STANAG 3910

Overview and History
As the EF2000 Typhoon enters the production stage of its development, STANAG3910, EFAbus will get its first chance to prove itself by meeting the mission critical avionics requirements for this highly sophisticated fighter aircraft. Since it was established at the early stages of the program that the data transfer capacity of the MIL-STD-1553B bus was not going to fulfill the requirements, STANAG3910 was selected by the Eurofighter (UK, Germany, Italy & Spain) consortium in 1989 to meet the demanding Avionics Systems needs of such an aircraft. Very simply STANAG3910, EFAbus is based on using the existing MIL-STD-1553B, 1Mbit/sec dual modular redundant Low Speed (LS) bus augmented by a High Speed, (HS) Fiber Optics (Reflexive Star Topology) dual modular redundant bus operating at 20Mbits/sec. The LS bus provides the command and control of the HS bus by use of ‘Action Words’ sent over the LS bus. The HS bus is used only for Data Transfers under the control of these ‘Action Words’. The bus architecture comprises a Bus Controller (BC) with up to 31 Remote Terminals (RT’s). Each device can have a LS/HS connection as shown in below figure:
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In the case of the EF2000 implementation, RT Sub-address 26 (decimal) on the LS bus is reserved as the HS Sub-address. All HS transfers are initiated via the LS bus with Command and Status words for the HS bus being transferred as LS data-words. The transfer types are as defined in the MIL-STD-1553B with no automatic acknowledgment of HS data transfers in the basic protocol. Therefore HS RT status must be polled by the transmitting terminal. It will be seen that this dual bus approach allows the mixed operation of both STANAG3910 and MIL-STD-1553B terminals. The first draft of this dual speed MIL-STD-1553B based bus was created in Germany during 1987. In 1988, this first draft was submitted to the AVS WP in Brussels. Following this in 1989, a project specific variant known as EFAbus was issued. This is the version used today (with some updates) for the EF2000 aircraft project. It should be appreciated that this standard was adopted due to the lack of a truly available off the shelf ‘High Speed Data Bus’ for avionics applications. This, in conjunction with the reasons listed below, drove the down selection of the STANAG3910, EFAbus for the EF2000, Typhoon aircraft:
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• Allow evolution from MIL-STD-1553B bus only to ‘Higher Speed’ Avionics Bus System
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• Mixing of MIL-STD-1553B/ STANAG3910 Avionics Systems
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• ‘Low Risk’ approach with first EF2000 Prototypes using MIL-STD-1553B only
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• Stay with a ‘Deterministic’ Master/ Slave Protocol
Test & Validation
A number of Test and Validation Test Plans documents have been created by the EF2000, Avionics Joint Team (AJT). These have been created for the suppliers of STANAG3910 Avionics equipment and components to the EF2000 project to be sure designs and production units conform to the EFAbus standards. These Test Plans have been created to define, as a minimum, what Protocol and Optical test must be performed before delivering Avionics equipment’s for use on the EF2000 or the aircraft rigs prior to flight.
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Test Plans include:
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• EFAbus RT and BC Production Test Plan
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• EFAbus RT and BC Validation Test Plan
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-- Validation Test is a ‘Super Set’ of the Production Test Plan
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-- Includes Optical and Protocol Tests
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• STANAG3838 Test Plans (MIL-HDBK-1553 and SAE AS4113 form part of the EFAbus Test Plans)
Data-bus Analyzer and Modules for STANAG3910 Test & Simulation
As with the MIL-STD-1553B avionics data-bus, it was recognized by company AIM GmbH that Data-bus Analyzer equipments and modules would be a requirement for the development, simulation and production equipment’s for the EF2000 project. With this in mind, AIM GmbH produced the worlds first commercially available ‘STANAG3910 VMEbus card’ and ‘Demonstrator System’ in 1989 for potential STANAG3910 Avionics users. Two such systems where supplied to Civil Aviation Safety Authority, British Aerospace for evaluation and test at the conceptual stages of the project.
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The Test and Validation requirements of the Protocol and Optical requirements of the STANAG3910 standard proved to be a big challenge. AIM GmbH rose to this challenge and created a STANAG3910 Fiber Optics and Protocol Test System (CTX) which allowed users to test STANAG3910 equipments against the EFAbus Validation and Production Test plans. This led to the creation of a Data-bus Analyzer system known commercially as the ‘MBA-90’ (Modular Bus Analyzer). Built using VMEbus cards and controlled via a host PC, the MBA-90 STANAG3910 Data-bus Analyzer soon became the ‘Defacto Standard’ across the entire EF2000 project.
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Today, AIM GmbH has the position as the leading supplier to three of the EF2000 Prime Contractors and major Sub-Contractors in the UK, Germany, Italy and Spain for all Data-bus Analyzers, VMEbus, VXIbus and PCI based Test & Simulation Modules. This has been no easy task, a private company funding has been put in by the AIM GmbH team to support STANAG3910 to make.

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