Interfacing a legacy data bus with a wideband data bus utilizing an embedded bus controller

Various methods and systems provide interfaces between legacy data buses such as MIL-STD 1553 buses and wideband data buses such as IEEE 1394 data buses. One technique for interfacing a legacy bus to a wideband data bus involves providing a hybrid bus controller/remote interface unit as an interface between the two buses. In operation, the legacy interface suitably receives data intended for a legacy node from a wideband data bus capable node. The legacy data is converted in the legacy interface/remote interface unit to at least one legacy word having a legacy format for transmission on the legacy data bus. The legacy interface may be further configured to receive a reply to the wideband data bus capable node message from the legacy component on the legacy data bus, and to forward the reply to the wideband data bus capable node component.

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to data communications technologies, and more particularly relates to systems and techniques for interfacing legacy equipment to high-speed data communications buses and networks.

BACKGROUND OF THE INVENTION

Modem computing and control systems such as those found in aircraft and spacecraft typically include multiple sensing and/or processing components that are interconnected by a data network. Systems used in a typical avionics environment include flight management systems, air data computers, engine and air sensors, flight control systems, cockpit instrumentation and the like.

As the various computing systems used in these environments become increasingly capable, wideband data communications technologies have evolved to support faster data transfer rates between components and systems in many aerospace, industrial, transportation and other settings. The IEEE 1394b standard, for example, describes a bus implementation that supports data transfer speeds of 800 Mbps or higher over a serial connection. Other wideband data connection technologies providing high-speed data transfer include fiber data definition interface (FDDI), asynchronous transfer mode (ATM), Fiber Channel, Fast Ethernet and the like.

Even as new data communications technologies become increasingly prevalent, however, legacy systems based upon older technologies continue in widespread use. Many of these systems remain in operation due to their high reliability, and due to the relatively long periods of time often required to design, build and obtain government certification for newer systems. Systems and components designed to communicate using the MIL-STD 1553 standard, for example, have been widely deployed in aviation, space and other environments for many years. MIL-STD 1553 networks typically include a bus controller (BC) that controls traffic on a redundant bus that interconnects various remote terminal (R/T) client nodes. MIL-STD 1553 generally specifies that data is transferred between nodes in packets of not more than thirty-two data words (with each word including sixteen data bits and four control bits) across redundant twisted-pair wires with a data rate on the order of 1 MHz. The MIL-STD 1553B standard (which was a revision of earlier MIL-STD 1553 standards) was released as a tri-service/NATO standard in 1978, and is widely available.

It is generally desirable for the legacy and non-legacy components within an aircraft, spacecraft or other environment to share data and otherwise interoperate with each other. In particular, it is generally desirable to interface legacy components with newer bus technologies to take advantage of the increased bandwidth available, and to eliminate the need to provide legacy wiring throughout the vehicle or other environment. Often, however, difficulties arise in interfacing older “legacy” systems to newer technologies. MIL-STD 1553 components, for example, are highly reliable, yet generally incompatible with newer wideband technologies without significant modification. Although several products are available to interface legacy components to newer data networks, problems often remain in implementation of these products. As an example of a design difficulty to be overcome, MIL-STD 1553 typically specifies that each transmitting component receive a “handshake” response from the receiving component within fourteen microseconds of the original data transmission. While this requirement is relatively easy to meet on a conventional MIL-STD 1553 bus, it is often difficult to meet in practice when legacy components communicate across other types of data connections. In particular, the fourteen microsecond handshake period limits the ability to locate bus controllers and remote terminals on separate bus segments, thereby limiting design flexibility. Accordingly, difficulties remain in achieving true integration between the various computing systems and components operating within an avionics or other environment. Moreover, the cost, weight and complexity of providing separate legacy and wideband networks can present significant issues in highly demanding environments.

It is therefore desirable to allow legacy systems such as those based upon MIL-STD 1553 to communicate across newer high-speed data buses such as those based upon IEEE 1394 and other standards. Further, it is desirable to use high-speed data buses to interconnect legacy bus controllers and remote terminals without requiring additional cabling or excessive modifications to the legacy components. It is therefore highly desirable to create systems and methods for interfacing legacy equipment to high-speed data buses. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.

BRIEF SUMMARY OF THE INVENTION

Various methods and systems provide interfaces between legacy data buses such as MIL-STD 1553 buses and wideband data buses such as IEEE 1394 data buses. One technique for interfacing a legacy bus to a wideband data bus involves providing a hybrid bus controller/remote interface unit as an interface between the two buses. In operation, the legacy interface suitably receives data intended for a legacy node from a wideband data bus capable node. The legacy data is converted to at least one legacy word having a legacy format for transmission on the legacy data bus. The legacy interface may be further configured to receive a reply to the wideband data bus capable node message from the legacy component on the legacy data bus, and to forward the reply to the wideband data bus capable node component.

DETAILED DESCRIPTION OF THE INVENTION

According to various embodiments, legacy systems such as those based upon MIL-STD 1553 technologies are appropriately interfaced to high-speed, wideband data networks and/or buses using one or more remote interface units (RIUs) or other legacy interfaces. Each interface suitably receives data intended for a legacy node from a wideband data bus capable node. The legacy data is converted to a legacy format for transmission on the legacy data bus. The legacy interface may be further configured to receive a reply to the wideband data bus capable node message from the legacy component on the legacy data bus, and to forward the reply to the wideband data bus capable node component. The legacy data may be divided into relatively small data packets to facilitate transmission in relatively narrow timeslots on the wideband bus, and to thereby reduce latency during transmission. In various embodiments, the functions of a legacy bus controller may be incorporated into a remote interface unit that bridges a legacy bus to the wideband network. In such embodiments the interface appropriately provides handshake responses and/or status responses to the legacy components as appropriate to avoid timeout errors.

By implementing the systems and techniques described herein, legacy nodes are suitably allowed to share data and/or to otherwise interoperate with wideband nodes without requiring significant modification. Moreover, the number of legacy buses (and associated cabling) required in many data sharing environments may be reduced by providing legacy traffic across wideband networks rather than the comparatively limited legacy buses.

As used herein, the terms “component” and “device” are intended to broadly encompass any computers, computing devices, sensors, input/output devices, modules and/or processes that are capable of processing or gathering data, and that are capable of communicating in any data communications environment. Unless context dictates otherwise, the term “bus” as used herein is intended to broadly encompass any serial or parallel bus architecture or topology, as well as any other network or other inter-connection between computing devices. “High speed” buses as described herein may include any wideband digital, optical, wireless or other networking or bus technology or protocol. Similarly, the term “legacy” systems is intended to encompass MIL-STD 1553, as well as any other technologies, systems, components and/or protocols that may be adapted for use on high-speed buses as described herein.

With reference now toFIG. 1A, an exemplary system100for interfacing legacy systems to a wideband data bus suitably includes one or more remote interface units (RIUs)104,108allowing a legacy bus controller102to communicate with one or more remote terminals (R/Ts)112,114across a wideband bus118. RIUs104,108are any systems, processing cards, or other computing devices capable of interfacing legacy components to wideband buses, and are described in additional detail below. Bus controller (BC)102is any conventional card, application or device that is responsible for directing the flow of data on one or more legacy bus segments120as appropriate. In the case of MIL-STD 1553 bus controllers, each bus segment116,120may have one or more bus controllers, although only one may be active at any time. R/Ts112,114are any devices and/or processes capable of communicating over legacy bus segments120A and120B, respectively, and may include data sensors (e.g. a radio altimeter), navigation aids, or the like. Although two legacy bus segments112,114are shown in system100, any-number of legacy buses and/or segments may be provided in a wide array of equivalent embodiments.

Wideband bus118is any bus or other network interconnection capable of transmitting data between RIUs104and108or between wideband capable nodes106and RIUs104and108. In an exemplary embodiment, wideband bus118includes several data bus segments118A–D operating in compliance with the IEEE 1394b specification, although other wideband bus or network technologies such as other versions of IEEE 1394, Fiber Channel or Fast Ethernet could be used in equivalent embodiments.FIG. 1also shows several nodes106operating on wideband bus118in a native mode. To continue the example using IEEE 1394b buses, the various nodes106and RIUs104,108are suitably inter-connected by various bus segments118A–D in a linear fashion, although other network topologies (e.g. tree, ring, hub and the like) could be used in alternate embodiments.

In operation, bus controller102suitably communicates with remote terminals112,114and manages traffic on legacy bus segments120A–B via remote interface units104,108. Data originating from BC102is provided in legacy format from BC102to RIU104via legacy bus segment116, which may operate using the same standards and/or protocols as bus segments120A–B. RIU104suitably receives data across bus segment116and contacts RIU108via wideband bus118to transfer the data as appropriate. In various exemplary embodiments, RIU104transfers legacy data from legacy BC102by dividing the data into several smaller portions and requesting immediate and/or acknowledge-accelerated arbitration access to wideband bus118. RIU108suitably receives the data portions from RIU104, re-assembles the data in legacy format, and provides the data to the destination R/T112,114via legacy bus segments120A–B. Return data is sent via an opposite path, with the sending R/T112,114providing data to RIU108via legacy bus segments120A–B, which obtains timeslots on wideband bus118to transfer the data to RIU104. RIU104, in turn, re-assembles the data and provides the resulting data in legacy format to BC102via legacy bus segment116. In a further embodiment, timeout limits (e.g. time budgets allocated for responses by R/Ts112,114) on the various legacy components are adjusted to compensate for the additional delays incurred during transit, as described more fully below. Alternatively, RIUs104,108may provide status words to transmitting legacy components to notify them that return data is in transit, thereby preventing timeout errors from occurring.

The exemplary system100shown inFIG. 1Amay be modified in many ways. Any number of native wideband nodes106(within the inherent node limits of the native wideband bus employed) may be present in equivalent embodiments, for example, as may any number of legacy nodes112,114operating on any number of legacy bus segments120A–B. Indeed, multiple RIUs108may be provided on wideband bus118, with each RIU108coupling any number of legacy bus segments120to wideband bus118. In such embodiments, a single bus controller102could be used to manage traffic on each of the various legacy buses, thereby reducing duplication in function and improving cost efficiency in some embodiments. Further, one or more of the RIUs104,108could be eliminated in alternate embodiments.FIG. 1B, for example, shows an alternate system150for controlling legacy data bus segments120A–B across wideband bus118that includes a bus controller node152that is able to natively communicate on wideband bus118without an additional RIU104. Further embodiments that combine the functionalities of BC102and RIU108are described in detail below.

As used herein, a “legacy interface” broadly refers to any device or component that provides an interface between a legacy bus and a wideband bus. Examples of legacy interfaces include RIUs104/108(FIGS. 1A–1B), bus controller152(FIG. 1B), and the like. With reference now toFIG. 2, an exemplary legacy interface200suitably includes a legacy input/output (I/O) module210, wideband PHY and LINK layer implementations208,206(respectively), an I/O subsystem204, and a data processing module202.

In an exemplary embodiment, legacy I/O module210is implemented with a conventional MIL-STD 1553 card or other implementation available from multiple commercial sources, including Data Device Corp. of Bohemia, N.Y., as well as Condor Engineering Inc. of Santa Barbara, Calif. and others. PHY module208and LINK module206may be implemented using conventional IEEE 1394b chips, cards or other implementations. Examples of PHY and LINK layer hardware implementations are available from Texas Instruments (TI) of Plano, Tex. and others. Exemplary TI part number TSB81BA3 for a 3-port Cable Transceiver/Arbiter could be used in an exemplary PHY implementation208, for example, and TI part number TSB82AA2 for a IEEE 1394b Open Host Controller Interface (OHCI) could be used in an exemplary LINK implementation206. Other protocols, products and/or implementations, however, could be used in a wide range of alternate embodiments. I/O subsystem204may be implemented using conventional hardware or software components (e.g. operating system components) that are capable of granting access to I/O resources on legacy interface200.

Processing module202includes any number of applications, applets, programs, routines, objects or the like executing on any processor and written in any programming language. The various programs included within processing module appropriately implement the various functions carried out by legacy interface200, including data transfer and/or bus control functionality. Bus control module212, for example, is any computer application, object or other implementation of a legacy bus controller (BC)102/152that is capable of being integrated within legacy interface200. In an exemplary embodiment, bus control module212is a software implementation of a legacy bus controller that is capable of communicating with legacy interface210to control traffic on legacy bus120. Examples of bus control software for MIL-STD 1553 buses are available from Condor Engineering and others. Because the BC is located in close proximity to the controlled bus segment, timeout concerns previously experienced on disjoint networks can be significantly reduced as appropriate.

In various embodiments, the computer-executable instructions for the various programs (e.g. BC module212) included within processing module202are stored in digital memory, and may also be stored on a hard drive, flash memory, EEPROM or other digital storage medium. The various components of legacy interface200shown inFIG. 2are intended as logical models, and may be implemented in practice with any type of hardware and/or software. Further, the various functions of the modules described may be organized in different fashions in the various alternate embodiments, with a wide range of equivalent interfaces200having additional, fewer, different, or differently combined modules.

A primary function of legacy interface200is to allow wideband capable nodes106to communicate with and to control legacy RTs112,114in their native format. In a typical scenario, wideband-capable nodes106normally initiate command requests for data from the RTs112,114, with the RTs responding as appropriate. In operation, legacy interface200suitably acts as a bridge or other interface between legacy network120and wideband network118in response to control instructions from processing module202. Accordingly, processing module202suitably includes instruction routines and/or modules to receive data from the wideband and legacy buses, and to re-transmit the data on the other network links118,120as appropriate to reach their intended destination, and as described more fully below. In various embodiments, processing module202is able to receive wideband data from wideband nodes106of appropriately sized multiword legacy messages for relay to legacy RTs112,114via interface200and RIU108. Processing module202conversely is able to receive data (e.g. reply data) from legacy bus120and to place such data onto wideband bus118to be received by wideband capable nodes106. Communications are therefore appropriately allowed to proceed in a bi-directional manner, with interface200acting as a bridge between bus118and bus120for communications originating on either bus.

With reference now toFIG. 3, an exemplary process300for providing bi-directional access between a wideband data bus118and a legacy bus120for passing legacy data between wideband nodes106and RTs112,114suitably includes the broad steps of receiving the legacy data on either legacy bus120or wideband bus118(step302), converting the legacy data to an appropriate format for transmission on the other bus (step303), issuing a request, as necessary, for access to the other bus (step304), obtaining access to the bus (step306), and transmitting the data on the other bus (steps308,310). In an exemplary embodiment, process300may be implemented and/or controlled in any manner, such as with a digital computer executing programming instructions stored on any digital storage medium such as a static or dynamic random access memory (RAM), floppy disk, compact disk, read-only memory (ROM), or any other digital, optical, and/or electromagnetic storage medium.

Legacy data may be received from a wideband-enabled node106on wideband bus118or from a RT112,114on legacy bus120as appropriate. As legacy data is received at a legacy interface200(step302), the legacy data is appropriately formatted (e.g. by processing module202) for transmission on the other bus. Legacy data from legacy bus120, for example, may be combined or broken into wideband messages of appropriate size and/or placed within wideband data packets for transmission on wideband bus118. Conversely, legacy data received on wideband data bus118can be joined, divided and/or formatted as appropriate for transmission on legacy bus120. To transmit the data on the desired bus, legacy interface200suitably places an access request, as necessary, on the bus to provide a bridge between the two buses (step304). The access request may be placed in any appropriate format, and in an exemplary embodiment the request conforms to the arbitration methods provided in IEEE 1394a and 1394b link level implementations. Access to wideband bus118may be obtained in any manner (step306).

Data may be formatted and/or placed on the bus in any number of appropriately-sized single or multi-word messages (steps303,308,310). In an exemplary embodiment, entire multiword legacy messages may be transmitted as single messages on wideband bus118. An appropriate number of transmitted words for each wideband bus access may be determined to accommodate particular system tolerances and to account for extra latency introduced to the data stream by buffering data cue-up times at legacy interface200. As an exemplary implementation involving the popular MIL STD 1553 legacy interface with maximum message lengths on the order of thirty words long, such added latency may be on the order of six hundred microseconds or so in each direction. For total messages comprising in excess of thirty words for any given command or RT response, such multiple message portions may be further aggregated into even larger groupings for each wideband bus access consistent with the acceptable level of extra latency thereby introduced. As such, a maximum message grouping length on the IEEE 1394 data bus may be set to be consistent with system tolerances to introduced data latency.

Accordingly, the functions of the bus controller and legacy interface may be combined into a single interface component and incorporated into a hybrid network environment400, as shown inFIG. 4. With reference now toFIG. 4, an exemplary system400includes a legacy interface200that suitably includes both bus controller102and RIU104functionality. BC functionality may be added to a legacy interface200through the addition of a bus controller card, for example, or by adding a software application, applet, daemon or the like, as described in conjunction withFIG. 2above.

Legacy interface200with an embedded BC102appropriately acts as a bridge for traffic passing between the legacy and wideband buses. For data exchanged between wideband nodes106and R/Ts112,114, each wideband node simply transmits data to interface200, which appropriately converts the data to a suitable legacy format for transmission to the RT on legacy bus120. Return (i.e. reply) data from legacy nodes112,114to wideband nodes106is similarly transmitted to interface200in legacy format across legacy bus120A–B, which appropriately forwards the reply data to wideband nodes106. Bus controller102suitably controls traffic transmitted on legacy bus120, including data transmitted between legacy interface200and the various legacy components112,114.

While several exemplary embodiments have been presented in the foregoing detailed description, it should be appreciated that a vast number of equivalent variations exist. Although the systems and techniques described herein are frequently described as interfacing MIL-STD 1553 devices to an IEEE 1394b network, for example, the invention is not so limited. Indeed, any legacy and/or wideband technologies such as Fiber Channel or the like could be used in various alternate but equivalent embodiments. It should also be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements and/or steps without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.