1750A
Encyclopedia
MIL-STD-1750A or 1750A is the formal definition of a 16-bit computer instruction set
architecture (ISA), including both required and optional components, as described by the military standard
document MIL-STD-1750A (1980).
In addition to the core ISA, the definition defines optional instructions, such as a FPU
and MMU
. Importantly, the standard does not define the implementation details of a 1750A processor.
that allows 220 16-bit words of memory using 512 page mapping registers (in the I/O space), defining separate instruction and data spaces, and keyed memory access control.
Most instructions are 16 bits, although some have a 16-bit extension. The standard computer has 16 general purpose 16-bit registers (0 through 15). Registers 1 through 15 can be used as index register
s. Registers 12 through 15 can be used as base registers.
Any of the 16 registers could be used as a stack
pointer for the SJS and URS instructions (stack jump subroutine and unstack return subroutine), but only register 15 was used as the stack pointer for the PSHM and POPM instructions (push multiple and pop multiple).
The computer has instructions for 16, and 32-bit binary arithmetic, as well as 32 and 48 bit floating point
. I/O is generally via the I/O instructions (XIO and VIO), which have a separate 216 16-bit word address space and may have a specialized bus.
, ECL
, SoS
).
Of particular interest is the fact that 1750A systems often offer very high levels of radiation and other hazardous environment protection, making them particularly suited for military, aviation and space applications.
Examples of MIL-STD-1750A implementations include:
, a high-level programming language
defined by the United States Department of Defense
which was derived from ALGOL 58
. To a lesser extent, Ada
was used.
There are also C
compilers, for example Cleanscape XTC-1750A. Older versions of GNU
GCC
contain support for MIL-STD-1750A; it was declared obsolete in version 3.1, and removed in subsequent versions.
needs. This includes embedded tasks such as aircraft and missile control systems as well as more mundane general military computing needs.
The advantages of this concept were recognized outside of the USAF and the 1750A was adopted by numerous other organizations, such as the European Space Agency
, NASA
, Israeli Aircraft Industries and many projects in academia.
Examples of military aircraft using the 1750A include:
(ISRO) and the Chinese aerospace industry continue to use the 1750 for new projects.
To necessarily say the CPU is technologically defunct can be nebulous. This CPU can run at 0.5 MIPS to 3 MIPS depending on the operating speed (from 1 MHz to 20 MHz). The lack of modern floating point capabilities makes this CPU less suitable for some (but not all) modern embedded applications. However, lack of familiarity (and modern compiler support) with this CPU makes its uptake in the civilian computing sector difficult.
More modern CPUs like the Mongoose-V
(used on the New Horizons spacecraft) and the higher performance RAD750
that are both based on more modern computer architectures are replacing the MIL-STD-1750A in the space sector over time. It is expected that by 2030 this CPUs use in aerospace may cease.
Instruction set
An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
architecture (ISA), including both required and optional components, as described by the military standard
Defense Standard
A United States defense standard, often called a military standard, "MIL-STD", "MIL-SPEC", or "MilSpecs", is used to help achieve standardization objectives by the U.S...
document MIL-STD-1750A (1980).
In addition to the core ISA, the definition defines optional instructions, such as a FPU
Floating point unit
A floating-point unit is a part of a computer system specially designed to carry out operations on floating point numbers. Typical operations are addition, subtraction, multiplication, division, and square root...
and MMU
Memory management unit
A memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to memory requested by the CPU...
. Importantly, the standard does not define the implementation details of a 1750A processor.
Internals
The 1750A supports 216 16-bit words of memory for the core standard. The standard defines an optional memory management unitMemory management unit
A memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to memory requested by the CPU...
that allows 220 16-bit words of memory using 512 page mapping registers (in the I/O space), defining separate instruction and data spaces, and keyed memory access control.
Most instructions are 16 bits, although some have a 16-bit extension. The standard computer has 16 general purpose 16-bit registers (0 through 15). Registers 1 through 15 can be used as index register
Index register
An index registerCommonly known as a B-line in early British computers. in a computer's CPU is a processor register used for modifying operand addresses during the run of a program, typically for doing vector/array operations...
s. Registers 12 through 15 can be used as base registers.
Any of the 16 registers could be used as a stack
Stack (data structure)
In computer science, a stack is a last in, first out abstract data type and linear data structure. A stack can have any abstract data type as an element, but is characterized by only three fundamental operations: push, pop and stack top. The push operation adds a new item to the top of the stack,...
pointer for the SJS and URS instructions (stack jump subroutine and unstack return subroutine), but only register 15 was used as the stack pointer for the PSHM and POPM instructions (push multiple and pop multiple).
The computer has instructions for 16, and 32-bit binary arithmetic, as well as 32 and 48 bit floating point
Floating point
In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...
. I/O is generally via the I/O instructions (XIO and VIO), which have a separate 216 16-bit word address space and may have a specialized bus.
Implementations
Because MIL-STD-1750A did not define implementation details, 1750A products are available from a wide variety of companies in the form of component, board, and system-level offerings implemented in a myriad of technologies, often the most advanced and exotic of their respective periods (e.g. GaAsGaas
Gaas is a commune in the Landes department in Aquitaine in south-western France....
, ECL
Emitter-coupled logic
In electronics, emitter-coupled logic , is a logic family that achieves high speed by using an overdriven BJT differential amplifier with single-ended input, whose emitter current is limited to avoid the slow saturation region of transistor operation....
, SoS
Silicon on sapphire
Silicon on sapphire is a hetero-epitaxial process for integrated circuit manufacturing that consists of a thin layer of silicon grown on a sapphire wafer. SOS is part of the Silicon on Insulator family of CMOS technologies...
).
Of particular interest is the fact that 1750A systems often offer very high levels of radiation and other hazardous environment protection, making them particularly suited for military, aviation and space applications.
Examples of MIL-STD-1750A implementations include:
- GEC-Plessey RH1750, a radiation-hardened version for aerospace and space flight applications.
- HoneywellHoneywellHoneywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
HX1750, fabricated on Honeywell's Silicon on Insulator CMOS (SOI-IV) process giving radiation hardness. The HX1750 includes an FPU and peripherals on chip. - CPU Technology, Inc. CPU1750A-FB, a high performance 1750A SOCSystem-on-a-chipA system on a chip or system on chip is an integrated circuit that integrates all components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and often radio-frequency functions—all on a single chip substrate...
designed to give existing applications a late life performance boost. - Pyramid Semiconductor PACE P1750A. The family includes the P1750A CPU, the P1750AE Enhanced CPU, the P1753 Memory Management UnitMemory management unitA memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to memory requested by the CPU...
(MMU), the P1754 Processor Interface Chip (PIC) and the P1757ME Multi-Chip Module. This line was acquired from Performance Semiconductor in 2003. - National SemiconductorNational SemiconductorNational Semiconductor was an American semiconductor manufacturer, that specialized in analog devices and subsystems,formerly headquartered in Santa Clara, California, USA. The products of National Semiconductor included power management circuits, display drivers, audio and operational amplifiers,...
F9450 series. - MarconiMarconi-People:*Guglielmo Marconi, Italian-born radio pioneer*David Marconi, American screenwriter*Dominic Anthony Marconi, American Roman Catholic bishop*Enrico Marconi, also known as Henryk Marconi, architect*Gloria Marconi, Italian long-distance runner...
Electronic Devices MIL-STD-1750A. - Royal Aircraft Establishment Farnborough MIL-STD-1750A implementation in AMDAdvanced Micro DevicesAdvanced Micro Devices, Inc. or AMD is an American multinational semiconductor company based in Sunnyvale, California, that develops computer processors and related technologies for commercial and consumer markets...
2901AMD Am2900Am2900 is a family of integrated circuits created in 1975 by Advanced Micro Devices . They were constructed with bipolar devices, in a bit-slice topology, and were designed to be used as modular components each representing a different aspect of a computer control unit...
bit-slice technology. http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA114029 - Johns Hopkins UniversityJohns Hopkins UniversityThe Johns Hopkins University, commonly referred to as Johns Hopkins, JHU, or simply Hopkins, is a private research university based in Baltimore, Maryland, United States...
Applied Physics Laboratory (JHU/APL) MIL-STD-1750AAV space flight qualified processor. A multi-board silicon on sapphireSilicon on sapphireSilicon on sapphire is a hetero-epitaxial process for integrated circuit manufacturing that consists of a thin layer of silicon grown on a sapphire wafer. SOS is part of the Silicon on Insulator family of CMOS technologies...
implementation specifically designed for space flight. - Dynex SemiconductorDynex SemiconductorDynex Semiconductor based in Lincoln, United Kingdom is a global supplier of products and services specialising in the field of power semiconductor devices and silicon on sapphire integrated circuit products...
MAS281. A radiation hardenedRadiation hardeningRadiation hardening is a method of designing and testing electronic components and systems to make them resistant to damage or malfunctions caused by ionizing radiation , such as would be encountered in outer space, high-altitude flight, around nuclear reactors, particle accelerators, or during...
SOSSystem-on-a-chipA system on a chip or system on chip is an integrated circuit that integrates all components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and often radio-frequency functions—all on a single chip substrate...
implementation on a 64-pin multichip module with an optional MMU.
Programming
Processors based on MIL-STD-1750A are usually programmed in JOVIALJOVIAL
JOVIAL is a high-order computer programming language similar to ALGOL, but specialized for the development of embedded systems .JOVIAL is an acronym for "Jules Own Version of the International...
, a high-level programming language
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
defined by the United States Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...
which was derived from ALGOL 58
ALGOL 58
ALGOL 58, originally known as IAL, is one of the family of ALGOL computer programming languages. It was an early compromise design soon superseded by ALGOL 60...
. To a lesser extent, Ada
Ada (programming language)
Ada is a structured, statically typed, imperative, wide-spectrum, and object-oriented high-level computer programming language, extended from Pascal and other languages...
was used.
There are also C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
compilers, for example Cleanscape XTC-1750A. Older versions of GNU
GNU
GNU is a Unix-like computer operating system developed by the GNU project, ultimately aiming to be a "complete Unix-compatible software system"...
GCC
GNU Compiler Collection
The GNU Compiler Collection is a compiler system produced by the GNU Project supporting various programming languages. GCC is a key component of the GNU toolchain...
contain support for MIL-STD-1750A; it was declared obsolete in version 3.1, and removed in subsequent versions.
Deployments
The U.S. Air Force defined the standard in order to have a common computing architecture and thereby reduce the costs of software and computer systems for all military computingMilitary computers
- MIL standards and specifications :The Armed Forces have many numerical designations for computers or other equipment, to guide the military buyer's choice of appropriate technology for their application. For instance, Mil-S-901D would indicate that the computer passed shock and vibration...
needs. This includes embedded tasks such as aircraft and missile control systems as well as more mundane general military computing needs.
The advantages of this concept were recognized outside of the USAF and the 1750A was adopted by numerous other organizations, such as the European Space Agency
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
, NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, Israeli Aircraft Industries and many projects in academia.
Examples of military aircraft using the 1750A include:
- USN F-18 RFCS Flight Control Computer
- USAF F-16 Digital Flight Control System and Fire Control Computer
- US Army AH-64D Apache Longbow Helicopter
- IAI LaviIAI LaviThe IAI Lavi was a combat aircraft developed in Israel in the 1980s. It was a multi-billion dollar fighter aircraft project that was disbanded when the Israeli government concluded it could not finance production on its own, could not achieve a consensus on the Lavi's cost-effectiveness and...
fighter - IBM Federal Systems AP-102 Avionics Computer (used in various roles including the USAF F-111 avionics upgrade)
Use in space
Fully space rated implementations make the 1750A one of the few types of computers that are applicable for use in deep space applications. Example spacecraft that use the 1750A are:- EOSEarth Observing SystemThe Earth Observing System is a program of NASA comprising a series of artificial satellite missions and scientific instruments in Earth orbit designed for long-term global observations of the land surface, biosphere, atmosphere, and oceans of the Earth. The satellite component of the program was...
AquaAqua (satellite)Aqua is a multi-national NASA scientific research satellite in orbit around the Earth, studying the precipitation, evaporation, and cycling of water. It is the second major component of the Earth Observing System preceded by Terra and followed by Aura .The name "Aqua" comes from the Latin word...
, AuraAura (satellite)Aura is a multi-national NASA scientific research satellite in orbit around the Earth, studying the Earth's ozone layer, air quality and climate. It is the third major component of the Earth Observing System following on Terra and Aqua...
and TerraTerra (satellite)Terra is a multi-national NASA scientific research satellite in a sun-synchronous orbit around the Earth. It is the flagship of the Earth Observing System... - ESA ClusterCluster missionCluster II is a space mission of the European Space Agency, with NASA participation, to study the Earth's magnetosphere over the course of an entire solar cycle. The mission is composed of four identical spacecraft flying in a tetrahedral formation...
- ESA Rosetta
- MSTI-1, 2 and 3
- NASA Cassini
- NASA Landsat 7
- NASA Mars Global SurveyorMars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on 2...
- Naval Research Laboratory Clementine Lunar Orbiter
- USAF Titan-4 Guidance Computer
- NOAA GOES-13, GOES-O and GOES-PGoesGoes is a municipality and a city in the southwestern Netherlands in Zuid-Beveland, in the province Zeeland. The city of Goes has approximately 27,000 residents.-History of Goes:...
- Midcourse Space Experiment (MSX) spacecraft developed at JHU/APL
- ISRO Space Recovery Experiment-1 Guidance and Navigation Computer
Technological obsolescence
With the release of the Notice 4 revision to the standard on July 31, 1996, MIL-STD-1750A was declared inactive for new military projects in the USA. However, both the Indian Space Research OrganisationIndian Space Research Organisation
The Indian Space Research Organisation is an independent Indian governmental agency established in 1969 for the research and development of vehicles and activities for the exploration of space within and outside of Earth’s atmosphere. Headquartered in Bangalore...
(ISRO) and the Chinese aerospace industry continue to use the 1750 for new projects.
To necessarily say the CPU is technologically defunct can be nebulous. This CPU can run at 0.5 MIPS to 3 MIPS depending on the operating speed (from 1 MHz to 20 MHz). The lack of modern floating point capabilities makes this CPU less suitable for some (but not all) modern embedded applications. However, lack of familiarity (and modern compiler support) with this CPU makes its uptake in the civilian computing sector difficult.
More modern CPUs like the Mongoose-V
Mongoose-V
The Mongoose-V 32-bit microprocessor for spacecraft onboard computer applications is a radiation-hardened and expanded 10–15 MHz version of the MIPS R3000 CPU. The Mongoose was developed by Synova, Inc...
(used on the New Horizons spacecraft) and the higher performance RAD750
RAD750
The RAD750 is a radiation-hardened single board computer, based on IBM's PowerPC 750. The successor of the RAD6000, the RAD750 is manufactured by BAE Systems Electronic Solutions. It is intended for use in high radiation environments such as experienced on board satellites and spacecraft...
that are both based on more modern computer architectures are replacing the MIL-STD-1750A in the space sector over time. It is expected that by 2030 this CPUs use in aerospace may cease.
External links
- Software Vendor Information
- Specification and vendor information
- Ada and ANSI C compilers
- MIL-STD-1750A, 2 July 1980, with updated Notice 1, 21 May 1982
- FlightLinux Project Target Architecture Technical Report References to use in spacecraft
- DODSSP U.S. Department of Defense Single Stock Point for Military Specifications, Standards and Related Publications
- Dynex Semiconductor MA31750 Processor
- Pyramid Semiconductor P1750A-SOS Processor
- http://www.realmarcom.com/documents/tools/data_1750a.pdf
- http://adsabs.harvard.edu/abs/1983naec....1..633H