CN103873387A - Industrial Ethernet-oriented deterministic communication scheduling method - Google Patents

Abstract

The invention discloses an industrial Ethernet-oriented deterministic communication scheduling method, which belongs to the technical field of industrial Ethernet data communication. According to the application requirements of industrial real-time Ethernet, this method designs a deterministic scheduling method based on dynamic priority and link delay matrix on the basis of realizing communication scheduling entity. The communication scheduling method provided by the invention not only solves the problem of infinite waiting for low-priority aperiodic messages in the industrial Ethernet, but also improves the timing accuracy and scheduling accuracy, and greatly improves the overall management quality and efficiency of the network.

Description

A Deterministic Communication Scheduling Method for Industrial Ethernet

technical field

The invention belongs to the technical field of industrial Ethernet data communication, and relates to an industrial Ethernet-oriented deterministic communication scheduling method.

Background technique

The traditional commercial Ethernet (IEEE802.3 standard) has the advantages of openness, rich resources, good compatibility and convenient integration, but it also has defects such as low reliability, insufficient anti-interference and intrinsic safety, and cannot be directly applied to field of industrial control. On the basis of commercial Ethernet, industrial Ethernet adds a communication scheduling management entity and a TDMA staggered transmission mechanism to avoid data conflicts and meet the needs of high real-time performance and high reliability in industrial sites.

At present, there are still some problems in the communication scheduling technology of industrial Ethernet. For example, the random sending mechanism of aperiodic messages will lead to changes in communication delay, which will affect the accuracy of time synchronization and deterministic communication scheduling, and may even cause data conflicts; , non-periodic packets adopt static priority measurement, and low-priority packets may be delayed indefinitely, thus causing node buffer overflow. Therefore, it is very necessary to design a reasonable and efficient deterministic communication scheduling mechanism for the application requirements of industrial Ethernet.

Contents of the invention

In view of this, the purpose of the present invention is to provide a deterministic communication scheduling method for industrial Ethernet. On the basis of realizing the communication scheduling entity, the method adopts a matrix based on dynamic priority and link delay, which can effectively avoid Low-priority packets are delayed for a long time, which improves the scheduling accuracy of communication resources.

There are two types of messages in Industrial Ethernet: one is periodic messages, such as the data collected by sensors cyclically; the other is non-periodic messages, such as alarm and management messages. Correspondingly, Industrial Ethernet also divides time into periodic message transmission phase and aperiodic message transmission phase, and these two phases constitute a macro cycle. Aperiodic packets compete for the access control right of the bus through packet priority and IP address. Since the IP address depends on the application, industrial Ethernet can only achieve stable, fast and accurate communication scheduling by increasing the priority of aperiodic messages. Dynamic priority technology is aimed at non-periodic messages with randomness. It adds time elements on the basis of static priority, that is, the longer the waiting time of an aperiodic message, the higher its priority. The sending time of the periodic message is determined, and its priority is usually the highest, so there is no need to dynamically adjust the priority of the periodic message.

The link delay matrix technology is mainly aimed at periodic messages. It calculates the link delay of periodic messages and schedules industrial Ethernet nodes to send them in advance to offset communication delays and improve scheduling accuracy. The byte size of the periodic message is fixed, and the offset of the sending time in each cycle is the same, which makes the communication delay of the periodic message of each node in the system basically the same. For aperiodic packets, the sending time cannot be fixed. When the system needs to reserve sending time, the sending matrix based on link delay can also be used.

The timer is the basis for resource scheduling and timing management of industrial Ethernet. The timer linked list based on time difference makes the management and scheduling of timers simple and fast. Inserting a timer node in the timer linked list can realize the setting of the timer, and deleting a node can stop the running of a timer.

The technical scheme provided by the invention is as follows:

A deterministic communication scheduling method for industrial Ethernet, the method adds time elements on the basis of static priority to form a dynamic priority strategy; the priority strategy specifically includes the following steps:

1) Classify the non-periodic data packets according to the priority, and put them into the corresponding priority queues;

2) After the message is loaded into the queue, the timer starts to count. If the message can be sent successfully within the specified time, record the adjustment factor K at this time; otherwise, the K value will continue to increase as the waiting time increases until it can until successfully sent;

3) The average waiting time of similar messages in this queue is based on the macro cycle. The longer the waiting time, the closer to the head of the queue, that is, the higher the priority in this queue;

4) When entering the stage of aperiodic message sending, send according to the calculated priority. If the IP addresses are the same, choose the one with the smaller address to send first. If the competition fails, use the previous method to continue to adjust the priority and prepare for the next round of sending.

Further, a link delay matrix is added in the scheduling method, thereby improving the scheduling accuracy of the industrial Ethernet.

Further, increasing the link delay matrix specifically includes the following steps:

a) Calculate the communication delay time ΔT between every two nodes, including sending processing delay t ₁ , queuing delay t ₂ , transmission delay t ₃ and receiving processing delay t ₄ ;

b) Advance the sending time T _send of the sending node by ΔT, that is, the adjusted sending time is T _adjust =T _send -ΔT;

c) The communication delay matrix of the entire industrial Ethernet is $\left(\begin{array}{c}{T}_{11\mathrm{send}}-\mathrm{\Δ}{T}_{11,......,}{T}_{1\mathrm{nsend}}-\mathrm{\Δ}{T}_{1\mathrm{no}}\\ T_{\mathrm{twenty\; one}\mathrm{send}}-\mathrm{\Δ}{T}_{\mathrm{twenty\; one},......,}{T}_{2\mathrm{nsend}}-\mathrm{\Δ}{T}_{2\mathrm{no}}\\ ...............................................\\ T_{\mathrm{no}1\mathrm{send}}-\mathrm{\Δ}{T}_{\mathrm{no}1,......,}{T}_{\mathrm{nnsend}}-\mathrm{\Δ}{T}_n\end{array}\right).$

Furthermore, the scheduling method also provides a timer linked list based on time difference, which is used to reduce processor overhead and improve system performance.

Further, the timer linked list based on time difference is specifically:

A. The head of the timer linked list always points to the timing time with the smallest relative offset of the macrocycle;

B. Each timing time value in the timer linked list is actually the sum of the previous several time values;

C. In the timer linked list, the previous timing events always occur before the latter ones, and cannot be out of sequence.

The beneficial effect of the present invention is that: the communication scheduling method provided by the present invention not only solves the problem of infinite waiting for low-priority aperiodic messages in the industrial Ethernet, but also improves the timing accuracy and scheduling accuracy, and greatly improves the efficiency of the network. Overall management quality and efficiency.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Figure 1 is the overall structure diagram of CSME communication scheduling;

Fig. 2 is the flow chart of CSME state machine;

Fig. 3 is a CSME scheduling timing state diagram;

Fig. 4 is the timer linked list based on time difference;

Figure 5 shows the communication delay of industrial Ethernet.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The Communication Scheduling Management Entity (CSME) of Industrial Ethernet supports not only the communication scheduling method based on CSMA/CD free competition, but also the deterministic communication scheduling method based on TDMA time-sharing transmission. The overall architecture of the deterministic communication scheduling method for industrial Ethernet is shown in Figure 1. Each component in the figure is shown in Table 1.

Table I

The CSME entity has four states: bypass state (Standby), ready state (Ready), periodic data sending phase (PeriodicDataSending) and non-periodic data sending phase (NonPeriodicDataSending). The meanings of each state are as follows:

(1) Bypass state: Indicates that the device is in a free bus competition state, and messages are not scheduled, which may easily lead to data conflicts. In this state, deterministic data communication cannot be ensured.

(2) Ready state: Indicates that the device is ready for communication scheduling. In this state, the device time synchronization accuracy meets the requirements, and the parameters required for communication scheduling have also been configured.

(3) Periodic data sending stage: When the current time reaches the time for sending periodic data information, the node can only switch from the bypass state to this state to send periodic messages such as IO data. After all periodic messages are sent, an aperiodic message declaration message will be sent immediately to report the highest level of its own aperiodic message to each node on the network.

(4) Aperiodic data sending stage: After the periodic message stage, it is the aperiodic message stage. It utilizes the aperiodic priority information given in the previous periodic message stage to select a highest priority to send. If the sending node still has relevant information, when it sends an aperiodic message, it still needs to send the remaining aperiodic messages of the node.

The flow of CSME’s communication scheduler is shown in Figure 2, and the detailed process is as follows:

After the device is powered on, it will first check the relevant system parameters. If no corresponding configuration and scheduling information is found, the device will enter the bypass state. Otherwise, when the configuration is complete and the relevant parameters meet the requirements (such as time synchronization accuracy), it will automatically enter the bypass state. At this time, the CSME will start the calculation of relevant time parameters to determine whether to enter the periodic data transmission state or the non-periodic data transmission state. The calculation formula is shown in equation (1).

T _de =T _c %T (1)

In the above formula, T _de is the deviation of the current local time from the start time of macrocycle T, and T _c is the current system time. If T _de is equal to the preset periodic message sending time deviation, the periodical message sending stage will be entered.

The timing status of CSME is shown in Figure 3.

When entering CSME for the first time, if T _de is less than the time T _pi of the current periodic message sending of the local node, then start a timer with an interval of ΔT _p , its expression:

ΔT _p =T _pi -T _de (T _pi >T _de ) (2)

Only when ΔT _p >0 can enter the periodic message sending phase; if ΔT _p <0, update ΔT _p as:

ΔT _p ＝(T+T _pi -T _de )%T (3)

Design of deterministic communication scheduling strategy:

On the basis of the original static priority scheduling strategy, time is used as one of the elements to adjust the priority of aperiodic packets to avoid the problem of infinite waiting for low priority aperiodic packets. The longer the waiting time of aperiodic message, the higher its priority, which solves the problem of infinite waiting for low-priority aperiodic message in industrial Ethernet.

The improved dynamic priority scheduling strategy is as follows:

a) Classify the non-periodic data packets according to the priority and put them into the corresponding priority queues respectively. Suppose there are n types of message priorities: PQ ₁ , PQ ₂ ,...,PQ _n , and the initial values of queue priorities are NPri ₁ =1, NPri ₂ =2,...,NPri _n =n. For aperiodic messages, NPri ₁ = 1 is the highest priority, and priority 0 is reserved for periodic messages.

b) After the message is loaded into the queue, the timer starts to count. If the message can be sent successfully within the specified time, record the adjustment factor K at this time; otherwise, the value of K will continue to increase as the waiting time increases until it can be sent until successfully sent. The formula for priority dynamic update is as follows:

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; P</span>}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; :</span>\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; Pri</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; NPr</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ \mathrm{<span\; class="notranslate">\; P</span>}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; :</span>\mathrm{<span\; class="notranslate">\; NPr</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; NPr</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>\\ <span\; class="notranslate">\; .</span>\\ \mathrm{<span\; class="notranslate">\; P</span>}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; :</span>\mathrm{<span\; class="notranslate">\; NPr</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; NPr</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In the above formula, K _n depends on the waiting time ti of the aperiodic phase, that is, K _n =f(t1,t2,...,tn); _NPrin is the initial priority of the packet at the head of the queue.

c) The previous step can complete the adjustment of queue messages with different priorities, but the corresponding arrangement will also be made between the same priority levels. The average waiting time of similar packets in this queue is based on the macro cycle. The longer the waiting time, the closer to the head of the queue, that is, the higher the priority in this queue.

d) Aperiodic message sending. When entering the aperiodic message sending stage, send according to the calculated priority, if the IP addresses are the same, choose the one with the smaller address to send first. If the competition fails, use the previous method to continue to adjust the priority and prepare for the next round of sending.

Timer linked list design:

In the industrial Ethernet system design, the timer linked list is very important, it is the basis of the timing management of scheduling. In the case of timing frequency and time deviation adjustment, a two-way timer linked list based on time difference is designed for more effective timer design, as shown in Figure 4. The Lefttime values in this figure need to be sorted according to the time difference. The time difference is calculated from the starting point of the macrocycle, and the scale unit is the time granularity unit of the hardware timer, not the beat in the conventional operating system.

In this differential timing linked list, the following elements need to be paid attention to: (1) the head of the timer linked list always points to the timing time with the smallest relative offset of the macrocycle; (2) each timing value in the linked list actually It is the sum of several previous time values; (3) The previous timing events in the linked list always occur before the latter, and cannot be out of order.

Through the design of differential fine-grained timing linked list, the timing accuracy is improved, and the problem of timing confusion is also avoided. Each event has a strict sequence.

Improved scheduling design based on link delay matrix:

Since the communication delay of every two nodes in the industrial Ethernet is not the same, the communication scheduling accuracy will also be affected by the communication delay, and even affect the scheduling sequence. Therefore, considering the delay of communication between nodes will have an important impact on communication scheduling.

For the transmission of periodic messages, since the number of bytes of the message is fixed and the offset of the sending time in each macrocycle is the same, the delay-based transmission matrix of each node in the system corresponds to The parameters do not change much, and the delay-based transmission matrix algorithm is mainly applied to the transmission of periodic phase messages. For aperiodic packets, the sending time cannot be fixed. When the system needs to reserve sending time, the sending matrix based on link delay can also be used.

The end-to-end communication delay in industrial Ethernet consists of sending processing delay t ₁ , queuing delay t ₂ , transmission delay t ₃ and receiving processing delay t ₄ , as shown in Figure 5. Considering that the deviation of time synchronization accuracy is T _ptp , the total delay time when two nodes communicate is ΔT, then:

ΔT=t ₁ +t ₂ +t ₃ +t ₄ +T _ptp (5)

In order to offset the communication delay, the time for nodes to send messages needs to be advanced, and the actual sending time is adjusted as follows:

T _adjust = T _send -ΔT (6)

When there are n nodes in the industrial Ethernet, the time between sending a message from the i-th node to the j-th node is adjusted to T _ijaadjust = T _ijsend -ΔT _ij , then the communication delay matrix is:

$\left(\begin{array}{c}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}\mathrm{<span\; class="notranslate">\; send</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; nsend</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}\mathrm{<span\; class="notranslate">\; send</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; nsend</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ <span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\\ {\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; send</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; nnsend</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; n</span>}}\end{array}\right)<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

When the synchronization accuracy of industrial Ethernet is stable, the deviation T _ptp of time synchronization accuracy will be far smaller than the communication delay ΔT of the message. If its value is too large, it will have a relatively large impact on communication scheduling.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (5)

1. a kind of deterministic communication scheduling method for industrial Ethernet, it is characterized in that: on the basis of static priority, increase time element, form dynamic priority strategy; Described priority strategy specifically comprises the following steps: 1) Classify the non-periodic data packets according to the priority, and put them into the corresponding priority queues; 2) After the message is loaded into the queue, the timer starts to count. If the message can be sent successfully within the specified time, record the adjustment factor K at this time; otherwise, the K value will continue to increase as the waiting time increases until it can until successfully sent; 3) The average waiting time of similar messages in this queue is based on the macro cycle. The longer the waiting time, the closer to the head of the queue, that is, the higher the priority in this queue; 4) When entering the aperiodic message sending stage, send according to the calculated priority. If the IP addresses are the same, choose the one with the smaller address to send first. If the competition fails, use the previous method to continue to adjust the priority. Prepare for the next round of sending. 2. A deterministic communication scheduling method for industrial Ethernet according to claim 1, characterized in that: a link delay matrix is added in the scheduling method to improve the scheduling accuracy of industrial Ethernet. 3. a kind of deterministic communication scheduling method for industrial Ethernet according to claim 2, is characterized in that: increasing link delay matrix specifically comprises the following steps: a) Calculate the communication delay time ΔT between every two nodes, including sending processing delay t ₁ , queuing delay t ₂ , transmission delay t ₃ and receiving processing delay t ₄ ; b) Advance the sending time T _send of the sending node by ΔT, that is, the adjusted sending time is T _adjust =T _send -ΔT; c) The communication delay matrix of the entire industrial Ethernet is $\left(\begin{array}{c}{T}_{11\mathrm{send}}-\mathrm{\&Delta;}{T}_{11,......,}{T}_{1\mathrm{nsend}}-\mathrm{\&Delta;}{T}_{1\mathrm{no}}\\ T_{\mathrm{twenty\; one}\mathrm{send}}-\mathrm{\&Delta;}{T}_{\mathrm{twenty\; one},......,}{T}_{2\mathrm{nsend}}-\mathrm{\&Delta;}{T}_{2\mathrm{no}}\\ ...............................................\\ T_{\mathrm{no}1\mathrm{send}}-\mathrm{\&Delta;}{T}_{\mathrm{no}1,......,}{T}_{\mathrm{nnsend}}-\mathrm{\&Delta;}{T}_n\end{array}\right).$ 4. A kind of deterministic communication scheduling method for industrial Ethernet according to claim 1, characterized in that: said scheduling method also provides a timer linked list based on time difference, for reducing processor overhead, Improve system performance. 5. a kind of deterministic communication scheduling method for industrial Ethernet according to claim 4, is characterized in that: the timer linked list based on time difference is specifically: A. The head of the timer linked list always points to the timing time with the smallest relative offset of the macrocycle; B. Each timing time value in the timer linked list is actually the sum of the previous several time values; C. In the timer linked list, the previous timing events always occur before the latter ones, and cannot be out of order.

Images