The IEEE 1394 and I2C Mixed-Signal Driver is one of two application-specific integrated circuits (ASICs) designed to function together as an interface among the following three digital-signal buses:
- A peripheral component interface (PCI) bus;
- A high-speed serial data bus that conforms to Institute of Electrical and Electronics Engineers (IEEE) standard 1394, also known as the FireWire standard; and
- An I2C (inter integrated circuit) bus, which was developed in the early 1980s by Philips Semiconductors for connecting a central processing unit to peripheral integrated-circuit chips in a television receiver.
Among other things that have been emphasized in the development effort are radiation hardness and compactness as required for intended use aboard spacecraft. As result of engineering compromises necessary for radiation hardness, the performance of this set of ASICs is expected to lag somewhat behind that of comparable circuitry previously developed for terrestrial use. Nevertheless, because the capability for communication among the three buses is not afforded by any plug-in circuit cards now commercially available, there could be a terrestrial market for these ASICs for applications in which the tri-bus communication is required.
In the original spacecraft application, the two ASICs would enable communication among multiple computers, scientific instruments, and spacecraft engineering systems via the three buses. The first ASIC, which could be characterized as a digital input/output (DIO) ASIC, would provide a digital interface (a link layer) among the three buses. The second ASIC, denoted the IEEE 1394 and I2C Mixed-Signal Input/Output Driver ASIC (“MSIO ASIC” for short) is the focus of this article. The MSIO ASIC would serve as the physical layer in the overall data-communication architecture.
The MSIO ASIC would implement an analog interface to the IEEE 1394 and I2C bus cables. The MSIO ASIC would be connected, either directly or through an isolation transformer, to the DIO ASIC. The MSIO ASIC would receive digital commands and data from the DIO ASIC and pass these data and commands out through the IEEE 1394 and I2C cables. The MSIO would contain a commercial controller core, custom analog bus cable-driver circuits, two I2C-bus cable-driver cores, and custom glue-logic circuitry. The MSIO ASIC would be a radiation-hardened, galvanically isolated, three-port implementation of the physical-layer functions described in the IEEE 1394a D2.0 draft specification. The MSIO ASIC would also contain two radiation- hardened, galvanically isolated sets of I2C drivers and receivers, independent of the 1394 interface and of each other.
This work was done by Huy Long, Peter Jones, Savio Chau, and Eric Holmberg of Caltech and Ross McTaggert of Digital MediaCom for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Electronic Components & Systems category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
Intellectual Property group
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109
(818) 354-2240
Refer to NPO-30121, volume and number of this NASA Tech Briefs issue, and the page number.
This Brief includes a Technical Support Package (TSP).
Mixed-Signal Driver ASIC for IEEE1394 and I2C Buses
(reference NPO-30121) is currently available for download from the TSP library.
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Overview
The document discusses the development of a Mixed-Signal Driver ASIC designed for communication among three digital-signal buses: the Peripheral Component Interface (PCI) bus, the IEEE 1394 (FireWire) bus, and the I2C (Inter-Integrated Circuit) bus. This technology was developed by a team from NASA's Jet Propulsion Laboratory (JPL) to address the unique communication needs of spacecraft, particularly in high-radiation environments.
The Mixed-Signal Input/Output Driver ASIC (MSIO ASIC) is part of a two-chip set that includes a Digital Input/Output (DIO) ASIC. Together, these ASICs enable robust communication between multiple computers, scientific instruments, and spacecraft engineering systems. The MSIO ASIC serves as the physical layer in the overall data-communication architecture, implementing an analog interface to the IEEE 1394 and I2C bus cables. It is designed to be radiation-hardened and galvanically isolated, ensuring reliable operation in the harsh conditions of space.
The document highlights the novelty of this work, emphasizing that it integrates the three bus standards into a single solution, which is not available in existing commercial plug-in circuit cards. The design aims to provide a unique communication network capability that can withstand high radiation levels, making it suitable for space applications. The use of commercial bus standards allows for the prototyping of components without the need for expensive and time-consuming development of unique technologies.
The motivation behind this development stems from the need to reduce costs and technical risks in JPL flight programs, as well as to facilitate cooperation between NASA and other government centers that have historically used differing avionics bus standards. The project was initiated under NASA's CISM and X2000 programs, which aimed to develop and validate required components for flight systems.
In summary, the document outlines a significant advancement in aerospace technology through the development of a Mixed-Signal Driver ASIC that enables tri-bus communication in spacecraft. This innovation not only addresses the specific needs of space applications but also has the potential to create a market for similar technologies in terrestrial applications, thereby bridging the gap between space and commercial technology.
