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|Written in||Ada, C|
|OS family||Real-time operating system|
|Source model||Open source|
|Latest release||5.1 / August 25, 2020|
|Marketing target||Embedded systems|
|Platforms||ARM, Blackfin, ColdFire, TI C3x/C4x, H8/300, x86, 68k, LatticeMico32, MIPS (Mongoose-V), Nios II, OpenRISC, PowerPC, SuperH, SPARC (ERC32, LEON)|
Real-Time Executive for Multiprocessor Systems (RTEMS), formerly Real-Time Executive for Missile Systems, and then Real-Time Executive for Military Systems, is a real-time operating system (RTOS) designed for embedded systems. It is free and open-source software.
Development began in the late 1980s with early versions available via File Transfer Protocol (ftp) as early as 1993. OAR Corporation is currently managing the RTEMS project in cooperation with a steering committee which includes user representatives.
RTEMS is designed for real-time, embedded systems and to support various open application programming interface (API) standards including Portable Operating System Interface (POSIX) and µITRON. The API now known as the Classic RTEMS API was originally based on the Real-Time Executive Interface Definition (RTEID) specification. RTEMS includes a port of the FreeBSD Internet protocol suite (TCP/IP stack) and support for various file systems including Network File System (NFS) and File Allocation Table (FAT).
RTEMS has been ported to various target processor architectures:
- Atmel AVR
- Freescale, now NXP ColdFire
- Texas Instruments – C3x/C4x DSPs
- Intel – x86 architecture members 80386, Pentium, and above
- Nios II
- Renesas – H8/300, M32C, M32R, SuperH
- RISC-V RV32, RV64 using QEMU
- SPARC – ERC32, LEON, V9
RTEMS is used in many application domains. The Experimental Physics and Industrial Control System (EPICS) community includes multiple people who are active RTEMS submitters. RTEMS is also popular for space uses since it supports multiple microprocessors developed for use in space including SPARC ERC32 and LEON, MIPS Mongoose-V, ColdFire, and PowerPC architectures, which are available in space hardened models. RTEMS is currently orbiting Mars as part of the Electra software radio on NASA's Mars Reconnaissance Orbiter, and the ESA's Trace Gas Orbiter.
RTEMS is distributed under a modified GNU General Public License (GPL), allowing linking RTEMS objects with other files without needing the full executable to be covered by the GPL. This license is based on the GNAT Modified General Public License with the language modified to not be specific to the programming language Ada.
- "RTEMS 5.1 Released". 2020-08-25. Retrieved 2020-10-02.
- "Real Time Mars Approach Navigation aided by the Mars Network" (PDF). NASA. Archived from the original (PDF) on 2006-09-30. Retrieved 2008-01-25.
- "NASA radio on Europe's new Mars Orbiter aces relay test". Retrieved 2016-12-01.