Data communication circuit and data communication method

Abstract

A data communication circuit according to one aspect of the present disclosure performs data communication between a first data processing unit and a second data processing unit. The data communication circuit comprises: a first transmission path for transmitting data from the first data processing unit to the second data processing unit by a CDR method; a second transmission path for transmitting data from the second data processing unit to the first data processing unit by the CDR method; and a control unit for controlling data communication. The control unit performs control such that: when data communication is performed via the first transmission path, notification data indicating the reception state of the second data processing unit is transmitted from the second data processing unit to the first data processing unit via the second transmission path; and when data communication is performed via the second transmission path, notification data indicating the reception state of the first data processing unit is transmitted from the first data processing unit to the second data processing unit via the first transmission path.

Description

Data communication circuit and data communication method

[0001] The present disclosure relates to a data communication circuit and a data communication method.

[0002] For example, as a method for performing high-speed data communication between LSIs, a clock and data recovery (CDR) method is used. The CDR method is a method of receiving a signal on a transmission line in which a clock is superimposed on data and separating the clock and data, and is used in USB (Universal Serial Bus), HDMI (registered trademark) (High-Definition Multimedia Interface), and the like.

[0003] In the CDR method, in an initial operation (training operation) in advance, a training pattern is sent from a transmission unit, and a reception unit receives the training pattern and adjusts the timing for receiving data. Thereafter, the transmission unit transmits data at the same timing as the training operation, and the reception unit receives data on the premise of the adjusted timing. As long as the transmission unit continues to transmit data at the same timing as the training operation, the reception unit can correctly receive the data of the transmission unit. This is called a locked state.

[0004] For some reason, for example, due to noise or the like, the timing transmitted from the transmission unit may deviate from the training operation. When communicating data at high speed, this timing deviation means that the reception unit cannot immediately receive the data. That is, the lock is released. When the lock is released, it is necessary for the transmission unit to perform some recovery process, for example, to retry training.

[0005] However, the transmission unit has no means of knowing that the lock has been released unless it is notified that the data has not been received from the reception unit. Therefore, in a data communication circuit that performs data communication by the CDR method, it is common to provide a feedback line for notifying the transmission unit from the reception unit that the lock has been released (see Non-Patent Document 1 and Non-Patent Document 2).

[0006] "V-by-One HS Standard", [online], THine Electronics Inc., [Retrieved November 28, 2024], Internet <URL: https: / / www.thine.co.jp / files / user / img / corporate / VBOSTD-V1P52-0000_Abridged%2BEdition.pdf> "Intel Aria 10 Transceiver PHY User Guide", [online], Intel Corporation, [Retrieved November 28, 2024], Internet <URL: https: / / www.intel.co.jp / jp / content / www / jp / ja / docs / programmable / 683617 / current / lock-to-data-mode. html>

[0007] The aforementioned return lines are required for each data communication circuit, thus increasing the number of signal lines needed for data communication. This increase in signal lines complicates system design and increases the overall system size.

[0008] This disclosure is made based on the circumstances described above, and aims to provide a data communication circuit that reduces the number of signal lines required for CDR-type data communication.

[0009] A data communication circuit according to one aspect of the present disclosure is a data communication circuit that performs data communication between a first data processing unit and a second data processing unit, comprising: a first transmission path for transmitting data from the first data processing unit to the second data processing unit using the CDR method; a second transmission path for transmitting data from the second data processing unit to the first data processing unit using the CDR method; and a control unit for controlling data communication, wherein when data communication is performed via the first transmission path, the control unit transmits notification data indicating the reception status of the second data processing unit from the second data processing unit to the first data processing unit via the second transmission path, and when data communication is performed via the second transmission path, the control unit controls the transmission of notification data indicating the reception status of the first data processing unit from the first data processing unit to the second data processing unit via the first transmission path.

[0010] A data communication method according to another aspect of the present disclosure is a data communication method in which data communication between a first data processing unit and a second data processing unit is performed by a first transmission path for transmitting data from the first data processing unit to the second data processing unit using the CDR method, and a second transmission path for transmitting data from the second data processing unit to the first data processing unit using the CDR method, wherein when data communication is performed by the first transmission path, notification data indicating the reception status of the second data processing unit is transmitted from the second data processing unit to the first data processing unit via the second transmission path, and when data communication is performed by the second transmission path, notification data indicating the reception status of the first data processing unit is transmitted from the first data processing unit to the second data processing unit via the first transmission path.

[0011] The data communication circuit and data communication method disclosed herein can reduce the number of signal lines required in CDR data communication.

[0012] Figure 1 is a circuit diagram of a data communication circuit according to one embodiment of the present disclosure. Figure 2 is a schematic diagram showing one-way data communication in the data communication circuit of Figure 1. Figure 3 is a schematic diagram showing two-way data communication in the data communication circuit of Figure 1.

[0013] [Description of Embodiments of the Present Disclosure] (1) A data communication circuit according to one aspect of the present disclosure is a data communication circuit that performs data communication between a first data processing unit and a second data processing unit, comprising: a first transmission path for transmitting data from the first data processing unit to the second data processing unit using the CDR method; a second transmission path for transmitting data from the second data processing unit to the first data processing unit using the CDR method; and a control unit for controlling data communication, wherein when data communication is performed via the first transmission path, the control unit transmits notification data indicating the reception status of the second data processing unit from the second data processing unit to the first data processing unit via the second transmission path, and when data communication is performed via the second transmission path, the control unit controls the transmission of notification data indicating the reception status of the first data processing unit from the first data processing unit to the second data processing unit via the first transmission path.

[0014] This data communication circuit is a data communication circuit that performs bidirectional data communication using the CDR method with a first transmission line and a second transmission line. When data communication is performed using the first transmission line, notification data is transmitted using the second transmission line, and when data communication is performed using the second transmission line, notification data is transmitted using the first transmission line. Therefore, this data communication circuit does not require a dedicated return line, and the number of required signal lines can be reduced.

[0015] (2) In the data communication circuit described in (1) above, it is preferable that the first transmission line and the second transmission line have two transmission modes with different data rates. For example, when performing high-speed data communication using only the first transmission line, stable data communication can be achieved by using the second transmission line as a low-speed signal line.

[0016] (3) In the data communication circuit described in (2) above, the ratio of the low-speed data rate to the high-speed data rate should be 1 / 100 or less in the two transmission modes described above. By keeping the ratio of the low-speed data rate to the high-speed data rate below the above upper limit, even more stable data communication can be achieved.

[0017] (4) It is possible to transmit data simultaneously to the first transmission line and the second transmission line using any of the data communication circuits described in (1) to (3) above. When transmitting data simultaneously, it is preferable to transmit the data to be transmitted and the notification data superimposed on each other on the first transmission line and the second transmission line. With this configuration, it is possible to transmit data simultaneously to the first transmission line and the second transmission line without providing a dedicated return line.

[0018] (5) In any of the data communication circuits described in (1) to (4) above, the first transmission line and the second transmission line are each composed of two signal lines, and data is transmitted via differential signals through these two signal lines. By using differential signals in the first transmission line and the second transmission line in this manner, it is possible to improve immunity to external noise and easily achieve low-voltage operation and high-speed operation.

[0019] (6) A data communication method relating to another aspect of the present disclosure is a data communication method which performs data communication between a first data processing unit and a second data processing unit using a first transmission path for transmitting data from the first data processing unit to the second data processing unit using the CDR method, wherein when data communication is performed using the first transmission path, notification data indicating the reception status of the second data processing unit is transmitted from the second data processing unit to the first data processing unit via the second transmission path, and when data communication is performed using the second transmission path, notification data indicating the reception status of the first data processing unit is transmitted from the first data processing unit to the second data processing unit via the first transmission path.

[0020] This data communication method uses a first transmission line and a second transmission line to perform bidirectional data communication using the CDR method. When data communication is performed using the first transmission line, notification data is transmitted using the second transmission line, and when data communication is performed using the second transmission line, notification data is transmitted using the first transmission line. Therefore, this data communication method does not require a dedicated return line, and the number of required signal lines can be reduced.

[0021] [Details of Embodiments of the Disclosure] A data communication circuit and a data communication method according to one embodiment of the Disclosure will be described below.

[0022] The data communication circuit 1 shown in Figure 1 is a data communication circuit that performs data communication between the first data processing unit 10 and the second data processing unit 20.

[0023] The first data processing unit 10 and the second data processing unit 20 may be mounted on separate semiconductor devices X1 and X2, respectively. Examples of semiconductor devices X1 and X2 include large-scale integrated circuits (LSIs). However, the mounting location is not limited to semiconductor devices, as long as the component performs data communication between components. Furthermore, there is no presumption that it can be used for data communication within a single component, for example, within a semiconductor integrated circuit.

[0024] The data communication circuit 1 can be used particularly well when communicating data at high speed. The lower limit of the data rate of the data communication circuit 1 is preferably 1 Gbps, more preferably 5 Gbps, and even more preferably 50 Gbps. On the other hand, the upper limit of the data rate of the data communication circuit 1 is not particularly limited, but is practically 100 Gbps.

[0025] The data communication circuit 1 comprises a first transmission line 30, a second transmission line 40, and a control unit 50.

[0026] <Transmission Path> The first transmission path 30 transmits data from the first data processing unit 10 to the second data processing unit 20 using the CDR method. The second transmission path 40 transmits data from the second data processing unit 20 to the first data processing unit 10 using the CDR method. In other words, the data communication circuit 1 is capable of bidirectional communication.

[0027] In the data communication circuit 1 shown in Figure 1, the first transmission line 30 and the second transmission line 40 are each composed of two signal lines (first signal lines 31 and 32 and second signal lines 41 and 42), and data is transmitted via differential signals through these two signal lines. For example, in the first transmission line 30, currents with opposite phases flow through the positive first signal line 31 and the negative first signal line 32, and the signal is transmitted by the potential difference between them. In this case, even if the same external noise is applied to the positive and negative first signal lines 31 and 32, the noise is canceled out and malfunctions are less likely because the potential difference between the signal lines is observed. By using differential signals in the first transmission line 30 and the second transmission line 40 in this way, immunity to external noise can be improved.

[0028] The first transmission line 30 and the second transmission line 40 have two transmission modes with different data rates. For example, when performing high-speed data communication using only the first transmission line 30, stable data communication can be achieved by using the second transmission line 40 as a low-speed signal line. Further details will be described later.

[0029] In the two transmission modes described above, the high-speed data rate corresponds to the data rate used when communicating data at high speed. On the other hand, the low-speed data rate should be set to a rate that allows for stable data communication even when disturbances such as clock period jitter occur.

[0030] The upper limit of the ratio of the low-speed data rate to the high-speed data rate is preferably 1 / 100, and more preferably 1 / 1000. By keeping the ratio of the low-speed data rate to the high-speed data rate below the above upper limit, more stable data communication can be achieved. On the other hand, there is no particular lower limit to the ratio of the low-speed data rate to the high-speed data rate, but it can be, for example, 1 / 2. If the ratio of the low-speed data rate to the high-speed data rate is above the above lower limit, the effect of improving the stability of data communication by providing a low-speed data rate may be insufficient.

[0031] <Data Processing Unit> The first data processing unit 10 includes a first output buffer 11 that drives the first transmission line 30 and a first input buffer 12 that receives signals from the second transmission line 40.

[0032] The first output buffer 11 generates a signal for the data to be transmitted from the first data processing unit 10 to the second data processing unit 20, and its inverted signal, and applies them as voltages to the + side first signal line 31 and the - side first signal line 32, respectively. As a result, the signals are transmitted from the first data processing unit 10 to the second data processing unit 20 through the first transmission line 30.

[0033] Meanwhile, the first input buffer 12 receives signals transmitted from the second data processing unit 20. Since these signals are transmitted via two signal lines, the positive second signal line 41 and the negative second signal line 42, the signals are reproduced by taking the potential difference between these signal lines.

[0034] The second data processing unit 20 includes a second output buffer 21 that drives the second transmission line 40 and a second input buffer 22 that receives signals from the first transmission line 30.

[0035] The configuration of the second output buffer 21 and the second input buffer 22 can be configured in the same way as the first output buffer 11 and the first input buffer 12 of the first data processing unit 10, except that the direction of the transmitted signals is reversed, so a detailed explanation is omitted.

[0036] <Control Unit> The control unit 50 controls data communication. Specifically, when data communication is performed via the first transmission line 30, the control unit 50 controls the transmission of notification data S indicating the reception status of the second data processing unit 20 from the second data processing unit 20 to the first data processing unit 10 via the second transmission line 40, and when data communication is performed via the second transmission line 40, the control unit 50 controls the transmission of notification data S indicating the reception status of the first data processing unit 10 from the first data processing unit 10 to the second data processing unit 20 via the first transmission line 30.

[0037] The control unit 50 is composed of a first control unit 51 located in the first data processing unit 10 and a second control unit 52 located in the second data processing unit 20. The first control unit 51 controls the data to be output to the first output buffer 11 and the data input by the first input buffer 12. The second control unit 52 controls the data to be output to the second output buffer 21 and the data input by the second input buffer 22. The two are controlled independently.

[0038] The data communication circuit 1 performs data communication using a data communication method which is another embodiment of the present disclosure. That is, the data communication method is a data communication method which performs data communication between the first data processing unit 10 and the second data processing unit 20 using a first transmission line 30 that transmits data from the first data processing unit 10 to the second data processing unit 20 using the CDR method, and a second transmission line 40 that transmits data from the second data processing unit 20 to the first data processing unit 10 using the CDR method. When data communication is performed using the first transmission line 30, notification data S indicating the reception status of the second data processing unit 20 is transmitted from the second data processing unit 20 to the first data processing unit 10 via the second transmission line 40, and when data communication is performed using the second transmission line 40, notification data S indicating the reception status of the first data processing unit 10 is transmitted from the first data processing unit 10 to the second data processing unit 20 via the first transmission line 30.

[0039] The operation of the control unit 50 will be explained below using the case where data communication is performed via the first transmission line 30 shown in Figure 2 as an example. The same applies when data communication is performed via the first transmission line 30.

[0040] First, a training operation is performed before data communication takes place. During the training operation, training data is sent from the first output buffer 11 of the first data processing unit 10 to the second data processing unit 20, and the reception timing of the second input buffer 22 of the second data processing unit 20 is determined when transmitting at a high data rate. By determining the reception timing of the second data processing unit 20 in this way, a clock signal is not required to synchronize the first output buffer 11 and the second input buffer 22. When the first control unit 51 transmits normal data D from the first output buffer 11 of the first data processing unit 10 at a high data rate, the second control unit 52 can receive that normal data D in the second input buffer 22 of the second data processing unit 20.

[0041] If, for some unavoidable reason, the transmission timing of the normal data D sent from the first output buffer 11 of the first data processing unit 10 deviates from the timing established during the training operation, the second input buffer 22 of the second data processing unit 20 may not be able to receive the normal data D. In such a case, it becomes necessary to perform the training operation again to readjust the timing. The second data processing unit 20, which is receiving the normal data D, can determine that it is no longer receiving the normal data D properly. However, since the transmission of the normal data D from the first output buffer 11 of the first data processing unit 10 and the reception of the normal data D in the second input buffer 22 of the second data processing unit 20 are performed independently, the first data processing unit 10 cannot recognize that the second data processing unit 20 is no longer receiving the normal data D properly. For this reason, the second control unit 52 needs to send notification data S from the second data processing unit 20 to the first data processing unit 10 to indicate whether or not the normal data D has been received properly.

[0042] In the data communication circuit 1, the second transmission path 40 is used to transmit the notification data S. The notification data S can be transmitted at a high data rate, but it is preferably transmitted at a low data rate. Since the data length (the number of bits required to represent the data) of the notification data S is shorter than that of the normal data D and the transmission frequency can also be set lower, even if the data rate is low, it is possible to timely transmit the necessary information to the first data processing unit 10. Further, when the data rate is low, even if there is a deviation in the transmission timing, it is less likely that the first data processing unit 10 cannot receive the notification data S because the rate is low. Conversely, the data rate of the low data rate is set to a rate such that there is no hindrance to receiving the notification data S even if there is a deviation in the transmission timing.

[0043] As shown in FIG. 2, both the normal data D and the notification data S can be composed of a header indicating which data it is and a body representing the data itself. If the data lengths of the normal data D and the notification data S are determined in advance, both can be received and processed separately.

[0044] In the data communication circuit 1 configured as described above, it is possible to simultaneously transmit data to the first transmission path 30 and the second transmission path 40. When simultaneously transmitting data, the normal data D and the notification data S to be transmitted are superimposed and transmitted to the first transmission path 30 and the second transmission path 40. By configuring in this way, it is possible to simultaneously transmit data to the first transmission path 30 and the second transmission path 40 without providing a dedicated return line.

[0045] When data is transmitted bidirectionally at the same time, the first transmission line 30 will have superimposed normal data D to be transmitted from the first data processing unit 10 to the second data processing unit 20 and notification data S indicating whether or not the first data processing unit 10 has successfully received the normal data D from the second data processing unit 20. Similarly, the second transmission line 40 will have superimposed normal data D to be transmitted from the second data processing unit 20 to the first data processing unit 10 and notification data S indicating whether or not the second data processing unit 20 has successfully received the normal data D from the first data processing unit 10.

[0046] In this case, the notification data S will also be transmitted at a high data rate. Therefore, if, for example, there is a delay in the transmission timing from the second data processing unit 20 to the first data processing unit 10, the first data processing unit 10 will not be able to properly receive the notification data S that indicates whether or not the second data processing unit 20 has received it properly. However, since this state is recognizable by the first data processing unit 10, it can readjust the timing and perform processing to restore the state in which the second data processing unit 20 can receive it properly.

[0047] In the example described above, the information in the notification data S is whether or not the reception was successful, and the second data processing unit 20 can notify this spontaneously even without a request from the first data processing unit 10. However, the information in the notification data S is not limited to this. In addition to the case where the second data processing unit 20 notifies spontaneously, for example, the first data processing unit 10 may specify the information that the second data processing unit 20 should return using the notification data S, and the first data processing unit 10 may return the information it needs using the notification data S from the second data processing unit 20.

[0048] <Advantages> The data communication circuit 1 and the data communication method are a data communication circuit 1 and a data communication method that perform bidirectional data communication by a CDR method using a first transmission line 30 and a second transmission line 40. When performing data communication by the first transmission line 30, the notification data S is transmitted using the second transmission line 40. When performing data communication by the second transmission line 40, the notification data S is transmitted using the first transmission line 30. Therefore, in the data communication circuit 1 and the data communication method, there is no need to provide a dedicated return line, and the required number of signal lines can be reduced.

[0049] [Other Embodiments] The above embodiments do not limit the configuration of the present disclosure. Therefore, in the above embodiments, omissions, substitutions, or additions of the constituent elements of each part of the above embodiments are possible based on the description in this specification and common technical knowledge, and all of them should be interpreted as belonging to the scope of the present disclosure.

[0050] In the above embodiment, the case where the first transmission line and the second transmission line transmit data by differential signals has been described. However, a configuration in which either one or both of the first transmission line and the second transmission line transmit data by a single signal line can also be adopted. In this case, although the noise resistance decreases, the required number of signal lines can be further reduced.

[0051] In the above embodiment, the case where the first transmission line and the second transmission line have two transmission modes with different data rates has been described. However, it is also the intention of the present disclosure that both the first transmission line and the second transmission line, or either one of them, have a single transmission mode. The data rate of one transmission mode in this case corresponds to the data rate in the case of communicating data at high speed.

[0052] In the above embodiment, the control unit is described as being composed of a first control unit located in the first data processing unit and a second control unit located in the second data processing unit. However, it is not essential that the first and second control units are located in the first and second data processing units, respectively, and they may be located elsewhere. Furthermore, the control unit does not need to be divided into two parts, a first control unit and a second control unit; it is also possible to have a configuration in which a single control unit controls everything. However, from the viewpoint of layout efficiency, it is preferable that the control unit is composed of a first control unit located in the first data processing unit and a second control unit located in the second data processing unit.

[0053] The data communication circuit disclosed herein can reduce the number of signal lines required in CDR-based data communication.

[0054] 1 Data communication circuit 10 First data processing unit 11 First output buffer 12 First input buffer 20 Second data processing unit 21 Second output buffer 22 Second input buffer 30 First transmission line 31, 32 First signal line 40 Second transmission line 41, 42 Second signal line 50 Control unit 51 First control unit 52 Second control unit X1, X2 Semiconductor device D Normal data S Notification data

Claims

1. A data communication circuit for performing data communication between a first data processing unit and a second data processing unit, comprising: a first transmission path for transmitting data from the first data processing unit to the second data processing unit using the CDR method; a second transmission path for transmitting data from the second data processing unit to the first data processing unit using the CDR method; and a control unit for controlling data communication, wherein the control unit controls the transmission of notification data indicating the reception status of the second data processing unit from the second data processing unit to the first data processing unit via the second transmission path when data communication is performed via the first transmission path, and the transmission of notification data indicating the reception status of the first data processing unit from the first data processing unit to the second data processing unit via the first transmission path when data communication is performed via the second transmission path.

2. The data communication circuit according to claim 1, wherein the first transmission line and the second transmission line have two transmission modes with different data rates.

3. The data communication circuit according to claim 2, wherein in the two transmission modes described above, the ratio of the low-speed data rate to the high-speed data rate is 1 / 100 or less.

4. A data communication circuit according to any one of claims 1 to 3, which is capable of simultaneously transmitting data to the first transmission line and the second transmission line, and when transmitting data simultaneously, transmits the data to be transmitted and the notification data superimposed on the first transmission line and the second transmission line.

5. The data communication circuit according to any one of claims 1 to 3, wherein the first transmission line and the second transmission line are each composed of two signal lines, and data is transmitted as a differential signal via the two signal lines.

6. A data communication method comprising a first data processing unit and a second data processing unit, wherein data communication between the first data processing unit and the second data processing unit is performed by a first transmission path that transmits data from the first data processing unit to the second data processing unit using the CDR method, and a second transmission path that transmits data from the second data processing unit to the first data processing unit using the CDR method, wherein when data communication is performed by the first transmission path, notification data indicating the reception status of the second data processing unit is transmitted from the second data processing unit to the first data processing unit via the second transmission path, and when data communication is performed by the second transmission path, notification data indicating the reception status of the first data processing unit is transmitted from the first data processing unit to the second data processing unit via the first transmission path.

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