Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1998-09-30
2001-03-20
Shin, Christopher B. (Department: 2182)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S120000, C710S108000, C710S005000
Reexamination Certificate
active
06205504
ABSTRACT:
TECHNICAL FIELD
The present invention relates in general to data processing systems, and in particular, to an inter-IC (I
2
C) bus in a data processing system.
BACKGROUND INFORMATION
The I
2
C bus is a 2-wire bidirectional serial bus for communication between bus devices in a data processing system. Bus devices may include microprocessors, microcontrollers, memory devices, peripheral devices, data converters, and application-oriented circuits. Two wires of the I
2
C bus constitute a serial data line (SDA) for communicating data between bus devices and a serial clock line (SCL) carrying clock signals that control bus access and data transfer.
Each device is recognized by a unique address and can operate as either a receiver-only device or a transmitter with the capability to both receive and send information. Transmitters and/or receivers can operate in either master or slave mode, depending on whether the chip has to initiate a data transfer or is only addressed.
There are two limitations to devices that use I
2
C buses. First, once the bus devices have been interconnected with the I
2
C bus, this configuration is not expandable by the addition of new devices to the circuit, without having to reprogram any one or more of the devices that operate as a controlling device. For example, once the I
2
C bus circuitry has been connected, a microcontroller coupled to the bus and controlling will be programmed with the addresses of each of the existing devices. But, when a device is added at a later time, the microcontroller will not recognize this new device, since it will not know the new device's address. The crude solution to this problem is to also replace the microcontroller with a newly programmed microcontroller having knowledge of the new bus device.
The second limitation is related to the first, in that once the devices have been interconnected by the I
2
C bus, the set of operations, or commands, possible between the devices over the I
2
C bus is also set and cannot be expanded without also replacing the microcontroller.
Therefore, there is a need in the art to be able to add new devices and/or to add new functionality to an existing I
2
C bus arrangement without also having to replace the microcontroller.
SUMMARY OF THE INVENTION
The present invention addresses the foregoing needs by providing programming within the microcontroller coupled to an I
2
C bus and an interface to an external control for externally providing signals for controlling commands performed by the microcontroller over the I
2
C bus.
In an embodiment of the present invention, an operating system external to the microcontroller sends messages to the microcontroller instructing the microcontroller to perform specified actions, such as, the read or write access of a particular bus device coupled to the microcontroller over the I
2
C bus.
In another embodiment of the present invention, the control signals from the operating system can instruct the microcontroller to address a new bus device of which the microcontroller was not previously programmed to recognize.
An advantage of the present invention is an ability for a host system to command and interrogate all devices attached to a microcontroller over an I
2
C bus in ways not envisioned when the microcontroller program was originally written.
Another advantage of the present invention is that the host system can command and interrogate new devices added to existing I
2
C channels, wherein the microcontroller coupled to the I
2
C channels was not programmed to recognize such new devices.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.
REFERENCES:
patent: 5613157 (1997-03-01), Davidson et al.
patent: 5764968 (1998-06-01), Ninomiya
patent: 5892933 (1999-04-01), Voltz
patent: 5897663 (1999-04-01), Stancil
patent: 5907557 (1999-05-01), Gandar
patent: 5913045 (1999-06-01), Gillespie et al.
patent: 5987554 (1999-11-01), Liu et al.
“Channel Simulator”,IBM Technical Disclosure Bulletin,vol. 26 No. 4, Sep. 1983, pp. 2125-2128.
“Philips Semiconductors; I2C-bus”, available via the Internet at http://www-us.semiconductors.philips.com/i2c/facts, copy printed Jul. 30, 1998, pp. 1-4.
“The I2C-bus and how to use it (including specifications)”,Phillips Semiconductors,Apr. 1995, pp. 1-24.
Faust Robert Allan
Kennel John C.
International Business Machines - Corporation
Kordzik Kelly K.
Leeuwen Leslie A. Van
Shin Christopher B.
Winstead Sechrest & Minick P.C.
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