable from the recording medium.
[0048]
Each embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0049]
【The invention's effect】
According to the present invention, in an asynchronous communication system, the side that receives packet data must be able to receive the next byte after the certain byte even after a predetermined time has elapsed after receiving a certain byte other than the last byte. Thus, the reception of the packet data received at that time can be terminated. That is, when the transmission side transmits the next packet data, the reception side can receive the next packet data without being reset. As a result, even if the data communication is interrupted in the asynchronous communication system, the data communication can be resumed without communication failure.
[0050]
Further, according to the present invention, with respect to packet data that has been received before receiving the final byte on the receiving side, the byte data of the packet data is discarded, so that the burden on the receiving side can be reduced. .
[0051]
In addition, by setting the above-described predetermined time in the present invention to 10 to 100 msec, it is possible for the receiving side to reliably recognize the interruption of communication as described above, and to avoid an unnecessarily long communication time.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a DVD playback apparatus according to an embodiment of the present invention.
FIG. 2 is a timing chart of data transmission at the front end when data communication is performed between the front end and the back end in the DVD playback apparatus of FIG. 1;
FIG. 3 is a flowchart of a reception process executed by a back-end CPU of the DVD playback apparatus in FIG. 1;
FIG. 4 is a timing chart of data reception corresponding to the data transmission shown in FIG.
[Explanation of symbols]
1 DVD player, 2 discs, 9 front end, 10 back end, 11, 21 serial communication processing unit, 15, 19 CPU, 15A, 19A RAM, 15A, 15B ROM, 20 control unit, 22 timer, 23 for received data Buffer memory.

Claims (8)

A data transmission / reception method for transmission / reception of packet data including a plurality of bytes from a transmission unit to a reception unit in an asynchronous communication system,
In the transmitter,
A plurality of bytes constituting the same packet data are transmitted so that the transmission of the next byte is completed before a predetermined time elapses after the transmission of the previous byte ends .
The time from the end of transmission of the last byte of the first packet data to the end of transmission of the header byte of the second packet data to be transmitted next to the first packet data is equal to or longer than the predetermined time. And sending the header byte of the second packet data, and
When the transmission of the first packet data is interrupted and the transmission of the second packet data is started, the transmission of the second packet data is completed after the transmission of the bytes included in the first packet data is completed. Transmitting the header bytes of the second packet data so that the time until the transmission of the header bytes is over the predetermined time,
The receiving unit is in a state where the receiving unit is receiving a header byte of certain packet data, has not yet received the final byte of the certain packet data, and the certain packet If reception of a byte next to the certain byte cannot be performed before the predetermined time has elapsed since the reception of a certain byte constituting the data, the certain packet data received so far is configured. The byte data to be discarded, the reception of the packet data is terminated, and the reception of the next packet data is waited.
The data transmission / reception method, wherein the predetermined time is 10 milliseconds or more and 100 milliseconds or less. A data transmission / reception method for transmission / reception of packet data including a plurality of bytes from a transmission unit to a reception unit in an asynchronous communication system,
In the transmitter,
A plurality of bytes constituting the same packet data are transmitted so that the transmission of the next byte is completed before a predetermined time elapses after the transmission of the previous byte ends .
The time from the end of transmission of the last byte of the first packet data to the end of transmission of the header byte of the second packet data to be transmitted next to the first packet data is equal to or longer than the predetermined time. And sending the header byte of the second packet data, and
When the transmission of the first packet data is interrupted and the transmission of the second packet data is started, the transmission of the second packet data is completed after the transmission of the bytes included in the first packet data is completed. Transmitting the header bytes of the second packet data so that the time until the transmission of the header bytes is over the predetermined time,
The receiving unit is in a state where the receiving unit is receiving a header byte of certain packet data, has not yet received the final byte of the certain packet data, and the certain packet If reception of the next byte of the certain byte cannot be performed before the predetermined time has elapsed since the reception of a certain byte constituting the data, the reception of the certain packet data is terminated. A data transmission / reception method for waiting for reception of the next packet data.   3. The data transmission / reception method according to claim 2, wherein when the reception unit ends the reception of the certain packet data, the reception unit discards the byte data constituting the certain packet data received so far.   The data transmission / reception method according to claim 2 or 3, wherein the predetermined time is 10 milliseconds or more and 100 milliseconds or less. In an asynchronous communication system, a data reception device that receives packet data including a plurality of bytes transmitted from a predetermined transmission unit,
The predetermined transmitter is
Transmit multiple bytes that make up the same packet data so that the transmission of the next byte is completed before the predetermined time elapses after the transmission of the previous byte ends .
The time from the end of transmission of the last byte of the first packet data to the end of transmission of the header byte of the second packet data to be transmitted next to the first packet data is equal to or longer than the predetermined time. Transmitting the header byte of the second packet data, and
When the transmission of the first packet data is interrupted and the transmission of the second packet data is started, the transmission of the second packet data is completed after the transmission of the bytes included in the first packet data is completed. Transmitting the header bytes of the second packet data so that the time until the transmission of the header bytes is over the predetermined time,
First determining means for determining that the data receiving apparatus is in a state of receiving a header byte of a certain packet data and has not yet received a final byte of the certain packet data. When,
The first determining means is in a state where the data receiving device is receiving a header byte of a certain packet data and has not yet received a final byte of the certain packet data. When the determination is made, it is determined whether or not a state in which reception of a byte subsequent to the certain byte has not been completed since reception of a certain byte constituting the certain packet data has continued for the predetermined time or more. 2 judgment means;
A reception end control for ending the reception of the certain packet data when the second determination means determines that the state where the reception of the next byte of the certain byte has not been completed has continued for the predetermined time or more; Means,
The data reception apparatus, wherein the reception end control means causes the data reception apparatus to wait for reception of the next packet data after completing the reception of the certain packet data. A buffer memory for temporarily storing data received from the predetermined transmitter;
6. The data receiving apparatus according to claim 5, wherein the reception end control means discards the certain packet data stored in the buffer memory when the reception of the certain packet data is terminated. An asynchronous communication system including a transmission unit and a reception unit, wherein packet data including a plurality of bytes is transmitted from the transmission unit to the reception unit;
1st transmission which makes the said transmission part transmit the some byte which comprises the same packet data so that transmission of the following byte may be completed before predetermined time passes after transmission of the previous byte is completed. A control unit;
The time until the transmission unit finishes transmitting the header byte of the second packet data to be transmitted next to the first packet data after the transmission of the last byte of the first packet data to the transmission unit is the predetermined time. A second transmission control unit that causes the header bytes of the second packet data to be transmitted so as to be equal to or longer than the time;
When the transmission unit suspends transmission of the first packet data and starts transmission of the second packet data, the second packet data is transmitted after the transmission of bytes included in the first packet data ends. A third transmission control unit that causes the header bytes of the second packet data to be transmitted so that the time until the transmission of the header bytes of the packet data is equal to or longer than the predetermined time;
The receiving unit is in a state where the receiving unit is receiving a header byte of certain packet data, has not yet received the final byte of the certain packet data, and the certain packet If reception of the next byte of the certain byte cannot be performed before the predetermined time has elapsed since the reception of a certain byte constituting the data, the reception of the certain packet data is terminated. And an asynchronous communication system including a reception control unit that waits for reception of the next packet data. The reception unit includes a buffer memory that temporarily stores data received from a predetermined transmission unit,
The asynchronous communication system according to claim 7, wherein the reception control unit discards the certain packet data stored in the buffer memory when the reception of the certain packet data is terminated.

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