A Synchronization Method for Aircraft Management System Based on 1394B Bus

Abstract

The present application belongs to the field of aircraft management system synchronization technology, and particularly relates to an aircraft management system synchronization method based on 1394B bus. The method includes step S1, powering on an aircraft management system with multiple synchronization channels to realize system booting and initialization of each channel; step S2, controlling each synchronization channel to send a custom synchronization block containing a synchronization word to other channels, and each synchronization channel determines whether the power-on time synchronization of each channel fails based on the collected synchronization words of other channels; step S3, controlling each synchronization channel to send a custom synchronization block containing a small frame number to other channels, and each synchronization channel determines whether the small frame number synchronization of each channel fails based on the collected small frame number; step S4, determining whether the small frame number of each channel is abnormal based on the sending cycle of the custom synchronization block containing the small frame number and the small frame number value of each channel itself. The present application ensures the correctness and integrity of the synchronization of the redundant aircraft management system.

Description

Technical Field

[0001] The present application belongs to the technical field of synchronization of aircraft management systems, and in particular to a synchronization method of an aircraft management system based on a 1394B bus. Background Art

[0002] The emergence of aircraft management systems has integrated the traditionally discrete flight control systems, engine control systems and electromechanical systems into an integrated system through the integration of control, physics and functions to improve the overall performance of the aircraft.

[0003] Based on the idea of ​​forward design, the bus selection requirements of the aircraft management system were extracted, and the quantitative and qualitative requirements analysis of the aircraft management system was carried out. According to the requirement indicators, the compliance analysis of the airborne bus was carried out, and it was found that the 1394B bus met the system requirements.

[0004] For redundant aircraft management systems, clock synchronization is the basis for the normal operation of system functions. Clock asynchrony will lead to system degradation. Traditionally, computers are synchronized using hard wires. However, with the development of electronic technology and bus technology, it is feasible to use 1394B bus to achieve system synchronization in redundant system design.

[0005] In the prior art, there are studies on the synchronization technology of triple-redundant optical transmission systems, but most of them focus on the system architecture research; while the research on the configuration and implementation technology of triple-redundant optical transmission buses usually focuses on the design of protocol chips. In addition, there is no complete public method for NVM fault recording of redundant system synchronization. Summary of the invention

[0006] In order to solve at least one of the above technical problems, the present application designs an aircraft management system synchronization method based on 1394B bus, records faults through NVM, and ensures the correctness and integrity of the synchronization of redundant aircraft management systems.

[0007] The aircraft management system synchronization method based on the 1394B bus of this application mainly includes:

[0008] Step S1, powering on an aircraft management system having multiple synchronous channels to boot the system and initialize each channel;

[0009] Step S2, controlling each synchronization channel to send a custom synchronization block containing a synchronization word to other channels, and each synchronization channel determines whether the power-on time synchronization of each channel fails according to the collected synchronization words of other channels, and records the failure of a channel according to a preset record table through the NVM;

[0010] Step S3, controlling each synchronization channel to periodically send the custom synchronization block containing the small frame number to other channels, and each synchronization channel determines whether the small frame number synchronization of each channel fails according to the collected small frame number, and if there is a channel failure, records it through the NVM according to a preset record table;

[0011] Step S4: determine whether the small frame number of each channel is abnormal according to the sending period of the custom synchronization block containing the small frame number and the small frame number value of each channel itself. If there is an abnormality, record it through NVM according to a preset record table.

[0012] Preferably, in step S2, the custom synchronization block at least includes a message ID and a message load for distinguishing different channels, and the message load at least includes a first synchronization word write bit, a second synchronization word write bit, a small frame number synchronization word write bit, a power-down mark write bit, and a comprehensive wheel load write bit;

[0013] Controlling each synchronization channel to send a custom synchronization block containing a synchronization word to other channels further includes:

[0014] The first synchronization is performed by writing data indicating a high level into the first synchronization word write bit, and setting the second synchronization word write bit and the small frame number synchronization word write bit to zero;

[0015] The second synchronization is performed by writing data representing a low level into the second synchronization word write bit and setting the first synchronization word write bit and the small frame number synchronization word write bit to zero.

[0016] Preferably, the first synchronization or the second synchronization each includes:

[0017] Read the first synchronization word or the second synchronization word of other channels;

[0018] If the first synchronization word or the second synchronization word of all other channels are collected, it means that the first synchronization or the second synchronization is successful. If there is a first synchronization word or a second synchronization word of a channel that has not been collected, the failure of the first synchronization word or the second synchronization word of the channel that has not been collected is recorded through NVM. If the first synchronization word or the second synchronization word of more than two channels has not been collected, the failure of this channel is further recorded through NVM.

[0019] Preferably, recording the synchronization word failure through NVM, or recording the channel failure through NVM further comprises:

[0020] Determine whether the aircraft is in a reset state when it currently starts multi-channel communication, and determine whether the aircraft is in the air or on the ground, and assign values ​​to the comprehensive wheel load write bits of the custom synchronization blocks sent externally by each channel;

[0021] In the recording parameters of the NVM, the synchronization state when the sending of the synchronization word fails or the channel fails is recorded as reset, air or ground according to the mapping relationship.

[0022] Preferably, in step S3, controlling each synchronization channel to periodically send a custom synchronization block containing a small frame number to other channels further comprises:

[0023] The small frame number is synchronized by writing the small frame number into the small frame number synchronization word write bit and setting the first synchronization word write bit and the second synchronization word write bit to zero.

[0024] Preferably, when performing small frame number synchronization, the method further includes:

[0025] The maximum value among the small frame numbers of each channel read is used as the small frame number of the current channel.

[0026] Preferably, in step S4, determining whether the small frame number of each channel is abnormal includes:

[0027] Determine that the sending period of the custom synchronization block containing the small frame number is n times the channel sampling period;

[0028] It is determined in turn whether the collected small frame numbers are all integer values ​​from 1 to n. If so, it indicates that the small frame number of the corresponding channel is normal, otherwise it indicates that the small frame number of the corresponding channel is abnormal.

[0029] The advantages and beneficial effects of this application are:

[0030] The present application provides a complete aircraft management system synchronization method based on 1394B bus, realizing redundant system synchronization; the name, type and length of the fault are recorded through NVM, so that the synchronization accuracy of multiple channels reaches the us level. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a method flow chart of a preferred implementation of the aircraft management system synchronization method based on 1394B bus of the present application.

[0032] Figure 2 This is a schematic diagram of power-on time synchronization for this application.

[0033] Figure 3 This is the small frame number synchronization flow chart of this application.

[0034] Figure 4 This is a schematic diagram of synchronous monitoring of this application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the implementation of this application will be described in more detail in combination with the drawings in the implementation of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and cannot be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in combination with the drawings.

[0036] The present application provides an aircraft management system synchronization method based on 1394B bus, such as Figure 1 As shown, it mainly includes:

[0037] Step S1, power on the aircraft management system with multiple synchronous channels to achieve system booting and initialization of each channel.

[0038] In this step, system power-on is the basis for the operation of the redundant aircraft management system. After the system is powered on, system booting, hardware initialization (including CPU basic hardware initialization, channel fault logic initialization, output initialization, and channel number determination) and software operation will be completed in sequence.

[0039] Step S2, control each synchronization channel to send a custom synchronization block containing a synchronization word to other channels, and each synchronization channel determines whether the power-on time synchronization of each channel fails based on the collected synchronization words of other channels. If there is a channel failure, record it through NVM according to a preset record table.

[0040] In some optional implementations, in step S2, the custom synchronization block includes at least a message ID and a message payload for distinguishing different channels, and the message payload includes at least a first synchronization word write bit, a second synchronization word write bit, a small frame number synchronization word write bit, a power-down mark write bit, and a comprehensive wheel load write bit;

[0041] Controlling each synchronization channel to send a custom synchronization block containing a synchronization word to other channels further includes:

[0042] The first synchronization is performed by writing data indicating a high level into the first synchronization word write bit, and setting the second synchronization word write bit and the small frame number synchronization word write bit to zero;

[0043] The second synchronization is performed by writing data representing a low level into the second synchronization word write bit and setting the first synchronization word write bit and the small frame number synchronization word write bit to zero.

[0044] In this embodiment, power-on time synchronization is used to eliminate the time error accumulated during the power-on reset process of the redundant aircraft management computer. The synchronization method uses a software-based double handshake synchronization algorithm to achieve synchronization between channels. Each channel outputs a "logic high" through the synchronization interface, and queries the "logic high" output by other channels within a specified time. If the "logic high" is read normally, the first handshake is judged to be successful; then each channel outputs a "logic low", and queries the "logic low" output by other channels within a specified time. If the "logic low" is read normally, the second handshake is judged to be successful; if both handshakes are successful, the channel synchronization is judged to be successful; if any handshake fails, the synchronization is judged to be a failure.

[0045] The custom synchronization block of this application is CCDL_DATA7, which has a length of 76 bytes. Taking quadruple-redundant communication as an example, the message IDs of the A / B / C / D channels (absolute coordinate system) of the quadruple-redundant aircraft management computer are 0x2216, 0x6216, 0xA216, and 0xE216, respectively. The hexadecimal data occupies a total of 32 bytes. The message payload length of CCDL_DATA7 is 32 bytes, including 4 bytes of health status word, 4 bytes of heartbeat word, first synchronization word (4 bytes, 0x5A), second synchronization word (4 bytes, 0xA5), small frame number synchronization word 4 bytes, power-off mark 4 bytes, comprehensive wheel load 4 bytes, spare 4 bytes, and the other bytes are the data block header and tail. It should also be noted that the absolute coordinate system of quadruple-redundant communication is A / B / C / D, and the corresponding relative coordinate system is L channel / X channel / Y channel / Z channel. In the following description, L channel or A channel is recorded as this channel. This channel sends custom synchronization block CCDL_DATA7 to other channels and receives custom synchronization block CCDL_DATA7 from other channels at the same time. Synchronization judgment is performed based on the first synchronization word, the second synchronization word or the small frame number synchronization word in the custom synchronization block CCDL_DATA7.

[0046] In some optional implementations, the first synchronization or the second synchronization each includes:

[0047] Read the first synchronization word or the second synchronization word of other channels;

[0048] If the first synchronization word or the second synchronization word of all other channels are collected, it means that the first synchronization or the second synchronization is successful. If there is a first synchronization word or a second synchronization word of a channel that has not been collected, the failure of the first synchronization word or the second synchronization word of the channel that has not been collected is recorded through NVM. If the first synchronization word or the second synchronization word of more than two channels has not been collected, the failure of this channel is further recorded through NVM.

[0049] In some optional implementations, recording the synchronization word failure through the NVM, or recording the channel failure through the NVM further includes:

[0050] Determine whether the aircraft is in a reset state when it currently starts multi-channel communication, and determine whether the aircraft is in the air or on the ground, and assign values ​​to the comprehensive wheel load write bits of the custom synchronization blocks sent externally by each channel;

[0051] In the recording parameters of the NVM, the synchronization state when the sending of the synchronization word fails or the channel fails is recorded as reset, air or ground according to the mapping relationship.

[0052] The following are examples of the above embodiments. Figure 2 , which gives a specific flow chart of power-on time synchronization. The power-on time synchronization of step S2 mainly includes the following steps:

[0053] S11: Send the first synchronization word through CCDL_DATA7;

[0054] S12: Read the first synchronization word of CCDL_DATA7 of other channels;

[0055] S13: Determine whether the first synchronization word of CCDL_DATA7 is received. For a four-redundant aircraft management system, it is necessary to receive the first synchronization words of the other three channels (relative coordinate system, the current channel is the L channel, and the other three channels are the X channel / Y channel / Z channel). If they are received, enter S14, otherwise enter S15;

[0056] S14: This channel delays and waits for 50ms, then enters S19;

[0057] S15: Determine whether the time is 1.5s out of time. If so, go to S16, otherwise go to S11;

[0058] S16: Taking reset startup as an example, "Reset-power-on synchronization channel n first synchronization word failure" is recorded in NVM, where n is A / B / C / D. It should be noted that other channels are recorded here. For example, when the L channel of this channel (corresponding to the A channel in the relative coordinate system) executes this step S16, if the first synchronization word of the X channel (corresponding to the B channel in the relative coordinate system) is not received, then "Reset-power-on synchronization channel B first synchronization word failure" is fed back. According to the NVM recording rule of Article 9 in Table 1, 0x1B1B needs to be fed back. In the feedback code, the first "1" from the left represents reset, the second "1" represents the first time, the first "B" from the left represents that there is a problem with the B channel, and the second "B" is a Bit word, indicating that the synchronization word fails.

[0059] For another example, taking air communication as an example, when the L channel of the current channel (corresponding to the A channel in the relative coordinate system) executes step S16, if the first synchronization word of the Y channel (corresponding to the C channel in the relative coordinate system) is not received, then the feedback is "Air-power-on synchronization channel C first synchronization word failed". According to the NVM recording rule in Article 13 of Table 1, 0x2C1B needs to be fed back. In the feedback code, "2" represents air, "C" represents that there is a problem with the C channel, "1" represents the first time, and "B" is a Bit word, indicating that the synchronization word fails.

[0060] S17: Determine whether the number of synchronization channels is greater than or equal to 2, if so, proceed to S19, otherwise proceed to S18;

[0061] S18: Record "Reset-power-on synchronization channel n first synchronization channel failure" in NVM, where n is A / B / C / D; it should be noted that, different from step S16, the channel recorded here has a problem. If there are 2 or more channels that have not fed back the first synchronization word when the L channel of the channel executes step S18, it is very likely that there is a problem with the L channel of the channel. Therefore, what is onboard here is the failure of the first synchronization channel of the channel. According to the 10th NVM recording rule in Table 1, 0x1A1C needs to be fed back. In the feedback code, the first "1" from the left represents reset, the second "1" represents the first time, "A" represents that there is a problem with the L channel of the channel, and "C" is the first letter of the Channel channel, indicating that the channel fails.

[0062] S19: Send the second synchronization word through CCDL_DATA7; wherein, the power-down mark signal and the integrated load signal are sent to the remote channel (X channel / Y channel / Z channel) CPU. Considering that the time difference of each channel has been eliminated in the power-on time synchronization, and the power-down mark and the integrated load are sent synchronously with the second synchronization word, when the second synchronization word is received, it is synchronously determined that the CPU of this channel obtains the load and power-down mark sent by the other three channels through CCDL_DATA7;

[0063] S20: Read the second synchronization word of CCDL_DATA7 of other channels;

[0064] S21: Determine whether the second synchronization word of CCDL_DATA7 is received. The second synchronization word needs to be performed on the basis of the first synchronization. If it is received, enter S26, otherwise enter S22;

[0065] S22: Determine whether the time is 500us overtime, if so, enter S23, otherwise enter S19;

[0066] S23: Recording "Reset-Power-On Synchronous Channel n Second Synchronous Word Failure" in NVM, where n is A / B / C / D. The channel n recorded here is similar to step S16, and is other channels recorded;

[0067] S24: Determine whether the number of synchronization channels is greater than or equal to 2, if so, proceed to S26, otherwise proceed to S25;

[0068] S25: Record “Reset-power-on synchronization channel n second synchronization channel failure” in NVM, where n is A / B / C / D; this step is similar to step S18, and the recorded channel n is the current channel.

[0069] S26: Record the "power-on time synchronization comprehensive result" in NVM, where the order of the interface function reporting the power-on time synchronization comprehensive result is A / B / C / D channels. For example, if the current channel is channel A, it is synchronized with channels B / C, but not synchronized with channel D. Then the interface function reports 0xA55A5A5A. In the reported parameters, starting from the left, A5 indicates that channel D is faulty, the first 5A indicates that channel C is normal, the second 5A indicates that channel B is normal, and the third 5A indicates that channel A is normal. See items 25 and 26 of Table 1 for the recording rules of NVM.

[0070] Step S3, control each synchronization channel to periodically send the custom synchronization block containing the small frame number to other channels, and each synchronization channel determines whether the small frame number synchronization of each channel fails based on the collected small frame number. If there is a channel failure, record it through NVM according to a preset record table.

[0071] In some optional embodiments, controlling each synchronization channel to periodically send a custom synchronization block containing a small frame number to other channels further includes: synchronizing the small frame number by writing the small frame number into the small frame number synchronization word write bit, and setting the first synchronization word write bit and the second synchronization word write bit to zero.

[0072] In some optional implementations, when performing small frame number synchronization, it further includes: taking the maximum value among the small frame numbers of each channel read as the small frame number of the current channel.

[0073] Small frame number synchronization is used to synchronize the small frame number of redundant aircraft management computers to eliminate the inconsistency of redundancy voting. The synchronization method uses a single handshake synchronization algorithm based on software to achieve synchronization between channels. Each channel outputs a "small frame number" through the synchronization interface, and queries the "small frame number" output by other channels within a specified time. If the "small frame number" is read normally, the maximum small frame number is selected as the small frame number of this channel. Reference Figure 3 ,The specific process of small frame number synchronization includes:

[0074] S31: Send the small frame number through CCDL_DATA7; wherein, CCDL_DATA7 is defined to achieve synchronization, and the small frame number synchronization word is 4 bytes;

[0075] S32: Read the CCDL_DATA7 small frame number of other channels;

[0076] S33: Determine whether the CCDL_DATA7 small frame number is received in full. For a four-redundant aircraft management system, the small frame numbers of the other three channels (X channel / Y channel / Z channel) need to be received. If they are received in full, enter S34, otherwise enter S35, where the small frame number needs to be synchronized based on the power-on time.

[0077] S34: Select the maximum value of the small frame number. For a four-redundant aircraft management system, it is necessary to select the maximum value of the small frame number of the current channel (L channel) and the other three channels (X channel / Y channel / Z channel);

[0078] S35: Send the small frame number again through CCDL_DATA7;

[0079] S36: Read the CCDL_DATA7 small frame number of other channels;

[0080] S37: Determine whether the CCDL_DATA7 small frame number is received in full. For a four-redundant aircraft management system, the small frame numbers of the other three channels (X channel / Y channel / Z channel) need to be received. If they are received in full, go to S38, otherwise go to S39;

[0081] S38: Select the maximum value of the small frame number. For the quad-redundant aircraft management system, it is necessary to select the maximum value of the small frame number of this channel (L channel) and the other three channels (X channel / Y channel / Z channel). The small frame number needs to be synchronized based on the power-on time.

[0082] S39: Record "small frame number synchronization channel n failed" in NVM, where n is A / B / C / D, as shown in the record of sequence number 32 in Table 1.

[0083] Step S4: determine whether the small frame number of each channel is abnormal according to the sending period of the custom synchronization block containing the small frame number and the small frame number value of each channel itself. If there is an abnormality, record it through NVM according to a preset record table.

[0084] In some optional embodiments, in step S4, determining whether the small frame number of each channel is abnormal includes: determining that the sending period of the custom synchronization block containing the small frame number is n times the channel sampling period; and judging in turn whether the collected small frame numbers are all integer values ​​from 1 to n, if so, it indicates that the small frame number of the corresponding channel is normal, otherwise it indicates that the small frame number of the corresponding channel is abnormal.

[0085] The value of n is usually 8, but it can also be other values. For the convenience of description, taking n=2 as an example, all integers between 1 and 2 are 1 and 2. Figure 4 The synchronous monitoring shown determines whether the small frame number of CCDL_DATA7 is equal to 1 or 2. The specific process is as follows:

[0086] S41: Read the small frame number of CCDL_DATA7, which is the current channel (L channel);

[0087] S42: Determine whether the small frame number of CCDL_DATA7 is equal to 1, if so, go to S43, otherwise go to S44;

[0088] S43: The small frame number is normal, not recorded in NVM, and the interface function is displayed normally;

[0089] S44: Determine whether the small frame number of CCDL_DATA7 is equal to 2, if so, go to S43, otherwise go to S5;

[0090] S45: Record “small frame number abnormal channel n” in NVM, where n is A / B / C / D, as shown in the record of sequence number 33 in Table 1.

[0091] Table 1 NVM record comparison table

[0092]

[0093]

[0094] The present application designs a synchronization method for an aircraft management system based on the 1394B bus, which realizes the synchronization of redundant aircraft management systems through system power-on, power-on time synchronization, small frame number synchronization, and synchronous monitoring. The synchronization accuracy is at the us level, and the NVM fault record format is provided to ensure the correctness and integrity of the synchronization of the redundant aircraft management system.

[0095] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A synchronization method for an aircraft management system based on a 1394B bus, characterized in that: include: Step S1, powering on an aircraft management system having multiple synchronous channels to boot the system and initialize each channel; Step S2, controlling each synchronization channel to send a custom synchronization block containing a synchronization word to other channels, and each synchronization channel determines whether the power-on time synchronization of each channel fails according to the collected synchronization words of other channels, and records the failure of a channel according to a preset record table through the NVM; Step S3, controlling each synchronization channel to periodically send the custom synchronization block containing the small frame number to other channels, and each synchronization channel determines whether the small frame number synchronization of each channel fails according to the collected small frame number, and if there is a channel failure, records it through the NVM according to a preset record table; Step S4: determine whether the small frame number of each channel is abnormal according to the sending period of the custom synchronization block containing the small frame number and the small frame number value of each channel itself. If there is an abnormality, record it through NVM according to a preset record table.

2. The 1394B bus-based aircraft management system synchronization method as claimed in claim 1, characterized in that: In step S2, the custom synchronization block at least includes a message ID and a message load for distinguishing different channels, and the message load at least includes a first synchronization word write bit, a second synchronization word write bit, a small frame number synchronization word write bit, a power-down mark write bit, and a comprehensive wheel load write bit; Controlling each synchronization channel to send a custom synchronization block containing a synchronization word to other channels further includes: The first synchronization is performed by writing data indicating a high level into the first synchronization word write bit, and setting the second synchronization word write bit and the small frame number synchronization word write bit to zero; The second synchronization is performed by writing data representing a low level into the second synchronization word write bit and setting the first synchronization word write bit and the small frame number synchronization word write bit to zero.

3. The 1394B bus-based aircraft management system synchronization method as claimed in claim 2, characterized in that: The first synchronization or the second synchronization each includes: Read the first synchronization word or the second synchronization word of other channels; If the first synchronization word or the second synchronization word of all other channels are collected, it means that the first synchronization or the second synchronization is successful. If there is a first synchronization word or a second synchronization word of a channel that has not been collected, the failure of the first synchronization word or the second synchronization word of the channel that has not been collected is recorded through NVM. If the first synchronization word or the second synchronization word of more than two channels has not been collected, the failure of this channel is further recorded through NVM.

4. The 1394B bus-based aircraft management system synchronization method as claimed in claim 3, characterized in that: Recording the synchronization word failure through NVM, or recording the channel failure through NVM further includes: Determine whether the aircraft is in a reset state when it currently starts multi-channel communication, and determine whether the aircraft is in the air or on the ground, and assign values ​​to the comprehensive wheel load write bits of the custom synchronization blocks sent externally by each channel; In the recording parameters of the NVM, the synchronization state when the sending of the synchronization word fails or the channel fails is recorded as reset, air or ground according to the mapping relationship.

5. The 1394B bus-based aircraft management system synchronization method as claimed in claim 2, characterized in that: In step S3, controlling each synchronization channel to periodically send a custom synchronization block containing a small frame number to other channels further includes: The small frame number is synchronized by writing the small frame number into the small frame number synchronization word write bit and setting the first synchronization word write bit and the second synchronization word write bit to zero.

6. The 1394B bus-based aircraft management system synchronization method as claimed in claim 5, characterized in that: When performing small frame number synchronization, it further includes: The maximum value among the small frame numbers of each channel read is used as the small frame number of the current channel.

7. The 1394B bus-based aircraft management system synchronization method as claimed in claim 1, characterized in that: In step S4, determining whether the small frame number of each channel is abnormal includes: Determine that the sending period of the custom synchronization block containing the small frame number is n times the channel sampling period; It is determined in turn whether the collected small frame numbers are all integer values ​​from 1 to n. If so, it indicates that the small frame number of the corresponding channel is normal, otherwise it indicates that the small frame number of the corresponding channel is abnormal.

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