Communication method and interface circuit

Abstract

One embodiment aims to provide a communication method and interface circuit that can improve data transfer efficiency. [Solution] According to one embodiment, a communication method is provided. The communication method includes performing a first operation when a first condition is met with respect to a first mode and a second mode. The first mode uses a first transmission unit. The second mode uses a second transmission unit. The first operation generates a data frame by adding a first error detection code and a second error detection code to the data. The first error detection code corresponds to a first transmission unit. The second error detection code corresponds to a second transmission unit. The communication method includes performing a second operation when a second condition is met with respect to the first mode and the second mode. The second operation generates a data frame by adding a first error detection code to the data without adding a second error detection code. The communication method includes transmitting the data frame generated by the first operation or the second operation.

Description

Technical Field

[0001] This embodiment relates to a communication method and an interface circuit.

Background Art

[0002] In a communication method in which a data frame including data and an error detection code is transmitted, it is possible to detect an error in the data using the error detection code on the receiving side of the data frame. In a communication method, it is desired to improve the transfer efficiency of data.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One embodiment aims to provide a communication method and an interface circuit capable of improving the transfer efficiency of data.

Means for Solving the Problems

[0005] According to one embodiment, a communication method is provided. The communication method includes performing a first operation when a first condition is met with respect to a first mode and a second mode. The first mode uses a first transmission unit. The second mode uses a second transmission unit. The second transmission unit is different from the first transmission unit. The first operation generates a data frame by adding a first error detection code and a second error detection code to the data. The first error detection code corresponds to a first transmission unit. The second error detection code corresponds to a second transmission unit. The communication method includes performing a second operation when a second condition is met with respect to the first mode and the second mode. The second operation generates a data frame by adding a first error detection code to the data without adding a second error detection code. The communication method includes transmitting the data frame generated by the first operation or the second operation. [Brief explanation of the drawing]

[0006] [Figure 1] A diagram showing the configuration of a system to which the communication method according to the first embodiment is applied. [Figure 2] A diagram showing the operation of the transmitting device in the first embodiment. [Figure 3] A diagram showing the format of the data frame in the first embodiment. [Figure 4] A diagram showing the operation of the receiving device in the first embodiment. [Figure 5] A sequence diagram showing the operation of the system in the first embodiment. [Figure 6] A sequence diagram showing the operation of the system in the first embodiment. [Figure 7] A diagram showing the operation of the transmitting device in the second embodiment. [Figure 8] A diagram showing the operation of the receiving device in the second embodiment. [Figure 9] A diagram showing the operation of the transmitting device in a modified example of the second embodiment. [Figure 10] A diagram showing the operation of the receiving device in a modified example of the second embodiment. [Figure 11] A diagram showing the format of the data frame in the third embodiment. [Modes for carrying out the invention]

[0007] The communication method according to the embodiments will be described in detail below with reference to the attached drawings. However, the present invention is not limited to these embodiments.

[0008] (First embodiment) In the communication method according to the first embodiment, a data frame containing data and an error detection code is transmitted, and the receiving end of the data frame can perform error detection on the data using the error detection code. However, measures are taken to improve the efficiency of data transfer.

[0009] The communication method can be applied to System 1 as shown in Figure 1. Figure 1 is a diagram showing the configuration of System 1 to which the communication method is applied.

[0010] System 1 includes device 10, device 20, and communication line 30.

[0011] Devices 10 and 20 are connected to each other via a communication line 30, enabling communication between them. The communication line 30 includes communication lines 31 and 32.

[0012] Device 10 can transmit data frames to device 20 via communication line 31. Device 20 can receive data frames from device 10 via communication line 31. Device 20 can transmit data frames to device 10 via communication line 32. Device 10 can receive data frames from device 20 via communication line 32.

[0013] The communication between device 10 and device 20 may be performed according to a predetermined communication standard. In the predetermined communication standard, an error detection code is defined to compensate for errors in the data frame and ensure that the data frame is correctly communicated. The error detection code includes a CRC (Cyclic Redundancy Check) code. Device 10 and device 20 can each extract the error detection code from the received data frame and check (error detection) the data in the data frame using the error detection code to confirm whether the data has been correctly received.

[0014] The predetermined communication standard may support a plurality of communication modes MD1 and MD2. Communication mode MD1 uses a transmission unit TU1. The transmission unit TU1 may have a fixed length. Communication mode MD2 uses a transmission unit TU2. The data length of the transmission unit TU2 may be different from that of the transmission unit TU1. The transmission unit TU2 may have a variable length.

[0015] The data length of the transmission unit TU1 and the data length of the transmission unit TU2 may be the same. When the data frame is transmitted using the transmission unit TU1, since there is an error detection code area for the transmission unit TU1, if the data length of the transmission unit TU1 and the data length of the transmission unit TU2 are the same, the data frame is transmitted across a plurality of transmission units TU1.

[0016] Device 10 performs operation OP1 when condition CD1 is satisfied with respect to communication mode MD1 and communication mode MD2. Operation OP1 is to add an error detection code CRC1 corresponding to the transmission unit TU1 to generate a data frame DF of the transmission unit TU1, and then add an error detection code CRC2 corresponding to the transmission unit TU2 to generate a TFS data frame TFS of the transmission unit TU2. Condition CD1 may include that a part of the data frame DF is transmitted in communication mode MD1 and another part of the data frame DF is transmitted in communication mode MD2.

[0017] Device 10 performs operation OP2 when condition CD2 is met with respect to communication modes MD1 and MD2. Operation OP2 generates a data frame DF by adding error detection code CRC1 to the data without adding error detection code CRC2 to the data. Condition CD2 may also include the condition that the entire data frame DF is transmitted in communication mode MD2.

[0018] Device 10 transmits the data frame DF generated by operation OP1 or operation OP2 to device 20 via communication line 31.

[0019] Similarly, the device 20 performs operation OP1 when condition CD1 is met with respect to communication modes MD1 and MD2. Operation OP1 generates a data frame DF by adding error detection code CRC1 corresponding to transmission unit TU1 and error detection code CRC2 corresponding to transmission unit TU2 to data DT. Condition CD1 may include the fact that a portion of data frame DF is transmitted in communication mode MD1 and another portion of data frame DF is transmitted in communication mode MD2.

[0020] Device 20 performs operation OP2 when condition CD2 is met with respect to communication modes MD1 and MD2. Operation OP2 generates a data frame DF for transmission unit TU1 without adding the error detection code CRC2 to the data, and then generates a TFS data frame TFS for transmission unit TU2 by adding the error detection code CRC2 corresponding to transmission unit TU2. Condition CD2 may also include the condition that the entire data frame DF is transmitted in communication mode MD2.

[0021] Device 20 transmits the data frame DF generated by operation OP1 or operation OP2 to device 10 via communication line 32.

[0022] Devices 10 and 20 may be configured as shown in Figure 1 in accordance with a predetermined communication standard.

[0023] For example, a given communication standard includes the Unipro standard. The Unipro standard defines a layered data transmission structure that includes the application layer, transport layer, network layer, data link layer (DL layer), and physical adapter layer (PA layer).

[0024] Unipro version 3.0 introduces Transport Frame Structure (TFS) at the PA layer. Two communication modes are available: TFS mode and non-TFS mode. When a device switches to TFS mode, it can send and receive data in TFS units.

[0025] Device 10 has an interface circuit 15 and an internal circuit 16. The interface circuit 15 performs interface operations for communication with device 20. The interface circuit 15 has a control unit 11, a DL layer 12, a PA layer 13, and a PHY 14.

[0026] The control unit 11 corresponds to the application layer, transport layer, and network layer in the layered data transmission structure. The DL layer 12 corresponds to the DL layer in the layered data transmission structure. The PA layer 13 and PHY 14 correspond to the PHY layer in the layered data transmission structure.

[0027] The DL layer 12 has a transmitter 12t and a receiver 12r. The PA layer 13 has a transmitter 13t and a receiver 13r. The PHY 14 has a transmitter 14t and a receiver 14r.

[0028] When the control unit 11 receives transmission information from the internal circuit 16, it sequentially converts the transmission information into application layer, transport layer, network layer, and DL layer formats. The control unit 11 then supplies the transmission information in DL layer format to the transmission unit 12t.

[0029] The transmitter 12t can receive the TFS mode status signal from the transmitter 13t.

[0030] When the transmitter 12t receives an active-level TFS mode status signal, it switches the communication mode to TFS mode and generates a data frame corresponding to the TFS mode based on the transmission information. The transmitter 12t then supplies the data frame to the transmitter 13t.

[0031] When the transmitter 12t receives a non-active level TFS mode status signal, it switches the communication mode to non-TFS mode and generates a data frame corresponding to the non-TFS mode based on the transmitted information. The transmitter 12t then supplies the data frame to the transmitter 13t.

[0032] The transmitter 13t converts the data frame to the PA layer format. In TFS mode, the transmitter 13t converts the data frame to TFS and supplies it to the transmitter 14t. In non-TFS mode, the transmitter 13t converts the data frame to data in the PA layer format and supplies it to the transmitter 14t.

[0033] In TFS mode, the transmitter 14t converts TFS to the PHY layer format and transmits it to the device 20 via the communication line 31. In non-TFS mode, the transmitter 14t converts data in the PA layer format to the PHY layer format and transmits it to the device 20 via the communication line 31.

[0034] When the receiving unit 14r receives data from the device 20 via the communication line 32, it supplies the data to the receiving unit 13r in TFS mode. In non-TFS mode, the receiving unit 14r supplies the data to the receiving unit 13r.

[0035] In TFS mode, the receiver 13r converts TFS data into a data frame in DL layer format and supplies it to the receiver 12r. In non-TFS mode, the receiver 13r converts PA layer data into a data frame in DL layer format and supplies it to the receiver 12r.

[0036] The receiver 12r can receive the TFS mode status signal from the receiver 13r.

[0037] When the receiver 12r receives an active-level TFS mode status signal, it switches the communication mode to TFS mode, generates received information according to the TFS mode based on the data frame, and converts the received information into a network layer format.

[0038] When the receiver 12r receives a non-active level TFS mode status signal, it switches the communication mode to non-TFS mode, generates received information corresponding to the non-TFS mode based on the data frame, and converts the received information into a network layer format.

[0039] The receiving unit 12r supplies the received information to the control unit 11.

[0040] When the control unit 11 receives the received information, it sequentially converts the received information into network layer, transport layer, and application layer formats. The control unit 11 then supplies the received information in application layer format to the internal circuit 16.

[0041] The device 20 has an interface circuit 25 and an internal circuit 26. The interface circuit 25 performs interface operations for communication with the device 20. The interface circuit 25 has a control unit 21, a DL layer 22, a PA layer 23, and a PHY 24.

[0042] The control unit 21 corresponds to the application layer, transport layer, and network layer in the layered data transmission structure. The DL layer 22 corresponds to the DL layer in the layered data transmission structure. The PA layer 23 and PHY 24 correspond to the PHY layer in the layered data transmission structure.

[0043] The DL layer 22 has a transmitter 22t and a receiver 22r. The PA layer 23 has a transmitter 23t and a receiver 23r. The PHY 24 has a transmitter 24t and a receiver 24r.

[0044] When the control unit 21 receives transmission information from the internal circuit 26, it sequentially converts the transmission information into application layer, transport layer, network layer, and DL layer formats. The control unit 21 then supplies the transmission information in DL layer format to the transmission unit 22t.

[0045] The transmitter 22t can receive the TFS mode status signal from the transmitter 23t.

[0046] When the transmitter 22t receives an active-level TFS mode status signal, it switches the communication mode to TFS mode and generates a data frame corresponding to the TFS mode based on the transmission information. The transmitter 22t then supplies the data frame to the transmitter 23t.

[0047] When the transmitter 22t receives a non-active level TFS mode status signal, it switches the communication mode to non-TFS mode and generates a data frame corresponding to the non-TFS mode based on the transmitted information. The transmitter 22t then supplies the data frame to the transmitter 23t.

[0048] The transmitter 23t converts the data frame to the PA layer format. In TFS mode, the transmitter 23t converts the data frame to TFS and supplies it to the transmitter 24t. In non-TFS mode, the transmitter 23t converts the data frame to data in the PA layer format and supplies it to the transmitter 24t.

[0049] In TFS mode, the transmitter 24t converts TFS to the PHY layer format and transmits it to the device 20 via the communication line 31. In non-TFS mode, the transmitter 24t converts data in the PA layer format to the PHY layer format and transmits it to the device 20 via the communication line 32.

[0050] When the receiving unit 24r receives data from the device 20 via the communication line 32, it supplies the data to the receiving unit 23r in TFS mode. In non-TFS mode, the receiving unit 24r supplies the data to the receiving unit 23r.

[0051] In TFS mode, the receiver 23r converts TFS data into a data frame in DL layer format and supplies it to the receiver 22r. In non-TFS mode, the receiver 23r converts PA layer data into a data frame in DL layer format and supplies it to the receiver 22r.

[0052] The receiver 22r can receive the TFS mode status signal from the receiver 23r.

[0053] When the receiver 22r receives an active-level TFS mode status signal, it switches the communication mode to TFS mode, generates received information according to the TFS mode based on the data frame, and converts the received information into a network layer format.

[0054] When the receiver 22r receives a non-active level TFS mode status signal, it switches the communication mode to non-TFS mode, generates received information corresponding to the non-TFS mode based on the data frame, and converts the received information into a network layer format.

[0055] The receiving unit 22r supplies the received information to the control unit 21.

[0056] When the control unit 21 receives the received information, it sequentially converts the received information into network layer, transport layer, and application layer formats. The control unit 21 then supplies the received information in application layer format to the internal circuit 26.

[0057] Next, the operation of the transmitting device will be explained using Figure 2. Figure 2 is a diagram illustrating the operation of the transmitting device. Figure 2 illustrates the case where the transmitting device is device 10. Figure 2 mainly explains the operation of the DL layer 12 and the PA layer 13.

[0058] At timing t1, the PA layer 13 supplies a non-active level TFS mode status signal to the DL layer 12. Both the DL layer 12 and the PA layer 13 are operating in non-TFS mode. Based on the transmitted information, the DL layer 12 begins to provide a data frame DF1 corresponding to the non-TFS mode.

[0059] The DL layer 12 may generate a data frame DF in the format shown in Figure 3(a) as a data frame DF1 corresponding to the non-TFS mode.

[0060] The data frame DF shown in Figure 3(a) includes the fields ESC_DL, SOF, TC, Reserved, DL_SDU_Byte0 to DL_SDU_Byte-1, ESC_DL, EOF, Frame_Seq._Number, and CCITT_CRC-16.

[0061] The SOF field stores "000" to indicate that the data frame DF is a data frame corresponding to non-TFS mode. The SOF field can have a length of 3 bits.

[0062] The CCITT_CRC-16 field stores the error detection code CRC2 used in DL layer 12. The CCITT_CRC-16 field can have 16 bits.

[0063] In Figure 2, the SOF field is labeled "SOF", the CCITT_CRC-16 field is labeled "DL CRC", and the rest of the field is labeled "data".

[0064] As shown in Figure 2, the DL layer 12 begins generating a data frame DF1 corresponding to the non-TFS mode and begins supplying the data frame DF1 to the PA layer 13. The PA layer 13 converts the data frame DF1 to the PA layer format.

[0065] Between timings t1 and t2, the PA layer 13 provides the PHY 14 with a portion of the data frame DF1 from the beginning, and the PHY 14 transmits it to the device 20 via the communication line 31. The PA layer 13 supplies a transmission stop request to the DL layer 12 as preparation before switching to TFS mode, and the DL layer 12 temporarily suspends the transmission of data frame DF1 in response to the transmission stop request. The PA layer 13 temporarily suspends the transmission of data frame DF1 to the PHY 14. The DL layer 12 supplies a transmission stop completion notification to the PA layer 13 as a notification of acceptance of switching to TFS mode.

[0066] At timing t3, the PA layer 13 transitions the TFS mode status signal from the non-active level to the active level in response to the transmission stop completion notification. The PA layer 13 begins supplying the active-level TFS mode status signal to the DL layer 12. The DL layer 12 and the PA layer 13 each begin operating in TFS mode.

[0067] Simultaneously, the PA layer 13 resumes transmission of data frame DF1 and sends a transmission resume request to the DL layer 12. The DL layer 12 resumes transmission of data frame DF1 in response to the transmission resume request. Although it has switched to TFS mode, there is still a portion of data frame DF1 in non-TFS mode, so the DL layer 12 continues to supply the remaining portion of data frame DF1 to the PA layer 13. The PA layer 13 begins converting data frame DF1 to TFS#1 according to the TFS mode.

[0068] At timing t4, DL layer 12, in response to SOF being "000", begins generating "DL CRC" using "data" in data frame DF1 and incorporating it into data frame DF1.

[0069] For example, DL layer 12 applies a polynomial X to "data". 16 +X 12 +X 5 +X 0You may also generate "DL CRC" by encoding "data" using the following method. In the polynomial, the power of X indicates the bit position, and X indicates the bit value at that bit position.

[0070] The DL layer 12 supplies the data frame DF1 to the PA layer 13. The PA layer 13 includes "data" and "DL CRC" in TFS#1.

[0071] At timing t5, PA layer 13 begins generating "TFS CRC" using "data" and "DL CRC" from TFS#1 and incorporating it into TFS#1.

[0072] Between timings t3 and t6, the PA layer 13 provides TFS#1 to the PHY 14, and the PHY 14 transmits it to the device 20 via the communication line 31.

[0073] At timing t6, the DL layer 12 begins to provide a data frame DF2 according to the TFS mode based on the transmitted information.

[0074] The DL layer 12 may generate a data frame DF in the format shown in Figure 3(b) as a data frame DF2 according to the TFS mode.

[0075] The data frame DF shown in Figure 3(b) differs from the data frame DF shown in Figure 3(a) in that the contents of the SOF field are different, and the CCITT_CRC-16 field is omitted.

[0076] The SOF field stores "100," indicating that the data frame DF is a data frame according to the TFS mode. The SOF field can have a length of 3 bits.

[0077] In the data frame DF shown in Figure 3(b), the CCITT_CRC-16 field (shown as "DL CRC" in Figure 2) is omitted, but since PA layer 13 generates "TFS CRC" as the error detection code, the receiving end can detect the error.

[0078] At timing t6 shown in Figure 2, the PA layer 13 begins converting data frame DF2 to TFS#2 depending on the TFS mode.

[0079] Between timings t6 and t7, the DL layer 12 supplies the first portion of the data frame DF2, up to "SOF,data", to the PA layer 13. The PA layer 13 includes "SOF,data" in TFS#2. The PA layer 13 uses "SOF,data" in TFS#2 to generate "TFS CRC" and incorporates it into TFS#2.

[0080] Between timings t6 and t8, the PA layer 13 provides TFS#2 to the PHY 14, and the PHY 14 transmits it to the device 20 via the communication line 31.

[0081] The DL layer 12 supplies the remaining portion "data" of data frame DF2. At this time, the DL layer 12 does not supply "DL CRC" as SOF is "100". The DL layer 12 supplies the remaining portion "data" of data frame DF2 to the PA layer 13. The PA layer 13 includes the remaining portion "data" of data frame DF2 in TFS#3.

[0082] At timing t9, the PA layer 13 sends a transmission stop request to the DL layer 12 as a request to switch to non-TFS mode. In response to the transmission stop request, the DL layer 12 begins generating a data frame DF3 corresponding to non-TFS mode. The DL layer 12 sends a transmission stop completion notification to the PA layer 13 as a notification of acceptance of switching to non-TFS mode.

[0083] Between timings t9 and t10, the DL layer 12 supplies the first portion of data frame DF3, "SOF,data", to the PA layer 13. The PA layer 13 includes "SOF,data" in TFS#3. At timing t10, the PA layer 13 uses both the remaining portion of data frame DF2, "data", in TFS#3 and the first portion of DF3, "SOF,data", to generate "TFS CRC" and begin incorporating it into TFS#3.

[0084] Between timings t8 and t11, the PA layer 13 provides TFS#3 to the PHY 14, and the PHY 14 transmits it to the device 20 via the communication line 31.

[0085] The DL layer 12 generates the remaining portion "data" in data frame DF3. Between timings t10 and t12, the DL layer 12 supplies the remaining portion "data" in data frame DF2 to the PA layer 13. The PA layer 13 includes the remaining portion "data" in data frame DF3 in TFS#4.

[0086] At timing t13, PA layer 13 generates "TFS CRC" using "data" in TFS#4 and begins to incorporate it as part of TFS#4.

[0087] Between timings t11 and t14, the PA layer 13 provides TFS#4 to the PHY 14, and the PHY 14 transmits it to the device 20 via the communication line 31.

[0088] At timing t14, the PA layer 13 sends a transmission stop request to the DL layer 12 as preparation before switching to non-TFS mode, and the DL layer 12 temporarily suspends the transmission of data frame DF3 in response to the transmission stop request. The DL layer 12 sends a transmission stop completion notification to the PA layer 13 as notification of acceptance of switching to non-TFS mode.

[0089] In response to the transmission stop completion notification, the PA layer 13 transitions the TFS mode status signal from the active level to the inactive level. The PA layer 13 then begins supplying the inactive level TFS mode status signal to the DL layer 12. The DL layer 12 and the PA layer 13 then begin operating in non-TFS mode.

[0090] At timing t15, the PA layer 13 sends a transmission restart request to the DL layer 12. The DL layer 12 resumes transmission of data frame DF3 in response to the transmission restart request. Depending on whether SOF is "000", the DL layer 12 generates "DL CRC" as the remaining part of data frame DF3 using "data" in data frame DF3. The DL layer 12 sends the remaining part of data frame DF3, "DL CRC", to the PA layer 13. The PA layer 13 provides the remaining part of data frame DF3, "DL CRC", and the PHY 14 transmits it to the device 20 via the communication line 31.

[0091] Next, the operation of the receiving device will be explained using Figure 4. Figure 4 illustrates the case where the receiving device is device 20. Figure 4 mainly explains the operation of the DL layer 22 and the PA layer 23.

[0092] At timing t21, the DL layer 22 and PA layer 23 are operating in non-TFS mode. The PA layer 23 begins receiving a portion of the data frame DF1 from the beginning, "SOF,data", from the device 10 via the communication line 31 and PHY 24.

[0093] Between timings t21 and t22, the PA layer 23 supplies a portion of the data frame DF1 from the beginning, "SOF,data", to the DL layer 22. The DL layer 22 holds this portion of the data frame DF1 from the beginning, "SOF,data". At this time, the DL layer 22 recognizes that the data frame DF1 is a data frame corresponding to non-TFS mode, based on the fact that SOF is "000".

[0094] At timing t23, the PA layer 23 receives TFS#1 from the device 10 via the communication line 31 and the PHY layer 21. In response, the PA layer 23 switches the communication mode from non-TFS mode to TFS mode.

[0095] At timing t25, the PA layer 23 performs error detection on the "data" and "DL CRC" contained in TFS#1 using "TFS CRC" to confirm whether TFS#1 was received correctly, and supplies the confirmation result to the control unit 21 via DL layer 22.

[0096] Once error detection is complete, PA layer 23 begins supplying "data" and "DL CRC" contained in TFS#1 to DL layer 22.

[0097] The PA layer 23 receives TFS#2 from the device 10 via the communication line 31 and the PHY layer 21.

[0098] At timing t26, the DL layer 22 performs error detection using DL CRC on the stored "SOF,data" and the supplied "data" to confirm whether the data frame DF1 was received correctly.

[0099] For example, DL layer 22 is a polynomial modulo 2 X for "SOF,data" and "data". 16 +X 12 +X 15 +X 0 The DL layer 22 performs division, and if the remainder is 0, it confirms that data frame DF1 was received correctly. If the remainder is not 0, it confirms that data frame DF1 was not received correctly.

[0100] The DL layer 22 supplies the verification result to the control unit 21.

[0101] Simultaneously, the DL layer 22 constitutes a data frame DF1 containing "SOF,data", "data", and "DL CRC". Based on the data frame DF1, the DL layer 22 generates received information corresponding to the non-TFS mode and supplies the received information to the control unit 21.

[0102] If it is determined that data frame DF1 was not received correctly, the control unit 21 may discard the received information and request the source device 10 to retransmit data frame DF1.

[0103] At timing t27, the PA layer 23 performs error detection on "SOF,data" included in TFS#2 using "TFS CRC" to confirm whether TFS#2 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22.

[0104] Once error detection is complete, PA layer 23 begins supplying "SOF,data" contained in TFS#2 to DL layer 22.

[0105] The PA layer 23 receives TFS#3 from the device 10 via the communication line 31 and the PHY layer 21.

[0106] At timing t29, the PA layer 23 performs error detection on "data" and "SOF,data" included in TFS#3 using "TFS CRC" to confirm whether TFS#3 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22.

[0107] Once error detection is complete, PA layer 23 begins supplying "data" and "SOF,data" contained in TFS#3 to DL layer 22.

[0108] The DL layer 22 holds "SOF,data" supplied from the PA layer 23 as a portion of the beginning of data frame DF2. The DL layer 22 recognizes that data frame DF2 is a data frame corresponding to TFS mode, depending on whether SOF is "100".

[0109] The PA layer 23 receives TFS#4 from the device 10 via the communication line 31 and the PHY layer 21.

[0110] At timing t30, the DL layer 22 holds the "data" supplied from the PA layer 23. The DL layer 22 constructs a data frame DF2 that includes the held "SOF,data" and "data". Based on the data frame DF2, the DL layer 22 generates received information according to the TFS mode and supplies the received information to the control unit 21.

[0111] Between timings t30 and t31, the PA layer 23 supplies the "data" contained in TFS#4 to the DL layer 22.

[0112] The DL layer 22 recognizes that data frame DF3 is a data frame corresponding to non-TFS mode, based on the "SOF,data" supplied from the PA layer 23, where SOF is "000".

[0113] At timing t32, the PA layer 23 performs error detection on the "data" contained in TFS#4 using "TFS CRC" to confirm whether TFS#4 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22.

[0114] Once error detection is complete, PA layer 23 begins supplying the "data" contained in TFS#4 to DL layer 22.

[0115] At timing t33, the DL layer 22 holds the first portion of the data frame DF3, "SOF,data" and "data".

[0116] Between timings t34 and t35, the PA layer 23 receives the remaining portion of the data frame DF3, "DL CRC," from the device 10 via the communication line 31 and the PHY layer 21. The PA layer 23 then supplies the remaining portion of the data frame DF3, "DL CRC," to the DL layer 22.

[0117] At timing t35, the DL layer 22 performs error detection on the held "SOF,data" and "data" using "DL CRC" to confirm whether the data frame DF3 was received correctly, and supplies the confirmation result to the control unit 21. At the same time, the DL layer 22 constructs the data frame DF3, which includes "SOF,data", "data", and "DL CRC". Based on the data frame DF3, the DL layer 22 generates reception information corresponding to the non-TFS mode and supplies the reception information to the control unit 21.

[0118] Next, the sequence of operations in which devices 10 and 20 transition from non-TFS mode to TFS mode in System 1 will be explained using Figure 5. Figure 5 is a sequence diagram showing the operation of System 1.

[0119] In device 10, when the control unit 11 supplies a TFS mode request to the PA layer 13 (S1), the PA layer 13 supplies a transmission stop request to the DL layer 12 (S2). The DL layer 12 stops transmitting the data frame DF and notifies the PA layer 13 that the transmission stop is complete (S3). When the PA layer 13 supplies a TFS mode request to the PHY 14 (S4), the PHY 14 transmits a TFS mode request to device 20 (S5).

[0120] In device 20, when PHY24 receives a TFS mode request, it supplies the TFS mode request to PA layer 23 (S6). PA layer 23 supplies the TFS mode request to control unit 21 (S7). Control unit 21 receives the TFS mode request (S8) and supplies a transmission stop request to PA layer 23 (S9). PA layer 23 supplies the transmission stop request to DL layer 22 (S10). DL layer 22 stops transmitting data frame DF and notifies PA layer 23 of the completion of transmission stop (S11). When PA layer 23 supplies TFS mode acceptance to PHY24 (S12), PHY24 transmits TFS mode acceptance to device 10 (S13).

[0121] In device 10, when PHY 14 receives TFS mode acceptance, it supplies TFS mode acceptance to PA layer 13 (S14). PA layer 13 supplies TFS mode acceptance to control unit 11 (S15). Control unit 11 receives TFS mode acceptance (S16) and supplies TFS mode transition request to PA layer 13 (S17). When PA layer 13 supplies TFS mode change instruction to PHY 14 (S18), PHY 24 sends TFS mode acceptance received notification to device 20 (S19).

[0122] In device 20, when PHY24 receives a TFS mode acceptance notification, it sends the TFS mode acceptance notification to PA layer 23 (S20). When PA layer 23 sends a TFS mode change instruction to PHY24 (S21), PHY24 sends a notification of receipt of the TFS mode acceptance notification to device 10 (S22).

[0123] In device 10, when PHY 14 receives a notification of acceptance of TFS mode, it supplies the notification of acceptance of TFS mode to PA layer 13 (S23). PA layer 13 supplies a TFS mode change instruction to PHY 14 (S24).

[0124] In parallel with this, in device 20, PA layer 23 supplies a TFS mode status notification to DL layer 22 (S25), and supplies a TFS mode status notification to control unit 21 (S26). When PA layer 23 supplies a transmission restart request to DL layer 22 (S27), DL layer 22 restarts data transmission. As a result, PA layer 23 and DL layer 22 switch the communication mode from non-TFS mode to TFS mode. DL layer 22 generates a data frame DF according to the TFS mode and supplies it to PA layer 23 (S28). PA layer 23 generates a TFS from the data frame DF according to the TFS mode and supplies it to PHY 24 (S29). PHY 24 transmits the TFS to device 10 (S30).

[0125] In parallel with this, in device 10, the PA layer 13 supplies a TFS mode status notification to the control unit 11 (S31), and supplies a TFS mode status notification to the DL layer 12 (S32). When the PA layer 13 supplies a transmission restart request to the DL layer 12 (S33), the DL layer 12 restarts data transmission. As a result, the PA layer 13 and the DL layer 12 switch the communication mode from non-TFS mode to TFS mode. The DL layer 12 supplies a data frame DF corresponding to the TFS mode to the PA layer 13 (S34). The PA layer 13 generates a TFS from the data frame DF according to the TFS mode and supplies it to the PHY 14 (S35). The PHY 14 transmits the TFS to device 20 (S36).

[0126] Next, the sequence of operations in which devices 10 and 20 transition from TFS mode to non-TFS mode in System 1 will be explained using Figure 6. Figure 6 is a sequence diagram showing the operation of System 1.

[0127] In device 10, when the control unit 11 supplies a non-TFS mode request to the PA layer 13 (S41), the PA layer 13 supplies a transmission stop request to the DL layer 12 (S42). The DL layer 12 stops transmitting the data frame DF and notifies the PA layer 13 that the transmission stop is complete (S43). When the PA layer 13 supplies a non-TFS mode request to the PHY 14 (S44), the PHY 14 sends a non-TFS mode request to device 20 (S45).

[0128] In device 20, when PHY 24 receives a non-TFS mode request, it supplies the non-TFS mode request to PA layer 23 (S46). PA layer 23 supplies the non-TFS mode request to control unit 21 (S47). Control unit 21 receives the non-TFS mode request (S48) and supplies a transmission stop request to PA layer 23 (S49). PA layer 23 supplies the transmission stop request to DL layer 22 (S50). DL layer 22 stops transmitting data frame DF and notifies PA layer 23 of the completion of transmission stop (S51). When PA layer 23 supplies non-TFS mode acceptance to PHY 24 (S52), PHY 24 transmits non-TFS mode acceptance to device 10 (S53).

[0129] In device 10, when PHY 14 receives non-TFS mode acceptance, it supplies non-TFS mode acceptance to PA layer 13 (S54). PA layer 13 supplies non-TFS mode acceptance to control unit 11 (S55). Control unit 11 receives non-TFS mode acceptance (S56) and supplies non-TFS mode transition request to PA layer 13 (S57). When PA layer 13 supplies non-TFS mode change instruction to PHY 14 (S58), PHY 24 sends non-TFS mode acceptance received notification to device 20 (S59).

[0130] In device 20, when PHY24 receives a non-TFS mode acceptance notification, it supplies the non-TFS mode acceptance notification to PA layer 23 (S60). When PA layer 23 supplies a non-TFS mode change instruction to PHY24 (S61), PHY24 sends a notification of receipt of the TFS mode acceptance notification to device 10 (S62).

[0131] In device 10, when PHY 14 receives a notification of acceptance of non-TFS mode, it supplies the notification of acceptance of non-TFS mode to PA layer 13 (S63). PA layer 13 supplies a non-TFS mode change instruction to PHY 14 (S64).

[0132] In parallel with this, in device 20, PA layer 23 supplies a non-TFS mode status notification to DL layer 22 (S65), and supplies a non-TFS mode status notification to control unit 21 (S66). When PA layer 23 supplies a transmission restart request to DL layer 22 (S67), DL layer 22 restarts data transmission. As a result, PA layer 23 and DL layer 22 switch the communication mode from TFS mode to non-TFS mode. DL layer 22 generates a data frame DF corresponding to the non-TFS mode and supplies it to PA layer 23 (S68). PA layer 23 converts the format from data frame DF according to the non-TFS mode and supplies it to PHY 24 (S69). PHY 24 transmits data frame DF to device 10 (S70).

[0133] In parallel with this, in device 10, PA layer 13 supplies a non-TFS mode status notification to control unit 21 (S71), and supplies a non-TFS mode status notification to DL layer 22 (S72). When PA layer 13 supplies a transmission restart request to DL layer 12 (S73), DL layer 12 restarts data transmission. As a result, PA layer 13 and DL layer 12 switch the communication mode from TFS mode to non-TFS mode. DL layer 12 supplies a data frame DF corresponding to the non-TFS mode to PA layer 13 (S74). PA layer 13 converts the format of the data frame DF according to the non-TFS mode and supplies it to PHY 14 (S75). PHY 14 transmits the data frame DF to device 20 (S76).

[0134] As described above, in the first embodiment, in the communication method, when the entire data frame DF is transmitted in TFS mode, the error detection code "TFS CRC" is added to the data instead of the error detection code "DL CRC" when the data frame DF is generated. This eliminates the need to transfer the error detection code "DL CRC", thereby improving data transfer efficiency.

[0135] (Second embodiment) Next, a communication method according to the second embodiment will be described. The following description will focus on the differences from the first embodiment.

[0136] In the first embodiment, a communication method is illustrated in which the generation of a data frame DF spanning multiple communication modes is permitted, while in the second embodiment, a communication method is illustrated in which the generation of a data frame DF spanning multiple communication modes is prohibited.

[0137] In the system 1 shown in Figure 1, when the communication mode switches from communication mode MD1 to communication mode MD2, the device 10 switches the operation for generating data frame DF from operation OP1 to operation OP2.

[0138] The contents of communication mode MD1, communication mode MD2, operation OP1, and operation OP2 are the same as in the first embodiment. Communication mode MD1 is, for example, a non-TFS mode. Communication mode MD2 is, for example, a TFS mode.

[0139] When the communication mode switches from communication mode MD2 to communication mode MD1, device 10 switches the operation for generating data frame DF from operation OP2 to operation OP1.

[0140] Similarly, when the communication mode switches from communication mode MD1 to communication mode MD2, the device 20 switches the operation for generating data frame DF from operation OP1 to operation OP2.

[0141] When the communication mode switches from communication mode MD2 to communication mode MD1, device 20 switches the operation for generating data frame DF from operation OP2 to operation OP1.

[0142] For example, the operation of the transmitting device differs from that of the first embodiment in the following respects, as shown in Figure 7. Figure 7 is a diagram showing the operation of the transmitting device in the second embodiment. Figure 7 illustrates the case where the transmitting device is device 10. Figure 7 mainly describes the operation of the DL layer 12 and the PA layer 13.

[0143] At timing t1, the same operations as in the first embodiment are performed, and then at timing t41, the PA layer 13 supplies a transmission stop request to the DL layer 12 as preparation before switching to TFS mode. In response to the transmission stop request, the DL layer 12 completes "SOF,data" in data frame DF11, generates "DL CRC" using "SOF,data" in data frame DF11, and makes it data frame DF11. The DL layer 12 supplies a transmission stop completion notification to the PA layer 13 as a notification of acceptance of switching to TFS mode.

[0144] Between timings t1 and t42, the DL layer 12 supplies the data frame DF11 to the PA layer 13. The PA layer 13 supplies the data frame DF11 to the PHY 14, which then transmits it to the device 20 via the communication line 31.

[0145] At timing t43, the PA layer 13 transitions the TFS mode status signal from the non-active level to the active level in response to the transmission stop completion notification. The PA layer 13 begins supplying the active-level TFS mode status signal to the DL layer 12. The DL layer 12 and the PA layer 13 each begin operating in TFS mode.

[0146] Simultaneously, the DL layer 12 begins generating a data frame DF12 according to the TFS mode based on the transmitted information. The DL layer 12 begins generating the data frame DF12 in a format that does not include "DL CRC".

[0147] The DL layer 12 may generate a data frame DF in a format in which the SOF field in the format shown in Figure 3(b) is replaced with "000" as a data frame DF12 according to the TFS mode. The DL layer 12 may also generate a data frame DF in a format in which the SOF field is "000" and the CCITT_CRC-16 field is omitted.

[0148] Although the SOF field value is the same for data frame DF corresponding to TFS mode and data frame DF corresponding to non-TFS mode, DL layer 12 can recognize that the current communication mode is TFS mode by checking the active-level TFS mode status signal.

[0149] The DL layer 12 begins supplying the data frame DF12 to the PA layer 13. The PA layer 13 begins converting the data frame DF12 to TFS#1, depending on the TFS mode. The PA layer 13 includes the first part of the data frame DF12, "SOF,data", into TFS#1.

[0150] At timing t44, PA layer 13 begins generating "TFS CRC" using "SOF,data" from TFS#1 and begins incorporating it into TFS#1.

[0151] Between timings t43 and t6, the PA layer 13 provides TFS#1 to the PHY 14, and the PHY 14 transmits it to the device 20 via the communication line 31.

[0152] Between timings t44 and t45, the DL layer 12 supplies the remaining portion of the data frame DF12, "data," to the PA layer 13. The PA layer 13 then includes "data" in TFS#2.

[0153] At timing t7, PA layer 13 begins generating "TFS CRC" using "data" from TFS#2 and begins incorporating it into TFS#2.

[0154] Between timings t6 and t8, the PA layer 13 provides TFS#2 to the PHY 14, and the PHY 14 transmits it to the device 20 via the communication line 31.

[0155] At timing t8, the DL layer 12 begins generating data frame DF13 according to the TFS mode based on the transmitted information. The DL layer 12 begins generating data frame DF12 in a format that does not include "DL CRC".

[0156] The DL layer 12 may generate a data frame DF as a data frame DF13 corresponding to the TFS mode, in which SOF in the format shown in Figure 3(b) is replaced with "000".

[0157] Between timings t8 and t10, the DL layer 12 supplies the first portion of the data frame DF13, up to "SOF,data", to the PA layer 13. The PA layer 13 includes "SOF,data" in TFS#3.

[0158] At timing t10, PA layer 13 begins generating "TFS CRC" using "SOF,data" from TFS#3, and begins incorporating it into TFS#3.

[0159] Between timings t8 and t11, the PA layer 13 provides TFS#3 to the PHY 14, and the PHY 14 transmits it to the device 20 via the communication line 31.

[0160] Between timings t10 and t12a, the DL layer 12 supplies the remaining portion of the data frame DF12, "data," to the PA layer 13. The PA layer 13 then includes "data" in TFS#4.

[0161] At timing t13, PA layer 13 begins generating "TFS CRC" using "data" in TFS#4 and begins incorporating it into TFS#4.

[0162] At timing t46, the PA layer 13 sends a transmission stop request to the DL layer 12 as a request to switch to non-TFS mode. In response to the transmission stop request, the DL layer 12 completes the remaining part "data" of the data frame DF13. The DL layer 12 sends a transmission stop completion notification to the PA layer 13 as a notification of acceptance of switching to non-TFS mode.

[0163] Between timings t11 and t47, the PA layer 13 supplies TFS#4 to the PHY 14, and the PHY 14 transmits it to the device 20 via the communication line 31.

[0164] In response to the transmission stop completion notification, the PA layer 13 transitions the TFS mode status signal from the active level to the inactive level. The PA layer 13 then begins supplying the inactive level TFS mode status signal to the DL layer 12. The DL layer 12 and the PA layer 13 then begin operating in non-TFS mode.

[0165] At timing t48, the PA layer 13 sends a transmission restart request to the DL layer 12. In response to the transmission restart request, the DL layer 12 begins generating a data frame DF14 corresponding to the non-TFS mode based on the transmission information.

[0166] The DL layer 12 may generate a data frame DF in the format shown in Figure 3(a) as a data frame DF14 corresponding to the non-TFS mode.

[0167] At timing t49, the DL layer 12 completes the "SOF,data" in data frame DF14, and uses "SOF,data" in data frame DF14 to generate "DL CRC" and begin incorporating it as part of data frame DF14.

[0168] Between timings t48 and t50, the DL layer 12 supplies the data frame DF14 to the PA layer 13. The PA layer 13 supplies the data frame DF14 to the PHY 14, which then transmits it to the device 20 via the communication line 31.

[0169] As shown in Figure 7, data frames DF11 and DF14, corresponding to non-TFS mode, are both transmitted within the period of operation in non-TFS mode. Data frames DF12 and DF13, corresponding to TFS mode, are both transmitted within the period of operation in TFS mode. This indicates that the generation of data frames DF that span multiple communication modes is prohibited.

[0170] The operation of the receiving device differs from that of the first embodiment in the following respects, as shown in Figure 8. Figure 8 is a diagram illustrating the operation of the receiving device in the second embodiment. Figure 8 illustrates the case where the receiving device is device 20. Figure 8 mainly describes the operation of the DL layer 22 and the PA layer 23.

[0171] Between timings t21 and t51, the PA layer 23 receives the data frame DF11 and provides it to the DL layer 22. Upon receiving "DL CRC", the DL layer 22 recognizes that the data frame DF11 has been completed.

[0172] The DL layer 22 performs error detection on "SOF,data" using "DL CRC" to confirm whether the data frame DF11 was received correctly. The DL layer 22 supplies the confirmation result to the control unit 21.

[0173] At timing t52, the PA layer 23 transitions the TFS mode status signal from the non-active level to the active level. The PA layer 23 begins supplying the active-level TFS mode status signal to the DL layer 22. The PA layer 23 begins operating in TFS mode.

[0174] At the same time, the PA layer 23 receives TFS#1 from the device 10 via the communication line 31 and PHY 24.

[0175] At timing t54, DL layer 22 begins receiving an active-level TFS mode status signal from PA layer 23. DL layer 22 begins operating in TFS mode.

[0176] At timing t54, the PA layer 23 performs error detection on "SOF,data" included in TFS#1 using "TFS CRC" to confirm whether TFS#1 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22. Once error detection is complete, the PA layer 23 begins supplying the data frame DF12's "SOF,data" to the DL layer 22.

[0177] PA layer 23 receives TFS#2 from device 10 via communication line 31 and PHY 24.

[0178] At timing t27, the PA layer 23 performs error detection on "SOF,data" included in TFS#2 using "TFS CRC" to confirm whether TFS#2 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22.

[0179] At timing t27, the PA layer 23 begins supplying the "data" contained in TFS#2 to the DL layer 22.

[0180] At timing t56, the DL layer 22 holds the "data" supplied from the PA layer 23. The DL layer 22 constructs a data frame DF12 that includes the held "SOF,data" and "data". The DL layer 22 constructs the data frame DF12 in a format that does not include "DL CRC". Based on the data frame DF12, the DL layer 22 generates received information according to the TFS mode and supplies the received information to the control unit 21.

[0181] After the same operation as in the first embodiment is performed at timings t28 to t29, at timing t57, the DL layer 22 holds the "SOF,data" supplied from the PA layer 23.

[0182] PA layer 23 supplies the "data" contained in TFS#4 to DL layer 22.

[0183] At timing t58, the PA layer 23 performs error detection on the "data" contained in TFS#4 using "TFS CRC" to confirm whether TFS#4 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22.

[0184] At timing t60, the PA layer 23 transitions the TFS mode status signal from the active level to the inactive level. The PA layer 23 begins supplying the inactive level TFS mode status signal to the DL layer 22. The PA layer 23 begins operating in non-TFS mode.

[0185] Between timings t58 and t59, the DL layer 22 receives "data" from the PA layer 23. The DL layer 22 recognizes that the data frame DF13 is complete. The DL layer 22 constructs the data frame DF13 containing the held "SOF,data" and "data". The DL layer 22 constructs the data frame DF13 in a format that does not include "DL CRC". Based on the data frame DF13, the DL layer 22 generates received information according to the TFS mode and supplies the received information to the control unit 21.

[0186] At timing t60, DL layer 22 begins receiving a non-active level TFS mode status signal from PA layer 23. DL layer 22 begins operating in non-TFS mode.

[0187] At the same time, the PA layer 23 supplies a portion of the data frame DF14 from the beginning, "SOF,data", to the DL layer 22.

[0188] At timing t61, the PA layer 23 receives the remaining portion of data frame DF14, "DL CRC," from the device 10 via the communication line 31 and the PHY layer 21. The PA layer 23 then supplies data frame DF3 to the DL layer 22.

[0189] The DL layer 22 performs error detection on the held "SOF,data" using "DL CRC" to confirm whether the data frame DF14 was received correctly and supplies the confirmation result to the control unit 21. At the same time, the DL layer 22 constructs the data frame DF14, which includes "SOF,data" and "DL CRC". Based on the data frame DF14, the DL layer 22 generates reception information corresponding to the non-TFS mode and supplies the reception information to the control unit 21.

[0190] As shown in Figure 8, data frames DF11 and DF14 corresponding to non-TFS mode were both received within the period of operation in non-TFS mode. Data frames DF12 and DF13 corresponding to TFS mode were both received within the period of operation in TFS mode. This indicates that the generation of data frames DF spanning multiple communication modes is prohibited.

[0191] As described above, in the second embodiment, the generation of data frame DF spanning multiple communication modes is prohibited in the communication method, and when the entire data frame DF is transmitted in TFS mode, the error detection code "TFS CRC" is added to the data instead of the error detection code "DL CRC" when generating the data frame DF. This eliminates the need to transfer the error detection code "DL CRC", thereby improving data transfer efficiency.

[0192] As a variation of the second embodiment, the control of switching between multiple communication modes may be performed using the value of the SOF field in the data frame DF format, instead of being performed at the level of the TFS mode status signal.

[0193] In this case, the operation of the transmitting device differs from that of the second embodiment in the following respects, as shown in Figure 9. Figure 9 is a diagram illustrating the operation of the transmitting device in a modified example of the second embodiment. Figure 9 illustrates the case where the transmitting device is device 10. Figure 9 mainly describes the operation of the DL layer 12 and the PA layer 13.

[0194] After the same operations as in the second embodiment are performed at timings t1 to t42, at timing t71, the PA layer 13 transitions the TFS mode status signal from a non-active level to an active level. The PA layer 13 begins supplying the active-level TFS mode status signal to the DL layer 12. The DL layer 12 and the PA layer 13 each begin operating in TFS mode.

[0195] Simultaneously, the DL layer 12 begins generating a data frame DF12 according to the TFS mode based on the transmitted information. The DL layer 12 begins generating the data frame DF12 in a format that does not include "DL CRC".

[0196] The DL layer 12 may generate a data frame DF in the format shown in Figure 3(b) as a data frame DF2 corresponding to the TFS mode. The DL layer 12 may also generate a data frame DF in a format where the SOF field is "100".

[0197] The DL layer 12 begins supplying the data frame DF12 to the PA layer 13. The PA layer 13 begins converting the data frame DF12 to TFS#1 depending on the TFS mode.

[0198] After the same operations as in the second embodiment are performed at timings t44 to t7, at timing t72, the DL layer 12 begins to generate a data frame DF12 according to the TFS mode based on the transmitted information. The DL layer 12 begins to generate the data frame DF12 in a format that does not include "DL CRC".

[0199] The DL layer 12 may generate a data frame DF in the format shown in Figure 3(b) as a data frame DF2 corresponding to the TFS mode. The DL layer 12 may also generate a data frame DF in a format where the SOF field is "100".

[0200] From timing t10 ​​onward, the same operation as in the second embodiment is performed.

[0201] The operation of the receiving device differs from that of the second embodiment in the following respects, as shown in Figure 10. Figure 10 is a diagram illustrating the operation of the receiving device in a modified example of the second embodiment. Figure 10 illustrates the case where the receiving device is device 20. Figure 10 mainly describes the operation of the DL layer 22 and the PA layer 23.

[0202] After the same operation as in the second embodiment is performed at timings t21 to t51, at timing t81, the PA layer 23 receives TFS#1 from the device 10 via the communication line 31 and the PHY layer 21.

[0203] After the same operation as in the second embodiment is performed at timing t53, at timing t82, the DL layer 22 begins to receive "SOF,data" of data frame DF12 from the PA layer 23. Depending on whether the SOF of data frame DF12 is "100", the DL layer 22 begins to operate in TFS mode.

[0204] At the same time, the PA layer 23 performs error detection on "SOF,data" contained in TFS#1 using "TFS CRC" to confirm whether TFS#1 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22.

[0205] The PA layer 23 receives TFS#2 from the device 10 via the communication line 31 and the PHY layer 21.

[0206] After the same operation as in the second embodiment is performed at timings t55 to t28, at timing t83, the PA layer 23 performs error detection on "SOF,data" included in TFS#3 using "TFS CRC" to confirm whether TFS#3 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22.

[0207] The PA layer 23 receives TFS#4 from the device 10 via the communication line 31 and the PHY layer 21.

[0208] Simultaneously, DL layer 22 begins receiving "SOF,data" for data frame DF13 from PA layer 23. DL layer 22 continues to operate in TFS mode, depending on the SOF of data frame DF12 being "100".

[0209] At timing t57, the same operation as in the second embodiment is performed. Then, at timing t84, the PA layer 23 performs error detection on the "data" contained in TFS#4 using "TFS CRC" to confirm whether TFS#4 was received correctly, and supplies the confirmation result to the control unit 21 via the DL layer 22.

[0210] At the same time, PA layer 23 begins operating in non-TFS mode.

[0211] PA layer 23 supplies a request to stop reception to DL layer 22.

[0212] At timing t59, the same operation as in the second embodiment is performed, and then at timing t85, the PA layer 23 supplies the data frame DF14 "SOF,data" and the error detection code "DL CRC" to the DL layer 22.

[0213] The DL layer 22 begins receiving "SOF,data" for data frame DF14 from the PA layer 23. Depending on whether the SOF of data frame DF14 is "000", the DL layer 22 begins operating in non-TFS mode.

[0214] Subsequently, at timing t61, the same operation as in the second embodiment is performed.

[0215] Even in this communication method, the generation of data frame DF that spans multiple communication modes is prohibited, and when the entire data frame DF is transmitted in TFS mode, the error detection code "TFS CRC" is added to the data instead of the error detection code "DL CRC" when the data frame DF is generated. This eliminates the need to transfer the error detection code "DL CRC," thereby improving data transfer efficiency.

[0216] (Third embodiment) Next, a communication method according to the third embodiment will be described. The following description will focus on the differences from the first and second embodiments.

[0217] In the first and second embodiments, a format of dataframe DF in which the error detection code field is omitted is illustrated, but in the third embodiment, a format of dataframe DF in which the error detection code field is replaced with AFC (Acknowledgement and Flow Control) information is illustrated.

[0218] In system 1, device 10 performs operation OP2 when condition CD2 is met with respect to communication mode MD1 and communication mode MD2.

[0219] Communication mode MD1 uses transmission unit TU1. Transmission unit TU1 may have a fixed length. Communication mode MD2 uses transmission unit TU2. Transmission unit TU2 may have a different data length from transmission unit TU1. Transmission unit TU2 may have a variable length.

[0220] Condition CD2 may include the condition that the entire data frame DF is transmitted in communication mode MD2.

[0221] Operation OP2 is similar to the first embodiment in that it generates data frame DF by adding error detection code CRC1 to the data without adding error detection code CRC2 to the data. However, it differs from the first embodiment in that it generates data frame DF by adding AFC (Acknowledgement and Flow Control) information to the data instead of error detection code CRC2.

[0222] Similarly, the device 20 performs operation OP2 when condition CD2 is met with respect to communication mode MD1 and communication mode MD2.

[0223] Operation OP2 is similar to the first embodiment in that it generates data frame DF by adding error detection code CRC1 to the data without adding error detection code CRC2 to the data. However, it differs from the first embodiment in that it generates data frame DF by adding AFC (Acknowledgement and Flow Control) information to the data instead of error detection code CRC2.

[0224] For example, in the first embodiment, the format of the data frame DF shown in Figure 3(b) is exemplified as a data frame DF corresponding to the TFS mode, but the omitted CCITT_CRC-16 field can also be considered as a 16-bit reserved field, as shown by the dotted line in Figure 11(a).

[0225] On the other hand, in communication between device 10 and device 20, in addition to data frame DF, AFC frames as shown in Figure 11(b) are also transmitted and received.

[0226] The AFC frame shown in Figure 11(b) includes the ESC_DL field, AFC field, TC field, CReq field, Reserved field, Frame_Seq._Number field, Reserved field, Credit Value field, and CCITT_CRC-16 field.

[0227] Of these, all fields except for the Frame_Seq._Number, TC, CReq, and Credit Value fields enclosed in the dotted lines can be omitted. The sum of the number of bits in the Frame_Seq._Number, TC, CReq, and Credit Value fields enclosed in the dotted lines is 16 bits, which is 16 bits or less.

[0228] Therefore, as indicated by the dotted arrows, the information from the Frame_Seq._Number, TC, CReq, and Credit Value fields of the AFC frame can be replaced with AFC information in the CCITT_CRC-16 field of the data frame DF format. This allows us to define the data frame DF format as shown in Figure 11(c).

[0229] The SOF field stores "111," indicating that the data frame DF is a data frame corresponding to the TFS mode and contains AFC information. The SOF field can have a length of 3 bits.

[0230] Devices 10 and 20 may each transmit and receive data frames corresponding to the TFS mode in the format shown in Figure 11(c) instead of the format shown in Figure 3(b). The specific operation of transmission and reception may be the same as in the first embodiment or the same as in the second embodiment. This allows data frame DF and AFC frames to be transmitted and received together in data frame DF, further improving data transfer efficiency.

[0231] As described above, in the third embodiment, in the communication method, when the entire data frame DF is transmitted in TFS mode, AFC information is added to the data in place of the error detection code "DL CRC" to generate the data frame DF. This eliminates the need to transfer the AFC frame, thereby further improving the data transfer efficiency.

[0232] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0233] 1 system, 10,20 devices, 15,25 interface circuits.

Claims

1. A first operation is performed to generate a data frame by adding a first error detection code corresponding to at least the first transmission unit to the data when a first condition is met with respect to a first mode using a first transmission unit and a second mode using a second transmission unit, A second operation is performed in which, when a second condition is met with respect to the first mode and the second mode, the first error detection code is added to the data without adding the second error detection code to the data and a data frame is generated. Transmitting the data frame generated by the first operation or the second operation, A communication method that includes this.

2. Performing the first operation described above means The first operation includes generating a data frame by adding the first error detection code and the second error detection code to the data when a portion of the data frame is transmitted in the first mode and another portion of the data frame is transmitted in the second mode, Performing the second operation described above means The second operation includes, when the entire data frame is transmitted in the second mode, adding the first error detection code to the data without adding the second error detection code to the data to generate the data frame. The communication method according to claim 1.

3. The present invention further includes switching the operation for generating a data frame from the first operation to the second operation when switching from the first mode to the second mode. The communication method according to claim 1.

4. The present invention further includes switching the operation for generating a data frame from the second operation to the first operation when switching from the second mode to the first mode. The communication method according to claim 3.

5. Performing the second operation described above means The second operation includes, when the second condition is met with respect to the first mode and the second mode, adding AFC (Acknowledgment and Flow Control) information to the data in place of the second error detection code to generate a data frame. The communication method according to claim 1.

6. A generation unit performs a first operation to generate a data frame by adding a first error detection code corresponding to at least the first transmission unit to the data when a first condition is met with respect to a first mode using a first transmission unit and a second mode using a second transmission unit, and a second operation to generate a data frame by adding the first error detection code to the data without adding a second error detection code when a second condition is met with respect to the first mode and the second mode, A transmission unit that transmits the data frame generated by the first operation or the second operation, An interface circuit is provided.

7. The first condition includes that a portion of the data frame is transmitted in the first mode and another portion of the data frame is transmitted in the second mode. The second condition includes that the entire data frame is transmitted in the second mode. The interface circuit according to claim 6.

8. The generation unit switches the operation for generating data frames from the first operation to the second operation when switching from the first mode to the second mode. The interface circuit according to claim 6.

9. The generation unit switches the operation for generating data frames from the second operation to the first operation when switching from the second mode to the first mode. The interface circuit according to claim 8.

10. The generation unit performs the second operation, which generates a data frame by adding AFC (Acknowledgment and Flow Control) information to the data in place of the second error detection code, when the second condition is met with respect to the first mode and the second mode. The interface circuit according to claim 6.

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