Electronic digital logic circuitry – Interface – Current driving
Reexamination Certificate
1999-02-10
2001-04-17
Tokar, Michael (Department: 2819)
Electronic digital logic circuitry
Interface
Current driving
C326S082000, C326S083000
Reexamination Certificate
active
06218862
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to devices for transmitting digital data, and more specifically to transmission of digital information on a two-way conductor.
2. Description of Related Art
There are several conventional two-way transmission busses that use one or more two-way conductors for transmitting digital data. For example, the I2C bus devised by Philips is commonly used in audio and video applications. The I2C bus has one-way supply lines in the form of a supply line for the positive supply voltage (e.g., 5 volts) and a supply line for ground. Additionally, the I2C bus has a clock line for transmitting a clock signal that can be a one-way signal or a two-way signal (e.g., when there are several master units on the bus), and a two-way data line for the digital data to be transmitted. When data is not being transmitted, the data line is pulled to a positive potential by a pulling device consisting of a resistor. To transmit on the two-way data line, a master or slave circuit takes over the data line and imposes negative pulses corresponding to the sequence of 1's and 0's of the information to be transmitted (i.e., addresses and data) at the clock rate in accordance with a specified protocol.
When making an electronic system for an application, the various electronic circuits required for the different functions of the system are chosen from the catalogs of suppliers of electronic circuits. Depending on the functions being sought (e.g., depending on if what is being sought is a microprocessor, an audio amplifier or tuner, a static or dynamic memory, and/or a non-volatile or other type of memory), the technologies of the electronic circuits that are available are not always equivalent. For example, there is a current trend towards the development of technologies and circuit structures capable of operating at low supply voltages (e.g., 2.5 volts or less). However, while microprocessors and memories that operate at 2.5 volts are currently available, other electronic circuits that require a great deal of power (e.g., tuners) are currently only available for operation at 5 volts. If it is desired to use circuits operating at different voltages in the same electronic system, it is necessary to provide for the matching of the levels of the data to be transmitted.
Furthermore, certain electronic circuits (e.g., amplifiers) are highly sensitive to noise. In a system having many electronic circuits that communicate through the same transmission bus, a sensitive circuit (such as the tuner) can be significantly disturbed by all of the information transmitted on the bus that is intended for other circuits.
SUMMARY OF THE INVENTION
In view of these drawbacks, it is an object of the present invention to remove the above-mentioned drawbacks and to allow circuits that operate at different voltages to be connected to the same two-way transmission bus. A circuit that requires a different supply voltage or that is to be isolated is connected to a two-way line through a two-way repeater. By achieving a matching of levels in both directions, the repeater allows circuits that operate at different supply voltages to be connected to the same two-way bus. Further, the repeater makes it possible to provide different pulling devices on each side of the repeater. Thus, the pulling devices can be matched with the line impedances on each side of the repeater.
Another object of the present invention is to limit noise on a two-way transmission bus. The repeater isolates the circuit by not allowing the circuit to receive any piece of information that is not intended for the circuit. Preferably, the repeater allows the circuit to be actively connected to the bus only when the information on the bus is intended for the circuit and/or when the circuit itself is transmitting information on the bus.
One embodiment of the present invention provides a device for two-way digital transmission on a bus having at least one two-way line. The device includes at least one two-way repeater that is connected between a first section and a second section of the two-way line, and each line section is connected to at least one electronic circuit. First and second pulling devices, which pull to a first logic level, are connected to the first and second line sections, respectively. Further, the repeater includes third and fourth pulling devices, which pull to a second logic level, that are connected to the first and second line sections, respectively. A logic circuit connected to the first and second line sections controls the third and fourth pulling devices so that the third and fourth pulling devices are not simultaneously active.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only and various modifications may naturally be performed without deviating from the present invention.
REFERENCES:
patent: 4982115 (1991-01-01), Lee
patent: 5202593 (1993-04-01), Huang et al.
patent: 5225722 (1993-07-01), Gotou et al.
patent: 5440182 (1995-08-01), Dobbelaere
patent: 5689196 (1997-11-01), Schutte
patent: 5923187 (1999-07-01), Maugars
French Search Report with Annex (Nov. 17, 1998).
Bongini Stephen C.
Fleit Kain Gibbons Gutman & Bongini P.L.
Galanthay Theodore E.
STMicroelectronics S.A.
Tokar Michael
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