1999-02-11 , ESC-9884
Technology News From Philips Semiconductors

Philips Semiconductors, Europe's largest semiconductor company, today announced that its de-facto world standard serial I²C-bus, used for communication between ICs, has been extended to support speeds of up to 3.4 Mbits/s. Combined with an elegant, inexpensive voltage level-shifting function, this High-speed mode (Hs-mode) offers an ideal solution for today's mixed technology systems, where high speeds and a variety of voltages (5 V, 3 V or lower) are commonly used.

Philips Semiconductors invented the two-wire I²C-bus for communication between ICs in 1980 and since then, it has become a de-facto serial bus standard, implemented in a very large number of ICs and licensed to more than 50 companies. "Already extensively used in microcontroller-based consumer and telecommunications products, it offers low cost and easy design-in," said Theo Claasen, Philips Semiconductors chief technology officer. "Now, these enhancements offer real 'future-proofing', with speeds well in excess of those in common use today, ensuring the I²C-bus will remain the serial bus of choice well into the next century."

Originally specified to 100 kbits/s and intended for simple control and status signals, the low cost, technical versatility and simplicity of the I²C-bus ensured its popularity and it quickly began to be used for other types of data transfer, such as text and display. Hs-mode equips the bus for developments in large high-speed serial RAM, EEPROM or Flash memory, and other applications where speeds are constantly increasing - such as serial transfer to LCD drivers for graphic display and data transfer between high-speed digital ICs and analog devices.

Hs-mode is compatible with all existing I²C-bus systems, including the original Standard-mode (S-mode) specification and the previous Fast-mode (F-mode) upgrade introduced in 1992, providing 400 kbits/s transfer. Different speed systems can easily be mixed and, if an Hs-mode master device with a specially-developed, low cost bridge is used to connect to slower parts of the system, all Hs-mode devices will communicate bi-directionally at full speed while using F/S (Fast/Standard)-mode speeds with the slower parts of the system. The bridge may also perform a bi-directional level shift function between the two speed sections to mix, for example, 3 V Hs-mode and 5 V F/S-mode devices.

An Hs-mode master/bridge has separate pins for Hs-mode transfers and, in a pure Hs-mode system or where no bridge is used, the two F/S-mode pins can be used for other I/O functions. And as a multi-master system, the I²C-bus is particularly simple and cost effective in comparison with other high-speed buses, where additional wires and pins are needed for each slave device.

For more information, please refer to the attached technical backgrounder, or visit our dedicated I²C-bus WWW site at  www.semiconductors.philips.com/I2C.

Philips Semiconductors, a division of Royal Philips Electronics, headquartered in Eindhoven, The Netherlands, is the eighth largest semiconductor supplier in the world (according to Dataquest's preliminary 1998 ranking by sales) and the third largest supplier of discretes 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 systems labs.

 I2C-bus specification