Multi-point ethernet bus

Abstract

The invention relates to an industrial system for controlling backplane communication, comprising: a cluster manager (CM) linked to input / output modules (IOM) via a multipoint low voltage differential signaling, MLVDS, bus through a passive substrate (BP), wherein the MLVDS bus comprises a transmit line and a receive line for the cluster manager (CM), wherein the transmit line of the MLVDS bus is shared by the input / output modules (IOM) for receiving data transmitted by the cluster manager (CM), wherein the receive line of the MLVDS bus is shared by the input / output modules (IOM) for transmitting data to the cluster manager (CM), wherein the input / output modules are time-synchronized with the cluster manager and configured to transmit data on the receive line of the MLVDS bus at respective scheduled time windows.

Description

Technical Field

[0001] This disclosure generally relates to industrial networks, and more specifically, to systems that support a variety of industrial Ethernet protocols, fieldbus protocols, and industrial application processing, and provide high-performance backplane communication for programmable logic controllers in industrial architectures. Background Technology

[0002] Industrial automation / control systems are employed to control the operation of various systems, including processes, machines, etc., and are typically adapted to different control applications through the configuration and interconnection of multiple control system components or devices, such as control modules, input / output (I / O) modules, I / O devices, etc. Existing industrial control systems typically include a processor that runs or executes control programs to interact with I / O systems (e.g., typically one or more I / O modules or devices) to receive system information in the form of analog and / or digital inputs from field sensors and to provide outputs (analog and / or digital) to one or more actuators. Industrial control systems are increasingly interconnected with management information and other systems within manufacturing facilities and can be operationally connected to any number of communication networks to facilitate various business management functions beyond process / machine control, such as inventory control, accounting, manufacturing control, etc.

[0003] The desire to integrate commercial and control network architectures to interconnect industrial control systems with general-purpose systems, along with the evolution and development of Fast Ethernet (e.g., in a switching mode with full-duplex capability), has allowed for the widespread use of industrial Ethernet networks (e.g., Ethernet / IP networks that allow field devices to connect directly to Ethernet networks) in industrial applications. In fact, Industrial Ethernet is becoming the dominant (if not the current) technology in industrial automation.

[0004] like Figure 1 As shown, in a slice I / O architecture, independent I / O islands are connected to control devices such as programmable logic controllers (PLCs) via fieldbuses such as Ethernet / IP, and contain headers (HDs) that drive the I / O module clusters individually via a cluster manager (CM). A cluster is a group of I / O modules (IOMs), up to 32 modules, physically linked together via a backplane. I / O modules (IOMs) are common automation modules that convert electrical signals into digital values. Within the cluster, communication between the cluster manager and different modules typically occurs using an external switch (SWE), which is directly connected to each I / O module and the cluster manager.

[0005] However, in situations with space constraints, external switch SWEs can become cumbersome and expensive, and the number of I / O modules is high, up to 32, making real-time solutions problematic.

[0006] Therefore, it is necessary to achieve efficient communication between the I / O module and the cluster manager, taking into account high-speed communication, real-time reliability constraints, and low-cost products. Summary of the Invention

[0007] This overview is provided to introduce concepts relevant to the subject matter of this invention. This overview is not intended to identify essential features of the claimed subject matter, nor is it intended to define or limit the scope of the claimed subject matter.

[0008] In one implementation, an industrial system for controlling backplane communication is provided, comprising:

[0009] The cluster manager (CM) is connected to the input / output module (IOM) via a passive baseboard (BP) and a multi-point low-voltage differential signaling (MLVDS) bus.

[0010] The MLVDS bus includes transmit and receive lines for the cluster manager.

[0011] The MLVDS bus transmit line is shared by the input / output modules (IOMs) for receiving data sent by the cluster manager (CM).

[0012] The MLVDS bus receive line is shared by the input / output modules (IOMs) for sending data to the cluster manager (CM).

[0013] The input / output module is synchronized with the cluster manager in time and is configured to send data on the receive line of the MLVDS bus during each scheduled time window.

[0014] Advantageously, this system provides multi-point Ethernet connectivity without involving switches or hubs, and achieves communication between I / O modules and the cluster manager while considering real-time constraints and low-cost products through the use of a passive substrate and MLVDS bus. The use of the MLVDS bus in a passive substrate allows for high reliability, eliminates active components in the backplane, minimizes failure risk, and provides a low-cost solution that does not require external switches.

[0015] From the cluster manager's perspective, the separation of the receive and transmit lines on the MLVDS bus enables full-duplex communication at 100 Mb / s or higher.

[0016] In this embodiment, the data is sent in an Ethernet frame.

[0017] In this embodiment, the data is formatted according to the Open Platform Communications Federation Architecture.

[0018] In one embodiment, each of the cluster manager and the input / output module includes a respective switch for sending and receiving data on the MLVDS bus.

[0019] In this embodiment, the switch described above is a time-sensitive networking switch.

[0020] Time-sensitive networking switches allow for the creation of time-shared multipoint communication from I / O modules to cluster managers without the need for external switches. The use of time-sensitive networking switches brings determinism, high levels of performance, and openness (standard Ethernet) to data transmission.

[0021] In this embodiment, the switches include their respective clocks synchronized based on a precision time protocol.

[0022] In one embodiment, the cluster manager sends data to all input / output modules in frames on the transmit line of the MLVDS bus during the scheduling time window.

[0023] In this embodiment, each input / output module processes only the data addressed to it in the frame and discards the rest of the data in the frame.

[0024] In this embodiment, the data may be input / output data or service data, wherein the input / output data corresponds to machine data including input and output values ​​of the input / output module, and the service data relates to service information from devices connected to the I / O module.

[0025] In this embodiment, input / output data is sent to the cluster manager in a deterministic manner within a static time window.

[0026] In this embodiment, service data is sent to the cluster manager in a best-effort manner within a dynamic time window. Using dynamically allocated time windows for service communication allows for optimized bandwidth usage on the MLVDS bus.

[0027] In this embodiment, the switch uses an IEEE 802.1Qbv time-aware scheduler to schedule static and dynamic time windows. Attached Figure Description

[0028] The detailed description is given with reference to the accompanying drawings. In the drawings, one or more numbers on the far left of the reference numerals indicate the drawing in which that reference numeral first appears. The same numbers are used throughout the drawings to refer to similar features and components. Some embodiments of the system and / or method according to this subject matter will now be described by way of example only and with reference to the accompanying drawings, wherein:

[0029] Figure 1 A schematic block diagram of an industrial communication system using an external switch between the cluster manager and I / O modules is shown.

[0030] Figure 2A schematic block diagram of an industrial communication system using a multi-point low-voltage differential signaling bus in a multi-point backplane according to an embodiment of the present invention is shown; and

[0031] Figure 3 A schematic block diagram of a multi-point low-voltage differential signaling system is shown.

[0032] In all the accompanying drawings, the same reference numerals denote the same elements or elements of the same type.

[0033] Those skilled in the art will understand that any block diagram herein represents a conceptual diagram of an illustrative system embodying the principles of the subject matter. Similarly, it will be understood that any flowchart, block diagram, state transition diagram, pseudocode, etc., represents various processes that can be substantially represented in a computer-readable medium and executed by a computer or processor, whether or not such a computer or processor is explicitly shown. Detailed Implementation

[0034] The accompanying drawings and the following description illustrate specific exemplary embodiments of the invention. Therefore, it should be understood that those skilled in the art will be able to design various arrangements, although not explicitly described or shown herein, that embody the principles of the invention and are included within its scope. Furthermore, any examples described herein are intended to aid in understanding the principles of the invention and are to be construed as not being limited to these specifically enumerated examples and conditions. Therefore, the invention is not limited to the specific embodiments or examples described below, but is defined by the claims and their equivalents.

[0035] refer to Figure 2 The industrial communication system includes a cluster manager (CM), a set of I / O modules (IOM), a base plate (BP), and an MLVDS bus that includes two multi-point low-voltage differential signaling (MLVDS) lines.

[0036] The cluster manager (CM) can manage communication with a group of I / O modules (IOMs) (up to 32) via the MLVDS bus, and optionally manage communication with another cluster manager via Ethernet and Controller Area Network (CAN) buses. The cluster manager (CM) is driven by a head that can drive other cluster managers. In one embodiment, the cluster manager is included in a head connected to a control device such as a PLC via a fieldbus. In another embodiment, the head is also included in the PLC.

[0037] I / O modules (IOMs) can include analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) for connecting sensors to the real world, communication modules, digital inputs and outputs, relays, etc. I / O modules communicate with the control manager (CM) via an MLVDS bus in a suitable packet format.

[0038] Each substrate BP is associated with an I / O module inserted therein. The substrate BP can be designed to form a backplane for that group of I / O modules, with each combination of the substrate and the associated I / O modules forming all the pieces of the backplane.

[0039] Each substrate is a passive substrate, which does not provide active bus driver circuitry; any necessary arbitration logic is placed on the I / O modules. Therefore, passive substrates are not expected to have a single point of failure (SPOF).

[0040] The MLVDS bus is a physical medium configured to couple to multiple I / O modules and a cluster manager, providing multi-drop capability. The MLVDS bus is designed to allow data transmission at rates exceeding 100 Mbps. For example, I / O modules, switches, or cluster managers connect to the MLVDS bus via a Reduced Gigabit Media Independent Interface (RGMII).

[0041] Figure 3 The concept of the MLVDS bus is explained, and a multi-point connection involving one driver and three receivers is shown. A single driver is connected to multiple receivers on the same lane.

[0042] Because LVDS is a differential signaling system, it transmits information using a voltage difference across a pair of lines; these two line voltages are compared at the LVDS receiver receiving the LVDS signal. In a typical implementation, the LVDS transmitter injects a constant current into the lines, the direction of which determines the logic level being transmitted. The current passes through a terminating resistor at the receiver (matched to the characteristic impedance of the cable to reduce reflections) and then returns in the opposite direction via the other line. The LVDS receiver senses the polarity of the voltage across the resistor to determine the logic level being transmitted. This provides the transmission of binary data.

[0043] MLVDS technology allows for multi-point connections of up to 32 nodes with signaling rates up to 500 Mbps. The common-mode range of MLVDS may limit applications to cables of 30 meters or less, depending on the environment.

[0044] In one embodiment of the MLVDS bus transmit line for the cluster manager, a single driver corresponds to the cluster manager, and a receiver corresponds to an I / O module. The MLVDS bus receive line for the cluster manager is constructed in a similar manner, where multiple I / O modules replace the receivers with drivers, and the cluster manager replaces the drivers with receivers. The cluster manager is the sole driver on the transmit line and the sole receiver on the receive line.

[0045] According to the TIA / EIA-899 standard, the MLVDS bus with transmit and receive lines allows for full-duplex communication of up to 200 Mbps between the driver and receiver.

[0046] Return to reference Figure 2 The MLVDS bus includes transmit lines for the cluster manager CM, which acts as a driver at terminal Tx. These transmit lines are shared with the I / O modules (IOMs) that act as receivers at their respective terminals Rx. The MLVDS bus also includes receive lines for the cluster manager CM, which acts as a receiver at terminal Rx. These receive lines are shared with the I / O modules (IOMs) that act as drivers at their respective terminals Tx.

[0047] Each of the cluster manager (CM) and I / O modules contains a switch, a MAC driver (MD), and a microcontroller (MC).

[0048] The switch SWC of the cluster manager CM can handle Ethernet frames exchanged with I / O modules and with other cluster managers and / or with headers (if the cluster manager is not included in the latter). The switch SWM of the I / O modules can handle Ethernet frames exchanged with the cluster manager.

[0049] MAC drivers (MDs) are typically used to control access to the MLVDS bus. For example, a MAC driver can control whether a switch sends or receives data and clock signals, and more specifically, it can control which ports of the switch are configured to send or receive data. For instance, a switch port can be configured to send specific frames within a scheduled time window.

[0050] The I / O module's switch SWM and MAC driver MD share the same clock. Similarly, the cluster manager's switch SWC and MAC driver MD share the same clock. It is assumed that all clocks are synchronized, for example via the Generic Precision Time Protocol (gPTP), which uses UDP messages to establish a clock hierarchy and synchronize time within the gPTP domains of the cluster manager and I / O modules. For real-time communication with non-negotiable time boundaries and end-to-end transmission delays, all switches have a common time reference because their clocks are synchronized with each other.

[0051] All switches are defined as Time-Sensitive Networking (TSN) switches, allowing full-duplex communication between the cluster manager and I / O modules without any collisions in the data traffic. Furthermore, these switches are programmable and utilize OPC-UA (Open Platform Communications Alliance) frame summing acceleration. OPC-UA is an industrial communication data exchange standard and a platform-independent, service-oriented architecture that integrates all the functionality of various OPC Classic specifications into a scalable framework. Typically, using OPC-UA frame summing acceleration, the switch is able to send Ethernet frames containing data from all nodes (cluster manager or I / O modules) connected to the MLVDS bus. The Ethernet frame passes through all nodes sequentially, returning when it reaches the last node on the trunk. As the frame travels in one direction, the nodes process the information within it. Each node dynamically reads the data addressed to it and inserts response data back into the frame.

[0052] More specifically, TSN switches are implemented using an IEEE 802.1Qbv time-aware scheduler and are aware of the cycle time of control traffic. TSN switches can block non-control traffic during specific time windows to ensure that the egress ports of control traffic are idle when control traffic is expected. TSN switches can be configured to have individual scheduling for each egress port.

[0053] The IEEE 802.1Qbv time-aware scheduler is designed to divide Ethernet frame communication on the MLVDS bus into fixed-length, recurring time periods. Within these periods, different time windows can be configured to be assigned to one or more priorities. Time window scheduling makes it possible to grant exclusive use of a transmit line for specific data traffic within a limited timeframe, for example, traffic requiring guaranteed transmission and uninterrupted access. Time window scheduling is based on a Time Division Multiple Access (TDMA) scheme. By establishing virtual communication channels for specific time periods, time-critical communication can be separated from non-critical background traffic.

[0054] The microcontroller MC is capable of processing the content of a frame and can include, for example, features Cortex TM The M7's main CPU platform and, for example, have Cortex TM M33's secure CPU platform.

[0055] The cluster manager CM's microcontroller MC also includes a packet processor that manages Ethernet frames from the I / O modules through the switch SWC. The packet processor is capable of extracting the payload of each Ethernet frame, verifying the signature of each payload, concatenating all payloads into a single concatenated Ethernet frame, calculating a new signature, and sending the concatenated Ethernet frame to the processing unit.

[0056] Data traffic can include at least three types of data: I / O data, service data, and control data. I / O data corresponds to machine data and can primarily consist of the input and output values ​​of the I / O module. Service data can involve information about services from devices connected to the I / O module. For example, service data can be processed by applications capable of providing information for specific requests such as status requests, log error requests, etc. Control data is processed to manage the behavior of the switch, particularly triggering the exchange of service data.

[0057] I / O data traffic is scheduled within a static time window, providing deterministic latency. Service data traffic is scheduled in a dynamic time window using a best-effort approach. Therefore, there is dual data flow management on the same transmit line of the MLVDS bus, with I / O data traffic having deterministic latency and best-effort service data. Control data is scheduled within a static time window, specifically the opening and closing of doors in the traffic queues for command service data.

[0058] Switches manage different traffic queues based on the Time-Aware Shaping (TAS) concept introduced in the IEEE 802.1Qbv standard. TAS achieves determinism by dividing traffic into different pre-configured time slots configured in a Gate Control List (GCL). A TAS consists of different traffic queues. Each queue is associated with a gate and has a transmission selection algorithm that selects the next packet to be sent from the queue. Queues can be organized in a first-in, first-out (FIFO) manner. Gates can be open or closed; only open gates can send packets. Time-aware gates open and close according to their configured time. The GCL specifies the timetable for each state. Each entry in the list consists of a set of gate states and their durations.

[0059] In one embodiment, some traffic queues are dedicated to I / O data and are scheduled for transmission within a static time window with deterministic latency. Other traffic queues are dedicated to service data and are planned for best-effort transmission within a dynamic time window.

[0060] Within each time period, the switch commands open doors within a scheduled time window to send data from the queues associated with those doors, while other doors remain closed. Within each time period, the switch may send I / O data in a static time window, control data in another static time window, and possibly service data in a dynamic time window scheduled by the cluster manager.

[0061] From the perspective of the I / O module cluster, in each time period, the I / O modules transmit data on the receive line of the MLVDS bus within their respective scheduling time windows. In each time period, the cluster manager transmits data on the transmit line of the MLVDS bus within its respective scheduling time window. All I / O modules receive the same Ethernet data frames sent by the cluster manager, using the OPC-UA format. Each I / O module processes only the specific data addressed to it and discards other data.

[0062] Due to the synchronized clock of the I / O module switch, all I / O modules can share the receive line of the MLVDS bus to send I / O data with a deterministic delay within their respective scheduled static time windows in each time period. Thanks to the IEEE 802.1Qbv time-aware scheduler, at least one I / O module is able to transmit service data via the receive line of the MLVDS bus in a best-effort manner within the scheduled dynamic time window.

[0063] Although the invention has been described above with reference to specific embodiments, it is not limited to the particular forms set forth herein. Rather, the invention is limited only by the appended claims, and other embodiments besides the specific embodiments described above are also possible within the scope of those appended claims.

[0064] Furthermore, although exemplary embodiments have been described above with reference to some exemplary combinations of components and / or functions, it should be understood that alternative embodiments may be provided by different combinations of components and / or functions without departing from the scope of this disclosure. In particular, it is contemplated that specific features described separately or as part of an embodiment may be combined with other separately described features or as part of other embodiments.

Claims

1. An industrial system for controlling backplane communication, comprising: The cluster manager (CM) is connected to the input / output module (IOM) via a passive baseboard (BP) through a multi-point low-voltage differential signaling (MLVDS) bus. The MLVDS bus includes transmit and receive lines for the cluster manager. In this configuration, the MLVDS bus transmit line is shared by the input / output modules for receiving data sent by the cluster manager. In this configuration, the receive line of the MLVDS bus is shared by the input / output modules and is used to send data to the cluster manager. The input / output modules are synchronized with the cluster manager in time and are configured to send data on the receive line of the MLVDS bus within their respective scheduling time windows. Each input / output module in the cluster manager and input / output modules includes its own switch for sending and receiving data on the MLVDS bus. The switch in question is a time-sensitive networking switch.

2. The industrial system according to claim 1, wherein, Data is sent in Ethernet frames.

3. The industrial system according to claim 1 or 2, wherein, The data is formatted according to the Open Platform Communication Joint Architecture.

4. The industrial system according to claim 1, wherein, The switches include their own clocks synchronized based on a precision time protocol.

5. The industrial system according to claim 1, wherein, The cluster manager sends data to all input / output modules in frames on the MLVDS bus transmit line during the scheduling time window.

6. The industrial system according to claim 5, wherein, Each input / output module processes only the data addressed to it in the frame and discards the rest of the data in that frame.

7. The industrial system according to claim 1, wherein, The data includes input / output data or service data, wherein the input / output data corresponds to machine data including input and output values ​​of the input / output module, and the service data relates to information about services from devices connected to the I / O module.

8. The industrial system according to claim 7, wherein, Input / output data is sent to the cluster manager in a deterministic manner within a static time window.

9. The industrial system according to claim 7 or 8, wherein, Service data is sent to the cluster manager in a best-effort manner within a dynamic time window.

10. The industrial system according to claim 1 or 9, wherein, The switch is implemented using an IEEE 802.1Qbv time-aware scheduler to schedule static and dynamic time windows.

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