See MIL-STD-1553


4000 Board

The EXC-4000 is a family of multiprotocol interface boards for avionics test and simulation applications. Boards may hold up to eight independent modules (depending on the size of the board), where each module can implement any of the following protocols: MIL-STD-1553A/B, MIL-STD-1760, MMSI, H009, ARINC-429/575, ARINC-708/453, Discrete, Serial (RS-232/422/485), CAN bus and others.


see ARINC-429



The Avionics Full Duplex Switched Ethernet standard, known as AFDX or ARINC 664, defines a reliable real-time environment for the use of Ethernet networks for the communication of avionics data. AFDX is widely becoming adopted within the avionics industry as the successor to ARINC 429 point-to-point communications.



Aeronautical Radio, Incorporated (ARINC), established in 1929, is the leading provider of transport communications and systems engineering solutions for five major industries: (aviation, airports, defense, government and transportation).



The most common avionics standard, used by all Airbus and Boeing aircraft. It provides a description of the functions and the supporting physical and electrical interfaces for the digital information transfer system. ARINC-429 is similar to the ARINC-561 standard and is based on the ARINC-575 standard. Messages consist of a single data word, 32 bits in length. Click for Arinc-429 tutorial and related products.



The ARINC-561specification provides a standard communications method for the "Air Transport Inertial Navigation System".  It uses 6 wires in 3 pairs to transmit clock, sync and data signals using NRZ encoding with voltage levels of 12V, and a word length of 32 bits.


ARINC-575 is the precursor to ARINC-429.  It is a 2 wire version which was used in the Digital Air Data System, later evolved to be ARINC-429.  It uses a low speed data rate, with 32 bit words.

ARINC-664 part 7

ARINC-664 part 7 is based on the IEEE 802.3 Ethernet standard.  It has been modified to remove the non-avionics-quality services and add new features such as bounded latency and guaranteed bandwidth.  The first popular implementation is known as AFDX (Avionics Full Duplex Switched Ethernet), but others are being currently developed.



An avionics standard used primarily for weather radar equipment. The ARINC 708 standard provides a description of the functions and the supporting physical and electrical interfaces for the digital information transfer system. It uses the ARINC-453 physical layer with each message consisting of 1600 bits.



Bus Controller

The Bus Controller (BC) is the unit responsible for directing the flow of data on a Mil-Std-1553 bus.  Other terminals on the bus may also have the capability to operate as BCs, but only one may be active at any one time.  The BC is the only terminal allowed to issue commands onto the bus - these commands may be for the transfer of data, or for the control and management of the Bus. 

Bus Coupler

A Bus Coupler is the device used to connect terminals to a Mil-Std-1553 bus, using the transformer coupling method.  Bus couplers utilize transformers to provide isolation between the terminals connected to the stubs and the bus.  They are available with different options such as mulitple stub connections and internal terminations.

Bus Monitor

A Bus Monitor (BM) is a terminal which monitors (and/or records) data on a Mil-Std-1553 bus.  It may record all data on the bus, or may only record selected data.  Since the Bus Monitor is a passive device, it does not transmit on the bus.

Bus Repeater

 A Bus Repeater is a device which when inserted in a bus, boosts the weak input signal back up to its specified levels on the output, thus enabling longer cable lengths than are normally used.

Bus Switch

A Bus Switch allows for switched connections between multiple buses. 



The Controller Area Network (CAN) bus was developed by Bosch GmbH for use in road vehicles.  It uses a differential 2 wire interface running over shielded twisted pair cable, at a maximum speed of 1Mbps.  It is currently gaining wider acceptance in the avionics industry.



The Central Control Complex (CCC) is the H009 equivalent of the Bus Controller in Mil-Std-1553.  It is the unit responsible for directing the flow of data on the H009 bus.  See also Bus Controller.

Compact PCI

Compact PCI (cPCI) is the standard used for PCI based industrial computers.  It is electrically a superset of desktop PCI with a different physical form factor. Compact PCI utilizes the Eurocard form factor popularized by the VME bus.  Due to its excellent shock and vibration characteristics, it is often used for ruggedized embedded systems.</

Conduction cooled

This is a method of transferring heat via thermally conductive solid materials eg: heatsinks.  It is the most common method of cooling used in operational embedded systems, since the solid heatsinks also provide mechanical ruggedization against vibration and shock. 

Conformal coating

Conformal coating is the process of spraying a dielectric material onto a device component to protect it from moisture, fungus, dust, corrosion, abrasion, and other environmental stresses. Common conformal coatings include silicone, acrylic, urethane, epoxy, and parylene.

Convection cooled

This is a method of transferring heat away from hot components by dissipating it into the surrounding air.  It is most commonly used in laboratory environments, or embedded systems which have forced air flow.


Data Recorder

often used in aircraft avionics systems to verify correct communications, and to allow an analysis of the buses performance to be carried out post-flight.


Excalibur's M4KDiscrete module supports twenty programmable I/O discretes that can record or control the external discretes that are connected to it. In addition, the module can record changes in the input discrete with an associated Time Tag via a built-in FIFO. Output discretes are open collector, capable of handling up to 32V with a maximum sink current of 100 mA each.


Drivers are a collection of software functions which drive the hardware product. Excalibur's drivers provide a set of C language functions available for use in writing application programs. These functions provide access to all of the hardwares functions in a structured and straightforward programming environment. They are available for Windows operating systems; written and tested using Borland C++ compiler, and Microsoft Visual C++ compiler.

Dual Redundant

A separate independent backup bus for greater reliability.


Embedded System

An embedded system is a special-purpose computer system designed to perform one or a few dedicated functions, often with real-time computingconstraints. It is usually embedded as part of a complete device including hardware and mechanical parts.


Engineering Units

A measurable attribute or characteristic within the data of some message, where the data is defined by the communications protocol under which the message is being transmitted. A defined portion of the data, i.e., some number of bits within some data word(s), comprises an Engineering Unit.


Ethernet is a large family of frame based computer networking technologies for local area networks (LANs). Its star topology and simple twisted pair cabling has made it the most popular LAN technology. It runs at data transfer rates of 10 and 100Mbps.  The official standard is IEEE 802.3, but ethernet is more commonly referred to as 10/100BASE-X.


Excalibur’s Analysis Laboratory Tools is a Windows application that takes advantage of the extraordinary capabilities of the EXC-4000 multiprotocol family of boards, EXC-1553PCMCIA/EPII and DAS-429PCMCIA/RTx.

Exalt can monitor buses based on MIL-STD-1553, H009, MMSI, ARINC-429, ARINC-708 and Discrete protocols. In addition, it can be adapted for use with other protocols.

Excalibur Systems

Excalibur is the innovative leader in the Avionics Communications protocol market. The company sets the standards and boasts the largest selection of board level products. Excalibur provides the hardware, software, and the support necessary for the test and simulation, embedded, and rugged applications markets. From connectors, cables, couplers, cards, and boxes to complete systems, Excalibur does it all.


FireWire (IEEE 1394)

A high-speed serial bus standard for transferring data to and from digital devices at data transfer rates of up to 400 Mbps. FireWire is Apple Computer's trademark name for their implementation of the IEEE 1394 standard. Other companies follow this standard but have names such as Lynx and I-Link.


Gigabit Ethernet

Gigabit Ethernet (GbE) is the latest version of the popular packet based network protocol, running at a data transfer rate of 1Gb/s.  The initial standardized version IEEE 802.3z from 1998 has evolved into the current version IEEE 802.3-2005, and is commonly referred to as 1000BASE-X.  GbE can operate over copper cables, or single/multi-mode optical fibers.



H009 (also called MacAir H009), introduced by McDonnell in 1967, was one of the first avionics data buses. It is a dual redundant bus controlled by a Central Control Complex (CCC), with up to 16 Peripheral Units (PUs), synchronously communicating using a 1MHz clock.  H009 was used in early F-15 fighter jets, but due its noise sensitivity and other reliability issues was replaced by MIL-STD-1553.


Inline Coupler

An inline coupler is a small, lightweight bus coupler as used on aircraft, missiles, etc.  See also Bus Coupler.


Irig is a serial time code format used to provide a common time source to many different units in a system.  This allows all the units and applications to be synchronized to a common time source.  Irig has 6 different time code formats, of which Irig-B is the most commonly used format in avionics applications.  Irig is controlled by the Range Commanders Council.



JTAG (Joint Test Action Group) is the name normally used for the IEEE 1149.1 standard called "Standard Test Access Port and Boundary Scan Architecture".  The Boundary Scan Description Language (BSDL) is used to test and debug on-chip blocks via the JTAG interface, which is a 5 pin electrical connection to internal electronics in silicon chips.


Kernel driver

A low level driver that provides the functional interface between the software drivers and the underlying operating system calls. The function calls provide access to system memory, provide a pointer to the memory on the board, handle interrupts, etc.



LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) is a platform and development environment for a visual programming language from National Instruments. Commonly used for data acquisition, instrument control, and industrial automation; it is also used in development of scalable test, measurement, and control applications.
LabVIEW programs/subroutines are called virtual instruments (VIs). Each VI has three components: a block diagram, a front panel (user interface) and a connector pane.

LabWindows CVI

LabWindows/CVI (C for Virtual Instrumentation) is an event-driven, ANSI C programming environment developed by National Instruments. It is a programming environment for developing measurement applications, in addition to being a powerful tool for writing data acquisition programs. It includes a large set of run-time libraries for instrument control, data acquisition, analysis, user interface, and features code generation tools and prototyping utilities.


Also known as GNU Linux, this Unix like operating system is one of the most prominent examples of open source development and free software.  All its underlying source code is available to the general public for use, modification and redistribution free of charge.  It can be found in systems ranging from supercomputers to mobile phones, with its major advantages being its security, reliability, low cost, and freedom from vendor lock-in.


Lynx-OS is a Real Time Operating System (RTOS) from LynuxWorks.  It features full POSIX conformance and Linux compatibility.  It can be found in real time embedded flyable avionics systems, aerospace, military and industrial controllers.



An Excalibur module designed specifically for the EXC-4000 family of cards. The module defined as single function 1553, can operate as a Bus Controller, Remote Terminal or Bus Monitor.  For a definition of 1553 please see "MIL-STD-1553".


An Excalibur module designed specifically for the EXC-4000 family of cards. The module defined as multi function 1553, can operate simultaneously as a Bus Controller and up to 32 Remote Terminals and as a Triggerable Monitor.  In addition, error injection (BC and RT modes) and error detection (all modes) are supported on each channel. For a definition of 1553 please see "MIL-STD-1553".


An Excalibur module designed specifically for the EXC-4000 family of cards. The module supports up to ten ARINC-429 channels in any combination of transmit and/or receive. All of the channels feature error injection and detection. For a definition of 429 please see "ARINC-429".


An Excalibur module designed specifically for the EXC-4000 family of cards. The module supports up to two ARINC-708/453 channels for the Weather Radar Display Databus. Each channel is selectable as transmit or receive and implements an 64K word FIFO and supports polling and/or interrupt driven operation. For a definition of 708 please see "ARINC-708".


An Excalibur module designed specifically for the EXC-4000 family of cards. The module supports the standard and extended message frames in CAN Specification 2.0 part B. They have the capability to transmit, receive, and perform message filtering on extended message frames with a 29-bit message identifier. For a definition of CAN please see "CAN Bus".


An Excalibur module designed specifically for the EXC-4000 family of cards. The module supports twenty programmable I/O discretes that can record or control the external discretes that are connected to it. For a definition of discrete please see "Discrete".


An Excalibur module designed specifically for the EXC-4000 family of cards. The module can operate as a Central Computer Complex (CCC) and/or up to sixteen Peripheral Units (PUs) simultaneously, or as a Bus Monitor.  In addition, a Concurrent Bus Monitor enables concurrent monitoring of the bus during CCC and PU simulation.  For a definition of H009 please see "H009".


An Excalibur module designed specifically for the EXC-4000 family of cards. The module supports up to four independent channels of serial communications, each of which can be selected as RS-485, RS-422 or RS-232 and has a programmable baud rate of up to 1Mbps. For a definition of serial please see "Serial".


A serial data bus standard used for integration of military avionics and weapon systems. It has been in use since 1973, and is widely used by all branches of the U.S. military and NATO. The standard has two variations, 1553A and 1553B. The 1553B standard increases compatibility between designs by different manufacturers by enabling them to be electrically interchangeable. Click for MIL-STD-1553 tutorial and related products.



MIL-STD-1760 implements an enhanced MIL-STD-1553 digital interface for the transfer of digital messages to a remote terminal. The enhancements include additional error detection in the form of a checksum. A checksum is mandated on critical control messages and provisional on the remainder of the messages. Implementing this level of error detection ensures a higher degree of error free data.



The MIL-STD-704 power connections provide the store with access to 28 VDC, three-phase wye 400 Hz, 115/200 VAC and 270 VDC aircraft power; it is usual to route only one of the last two supplies, however, if both are made available, then they are never made active simultaneously. The MIL-STD-1760 interface provides power through the primary interface (2 off 28 VDC and either one or both 115/200V VAC and 270 VDC), where it is routed to the store along with all of the other signal types. The standard also allows for an optional auxiliary power interface (1 off 28 VDC and either 115/200 VAC or 270 VDC) for stores with more demanding power requirements. The auxiliary power interface includes its own interlock discrete signals so that the aircraft can determine whether the store's auxiliary power connector is attached to the aircraft.


Allows operation in all modes simultaneously: BC (Bus Controller) Mode, multiple RT (Remote Terminal) Mode, Bus Monitor Mode and RT/Concurrent Bus Monitor Mode. Allows you to test and monitor up to 32 RTs simultaneously, and includes error injection.


Allows the use of many different communication protocols at the same time, on the same board.  The 4000 family of boards allows the concurrent use of MIL-STD-1553A/B, MIL-STD-1760, MMSI, H009, ARINC-429/575, ARINC-708/453, Discrete, Serial (RS-232/422/485) and CAN bus.



A network is a group of electronic components or systems connected in such a fashion that they may exchange data with each other.  They can come in many different forms, such as buses, point to point, star topology, and wireless.


Operating Temperature

The operating temperature is the specified temperature range that equipment may be operated in. Excalibur Systems provides two ranges of operating temperatures for boards: Commercial (0°C to +70°C) and Extended (-40°C to +85°C).



An embedded computer standard that defines both a form factor and computer bus. This standard is intended for environments that require reliable data transfer in harsh environmental conditions.

PC/104 Plus

An embedded computer standard based on PC/104 with the addition of a high-speed PCI bus.


Peripheral Component Interconnect. A high-speed I/O bus connection for devices including SCSI cards, video cards, sound cards, modems, video capture cards, etc. This is the primary way of adding peripheral devices to your computer. PCI may be a 64-bit bus, though it is usually implemented as a 32-bit bus.  It can run at clock speeds of 33 or 66 MHz. 


PCI-Extended is an enhanced version of the PCI bus, running at twice the speed.  The 32 or 64 bit bus speed has been doubled to 133MHz giving a theoretical maximum throughput of 1.06Gb/s.  PCI-X is backwards compatible with PCI, meaning that a regular PCI card can run in a PCI-X slot.


Pulse Code Modulation. A standard method of encoding analog audio signals in digital form.


PCMCIA stands for Personal Computer Memory Card International Association. It is a standard for small memory cards or devices, designed for portable computers or laptops. The dimension of the card is 85.6 by 54 millimeters. The thickness varies depending on the type: Type I (up to 3.3 mm), Type II (up to 5.5 mm), Type III (up to 10.5mm).


PCI Mezzanine Card (PMC) is defined by the IEEE P1386.1 standard. It combines the electrical characteristics of the PCI bus, with the mechanical form factor of the Common Mezzanine Card (CMC) defined in IEEE 1386.  PMC cards are small, light and rugged, making them ideal for embedded operational systems.


POSIX or "Portable Operating System Interface for uniX" is the collective name of a family of related standards specified by the IEEE to define the application programming interface (API) for software compatible with variants of the Unix operating system.


A  Peripheral Unit (PU) is the H009 equivalent of a Remote Terminal (RT) in Mil-Std-1553.  Up to 16 PUs are allowed on a H009 bus.



A Quality Management System (QMS) is a system which defines procedures and policies to govern the various processes that occur in business.  They often include feedback and controls, so that continual improvements can be made, thus resulting in a better process.



see Data Recorders

Remote Terminal

A Remote Terminal (RT) is defined in Mil-Std-1553 as "all terminals not operating as the Bus Controller or as a Bus Monitor".   It is an electronic unit which transfers data between the 1553 bus, and its own subsystem.  An RT may only respond when it has been specifically commanded by the Bus Controller. A maximum of 32 RTs may be used on a 1553 bus.


Real Time Operating System. This is a type of operating system which provides predictable latency for software function calls. RTOS is normally used in mission critical systems.



Excalibur's M4KSerial module supports up to four independent channels of serial communications, each of which is software-selected as RS485, RS422 or RS232. The on-board, high speed processor and true dual-port RAM offer a simple and powerful interface to the module. The module operates independently of the host computer, reducing the need for host intervention.

Single Function

Allows operation in one mode at a time: BC (Bus Controller) Mode, RT (Remote Terminal) Mode, Bus Monitor Mode or RT/Concurrent Bus Monitor Mode.



A device which provides isolation for electronic signals.

Transformer coupling

see Bus Coupler



Unix is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T employees at Bell Labs. Today's Unix systems are split into various branches, developed over time by AT&T as well as various commercial vendors and non-profit organizations.

Unix operating systems are widely used in both servers and workstations The Unix environment and the client-server program model were essential elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers.

Unix was designed to be portable, multi-tasking and multi-user in a time-sharing configuration. Unix systems are characterized by various concepts: the use of plain text for storing data; a hierarchical file system; treating devices and certain types of inter-process communication (IPC) as files; and the use of a large number of small programs that can be strung together through a command line interpeter using pipes as opposed to using a single monolithic program that includes all of the same functionality.

Under Unix, the "operating system" consists of many of these utilities along with the master control program, the kernel. The kernel provides services to start and stop programs, handle the file system and other common "high level" tasks that most programs share, and, perhaps most importantly, schedules access to hardware to avoid conflicts if two programs try to access the same resource or device simultaneously. To mediate such access, the kernel was given special rights on the system and led to the division between user-space and kernel-space.


Universal Serial Bus (USB) is one of the most popular methods of peripheral connection in PCs today. It consists of a host controller, and mutiple daisy chained devices, often connected via hubs.  Its popularity stems from its ease of use, hot swap, and plug and play capabilities.  The latest version, USB2.0 supports data rates up to 480Mbit/s.



Versa Module Eurocard. An 8-, 16- and 32-bit parallel-bus computer architecture that can implement single and multiprocessor systems, developed by the VMEbus Manufacturers Group (now called VITA). The bus includes four sub-buses, Data Transfer Bus, Priority Interrupt Bus, Arbitration Bus, and Utility Bus.


VME EXtensions for Instrumentation. A peripheral bus specializing in data acquisition and realtime control systems. Introduced in 1987, VXI uses all Eurocard form factors and adds trigger lines, a local bus and other functions suited for measurement applications. See also VME.


A Real Time Operating System (RTOS) by Wind River Systems, which is similar to Unix.  Like most RTOSs, it includes a multi-tasking kernel with pre-emptive scheduling and fast interrupt response, extensive intertask communications and synchronization facilities.

Unlike native systems such as Unix, VxWorks development is done on a host computer running Unix or Windows, using a cross-compiling target software to target specific computer architectures.


Windows operating system

Microsoft Windows is a family of Operating Systems which can run on different types of platforms such as embedded controllers, servers, and most typically personal computers.  Microsoft added their popular graphical user interface (GUI) to MS-DOS in the early 90s, and have gone on to become the most popular operating system for PCs in the world.  Its popularity is due to its ease of use, and intuitive interface.

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