CN115037571B - A hub applied to star-shaped TTP network and its implementation method - Google Patents

Abstract

The present invention relates to the technical field of aircraft management system communication bus, and discloses a hub applied to a star-type TTP network, including a gating module and a transceiver module arranged at a physical link layer, and a startup control module, a synchronization control module, a clock generation and synchronization module, a MEDL parsing module, a frame parsing module, a cluster mode switching module, a shaping module, a frame length calculation module, and an online configuration module arranged at a protocol layer. The present invention also discloses an implementation method of a hub applied to a star-type TTP network, using the above-mentioned hub applied to a star-type TTP network. Based on the startup principle of the hub, the present invention proposes a startup scheme based on the Bigbang mechanism. At the same time, the startup scheme of the present invention includes three startup paths, which are adapted to various startup scenarios.

Description

A hub applied to star-shaped TTP network and its implementation method

Technical Field

The present invention relates to the technical field of aircraft management system communication bus, and in particular to a hub applied to a star-shaped TTP network and an implementation method thereof.

Background technique

In recent years, computer systems with high reliability, safety and criticality have been widely used in safety-critical fields such as aerospace, automotive and industrial control. Such computer systems essentially require a distributed solution so that damage to one part of the system will not cause the entire system to fail. However, spatial distribution means the implementation of a communication infrastructure that enables participants in the system to exchange information. For economic reasons, the communication infrastructure usually needs to be implemented as a shared resource, and a dedicated communication protocol must be implemented to coordinate its use. This communication protocol can be based on the synchronization of the local clocks of the participants, and a bus guard (BG) is used to protect and coordinate the use of shared resources. This network that protects and coordinates shared resources can be protected and coordinated by a bus-type time-triggered network, as shown in Figure 7; however, the use of a bus-type time-triggered network, because it is a dual-redundant system, requires 2n bus protectors, so the cost will be very high. In order to realize the function of protecting and coordinating shared resources, fewer hubs can be used in the star-type time-triggered network to realize the function of bus protection and coordination of TTP node shared resources. At present, there is little research on the hub of star-type time-triggered network TTP in China. Therefore, it is urgent to design a hub for star-type TTP network with better real-time, deterministic and better fault-tolerant performance.

Summary of the invention

The present invention provides a hub applied to a star-type TTP network and an implementation method thereof. The star-type time trigger network is based on time division multiplexing technology. The design of the hub makes the star-type time trigger network have better fault tolerance and lower cost than a bus-type time trigger network.

The present invention is achieved through the following technical solutions:

A hub applied to a star-shaped TTP network comprises a gating module and a transceiver module arranged at a physical link layer, and a startup control module, a synchronization control module, a clock generation and synchronization module, a MEDL parsing module, a frame parsing module, a cluster mode switching module, a shaping module, a frame length calculation module and an online configuration module arranged at a protocol layer.

The input end of the transceiver module is respectively connected to the shaping module, the gating module, and the frame length calculation module, and the output end of the transceiver module is respectively connected to the gating module, the frame parsing module, and the online configuration module;

The input end of the time generation and synchronization module is connected to the frame analysis module, the shaping module, and the MEDL analysis module respectively, and the output end of the time generation and synchronization module is connected to the start control module and the synchronization control module respectively;

The input end of the MEDL parsing module is respectively connected to the startup control module, the synchronization control module, the cluster mode switching module and the online configuration module, and the output end of the MEDL parsing module is also respectively connected to the frame length calculation module, the startup control module and the synchronization control module;

The output end of the frame parsing module is also connected to the cluster mode switching module;

The output end of the startup control module is also connected to the door control module and the synchronization control module respectively;

The output end of the synchronization control module is also connected to the gate control module.

As an optimization, the startup control module is used to realize the transition of the hub from an asynchronous state to a synchronous state during the startup phase of the hub, and according to the Sender Membershp Flag signal provided by the MEDL parsing module and the system time provided by the clock generation submodule, the hub generates a startup input enable signal and a startup output enable signal during the startup phase, and the startup input enable signal and the startup output enable signal control the input and output of the external node connected to the hub. At the same time, after the startup is completed, the PSP start time point, TP start time point, PRP start time point and time slot end time point in the time slot when the startup is completed and the current time slot number are passed to the synchronization control module;

The synchronization control module is used to generate a synchronization input enable signal and a synchronization output enable signal of the control gating module after the hub enters the synchronization state according to each time point when the hub enters the synchronization state and the time slot information provided by the MEDL parsing module, and divide each time slot of the hub in the synchronization phase into stages, each of which includes an IDLE stage, i.e., an idle stage; a PSP stage, i.e., a stage before sending; a TP stage, i.e., a stage for sending data; and a PRP stage, i.e., a stage after sending; the hub performs state jumps according to the time of each stage;

The clock generation and synchronization module includes a clock generation submodule and a clock synchronization submodule. The clock generation submodule works in the startup phase of the hub, and obtains the initial time of the hub according to the Global time/startup time and frame parsing time obtained from the frame parsing module in combination with the sending delay and propagation delay provided by the MEDL parsing module, and forms the local time of the hub through the initial time; the clock synchronization submodule works when the hub is in the synchronization phase, obtains the time difference transmitted by the shaping module, calculates the correction item and corrects the local clock (local time) of the hub according to the correction item, so as to realize at least one time synchronization in a TDMA Round, wherein the correction is divided into single-step correction and multi-step correction, and the correction rule is determined by the scheduling table in the MEDL parsing module;

The MEDL parsing module includes a global entry table, a protocol parameter table, a MEDL identification table, a time slot parameter table and seven cluster mode tables; each cluster mode table includes a mode control table and a number of time slot entries. After the hub is powered on, the online configuration module transfers the loaded configuration data to the storage unit RAM of the MEDL parsing module. After the hub self-check is completed, at the beginning of each time slot, the startup control module or the synchronization control module sends a time slot request signal or a global protocol parameter acquisition request signal to the MEDL parsing module. The MEDL parsing module receives the time slot request signal or the global protocol parameter acquisition request signal, and sends the corresponding information in the scheduling table to the startup control module or the synchronization control module according to the starting address and length of each table configured by the global entry and the request signal type.

The frame parsing module parses the input frame to obtain the GlobalTime/Startup Time field, the DMC field, and the Cluster position field of the control status field in the frame, and transmits the Global Time/Startup Time field of the control status field in the frame to the clock generation and synchronization module, and transmits the DMC field and the Cluster position field to the cluster mode switching module to trigger the cluster mode switching module to send a cluster switching signal to the MEDL parsing module;

The cluster mode switching module is used to check whether the mode change request is allowed in the PRP phase of the hub. If allowed, the content of the mode change request is set to the content of the delayed mode change. When it is detected that the field EOC representing the last time slot in the current cluster mode is valid and the current time slot is about to end, the subsequent mode corresponding to the content of the delayed mode change is assigned to the cluster mode, and the changed cluster mode is transmitted to the MEDL parsing module, and the next time slot enters a new cluster mode.

The transceiver module is used for the hub to transmit and receive data, and includes a baud rate generation submodule, a receiving submodule, a sending submodule, a storage submodule and a CRC check submodule;

The shaping module isolates the time domain SOS fault, adds a shaping delay at the end of the receiving window in the TP phase, and generates a shaping output enable signal to the transceiver module when the system time of the hub reaches the shaping delay completion;

The gating module inputs and outputs data according to the startup input enable signal and the startup output enable signal during the hub startup phase, and opens and closes the ports corresponding to the nodes according to the synchronization input enable signal and the synchronization output enable signal transmitted by the synchronization control module during the hub synchronization phase. The gating module includes a startup gating submodule, a synchronization gating submodule and an output selection submodule;

The frame length generation module is used to calculate the frame length of each transmission according to the data length and frame type provided by the MEDL parsing module and the fixed frame length overhead of each frame type, and output the calculated frame length to the transceiver module and the gating module;

The online configuration module is used to configure data for nodes or hubs. When the configuration host transmits configuration data, a destination field for identifying the destination is added to the front end of the configuration data. The destination field of the hub and the destination field of the node are unique and different. Therefore, the hub will first determine the identification field. If the field is determined to be the configuration data sent to the hub, then check whether the global entry table in the configuration data is correct. If this part of the configuration data is verified to be correct, the data will be configured to the RAM of the MEDL parsing module. At the same time, the hub will also forward the configuration data; if the field is determined to be the configuration data of the sending node, the data will be forwarded to the corresponding node.

The present invention also discloses a method for implementing a hub applied to a star-shaped TTP network, using the hub applied to the star-shaped TTP network, comprising the following steps:

S1. Connect two hubs and a plurality of nodes, so that the two hubs and the plurality of nodes form a star network;

S2, powering on the hub and the node, and entering the startup phase after the hub is initialized;

S3. In the startup phase, the clock generation and synchronization module obtains the global time/startup time and frame parsing time from the frame parsing module in combination with the sending delay and propagation delay provided by the MEDL parsing module to obtain the initial time of the hub. At the same time, the frame length calculation module obtains the data length of the current time slot from the MEDL parsing module and the IF field to calculate the frame length of the current time slot to determine whether the frame transmission is completed. The scheduling information of the MEDL parsing module and the initial time of the hub are transmitted to the startup control module. The startup control module enables the hub to generate a startup input enable signal and a startup output enable signal in the startup phase according to the information provided by the MEDL parsing module and the system time provided by the clock generation submodule. At the same time, the startup control module verifies the scheduling information. After the verification, the hub enters the frame listening state and changes the state according to the frames received within the specified time range. When the hub is started, the corresponding hub time is transmitted to the synchronization control module, and the hub enters the synchronization phase.

S4, the synchronization control module outputs the synchronization input enable signal and the synchronization output enable signal of the control gating module, and divides each time slot of the hub in the synchronization stage into stages, and the hub jumps the state according to the IDLE, PSP, TP and PRP stages of each time slot; the clock generation and synchronization module performs time synchronization at least once in each TDMA Round, each port of the gating module is turned on/off according to the input and output enable control signal, and the transceiver module outputs data to the gating module through the output enable signal given by the shaping module, and determines whether the transmission is completed according to the frame length of the data obtained by the frame length calculation module.

As an optimization, the startup control module of the hub includes a validity check state, a frame listening state, a cold start state, an integration state, a synchronization state, a waiting integration state and a waiting synchronization state; in S3, the startup control module verifies the schedule information, and after the verification, the hub enters the frame listening state, and the specific steps of the state transition according to the frames received within the specified time range are:

Start the control module to check the validity: after the hub is powered on and initialized, perform CRC checks on the three tables of MEDL identification table, protocol parameter table, and global entry table transmitted by the MEDL parsing module. After the CRC checks on the three tables are completed, the hub jumps to the frame listening state;

When the hub is in the frame listening state, it is used for frame identification. The hub continues to receive frames in the frame listening state. If no frame is detected within 2 TDMA Round time ranges, the hub jumps to the cold start state. If a valid cold start frame (sent by the cold start node) is detected within 2 TDMA Round time ranges, the hub jumps to the waiting integration state. If a valid synchronization frame is detected within 2 TDMA Round time ranges, the hub jumps to the waiting synchronization state.

The hub is in the cold start state, which includes the first cold start stage and the second cold start stage. When the hub is in the cold start state, the hub continues to receive frames. The hub is first in the first cold start stage. The hub executes the Bigbang mechanism in the first cold start stage. If a valid cold start frame is detected within 1 TDMA Round and the CRC check succeeds, it jumps to the second cold start stage, otherwise it remains in the first cold start stage.

If the hub is in the second cold start phase, frame recognition is performed. If a valid cold start frame is detected within one TDMA Round, the hub jumps to the integrated state, otherwise the hub jumps back to the first cold start phase;

If the hub is in the waiting integration state, if the CRC check is correct before the end of the current time slot, the hub changes to the integration state, otherwise the hub changes to the frame listening state again;

If the hub is in the integrated state, if there is no valid frame or no frame within a TDMA Round range, the hub will change to the frame listening state again. If a valid frame sent from another node different from the last sending node is detected within a TDMA Round range, the hub will jump to the synchronous state;

If the hub is in the waiting synchronization state, if a valid frame is detected before the end of the current time slot, the hub changes to the synchronization state, otherwise the hub changes to the frame listening state again;

When the hub enters the synchronization state, the PSP start time point, TP start time point, PRP start time point and time slot end time point in the time slot when the startup is completed and the current time slot number are passed to the synchronization control module.

As an optimization, in S4, the synchronization control module outputs the input and output enable control signal of the control gate module and divides each time slot of the hub in the synchronization phase into stages. The specific steps of the hub switching the state according to each time slot are:

S4.1. In the synchronization phase, at the beginning of each time slot, the hub will enter the S_Init state to determine whether the current system is active and whether the cluster mode is switched. Then, it will enter the IDLE phase of each time slot in the synchronization phase, and the hub will jump to the S_IDLE state, that is, the idle state.

S4.2, the synchronization control module continues to obtain the current time slot information in the MEDL parsing module, and after the current time slot information is updated, it enters step 4.3,

S4.3, assigning the time slot information stored in the online configuration module to the register in the synchronization control module, and the synchronization control module calculates the end time of the current time slot information, the start time of the PSP phase, the start time of the TP phase, the start time of the PRP phase, and the start time and end time of the receiving window in the TP phase according to the acquired time slot information;

S4.4. Determine whether any time calculated in S4.3 exceeds the maximum threshold. If so, subtract the maximum threshold from the local time of the hub as the system time. Otherwise, directly use the local time of the hub as the system time.

In the code design, it is stipulated that the bit width of the ma counter of the node and the hub is 16 bits. The ma counter is a time calculator, and the 16-bit width means that the maximum value is 65535. However, the local clock (local time) of the hub runs in units of mi, and the ratio of ma*ma/mi needs to be converted into a clock in units of mi. The ratio of ma/mi is not fixed, so the bit width of the mi counter is defined as 28, that is, the maximum value of the mi counter is much larger than the ma counter. Usually, the maximum value of the mi counter is larger than the maximum value of the ma counter, ma/mi. Therefore, if the local clock counter mi of the hub is always increased by 1, if it exceeds the maximum threshold without subtracting the maximum threshold, the clocks of the hub and the node will lose synchronization, which is a fatal error for the time-triggered network.

S4.5, check whether the system time reaches the start time of the PSP stage. If it reaches the start time of the PSP stage, the hub jumps to the PSP stage, enters the S_PSP state, and sets IDLE_flg to 0 and PSP_flg to 1; otherwise, it stays in the S_IDLE state, sets IDLE_flg to 1 and PSP_flg to 0, IDLE_flg indicates that the synchronization control module is in the IDLE stage of the current time slot, and PSP_flg indicates that the synchronization control module is in the PSP stage of the current time slot;

S4.6, check whether the system time has reached the start time of the TP phase. If so, jump to the TP phase and enter the S_TP state, and set TP_flg to 1 and PSP_flg to 0. In this phase, the transceiver module performs data transmission; otherwise, stay in the S_PSP state and set TP_flg to 0 and PSP_flg to 1. TP_flg indicates that the synchronization control module is in the TP phase of the current time slot, and PSP_flg indicates that the hub is in the PSP phase of the current time slot;

S4.7, check whether the system time has reached the start time of the PRP phase, if so, jump to the PRP phase, enter the S_PRP state, and set PRP_flg to 1 and TP_flg to 0; otherwise, stay in the S_TP state and set TP_flg to 1 and PRP_flg to 0, where PRP_flg indicates that the hub is in the PRP phase of the current time slot;

S4.8. When the system time is equal to the end time of the current time slot, the state of the synchronization control module changes to the S_Init state described in S4.1, and next_slot_flg is set to 1 and PRP_flg is set to 0; otherwise, it stays in the S_PRP state, with PRP_flg being 1 and next_slot_flg being 0.

As an optimization, in S4.6, the TP phase includes the pre-receiving window phase, the receiving window phase, and the receiving window end phase. The specific process in the TP phase includes:

S4.6.1. In the pre-receive window stage, when the system time is equal to the receive window start time point, jump to the receive window stage and set receve_window_phase_flg to 1, before_window_phase_flg to 0, and unconditionally set the input enable to the corresponding value, that is, enable_in[Sender_membership_flg] = 0, that is, the input enable is valid at a low level; otherwise, stay in the current pre-receive window stage and set enable_in to an invalid value, where receve_window_phase_flg indicates that it is in the receive window stage; before_window_phase_flg indicates the stage before the receive window; enable_in[Sender_membership_flg] = 0, enable_in indicates input enable, and Sender_membership_flg indicates the node identifier currently being sent;

S4.6.2, in the receiving window stage, when the system time is equal to the receiving window end time point, jump to the receiving window end stage; otherwise, stay in the receiving window stage and detect whether the corresponding node of the current time slot has data input. If the corresponding node of the current time slot has input data, set the corresponding flg to 1, otherwise set it to 0;

S4.6.3. In the post-receive window stage, when the system time is equal to the start time of PRP, jump to the PRP stage and enter the S_PRP state, otherwise stay in the S_TP state. In the S_TP state, the flg in S4.6.2 is judged. If flg is 1, enable_in[Sender_membership_flg]=0 is maintained, otherwise enable_in[Sender_membership_flg]=1 and is set to invalid.

As an optimization, the specific process of the clock generation and synchronization module performing time synchronization at least once in each TDMA Round is as follows:

A1. Obtain the time difference diff between the actual acquisition time of the data and the theoretical acquisition time in the shaping module, and store the time difference diff in the time synchronization module;

A2. Calculate the correction term according to the fault-tolerant median algorithm;

A3. If the Clksyn field of the current time slot is parsed as 1 in the MEDL parsing module, clock correction is performed in the PRP stage of the current time slot. If the MEDL parsing module parses the field Free_running_MAcroticks_t[0] in the current time slot as 1, single-step correction is performed, otherwise multi-step correction is performed.

As an optimization, the transceiver module is used to transmit and receive data in the synchronization phase of the hub, including a baud rate generation submodule, a receiving submodule, a sending submodule, a register submodule and a CRC check submodule.

The baud rate generation submodule is used to generate a baud rate;

The receiving submodule is configured to determine whether data transmission starts when a falling edge is received, and whether data transmission ends when the frame length provided by the frame length calculation module is used to determine whether the transmission ends;

The start of transmission of the sending submodule is determined by the enable signal provided by the shaping module, and the end of transmission of the sending submodule is determined by the frame length;

The storage submodule cooperates with the shaping module to store the input data for a shaping period of time;

The CRC check submodule is used to perform CRC check on the input data, and the CRC check mode is to check while inputting.

As an optimization, the shaping module adds a shaping delay at the end of the receiving window phase of the TP phase, and generates an output enable when the system time reaches the shaping delay completion moment. The output enable controls the transceiver module to forward the data cached in the register submodule.

As an optimization, the gating module includes a start gating submodule, a synchronous gating submodule and an output selection submodule. The start gating submodule is used to receive or output data during the startup phase of the hub, the synchronous gating submodule is used to receive or output data according to the synchronous input enable signal and the synchronous output enable signal during the synchronization phase of the hub, and the output selection submodule is used to select the output data of the start gating submodule or the data of the synchronous gating submodule according to the startup state or synchronization state of the hub.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The present invention proposes a complete hub design scheme. A star-type time trigger network only needs two hubs to play a bus protection role, and compared with the bus-type TTP network, the cost is greatly reduced, and the system has better fault tolerance performance.

2. The hub of the present invention can avoid gibberish failures and time domain SOS failures, and therefore has higher fault tolerance than a bus-type time-triggered network.

3. Based on the startup principle of the hub, the present invention proposes a startup solution based on the Bigbang mechanism. At the same time, the startup solution of the present invention includes three startup paths to adapt to various startup scenarios.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

FIG1 is a framework diagram of a hub applied to a star-type TTP network;

FIG2 is a schematic diagram of the system structure of a star-shaped time-triggered network;

FIG3 is a start-up control state diagram of the start-up control module;

FIG4 is a flow chart of synchronous control of the startup control module;

Fig. 5 is a time slot diagram;

FIG6 is a schematic diagram of the shaping module for SOS shaping in the time domain;

FIG. 7 is a schematic diagram of the system structure of a bus-type time-triggered network.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

Example

As shown in FIG1 , a hub applied to a star-type TTP network includes a gating module 9 and a transceiver module 7 arranged at a physical link layer, and a startup control module 1, a synchronization control module 2, a clock generation and synchronization module 3, a MEDL parsing module 4, a frame parsing module 5, a cluster mode switching module 6, a shaping module 8, a frame length calculation module 10 and an online configuration module 11 arranged at a protocol layer. The input end of the transceiver module 7 is respectively connected to the shaping module 8, the gating module 9, and the frame length calculation module 10, and the output end of the transceiver module 7 is respectively connected to the gating module 9, the frame parsing module 5, and the online configuration module 11; the input end of the time generation and synchronization module 3 is respectively connected to the frame parsing module 5, the shaping module 8, and the frame length calculation module 10. Module 8 and MEDL parsing module 4 are connected, the output end of the time generation and synchronization module 3 is respectively connected to the start control module 1 and the synchronization control module 2; the input end of the MEDL parsing module 4 is respectively connected to the start control module 1, the synchronization control module 2, the cluster mode switching module 6 and the online configuration module 11, the output end of the MEDL parsing module 4 is also respectively connected to the frame length calculation module 10, the start control module 1 and the synchronization control module 2; the output end of the frame parsing module 5 is also connected to the cluster mode switching module 6; the output end of the start control module 1 is also respectively connected to the gating module 9 and the synchronization control module 2; the output end of the synchronization control module 2 is also connected to the gating module 9.

MEDL refers to the message descriptor list, which is understood as a scheduling table in the present invention.

Next, an implementation method of a hub applied to a star-type TTP network according to another embodiment of the present invention will be introduced.

A method for implementing a hub applied to a star-type TTP network in the present invention uses the above-mentioned hub applied to a star-type TTP network, and comprises the following steps:

S1, connecting two hubs and a plurality of nodes, the two hubs and the plurality of nodes forming a star network, as shown in FIG2, the number of hubs in the present invention is set to 2, and the number of nodes is set to 10;

S2, powering on the hub and the node, and entering the startup phase after the hub is initialized;

S3, in the startup phase, the clock generation and synchronization module obtains the Globaltime/startup from the frame parsing module time and frame parsing time combined with the sending delay and propagation delay provided by the MEDL parsing module to obtain the initial time of the hub. At the same time, the frame length calculation module obtains the data length of the current time slot and the IF field of the MEDL parsing module to calculate the frame length of the current time slot to determine whether the frame transmission is completed, and transmits the scheduling table information of the MEDL parsing module and the initial time of the hub to the startup control module. The startup control module generates a startup input enable signal and a startup output enable signal in the startup phase according to the information provided by the MEDL parsing module (sending delay field, TP duration field, PSP duration field, duration field of a time slot, ratio field of ma and mi, number of time slots contained in the current round) and the system time provided by the clock generation submodule. At the same time, the startup control module verifies the scheduling table information. After the verification, the hub enters the frame listening state and performs state transition according to the frames received within the specified time range. When the hub is started, the corresponding hub time is transmitted to the synchronization control module, and the hub enters the synchronization phase;

S4, the synchronization control module outputs the synchronization input enable signal and the synchronization output enable signal of the control gating module, and divides each time slot of the hub in the synchronization stage into stages, and the hub jumps the state according to the IDLE, PSP, TP and PRP stages of each time slot; the clock generation and synchronization module performs time synchronization at least once in each TDMA Round, each port of the gating module is turned on/off according to the input and output enable control signal, and the transceiver module outputs data to the gating module through the output enable signal given by the shaping module, and determines whether the transmission is completed according to the frame length of the data obtained by the frame length calculation module.

In this embodiment, the startup control module 1 is used to realize the transition of the hub from an asynchronous state to a synchronous state during the startup phase of the hub. According to the Sender Membershp Flag signal provided by the MEDL parsing module and the system time provided by the clock generation submodule, the hub generates a startup input enable signal and a startup output enable signal during the startup phase. The startup input enable signal and the startup output enable signal control the input and output of the external nodes connected to the hub. At the same time, after the startup is completed, the PSP start time point, TP start time point, PRP start time point and time slot end time point in the time slot when the startup is completed and the current time slot number are passed to the synchronization control module.

The startup control module will generate startup input enable signals and startup output enable signals based on the Sender Membershp Flag signal provided by the MEDL parsing module and the local time provided by the clock generation submodule. These enable signals control the input and output of each port of the hub gating module. In the startup phase, the hub startup module will grant input enable to 10 ports at the same time, and the gating module will open the corresponding ports according to these enable signals. When a correct node inputs data and there is no nonsense node, after the shaping time arrives, the startup module will grant output enable signals to the ports corresponding to other nodes except the sending node. The transceiver module outputs the data to the gating module, and the gating module forwards the data to other nodes according to the output enable signal. After the startup process is completed, the various time points in the time slot when the startup is completed (PSP start time point, TP start time point, PRP start time point and time slot end time point) and the current time slot number are passed to the synchronization control module.

As shown in FIG3 , the startup control module of the hub includes a validity check state, a frame listening state, a cold start state, an integration state, a synchronization state, a waiting integration state, and a waiting synchronization state; in S3, the startup control module verifies the schedule information, and after the verification, the hub enters the frame listening state, and the specific steps of the state transition according to the frames received within the specified time range are as follows:

Start the control module to check the validity: after the hub is powered on and initialized, perform CRC checks on the three tables of the global entry table, the schedule/protocol parameter table, and the MEDL identifier table transmitted by the MEDL parsing module. After the CRC checks on the three tables are completed, the hub jumps to the frame listening state listen;

When the hub is in the frame listening state, it performs frame identification according to the frame type identified by the frame parsing module. When the hub is in the frame listening state, it continues to receive frames. If no frame is detected (no valid frame or no frame) within 2 TDMA Round time ranges (determined by the system time provided by the clock generation submodule), the hub jumps to the cold start state Col d_start. If a valid cold start frame (cold start frame sent by the cold start node) is detected within the 2 TDMA Round time ranges, the hub jumps to the waiting integration state. If a valid synchronization frame (I frame) is detected within the 2 TDMA Round time ranges, the hub jumps to the waiting synchronization state. See Figure 5 for a detailed explanation of TDMA round.

If the hub is in a cold start state, it needs to execute two stages (first the first cold start stage, then the second cold start stage) of actions in sequence. When the hub is in a cold start state, the hub continues to receive frames. When the hub is in the first cold start stage, it executes the Bigbang mechanism, that is, it directly forwards the received frames without integrating them into the frames, and performs frame type judgment and CRC check while forwarding. If a valid cold start frame is detected within one TDMA Round and the CRC check of the cold start frame is successful, it jumps to the second cold start stage, otherwise it remains in the first cold start stage.

If the hub is in the second cold start phase, frame recognition is performed. If a valid cold start frame is detected within one TDMA Round, the hub jumps to the integrated state, otherwise the hub jumps back to the first cold start phase;

If the hub is in the waiting integration state, if the CRC check is correct before the end of the current time slot, the hub changes to the integration state, otherwise the hub changes to the frame listening state again;

If the hub is in the integrated state, if there is no valid frame or no frame within a TDMA Round range, the hub will change to the frame listening state again. If a valid frame sent from another node different from the last sending node is detected within a TDMA Round range, the hub will jump to the synchronous state;

If the hub is in the waiting synchronization state, if a valid frame is detected before the end of the current time slot, the hub changes to the synchronization state, otherwise the hub changes to the frame listening state again;

When the hub enters the synchronization state, the PSP phase start time point, TP phase start time point, PRP phase start time point and current time slot end time point of the start state end time slot are transmitted to the synchronization control module.

The startup control module has three startup paths. The first startup path: the node is powered on before the hub. After the node starts communication activities, the hub is powered on and started. The hub can receive the cold start frame as soon as it is powered on. The hub can directly integrate the received cold start frame, that is, the 2→7→5→6 path in Figure 3; the second startup path: when the hub is powered on but no node is powered on, the hub needs to wait until the node starts communication activities and then integrate it into the corresponding cold start node to complete the startup. In the second startup path, the hub needs to execute the bigbang mechanism. The hub's B The igbang mechanism is different from the node directly refusing to receive frames. Instead, it directly forwards the cold start frame received for the first time to ensure that the node can receive the frame normally this time. Direct forwarding also means that the hub will not be integrated into the cold start frame, that is, the local C state will not be updated based on the C state of the cold start frame received for the first time. The corresponding path is 2→3→4→5→6. For the third startup path, there is already a running synchronization cluster. When a node wants to join the cluster, it can be integrated into the synchronization frame (I frame) sent by the synchronization node to complete the startup. The corresponding path is 2→8→6.

The synchronization control module is used to generate a synchronization input enable signal and a synchronization output enable signal of the control gating module 9 after the hub enters the synchronization state according to the initial time point when the hub enters the synchronization state and the time information provided by the MEDL parsing module, and to divide the various time slots of the hub in the synchronization stage into stages. As shown in Figure 5, each of the time slots includes an IDLE stage, i.e., an idle stage; a PSP stage, i.e., a stage before sending; a TP stage, i.e., a stage for sending data; and a PRP stage, i.e., a stage after sending. The synchronization control module will generate corresponding IDLE_flg, PSP_flg, TP_flg and PRP_flg identifiers; and the hub will perform state jumps according to the time of each stage.

Figure 5 shows a 4-node time-triggered system. One TDMA round contains 4 nodes. The cluster cycle contains 2 TDMA rounds. This can be more depending on the actual situation. A time slot consists of four phases: IDLE, PSP, TP, and PRP. IDLE means idle phase; PSP means pre-send phase, i.e., the phase before sending; TP means transmission phase, i.e., the phase of sending data; PRP means post-receive phase, i.e., the phase after sending.

Next, the implementation of the synchronization control module in the implementation method is described in detail, as shown in FIG4 .

S4.1. In the synchronization phase, at the beginning of each time slot, the hub will enter the S_Init state to determine whether the current system is active (whether there are nodes sending data) and whether the cluster mode is switched. Then, the hub enters the IDLE phase of each time slot in the synchronization phase and jumps to the S_IDLE state, that is, the idle state.

S4.2, the synchronization control module continues to obtain the current time slot information in the MEDL parsing module, and after the current time slot information is updated, it goes to step 4.3;

S4.3, assigning the time slot information stored in the online configuration module to the register in the synchronization control module, and the synchronization control module calculates the end time of the current time slot information, the start time of the PSP phase, the start time of the TP phase, the start time of the PRP phase, and the start time and end time of the receiving window in the TP phase according to the acquired time slot information;

S4.4. Determine whether any time calculated in S4.3 exceeds the maximum threshold. If so, subtract the maximum threshold from the local time of the hub as the system time. Otherwise, directly use the local time of the hub as the system time.

In the code design, it is stipulated that the bit width of the ma counter of the node and the hub is 16 bits. The ma counter is a time calculator, and the 16-bit width means that the maximum value is 65535. However, the local clock (local time) of the hub runs in units of mi, and the ratio of ma*ma/mi needs to be converted into a clock in units of mi. The ratio of ma/mi is not fixed, so the bit width of the mi counter is defined as 28, that is, the maximum value of the mi counter is much larger than the ma counter. Usually, the maximum value of the mi counter is larger than the maximum value of the ma counter multiplied by the ratio of ma/mi. Therefore, if the local clock counter mi of the hub is always increased by 1, if it exceeds the maximum threshold without subtracting the maximum threshold, the clocks of the hub and the node will lose synchronization, which is a fatal error for the time-triggered network.

S4.5, detect whether the system time reaches the start time of the PSP stage. If the start time of the PSP stage is reached (PSP_start_T_mi: the unit is mi, which is calculated by the synchronization control module by obtaining the time slot information in the scheduling table), the hub jumps to the PSP stage, enters the S_PSP state, and sets IDLE_flg to 0 and PSP_flg to 1; otherwise, it stays in the S_IDLE state, IDLE_flg is set to 1, and PSP_flg is set to 0. IDLE_flg indicates that the synchronization control module is in the IDLE stage of the current time slot, and PSP_flg indicates that the synchronization control module is in the PSP stage of the current time slot;

S4.6, check whether the system time has reached the TP phase start time (TP_start_T_mi, the unit is mi, calculated by the synchronization control module by obtaining the time slot information in the schedule table), if reached, jump to the TP phase, enter the S_TP state, and set TP_flg to 1, PSP_flg to 0, and the transceiver module performs data transmission in the TP phase; otherwise, stay in the S_PSP state and set TP_flg to 0, PSP_flg to 1, TP_flg indicates that the synchronization control module is in the TP phase of the current time slot, and PSP_flg indicates that the hub is in the PSP phase of the current time slot;

S4.7, check whether the system time has reached the start time of the PRP phase (PRP_start_T_mi: the unit is mi, which is calculated by the synchronization control module by obtaining the time slot information in the scheduling table). If it has reached the start time, jump to the PRP phase, enter the S_PRP state, and set PRP_flg to 1 and TP_flg to 0; otherwise, stay in the S_TP state and set TP_flg to 1 and PRP_flg to 0, where PRP_flg indicates that the hub is in the PRP phase of the current time slot;

S4.8. When the system time is equal to the end time of the current time slot (Slot_end_T_mi, in units of mi, calculated by the control module by obtaining the time slot information in the scheduling table), the state of the synchronization control module changes to the S_Init state described in S4.1, and next_slot_flg is set to 1 and PRP_flg is set to 0; otherwise, it stays in the S_PRP state, PRP_flg is 1, and next_slot_flg is 0.

After entering the synchronization phase, determine whether to switch the cluster mode in the PRP phase of each time slot. If the mode change request parsed in the frame parsing module is 001, determine whether M1 in the scheduling table in the MEDL parsing module is 1. If it is 1, it means that the current time slot allows the cluster mode to be switched to the subsequent mode 1. When the last time slot of the current cluster mode ends, the new cluster mode mode is output to the MEDL parsing module for subsequent MEDL parsing.

Specifically, in S4.6, the TP phase includes a pre-receiving window phase, a receiving window phase, and a post-receiving window phase. The specific process in the TP phase includes:

S4.6.1. In the pre-receive window stage, when the system time is equal to the receive window start time (Receive_window_S_T_mi, in units of mi, calculated by the synchronization control module by obtaining the time slot information in the schedule table), jump to the receive window stage and set receve_window_phase_flg to 1, before_window_phase_flg to 0, and unconditionally set the input enable to the corresponding value, that is, enable_in[Sender_membership_flg] = 0, that is, the input enable is low-level valid; otherwise, stay in the current pre-receive window stage and set enable_in to an invalid value, where receve_window_phase_flg indicates that it is in the receive window stage; before_window_phase_flg indicates the stage before the receive window; enable_in[Sender_membership_flg] = 0, enable_in indicates input enable, and Sender_membership_flg indicates the node identifier currently being sent;

S4.6.2, in the receiving window stage, when the system time is equal to the receiving window end time (Receive_window_e_T_mi, in units of mi, calculated by the synchronization control module by obtaining the time slot information in the scheduling table), jump to the receiving window end stage; otherwise, stay in the receiving window stage, and detect whether the corresponding node of the current time slot has data input. If the corresponding node of the current time slot has input data, set the corresponding flg to 1, otherwise set it to 0;

S4.6.3, in the post-end stage of the receiving window, when the system time is equal to the start time of PRP (PRP_start_T_mi, in units of mi, calculated by the control module by obtaining the time slot information in the scheduling table), jump to the PRP stage and enter the state S_PRP, otherwise stay in the S_TP state, and judge the flg in S4.6.2 in the S_TP state. If flg is 1, continue to keep enable_in[Sender_membership_flg]=0, otherwise enable_in[Sender_membership_flg]=1 and set it to invalid.

In the synchronization phase, the hub obtains the information of the current time slot in the IDLE phase of each time slot, that is, obtains the time slot entry table of the current time slot from the MEDL parsing module. The Sender Membership Flag signal in the time slot entry table indicates the sending node flag of the current time slot. The synchronization control module generates a synchronization input enable signal of the node indicated by the Sender Membership Flag at the beginning of the receiving window of the TP phase according to this signal. After the gate control module detects this synchronization input enable signal, it opens the port of the node indicated by the Sender Membership Flag. If the correct node is detected to have data input in the receiving window phase, the synchronization control module continues to send a synchronization input enable signal to the corresponding port and generates a synchronization output enable signal to other ports in the TP phase after the receiving window phase ends. The gate control module forwards the data to other ports according to the synchronization input enable signal and the synchronization output enable signal.

The clock generation and synchronization module 3 includes a clock generation submodule and a clock synchronization submodule. The clock generation submodule works in the startup phase of the hub, and obtains the initial time of the hub based on the Global time/startuptime and frame parsing time obtained from the frame parsing module 5 combined with the sending delay and propagation delay provided by the MEDL parsing module 4, and forms the local time of the hub through the initial time (the unit is mi, one mi is equal to one system clock cycle); the clock synchronization submodule works in the synchronization phase of the hub, obtains the time difference transmitted by the shaping module 8, calculates and corrects the correction item, so as to achieve at least one time synchronization in a TDMA Round, wherein the correction is divided into single-step correction and multi-step correction, and the correction rule is determined by the scheduling table in the MEDL parsing module 4.

According to protocol AS6003, the clock generation and synchronization module needs to perform three steps to perform time synchronization at least once in each TDMA Round:

A1. Obtain the time difference diff between the actual acquisition time of the data and the theoretical acquisition time in the shaping module, and store the time difference diff in the time synchronization module;

A2. Calculate the correction term according to the fault-tolerant median algorithm;

A3. If the Clksyn field of the current time slot is parsed as 1 in the MEDL parsing module, clock correction is performed in the PRP stage of the current time slot. If the MEDL parsing module parses the field Free_running_MAcroticks_t[0] in the current time slot as 1, single-step correction is performed, otherwise multi-step correction is performed.

The MEDL parsing module 4 includes a global entry table, a protocol parameter table (Schedule/Protocol parameter), a MEDL identifier table, a time slot parameter table (Slot entry table) and 7 cluster mode tables; each cluster mode table includes a mode control table and a number of time slot entries. After the hub is turned on, the online loading configuration module transfers the loading configuration data to the storage unit RAM of the MEDL parsing module 4. After completing the hub self-test, at the beginning of each time slot, the startup control module 1 or the synchronization control module 2 sends a time slot request signal or a global protocol parameter acquisition request signal to the MEDL parsing module 4. After receiving the time slot request signal or the global protocol parameter acquisition request signal, the MEDL parsing module 4 sends the corresponding information in the schedule table to the startup control module or the synchronization control module according to the starting address and length of each table configured by the global entry and the type of the request signal.

The frame parsing module 5 parses the input frame to obtain the Global Time/Startup Time field (global time/initial time field), the DMC field (delay mode change) and the Cluster position field (cluster position) of the control status field (C state) in the frame, and transmits the Global Time/StartupTime field of the control status field in the frame to the clock generation and synchronization module 3, and transmits the DMC field (delay mode change) and the Clusterposition field (cluster position) to the cluster mode switching module 6 to trigger the cluster mode switching module 6 to send a cluster switching signal to the MEDL parsing module 4.

During the startup process, the frame parsing module receives the input frame and parses the time, cluster position (including DMC, Cluster Mode, Round slot fields) and frame header (including Mode Change Request, Type) in the C state of the frame; and passes the startup time in the cold start frame to the time generation module for generating the local clock; according to the DMC, Cluster Mode, Type and other fields, it determines whether the frame is an I frame, N frame or cold start frame, and outputs the frame type flag to the startup control module and the synchronization control module for state jump judgment.

The cluster mode switching module 6 is used to check whether the content of the mode change request is allowed in the PRP stage of the hub. If allowed, the content of the mode change request is set to DMC (delayed mode change). When it is detected that the EOC field of the last time slot in this cluster mode is valid and the current time slot is about to end, the successor mode corresponding to DMC is assigned to the cluster mode, and the changed cluster mode is transmitted to the MEDL parsing module. The next time slot represents the start of a new cluster mode.

The transceiver module 7 is used to transmit and receive data in the synchronization phase of the hub, and includes a baud rate generation submodule, a receiving submodule, a sending submodule, a register submodule and a CRC check submodule;

The baud rate generation submodule is used to generate a baud rate; in the present invention, the baud rate is set to 5M;

The receiving submodule is configured to consider that data transmission starts when a falling edge is received (because the input enable is low level valid), and whether data transmission ends is determined by the frame length provided by the frame length calculation module;

The start of transmission of the sending submodule is determined by the shaping enable signal provided by the shaping module, and the end of transmission of the sending submodule is determined by the frame length;

The storage submodule cooperates with the shaping module to cache the input data for a shaping period of time;

The CRC check submodule is used to perform CRC check on the input data, and the CRC check mode is to check while inputting.

The shaping module 8 is used to isolate the time domain SOS fault, add a shaping delay at the end of the receiving window in the TP phase, and generate a shaping output enable signal to the transceiver module 7 when the system time of the hub reaches the shaping delay completion.

The shaping of the shaping module of the present invention refers to shaping in the time domain, which is mainly to avoid time domain SOS failure. Since the hub and the node both have an ideal receiving time point, when the frame arrives earlier than the ideal receiving time point, the hub can wait until the system time is the ideal receiving time point before forwarding the data. However, when the frame arrives later than the ideal receiving time point, the hub cannot cache the frame until the system time is equal to the ideal receiving time point. In addition, by adjusting the ratio of ma and mi, the clock error between nodes can also be reduced, but the ratio of Ma and Mi is a fixed value after each configuration is completed. If it needs to be modified, the configuration data needs to be modified, which is inconvenient to operate. Therefore, the present invention proposes the following shaping scheme.

Specifically, the shaping module adds a shaping delay at the end of the receiving window phase of the TP phase, and waits until the system time reaches the shaping delay completion moment, and then generates a shaping output enable signal. The shaping output enable signal controls the transceiver module to forward the data cached in the register submodule, and the node regards this shaping delay as a propagation delay. In this way, no matter whether the data input to the hub is in any time period within the hub receiving window range (no matter whether it comes early or late), it can ensure that all receiving nodes receive the completed data, and some nodes will not receive the correct frame, and some nodes will not receive the correct frame. The shaping module effectively avoids the time domain SOS failure (slightly-off-specifiacation) between nodes. As shown in Figure 6, the best receiving time point is artificially delayed by a time period hub_delay (at least half of the receiving window), and then this hub delay is counted into the node propagation delay, that is, the propagation delay between node 0 and node 1 needs to be set to the sum of node 0 propagation delay corr0, hub delay hub_delay and hub propagation delay corr_h. When no shaping is done on the input data, as shown by the red line in the time domain SOS shaping principle diagram, when the data of node 0 arrives at the hub receiving window earlier, it cannot arrive within the receiving window of node 1 after being forwarded by the hub.

The gating module 9 inputs and outputs data according to the startup input enable signal and the startup output enable signal in the hub startup phase, and opens and closes the ports corresponding to the nodes according to the synchronization input enable signal and the synchronization output enable signal transmitted by the synchronization control module in the hub synchronization phase. The gating module includes a startup gating submodule, a synchronization gating submodule and an output selection submodule;

The gating module includes a start gating submodule, a synchronous gating submodule and an output selection submodule. The start gating submodule is used to receive or output data during the startup phase of the hub, the synchronous gating submodule is used to receive or output data according to a synchronous input enable signal and a synchronous output enable signal during the synchronization phase of the hub, and the output selection submodule is used to select the output data of the start gating submodule or the data of the synchronous gating submodule according to the startup state or synchronization state of the hub.

In the startup phase, there may be data conflicts at the beginning. In the second startup path, due to the Bigbang mechanism, the hub can select any port to forward data. In the first and third startup paths, the running first hub will give the second hub the current time slot information, so the second hub can also correctly select the input data. After the second hub is successfully integrated, the correct data selection can be made according to the time slot information provided by the scheduling table. According to the idea of time division multiplexing, at most one port input enable is valid in a time slot, that is, only the node corresponding to the current time slot specified in the scheduling table is allowed to input data. After the data is shaped, it is sent to the gating module through the transceiver module. The transceiver module is the physical layer interface of the present invention. The present invention adopts a half-duplex method for transceiver, so the gating module will forward the data to all ports except the input data port.

After entering the synchronization phase, the data is sent and received by passing the data sent by the correct node of the current time slot to the receiving submodule in the transceiver module through the synchronous gating submodule, while shielding the data sent by the node that should not send data in this time slot. The receiving submodule detects the falling edge to determine whether the data transmission has started, and then determines whether the data transmission of the current time slot has ended according to the frame length provided by the frame length calculation module. The data in the synchronization phase will not be forwarded directly, but will enter the fifo in the storage submodule. After the shaping module gives the shaping enable signal, the data in the storage submodule will be output to the sending submodule. The sending submodule determines whether the transmission is over by judging the frame length. The sending submodule forwards the data to the gating module, and the gating module forwards the data to other nodes according to the synchronous output enable signal output by the synchronous control module.

The gating function of the startup phase and the gating function of the synchronization phase are designed separately, so an output selection module is also required. The output selection module selects the output data of the startup gating and the synchronization gating, outputs the output data of the startup gating submodule in the startup phase, and outputs the output data of the synchronization gating submodule in the synchronization phase.

The frame length generation module 10 is used to calculate the frame length of each transmission according to the data length and frame type provided by the MEDL parsing module and the fixed frame length overhead of each frame type, and output the calculated frame length to the transceiver module 7 and the gating module 9.

The frame length calculation module obtains the data length APPdata lengthe and IF fields of the current time slot according to the MEDL parsing module to determine whether the data input in the current time slot is a display frame or an implicit frame. If it is an implicit frame, there is no C state, and if it is a display frame, there is a C state. Both the display frame and the implicit frame have a fixed frame overhead. After determining the frame type, the fixed frame overhead and data length can be used to calculate the frame length of the sending node in the current time slot, which is used to determine whether the frame transmission is completed.

The online configuration module 11 is used to configure data for nodes or hubs. When the configuration host transmits the configuration data, a destination field for identifying the destination is added to the front end of the configuration data. The destination field of the hub and the destination field of the node are unique and different. Therefore, the hub will first determine the identification field. If the field is determined to be the configuration data sent to the hub, then check whether the global entry table in the configuration data is correct. If this part of the configuration data is verified to be correct, the data is configured to the RAM Random access memory (RAM) of the MEDL parsing module. At the same time, the hub will also forward the configuration data; if the field is determined to be the configuration data of the sending node, the data will be forwarded to the corresponding node.

The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims (9)

1. A hub applied to a star-shaped TTP network, characterized in that it comprises a gating module (9) and a transceiver module (7) arranged at a physical link layer, and a startup control module (1), a synchronization control module (2), a clock generation and synchronization module (3), a MEDL parsing module (4), a frame parsing module (5), a cluster mode switching module (6), a shaping module (8), a frame length calculation module (10) and an online configuration module (11) arranged at a protocol layer, wherein the TTP network is a time-triggered network, and the MEDL parsing module is a message description list parsing module; The input end of the transceiver module (7) is respectively connected to the shaping module (8), the gate control module (9), and the frame length calculation module (10), and the output end of the transceiver module (7) is respectively connected to the gate control module (9), the frame analysis module (5), and the online configuration module (11); The input end of the clock generation and synchronization module (3) is respectively connected to the frame analysis module (5), the shaping module (8), and the MEDL analysis module (4); the output end of the clock generation and synchronization module (3) is respectively connected to the start control module (1) and the synchronization control module (2); The input end of the MEDL parsing module (4) is respectively connected to the startup control module (1), the synchronization control module (2), the cluster mode switching module (6) and the online configuration module (11), and the output end of the MEDL parsing module (4) is also respectively connected to the frame length calculation module (10), the startup control module (1) and the synchronization control module (2); The output end of the frame analysis module (5) is also connected to the cluster mode switching module (6); The output end of the start control module (1) is also connected to the gate control module (9) and the synchronization control module (2) respectively; The output end of the synchronization control module (2) is also connected to the gate control module (9); The startup control module (1) is used to realize the transition of the hub from an asynchronous state to a synchronous state during the startup phase of the hub, and generates a startup input enable signal and a startup output enable signal during the startup phase according to the Sender Membership Flag signal provided by the MEDL parsing module and the system time provided by the clock generation submodule, wherein the startup input enable signal and the startup output enable signal control the input and output of the external node connected to the hub, and at the same time, after the startup is completed, the PSP start time point, TP start time point, PRP start time point and time slot end time point in the time slot when the startup is completed and the current time slot number are transmitted to the synchronization control module; the Sender Membership Flag signal is a sender member variable flag signal; The synchronization control module is used to generate a synchronization input enable signal and a synchronization output enable signal of the control gating module (9) after the hub enters the synchronization state according to each time point when the hub enters the synchronization state and the time slot information provided by the MEDL parsing module, and divide each time slot of the hub in the synchronization phase into stages, each of which includes an IDLE stage, i.e. an idle stage; a PSP stage, i.e. a stage before sending; a TP stage, i.e. a stage for sending data; and a PRP stage, i.e. a stage after sending; the hub performs state jumps according to the time of each stage; The clock generation and synchronization module (3) comprises a clock generation submodule and a clock synchronization submodule. The clock generation submodule operates in the startup phase of the hub, obtains the initial time of the hub based on the Global time/startuptime and the frame parsing time obtained from the frame parsing module (5) combined with the sending delay and the propagation delay provided by the MEDL parsing module (4), and forms the local time of the hub through the initial time; the clock synchronization submodule operates when the hub is in the synchronization phase, obtains the time difference transmitted by the shaping module (8), calculates the correction item and corrects the local clock of the hub based on the correction item, so as to achieve at least one time synchronization in a TDMA Round, wherein the correction is divided into single-step correction and multi-step correction, and the correction rule is determined by the scheduling table in the MEDL parsing module (4); Global time/startup time refers to global time/startup time, and TDMA Round refers to a period arranged in the form of time division multiple access; The MEDL parsing module (4) comprises a global entry table, a protocol parameter table, a MEDL identification table, a time slot parameter table and seven cluster mode tables; wherein each cluster mode table comprises a mode control table and a plurality of time slot entries; after the hub is powered on, the online configuration module transfers the loaded configuration data to the storage unit RAM of the MEDL parsing module (4); after the hub self-check is completed, at the beginning of each time slot, the startup control module or the synchronization control module sends a time slot request signal or a global protocol parameter acquisition request signal to the MEDL parsing module (4); after receiving the time slot request signal or the global protocol parameter acquisition request signal, the MEDL parsing module (4) sends the corresponding information in the scheduling table to the startup control module or the synchronization control module according to the starting address and length of each table configured by the global entry and in combination with the request signal type; The frame parsing module (5) parses the input frame to obtain the GlobalTime/Startup Time field, the DMC field and the Cluster position field of the control status field in the frame, and transmits the GlobalTime/Startup Time field of the control status field in the frame to the clock generation and synchronization module (3), and transmits the DMC field and the Cluster position field to the cluster mode switching module (6) to trigger the cluster mode switching module (6) to send a cluster switching signal to the MEDL parsing module (4); the DMC field is the delay mode change field, and the Cluster position field is the cluster position field; The cluster mode switching module (6) is used to check whether the mode change request is allowed in the PRP phase of the hub. If allowed, the content of the mode change request is set to the content of the delayed mode change. When it is detected that the field EOC representing the last time slot in the current cluster mode is valid and the current time slot is about to end, the subsequent mode corresponding to the content of the delayed mode change is assigned to the cluster mode, and the changed cluster mode is transmitted to the MEDL parsing module, and the next time slot enters a new cluster mode; EOC means the end of the cluster cycle; The transceiver module (7) is used for the hub to perform data transmission and reception, and comprises a baud rate generation submodule, a receiving submodule, a sending submodule, a storage submodule and a CRC check submodule; the CRC check submodule is a cyclic redundancy check submodule; The shaping module (8) is used to isolate the time domain SOS fault, add a shaping delay at the end of the receiving window in the TP phase, and generate a shaping output enable signal to the transceiver module (7) when the system time of the hub reaches the shaping delay completion; the SOS fault is to isolate the minor non-compliance fault in the time domain; The gating module (9) inputs and outputs data according to a startup input enable signal and a startup output enable signal during the hub startup phase, and opens and closes each port corresponding to the node according to a synchronization input enable signal and a synchronization output enable signal transmitted by the synchronization control module during the hub synchronization phase. The gating module (9) includes a startup gating submodule, a synchronization gating submodule and an output selection submodule; The frame length calculation module (10) is used to calculate the frame length of each transmission according to the data length and frame type provided by the MEDL parsing module and the fixed frame length overhead of each frame type, and output the calculated frame length to the transceiver module (7) and the gate control module (9); The online configuration module (11) is used to configure data for a node or a hub. When the configuration host transmits the configuration data, a field for identifying the destination is added to the front end of the configuration data. The identification fields of the hub and the node are unique and different. If the field is determined to be the configuration data sent to the hub, the global entry table in the configuration data is checked to see if it is correct. If this part of the configuration data is checked to be correct, the data is configured to the RAM of the MEDL parsing module. At the same time, the hub also forwards the configuration data. If the field is determined to be the node, the hub forwards the data. 2. A method for implementing a hub applied to a star-shaped TTP network, using the hub applied to a star-shaped TTP network according to claim 1, characterized in that it comprises the following steps: S1. Connect two hubs and a plurality of nodes, so that the two hubs and the plurality of nodes form a star network; S2, powering on the hub and the node, and entering the startup phase after the hub is initialized; S3. In the startup phase, the clock generation and synchronization module obtains the global time/startuptime and frame parsing time from the frame parsing module in combination with the sending delay and propagation delay provided by the MEDL parsing module to obtain the initial time of the hub. At the same time, the frame length calculation module obtains the data length of the current time slot from the MEDL parsing module and the IF field to calculate the frame length of the current time slot to determine whether the frame transmission is completed, and transmits the scheduling table information of the MEDL parsing module and the initial time of the hub to the startup control module. The startup control module enables the hub to generate a startup input enable signal and a startup output enable signal in the startup phase according to the information provided by the MEDL parsing module and the system time provided by the clock generation submodule. At the same time, the startup control module verifies the scheduling table information. After the verification, the hub enters the frame listening state and changes the state according to the frames received within the specified time range. When the hub is started, the corresponding hub time is transmitted to the synchronization control module, and the hub enters the synchronization phase; the IF field is the synchronization frame flag field; S4. The synchronization control module outputs the synchronization input enable signal and the synchronization output enable signal of the control gating module and divides each time slot of the hub into stages in the synchronization stage. The hub jumps the state according to the IDLE, PSP, TP and PRP stages of each time slot; the clock generation and synchronization module performs time synchronization at least once in each TDMARound, and each port of the gating module is turned on/off according to the input and output enable control signal. The transceiver module outputs data to the gating module through the output enable signal given by the shaping module, and determines whether the transmission is completed according to the frame length of the data obtained by the frame length calculation module. 3. According to claim 2, a method for implementing a hub applied to a star-type TTP network is characterized in that the startup control module of the hub includes a validity check state, a frame listening state, a cold start state, an integration state, a synchronization state, a waiting integration state and a waiting synchronization state; in S3, the startup control module verifies the schedule information, and after the verification, the hub enters the frame listening state, and the specific steps of changing the state according to the frames received within the specified time range are: Start the control module to check the validity: after the hub is powered on and initialized, perform CRC checks on the three tables of MEDL identification table, protocol parameter table, and global entry table transmitted by the MEDL parsing module. After the CRC checks on the three tables are completed, the hub jumps to the frame listening state; When the hub is in the frame listening state, it is used for frame recognition. The hub continues to receive frames in the frame listening state. If no frame is detected within 2 TDMA Round time ranges, the hub jumps to the cold start state. If a valid cold start frame is detected within 2 TDMA Round time ranges, the hub jumps to the waiting integration state. If a valid synchronization frame is detected within 2 TDMA Round time ranges, the hub jumps to the waiting synchronization state. The hub is in the cold start state, which includes the first cold start stage and the second cold start stage. When the hub is in the cold start state, the hub continues to receive frames. The hub is first in the first cold start stage. The hub executes the Bigbang mechanism in the first cold start stage. If a valid cold start frame is detected within 1 TDMA Round and the CRC check succeeds, it jumps to the second cold start stage, otherwise it still stays in the first cold start stage; the Bigbang mechanism is a collision avoidance mechanism; If the hub is in the second cold start phase, frame recognition is performed. If a valid cold start frame is detected within one TDMA Round, the hub jumps to the integrated state, otherwise the hub jumps back to the first cold start phase; If the hub is in the waiting integration state, if the CRC check is correct before the end of the current time slot, the hub changes to the integration state, otherwise the hub changes to the frame listening state again; If the hub is in the integrated state, if there is no valid frame or no frame within a TDMA Round range, the hub will change to the frame listening state again. If a valid frame sent from another node different from the last sending node is detected within a TDMA Round range, the hub will jump to the synchronous state; If the hub is in the waiting synchronization state, if a valid frame is detected before the end of the current time slot, the hub changes to the synchronization state, otherwise the hub changes to the frame listening state again; When the hub enters the synchronization state, the PSP start time point, TP start time point, PRP start time point and time slot end time point in the time slot when the startup is completed and the current time slot number are passed to the synchronization control module. 4. The implementation method of a hub applied to a star-type TTP network according to claim 2 is characterized in that, in S4, the synchronization control module outputs an input and output enable control signal of the control gate module and divides each time slot of the hub in the synchronization phase into stages, and the specific steps of the hub jumping the state according to each time slot are: S4.1. In the synchronization phase, at the beginning of each time slot, the hub will enter the S_Init state to determine whether the current system is active and whether the cluster mode is switched, and then enter the IDLE phase of each time slot. The hub jumps to the S_IDLE state, that is, the idle state; the S_Init state is the initial state under the synchronization state; S4.2, the synchronization control module continues to obtain the current time slot information in the MEDL parsing module, and after the current time slot information is updated, it goes to step 4.3; S4.3, assigning the time slot information stored in the online configuration module to the register in the synchronization control module, and the synchronization control module calculates the end time of the current time slot information, the start time of the PSP phase, the start time of the TP phase, the start time of the PRP phase, and the start time and end time of the receiving window in the TP phase according to the acquired time slot information; S4.4, determine whether any time calculated in S4.3 exceeds the maximum threshold. If so, subtract the maximum threshold from the local time of the hub as the system time. Otherwise, directly use the local time of the hub as the system time. S4.5, check whether the system time reaches the start time of the PSP stage. If it reaches the start time of the PSP stage, the hub jumps to the PSP stage, enters the S_PSP state, and sets IDLE_flg to 0 and PSP_flg to 1; otherwise, it stays in the S_IDLE state, IDLE_flg is set to 1, PSP_flg is set to 0, IDLE_flg indicates that the synchronization control module is in the IDLE stage of the current time slot, and PSP_flg indicates that the hub is in the PSP stage of the current time slot; the S_PSP state is the pre-sending stage state under the synchronization state; S4.6, check whether the system time has reached the start time of the TP phase, if it has reached it, jump to the TP phase, enter the S_TP state, and set TP_flg to 1, PSP_flg to 0, in this phase, the transceiver module performs data transmission; otherwise, stay in the S_PSP state and set TP_flg to 0, PSP_flg to 1, TP_flg indicates that the synchronization control module is in the TP phase of the current time slot, PSP_flg indicates that the hub is in the PSP phase of the current time slot; S_TP state is the transmission phase state under the synchronization state; S4.7, check whether the system time has reached the start time of the PRP phase, if it has reached it, jump to the PRP phase, enter the S_PRP state, and set PRP_flg to 1, TP_flg to 0; otherwise, stay in the S_TP state and set TP_flg to 1, PRP_flg to 0, where PRP_flg indicates that the hub is in the PRP phase of the current time slot; the S_PRP state is the post-receive phase state in the synchronous state; S4.8. When the system time is equal to the end time of the current time slot, the state of the synchronization control module changes to the S_Init state described in S4.1, and next_slot_flg is set to 1 and PRP_flg is set to 0; otherwise, it stays in the S_PRP state, PRP_flg is 1, next_slot_flg is 0, and next_slot_flg is the arrival flag of the next time slot. 5. The implementation method of a hub applied to a star-type TTP network according to claim 4 is characterized in that, in S4.6, the TP stage includes a pre-receiving window stage, a receiving window stage, and a post-receiving window stage, and the specific process in the TP stage includes: S4.6.1. In the pre-receive window stage, when the system time is equal to the receive window start time point, jump to the receive window stage and set receve_window_phase_flg to 1, before_window_phase_flg to 0, and unconditionally set the input enable to the corresponding value, that is, enable_in[Sender_membership_flg]=0, that is, the input enable is low-level valid; otherwise, stay in the current pre-receive window stage and set enable_in to an invalid value, where receve_window_phase_flg indicates that it is in the receive window stage; before_window_phase_flg indicates the stage before the receive window; enable_in[Sender_membership_flg]=0, enable_in indicates input enable, and Sender_membership_flg indicates the node identifier currently being sent; S4.6.2, in the receiving window stage, when the system time is equal to the receiving window end time point, jump to the receiving window end stage; otherwise, stay in the receiving window stage and detect whether the corresponding node of the current time slot has data input. If the corresponding node of the current time slot has input data, set the corresponding flg to 1, otherwise set it to 0, flg is the flag bit; S4.6.3. In the post-receive window phase, when the system time is equal to the start time of PRP, jump to the PRP phase and enter the S_PRP state, otherwise stay in the S_TP state. In the S_TP state, the flg in S4.6.2 is judged. If flg is 1, enable_in[Sender_membership_flg]=0 is maintained, otherwise enable_in[Sender_membership_flg]=1 and is set to invalid. 6. The implementation method of a hub applied to a star-type TTP network according to claim 2, characterized in that the specific process of the clock generation and synchronization module performing time synchronization at least once in each TDMARound is: A1. Obtain the time difference diff between the actual acquisition time of the data and the theoretical acquisition time in the shaping module, and store the time difference diff in the time synchronization submodule; A2. Calculate the correction term according to the fault-tolerant median algorithm; A3. If the Clksyn field of the current time slot is parsed as 1 in the MEDL parsing module, clock correction is performed in the PRP stage of the current time slot. If the MEDL parsing module parses the field Free_running_MAcroticks_t[0] in the current time slot as 1, single-step correction is performed, otherwise multi-step correction is performed. The Clksyn field is the flag field that indicates whether to perform clock correction, and Free_running_MAcroticks_t[0] is the macro-scale free running flag. 7. The implementation method of a hub applied to a star-type TTP network according to claim 2, characterized in that the transceiver module (7) is used to transmit and receive data in the synchronization phase of the hub, and comprises a baud rate generation submodule, a receiving submodule, a sending submodule, a register submodule and a CRC check submodule, The baud rate generation submodule is used to generate a baud rate; The receiving submodule is configured to determine whether data transmission starts when a falling edge is received, and whether data transmission ends when the frame length provided by the frame length calculation module is used to determine whether the transmission ends; The start of transmission of the sending submodule is determined by the enable signal provided by the shaping module, and the end of transmission of the sending submodule is determined by the frame length; The storage submodule cooperates with the shaping module to store the input data for a shaping period of time; The CRC check submodule is used to perform CRC check on the input data, and the CRC check mode is to check while inputting. 8. According to claim 2 or 7, a method for implementing a hub applied to a star-type TTP network is characterized in that the shaping module adds a shaping delay at the end of the receiving window phase of the TP phase, and generates an output enable when the system time reaches the shaping delay completion moment, and the output enable controls the transceiver module to forward the data cached in the storage submodule. 9. According to claim 2, a method for implementing a hub applied to a star-type TTP network is characterized in that the gating module includes a startup gating submodule, a synchronization gating submodule and an output selection submodule, the startup gating submodule is used to receive or output data in the startup phase of the hub, the synchronization gating submodule is used to receive or output data according to a synchronization input enable signal and a synchronization output enable signal in the synchronization phase of the hub, and the output selection submodule is used to select and output the output data of the startup gating submodule or the data of the synchronization gating submodule according to the startup state or synchronization state of the hub.