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Issued by SGS-THOMSON Microelectronics on behalf of Advanced RISC Machines, Philips Semiconductors, SGS-THOMSON Microelectronics, Siemens, TEMIC/MATRA MHS
September 11th, 1995. Five of Europe's major semiconductor companies - Advanced RISC Machines (ARM), Philips Semiconductors, SGS-THOMSON Microelectronics, Siemens and Temic/Matra MHS - have announced an agreement to licence a jointly developed on-chip bus protocol to other companies.

The bus, known as the Peripheral Interconnect Bus (PI Bus), was developed by the five partners within the framework of a 3-year European Union ESPRIT Open Microprocessor Initiative (OMI) project. It is particularly suitable for use in very large scale integrated circuits using deep submicron technologies and modular architectures.

With today's advanced semiconductor technology allowing systems containing several million transistors to be integrated on to a single silicon chip, there is a growing demand for chips incorporating processors that can orchestrate the highly complex functions for specific applications.

To minimise the design cycle time, such complex chips can be built by selecting appropriate functions from a library of previously designed and tested macrocells, using a high speed communications bus to interconnect them.

The PI Bus was developed specifically to provide high speed on-chip communications.

The high bandwidth and low overhead of the PI Bus makes it ideal for connecting processor cores, memories,coprocessors, I/O controllers and other functional blocks in high performance chips, for time-critical applications.

With the successful completion of the project, the PI Bus has been incorporated as OMI Standard OMI 324.3D and is the subject of a European Patent Application, with the five partners jointly owning the patent rights.

Some of the partners have already incorporated the PI Bus into proprietary semiconductor products such as 32-bit micro core architecture. The PI Bus standard will also serve as a basis for future on-chip bus developments.

To encourage worldwide adoption of this European development, the partners are now offering licences at nominal cost that allow other parties to make, use and sell products incorporating the PI Bus, provided that the licencees comply with the OMI Standard OMI 324 PI Bus Rev 0.3D.

Ian Pearson, Director of Strategic Partnerships commented, "The 'open' licensing and standardisation of this development will encourage other companies to incorporate PI Bus-compatible macrocells in their libraries, which will facilitate the exchange of functional blocks between different chip manufacturers."

Advanced RISC Machines Ltd (ARM) designs, licenses and markets fast, low cost, power efficient RISC processors, peripherals and development tools for embedded control, consumer/educational multimedia, DSP and portable applications.

ARM also provides design services and training. ARM licenses its technology to semiconductor partner companies, who focus on manufacturing, applications and marketing. Each partner offers unique ARM related services, which together satisfy a wide range of applications needs.

Philips Semiconductors, a division of Philips Electronics NV headquartered in Eindhoven, The Netherlands, is the eleventh largest semiconductor supplier in the world.

Philips Semiconductors' innovations in digital audio, video, and mobile technology position the company as a leader in the consumer, multimedia, and wireless communications markets. Sales offices are located in all major markets around the world and are supported by regional customer application labs.

SGS-THOMSON Microelectronics is a global independent semiconductor supplier listed on the New York Stock Exchange (NYSE:STM) and on the Bourse de Paris.

It designs, develops, manufactures and markets a broad range of semiconductor integrated circuits (ICs) and discrete devices used in a wide variety of microelectronics applications, including telecommunications systems, computer systems, consumer products, automotive products and industrial automation and control systems.

Siemens is one of the three largest semiconductor manufacturers in Europe. The company's products range from dynamic memory (DRAM) chips to ICs (including a wide variety of optoelectronic devices) for information processing, communications and industrial applications.

Temic member MATRA MHS has more than 15 years' experience in the design and fabrication of products based on advanced digital CMOS technology.

The Semiconductor Division of TEMIC includes Telefunken Semiconductors, Siliconix, MATRA MHS and Dialog Semiconductor.

A leader in the design of semiconductor products for communications, automotive, computer, hi-rel, industrial and consumer applications, TEMIC's worldwide semiconductor operations include ISO 9001 certified manufacturing facilities in Europe, the United States and Asia Pacific. Sales are handled by the worldwide TEMIC network and by regional sales representatives and distributors.

For further information please contact:
Advanced RISC Machines
Trent Poltronetti Marcom Manager, ARM
Tel: +44 1223 400449
Fax: +44 1223 400410
Steve Waddington A+ Group
Tel: +44 753 790700
Fax: +44 753 790701
Philips Semiconductors
Jeannet Harpe Press Officer

Tel: +31 40 722091
Fax: +31 40 724825
Georg-Ludwig Radke

Tel: +49 89 4144 8485
Fax: +49 89 4144 8482
Veronique Sablereau Communications

Tel: +33 1 3060 7068
Notes to Editors
PI Bus Overview
The Peripheral Interconnect Bus (PI Bus) specifies a bus protocol to be used on-chip. The PI Bus connects on-chip function blocks (modules), in particular macrocells, and offers a wide range of functions, with primary focus on the communication requirements of various types of on-chip peripherals.

The PI Bus is an on-chip bus to be used in modular, highly integrated microprocessors and microcontrollers (systems-on-chips), and is designed for memory mapped data transfers between its bus agents. Bus agents are on-chip function blocks (modules), equipped with a PI Bus interface and connected via PI Bus signals.

A PI Bus agent acts as a PI Bus master when it initiates data read or data write operations once bus ownership has been granted to the agent. A PI Bus agent which is addressed at a PI Bus operation acts as a PI Bus slave when it performs the requested data read or write operation.

Typical masters are processors modules, coprocessors, or DMA controllers. Typical slaves are on-chip memory and interfaces to the external world.

Some PI Bus interfaces have to provide master as well as slave functionality. For example, a coprocessor may need to be initialised by the processor before it can be started.

To initialise, the processor has to write values into the coprocessors's registers via the PI Bus interface. In this case the PI Bus interface operates as a slave. When the coprocessor is allowed to run, it reads from or writes to memory or communication interfaces. The PI Bus interface now acts as a master.

To operate, the PI Bus requires an additional bus controller which performs arbitration, address decoding, and time-out control functions. The bus controller may also be equipped with implementation dependent functionality, like slave access control features.

The PI Bus protocol is oriented towards fast PI Bus agent accesses as well as to a high transfer bandwidth. A low-overhead protocol guarantees short response times at PI Bus accesses which are needed for time-critical applications. Multiple data transfers allow the PI Bus to operate at a high bandwidth.

Macrocells with a PI Bus interface can easily be integrated into a chip layout even if they are designed by different manufacturers.

The potential bus agents require only a PI Bus interface of low complexity. Since there is no concrete implementation specified, PI Bus can be adapted to the individual requirements of the target chip design.

For example, the widths of the address and data bus may be varied.

The PI Bus is designed with requirements of high performance systems in mind. The main features of the PI Bus are:
- Processor independent
- Demultiplexed operation
- Clock synchronous
- Peak transfer rate of 200 Mbytes/s (50 MHz bus clock)
- Address and data bus scalable (up to 32 bits)
- 8-/16-/32-bit data access
- Broad range of transfer types from single to multiple data transfers
- Multimaster capability
The PI Bus does not provide:
- Cache coherency support
- Broadcasts
- Dynamic bus sizing
- Unaligned data access