Radiation Hardened CPU

Source: https://wikivisually.com/wiki/RTX2010

Due to the extensive development and testing required to produce a radiation-tolerant design of a microelectronic chip, radiation-hardened chips tend to lag behind the most recent developments. Environments with high levels of ionizing radiation create special design challenges, a single charged particle can knock thousands of electrons loose, causing electronic noise and signal spikes. In the case of digital circuits, this can cause results which are inaccurate or unintelligible and this is a particularly serious problem in the design of satellites, military aircraft, nuclear power stations, and nuclear weapons. In order to ensure the operation of such systems, manufacturers of integrated circuits. The resulting systems are said to be rad-hardened, rad-hard, or hardened, cosmic rays come from all directions and consist of approximately 85% protons, 14% alpha particles, and 1% heavy ions, together with x-ray and gamma-ray radiation. Most effects are caused by particles with energies between 0.1 and 20 GeV, the atmosphere filters most of these, so they are primarily a concern for spacecraft and high-altitude aircraft.

Solar particle events come from the direction of the sun and consist of a flux of high-energy protons and heavy ions. Van Allen radiation belts contain electrons and protons trapped in the geomagnetic field, the particle flux in the regions farther from the Earth can vary wildly depending on the actual conditions of the Sun and the magnetosphere. Due to their position they pose a concern for satellites, secondary particles result from interaction of other kinds of radiation with structures around the electronic devices. Nuclear reactors produce gamma radiation and neutron radiation which can affect sensor, in case of a nuclear war they pose a potential concern for all civilian and military electronics. Chip packaging materials were a source of radiation that was found to be causing soft errors in new DRAM chips in the 1970s. Traces of radioactive elements in the packaging of the chips were producing alpha particles and these effects have been reduced today by using purer packaging materials, and employing error-correcting codes to detect and often correct DRAM errors.

Two fundamental damage mechanisms take place, Lattice displacement, caused by neutrons, alpha particles, heavy ions, components certified as ELDRS free, do not show damages with fluxes below 0.01 rad/s =36 rad/h. Ionization effects are caused by charged particles, including the ones with energy too low to cause lattice effects, the ionization effects are usually transient, creating glitches and soft errors, but can lead to destruction of the device if they trigger other damage mechanisms. Photocurrent caused by ultraviolet and x-ray radiation may belong to category as well. Gradual accumulation of holes in the layer in MOSFET transistors leads to worsening of their performance. The end-user effects can be characterized in several groups, Neutron effects and this leads to an increase in the count of recombination centers and deep-level defects, reducing the lifetime of minority carriers, thus affecting bipolar devices more than CMOS ones. Bipolar devices on silicon tend to show changes in electrical parameters at levels of 1010 to 1011 neutrons/cm², the sensitivity of the devices may increase together with increasing level of integration and decreasing size of individual structures

The RTX2010

Manufactured by Intersil is a radiation hardened stack machine microprocessor which has been used in numerous spacecraft. Characteristics

It is a two-stack machine, each stack 256 words deep, that supports direct execution of Forth. Subroutine calls and returns only take one processor cycle and it also has a very low and consistent interrupt latency of only four processor cycles, which lends it well to realtime applications.

RTX2010 History

In 1983, Chuck Moore implemented a processor for his programming language Forth as a gate array. As Forth can be considered a dual stack virtual machine, he made the processor, Novix N4000, as a dual-stack machine. In 1988, an improved processor was sold to Harris Semiconductor, who marketed it for space applications as the RTX2000.

Example spacecraft that use the RTX2010

  • Advanced Composition Explorer (ACE)

  • NEAR/Shoemaker

  • TIMED

  • Rosetta’s lander - Philae

Philae Lander

Philae is controlled by 2 RTX2010 CPUs and a further 8 control the Experiments. 13 CPUs (10* RTX2010, 1* ADSP-21020, 2* 80C3x) in total.