ARINC 653 (Avionics Application Software Standard Interface) is a software specification for space and time partitioning in

safety-critical A safety-critical system (SCS) or life-critical system is a system whose failure or malfunction may result in one (or more) of the following outcomes: * death or serious injury to people * loss or severe damage to equipment/property * environme ...

avionics Avionics (a blend of ''aviation'' and ''electronics'') are the electronic systems used on aircraft. Avionic systems include communications, navigation, the display and management of multiple systems, and the hundreds of systems that are fit ...

real-time operating system A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which m ...

s (RTOS). It allows the hosting of multiple applications of different software levels on the same hardware in the context of an

Integrated Modular Avionics Integrated modular avionics (IMA) are real-time computer network airborne systems. This network consists of a number of computing modules capable of supporting numerous applications of differing criticality levels. In opposition to traditional ...

architecture. It is part of ARINC 600-Series Standards for Digital Aircraft & Flight Simulators.

Overview

In order to decouple the real-time operating system

platform Platform may refer to: Technology * Computing platform, a framework on which applications may be run * Platform game, a genre of video games * Car platform, a set of components shared by several vehicle models * Weapons platform, a system or ...

from the application software, ARINC 653 defines an

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

called APplication EXecutive (APEX). Each application software is called a partition and has its own memory space. It also has a dedicated time slot allocated by the APEX API. Within each

partition Partition may refer to: Computing Hardware * Disk partitioning, the division of a hard disk drive * Memory partition, a subdivision of a computer's memory, usually for use by a single job Software * Partition (database), the division of a ...

, multitasking is allowed. The APEX API provides services to manage partitions, processes and timing, as well as partition/process communication and error handling. The partitioning environment can be implemented by using a

hypervisor A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called ...

to map partitions to virtual machines, but this is not required. The current work of the AEEC APEX Subcommittee includes the enhancement of ARINC 653 for

multicore A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such ...

processor architectures. The position paper CAST-32A defines a set of requirements and guidance that should be met to certify and use multi-core processors in civil aviation by FAA and EASA and is expected to be replaced by an

Advisory Circular __NOTOC__ Advisory circular (AC) refers to a type of publication offered by the Federal Aviation Administration (FAA) to provide guidance for compliance with airworthiness regulations, pilot certification, operational standards, training standards, ...

(AC) in late 2020.

History

Initial version

The initial version of ARINC 653 was published on October 10, 1996.

ARINC 653-1

Supplement 1 was published in January 1997 and introduced the concepts of APEX and Time and Space partitioning.

ARINC 653-2

Supplement 2 was published in 3 parts between March 2006 and January 2007: * Part 1 (mandatory services): ARINC 653 partition management, Cold start and warm start definition, Application software error handling, ARINC 653 compliance,

Ada Ada may refer to: Places Africa * Ada Foah, a town in Ghana * Ada (Ghana parliament constituency) * Ada, Osun, a town in Nigeria Asia * Ada, Urmia, a village in West Azerbaijan Province, Iran * Ada, Karaman, a village in Karaman Province, ...

and C language bindings; * Part 2 (optional services): File system access,

Data logging A data logger (also datalogger or data recorder) is an electronic device that records data over time or about location either with a built-in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they ar ...

, Service Access points, ... * Part 3 (Conformity Test Specification);

Current Organization of Standard

* Part 0 - Introduction to ARINC 653 (currently at revision 3, released November 2021) * Part 1 - Required Services (currently at revision 5, released December 2019) * Part 2 - Extended Services (currently at revision 4, released December 2019) * Part 3A - Conformity Test Specification for Required Services (currently at revision 2, released November 2021) * Part 3B - Conformity Test Specification for Extended Services (currently at revision c1, released July 2019) * Part 4 - Subset Services (currently at revision 0, released June 2012) * Part 5 - Core Software Recommended Capabilities (currently at revision 1, released August 2019)

Basic principles of partitioning

ARINC 653 Platform

An ARINC 653

contains: * A hardware platform allowing

real-time computing Real-time computing (RTC) is the computer science term for hardware and software systems subject to a "real-time constraint", for example from event to system response. Real-time programs must guarantee response within specified time constra ...

deterministic services. * An abstraction layer managing the timer and space partitioning constraints of the platform (

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered ...

, CPU,

Input/output In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals ...

). * An implementation for the ARINC 653 services (the APEX API). * An interface to be able to configure the platform and its domain of use. * Various instrumentation tools.

Initialization

Initialization of an ARINC 653 partition creates resources used by the partition. Resources creation (PROCESS, EVENT, SEMAPHORE...) is performed by calling API services named CREATE_xxxx.

Error handling

The process error handler is a preemptive

process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

of the highest priority dedicated to handle partition exceptions. It is created by the service CREATE_ERROR_HANDLER during partition initialization. The API allows the error handler to stop a faulty process (STOP_SELF). In that case, the RTOS

scheduler A schedule or a timetable, as a basic time-management tool, consists of a list of times at which possible tasks, events, or actions are intended to take place, or of a sequence of events in the chronological order in which such things are i ...

will elicit the next process with the highest priority. ARINC 653 does not specify how the scheduler should behave if the error handler does not stop a faulty process. In some (theoretical) cases, this could lead to an infinite loop between the faulty process and the error handler. The error handler can obtain information about the source and the context of the exception.

Mode management

Each partition can be in several activation modes: * COLD_START and WARM_START: Only the initialization process is executed, * NORMAL: The initialization process is stopped, and the other partition processes are called by the RTOS

depending on their priority, * IDLE: No process is executed. However an implementation could still in theory execute a hidden process of the lowest priority, for example to start an infinite loop. The SET_PARTITION_MODE service allows to manage these states. It can be called by any process in the partition. Entering the IDLE state is irreversible for the partition. Only an external event (such as a platform restart) can change the state to another mode when the partition is in this state.

Partition and Process Scheduling

The standard defines a two-level hierarchical schedule. The first level schedules the partitions. This is a round-robin, fixed schedule that repeats a Major Time Frame. The Major Time Frame schedules each partition in a fixed duration Minor Time Frame with a fixed offset from the start of the Major Time Frame. ARINC653 schedule

Within the Minor Time Frame, the second level uses process scheduling. Each partition has at least one

. Process scheduling within a Minor Time Frame is preemptive. The scheduler is called either by a timer or by API services.

API services

The ARINC 653 APEX services are

calls belonging in six categories: * Partition management * Process management * Time management * Inter-partition communication * Intra-partition communication * Error handling No ARINC 653 services are provided for the

memory management Memory management is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when ...

of partitions. Each partition has to handle its own memory (still under the constraints of memory partitioning enforced by ARINC 653). Each service returns a RETURN_CODE value which indicates if the call has been successful: * NO_ERROR: the service performed nominally after a valid request * NO_ACTION: the state of the system has not changed after executing the service * NOT_AVAILABLE: the service is temporarily unavailable * INVALID_PARAM: at least one of the service's parameters is invalid * INVALID_CONFIG: at least one of the service's parameters is incompatible with the current configuration of the system * INVALID_MODE: the service is incompatible with the current mode of the system * TIMED_OUT: the delay for the execution of the service has expired

Links to POSIX and ASAAC

The field covered by ARINC 653 is similar to ASAAC ''Def Stan 00-74''. However, there are differences between the two standards. Some ARINC 653 (APEX) calls have a

POSIX The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming inter ...

equivalent, but are different from how they are defined in POSIX. For example, the following call defined in ASAAC: receiveBuffer would be translated in ARINC 653 by: RECEIVE_BUFFER() and also in POSIX by: recv()