Multipurpose Bus Interface

This invention generally relates to a multipurpose interface circuit for use to interface one communication bus to another. More specifically, the present invention is in the form of a PC card that provides interface between a computer bus such as that of a general purpose computer and a command/response, time division multiplexing data bus such as, for example, a MIL-STD-1553 bus. This military standard contains requirements for aircraft internal command/response, time division multiplexing data bus techniques utilized in systems integration of aircraft subsystems. This MIL-STD applies to a variety of avionics applications including, for example, the F-15. The multipurpose interface of the present invention is particularly adapted for use with data buses where this MIL-STD applies, but more generally may also be adapted for use to interface other data buses as well. For purposes of explaining the features and advantages of the invention and its preferred embodiment, the invention will be described with reference to its application with a MIL-STD-1553 bus. It is to be understood that the version of MIL-STD-1553 being referred to throughout is the most current version as of the filing of this application.

The multipurpose interface of the present invention provides a host computer, such as a microcomputer, with a capacity of communicating on a MIL-STD-1553 avionics multiplex bus or the like. This allows the host computer to be used to emulate avionics for the purpose of simulation or testing. The invention provides an intelligent interface. It handles all of the communication protocol per the MIL-STD-1553 specification. 64K bytes of on-board RAM are used for all communication to and from the interface. It includes a modular memory mapped design allowing the PC card to be modified for use with different microcomputer bus systems, such as those known as the Multibus I, Multibus II, and Q-Bus Systems. The interface of the present invention functions in several modes: a bus controller mode, a remote terminal mode, a bus monitor mode, and a bus analyzer mode. In the bus controller mode the interface functions to provide the host computer with the capability of simulating the controller of a typical avionics bus. It is capable of handling all of the scheduling of the mux messages without intervention from the processor of the host computer. In the remote terminal mode the interface functions to provide the host computer with the capability to simulate any or all of the remote terminals of a typical avionics bus. In the monitor mode the interface functions to provide the host computer with the capability of monitoring the operation of any or all of the remote terminals. In the bus analyzer mode the interface functions to provide the host computer with the capability of taking a "snap shot" of the bus, thus giving an analysis of bus traffic versus time. In the bus analyzer mode bus traffic may be conditionally traced by a remote terminal address and/or subaddress. Using an on-board co-processor, the analyzer mode provides a message trapping capability similar to a logic analyzer.

The interface of this invention generally comprises a main controller which includes a 16-bit controller and a firmware microstore in the form of PROM which contains the software for the controller. The main controller primarily handles input/output functions and controls the transfer of data to and from the 1553 Bus into a shared RAM memory. The software stored in the microstore controls how the data is handled and interpreted making it easier to modify the controller's operation to accommodate its use with different bus standards and data protocols/formats. The interface also includes a co-processor which has direct access to the shared RAM. The main controller primarily handles input/output functions, while data processing is primarily handled by the co-processor. By using the on-board co-processor within the interface PC card, a greater number of interface PC cards of the present invention may be used with a single host computer.

The interface of the present invention also includes an interface module that formats and protocols data from the RAM as appropriate for the bus protocol and format of the host computer.

There are other known interface devices for use in providing interface between buses including a MIL-STD-1553 bus. These other known devices also are believed to operate in the various modes identified above. However, it is believed that the interface of the present invention has novel advantages over these other devices.

As mentioned previously, the interface of the present invention is an intelligent interface. Its modular memory mapped design allows the card to be modified to different microcomputers systems including the Multibus I, Multibus II, and Q-Bus Systems. Different derivatives of the 1553 specification can be accommodated with firmware changes. The timing requirements of all specifications including MIL-STD-1553A and McAir A3818 can be satisfied. Hence the interface of the present invention provides substantial versatility by making firmware and software as opposed to hardware changes.

In the bus controller mode the interface card is capable of scheduling bus traffic per the mux specifications without host processor intervention making sophisticated bus controller simulation possible. In the remote terminal and monitor modes the card can simulate or monitor any combination of remote terminals. For example, one or more terminals can be simulated while monitoring any or all of the remaining terminals. In the bus analyzer mode mux data can be conditionally collected according to remote terminal address and subaddress. This allows only the data of interest to be collected. Complex trigger conditions can be set up to stop data collection on certain events making the card a true mux analyzer. Messages are also time-tagged providing timing information. Another advantage of the interface of the present invention is that the on-board co-processor can be programmed to perform a wide range of user required processing of data or controlling of the mux interface. The co-processor software performs bus controller scheduling and bus analyzer triggering. In addition, the interface module for the host computer does not require that the interface card operate as a bus master. This simplifies modification for use with any system bus. The on-board memory also allows use of as many interfaces of this invention as needed for operation in a single host computer system without bus contention problems.

These and other advantages of the invention are apparent from the additional description to follow:

FIG. 1 is a general schematic block diagram showing a multipurpose bus interface of the present invention connected between two communications buses I and II;

FIG. 2 is a schematic block diagram illustrating an avionics multiplex bus of a type with which a multipurpose bus interface of the present invention may be used;

FIG. 3 is a more detailed schematic block diagram of a multipurpose bus interface of the present invention shown connected between redundant buses IA and IB of the type illustrated in FIG. 2, and bus II of a host computer; and

FIGS. 4A and 4B illustrate the PC card component layout for a multipurpose bus interface of the present invention.

With reference to FIG. 1 a multipurpose bus interface 10 of the present invention is shown connected between buses I and II. The multipurpose interface 10 provides intelligent interface between the two communication buses. In a more specific sense the present invention is particularly adapted to provide a host computer with the capability of communicating on an avionics multiplexed bus such as a MIL-STD-1553 bus. Such a bus is illustrated in FIG. 2 and may, for example, include a bus controller 12 connected with multiple terminals 14, 16, 18, and 20 over redundant buses A and B. Further by way of example, the terminals may be a display processor, a stores management system, an inertial navigation system and a flight control computer, respectively. Although four such terminals are shown, it is to be understood that an avionics bus may include a lesser or a substantially greater number of terminals, the ones shown being for illustration only.

With reference to FIG. 3 the multipurpose bus interface 10 is shown connected between the redundant BUSES IA and IB which may be the redundant buses of FIG. 2, and BUS II which may be the bus of a host computer 30. The interface 10 functions as an interface between the BUS II of the host computer and the redundant BUSES IA and IB to allow the host computer to function in any of several modes, namely, a bus controller mode, a remote terminal mode, a bus monitor mode, and a bus analyzer mode. The interface 10 is a PC Card that may be plugged into the host computer.

The multipurpose bus interface 10 includes a microcoded high-speed 16 bit processor or controller 32 and its associated PROM microstore 34. This is the main controller of the interface card and handles all of the MIL-STD-1553 interface control and data transfers to and from memory. The processor 32 operates at 8 Mhz with an architecture which allows many operations to be performed in parallel. Appendix A is a listing defining the instructions for the source code software for the microstore 34, and Appendix B is the source code listing for the microstore 34 in accordance with the preferred embodiment. The main controller 32 controls the transfer of data between the redundant BUSES IA and IB and a shared RAM memory 36. The software stored in the microstore 34 controls how the data is handled and interpreted making it easier to modify the main controller's operation to accommodate its use with different bus standards and data protocols/formats.

The interface 10 also includes another micro processor or co-processor 38 which has direct access to the shared RAM memory 36. The RAM memory 36 is used for all control information and data storage. This memory can be accessed by the main controller 32, the on-board co-processor 38, and the host computer bus. Programmable logic is used to arbitrate the memory between the three users.

The main controller 32 handles input/output functions while data processing is handled by the co-processor 38. By using the on-board co-processor within the interface PC card a greater number of interface cards of the present invention may be used with a single host computer 30. In other words, without the on-board co-processor, the host computer 30 would be required to process the data received by the interface card 10. If more than one card 10 were installed in the host computer, the data processing capability of the host would be forced to handle all of the data received by all of the cards, thus severely limiting the number of cards that could be used. The on-board co-processor 38 provides the card with on-board data processing capability and permits use of a substantially larger number of PC cards of the present invention with a single host computer. Appendix C is a source code listing for the co-processor 38 in accordance with this preferred embodiment of the invention and provides software for use of the interface 10 in the analyzer mode. One of the advantages of the on-board co-processor is that it may be programmed by the user to perform a wide variety of functions. The analyzer mode is one such function.

The interface 10 further includes a host computer bus interface module 40 that includes a multimodule 42 and interface controller 44. By way of example, BUS II may be what is known as MULTIBUS II. Interfaces to MULTIBUS I and Q Buses are less complex and consist mainly of address and data buffers. The host computer bus interface module 40 formats and protocols data into and out of the RAM as appropriate for the bus protocol and format of the host computer. Appendix D is a source code program listing for the interface controller 44 for use with a MULTIBUS II in accordance with a preferred embodiment of the invention.

The interface 10 further includes a dual redundant interface module 50 to interface with the redundant BUSES IA and IB. The module consists of Manchester incoders/decoders 52 and receivers 54 providing bus isolation. Interface to the controller 32 is over a bidirectional 16 bit parallel data bus.

FIGS. 4A and 4B show a printed circuit board layout for the interface card 10 of the present invention showing the locations of the various components that comprise the circuitry in FIG. 3 in accordance with a preferred embodiment of this invention. Appendix E is a component listing by reference designations as shown in FIGS. 4A and 4B in accordance with this preferred embodiment of the invention. Appendix F is a network listing of all of the connections for the components of Appendix E and FIGS. 4A and 4B in accordance with the preferred embodiment. Appendix G is a program listing for the programmable logic arrays used in the circuitry of the preferred embodiment.

Hence, the present invention provides a multipurpose bus interface PC card which can be plugged into a general purpose computer (host computer) to provide that computer with the capability of communicating with another bus such as a dual redundant avionics bus of the type to which MIL-STD-1553 applies. This allows the host computer to function in any of several modes. The interface of the present invention has particular application for use with a MIL-STD-1553 avionics multiplexed bus for use in emulating avionics for the purpose of simulation or testing. Other applications may include use with diagnostic equipment, integration benches, ground support equipment, automatic test equipment and flight simulation facilities. It can be used to implement a high-speed data link between computer systems. Among its advantages the interface of the present invention, being microcontroller based, allows many changes to be made and additional capability added with firmware changes. The main controller 32 can control the interface without intervention by the host computer 30. The on-board co-processor can be used to perform many tasks in parallel with the interface operation. The on-board memory simplifies the host computer interface 40, allowing modification for use with other host computers. The on-board memory and co-processor also eliminate any bus contention problems. Also incorporation of several modes of operation on one interface PC card allows switching between modes under host computer control. Error generating capability is incorporated in the system for mux bus test applications.

There are various changes and modifications which may be made to the invention as would be apparent to those skilled in the art. However, these changes or modifications are included in the teaching of the disclosure, and it is intended that the invention be limited only by the scope of the claims appended hereto. ##SPC1##