Appendix 2.6 to ETSO-C153a – Integrated Modular Avionics (IMA) Module Minimum Performance Standard (MPS)

CLASS IF: Interface

1. Purpose and scope

1.1. Introduction

This Appendix contains the Minimum Performance Standards (MPS) for the CLASS IF Intended Function: Interface.

These standards specify characteristics that should be useful to designers, manufacturers, installers and users of the IMA module.

1.2. Definitions

For ETSO-C153a CLASS IF, the IMA module provides shared resources in terms of interfaces between hosted applications, modules and/or components.

The following definitions are used:

— Interface Unit: a set of hardware and/or software components in charge of supplying and managing a shared information resource.

— Data Thread: a well-defined set of data which is a primary form of information and for which a level of isolation would be guaranteed by the IMA module.

Each data thread handled by the Interface, if so wished by the applicant, may be bidirectional or symmetrical between interconnected components, modules, or hosted applications.

In the context of IF class, the ‘concurrent item’ defined in Appendix 2.1, paragraph 1 means ‘Data Thread’.

1.3. Intended Function

For ETSO-C153a CLASS IF, the intended function is to provide the capability to share information supplied by one or several interfaces units.

This intended function is Information Sharing composed of:

— information acquisition and control;

— information conversion and; and

— information forwarding and control.

The information-forwarding and control function is the means that allows sharing information between components, modules and/or hosted applications.

The following figure provides an overview of the above-mentioned intended function and the associated definitions:

Figure 20: IMA module overview for ETSO-C153a CLASS IF

2. Requirements

For ETSO-C153a CLASS IF, the IMA module provides shared resources for the communication needs of hosted applications, modules and/or components.

2.1. Functional requirements for ETSO-C153a CLASS IF:

IF.a) The IMA module shall provide to hosted applications, modules and/or components, an Information Resource which has the capacity to acquire from or to forward to an interface unit a set of data by performing information coding and decoding operations.

IF.b) The IMA module shall provide to hosted applications, modules and/or components, the capacity to use shared Information Resource thanks to Data Threads handled through logical and/or physical interface(s).

Figure 21: The relationship between CLASS IF interface (IF) elements

1.1. Characterisation requirements for ETSO-C153a CLASS IF:

IF.c) All performances of the shared Interface Unit of the IMA module shall be characterised, including but not limited to the following:

1. performance of each Interface, including its throughput, acquisition speed, forwarding speed, latency, jitter, coding rate and decoding rate;

2. performance of (a) User Interface Mechanism(s), Protocol(s) and Service(s) (e.g. socket timing, communication port timing, technological time delay, etc.); and

3. performance of supported Data Thread Type (e.g. virtual link, channel, pipe-and-filter, physical connection pin, etc.).

Note: These performance requirements are additional to those applicable in Appendix 2.1 — COMMON.

IF.d) In addition to the Common Requirement 0, the characterisation shall address the safety aspects of frozen data.

2. Verification procedures

The following table gives the verification method for each MPS; nevertheless, an alternative method may be proposed to the certification authority:

Requirement identifier	Verification method	Test under normal conditions	Test under environmental conditions	Comment
IF.a)	T	Y	Y
IF.b)	T	Y	Y
IF.c)	T(A*)	Y	Y(1)
IF.d)	T or A*

Table 6: Verification Acceptance Criteria

(A*) means that verification by the Analysis method is possible for the item that cannot be tested.

Note (1): applicable for a functional subset  cf. CO.gg).

[Amdt ETSO/10]

[Amdt ETSO/16]