Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1997-11-20
2001-08-28
Decady, Albert (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S752000, C714S802000
Reexamination Certificate
active
06282685
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to communication systems and methods, in particular, to serial communications systems and methods.
BACKGROUND OF THE INVENTION
Typically, serial communication systems use parity to safeguard data integrity during transmission from a transmitter to a receiver. Communications standards are used to ensure compatibility between different systems and to facilitate software development and portability. Hardware has also been developed that incorporates these standards. One such standard specifies that parity may accompany each transmission of serial data. The transmitted parity bit can then be used by the receiver to check data integrity of the serial data. This technique, however, may require additional time or bandwidth for data transmission because a parity bit must be added to the stream of data.
Data integrity, however, has become less of a problem in some situations. Specifically, low noise cables, system enclosures and interconnects reduce the frequency of such errors to a very low level. In other words, in some circumstances errors do not happen as frequently as had been assumed when the standards arose. Moreover, the level of protection afforded by simple parity checking generally has become inadequate for many situations that require error protection. Despite these developments, hardware and software produced today still support the standard referenced above. Parity checking, therefore, is sometimes unnecessary and goes unused in systems that support it. Consequently, the time or bandwidth allocated for transmitting the parity bit is frequently wasted.
A related problem is the need for the exchange of control messages between two asynchronous entities. For example, when a personal computer is communicating with a modem through a EIA232/V.24 cable, sometimes one entity must instruct the other entity to stop or resume sending data. This is commonly referred to as flow control. Flow control may be implemented in two ways: hardware flow control and software flow control. Hardware flow control is typically accomplished by adding wires to the cable. The additional wires carry signals dedicated to flow control. Consequently, hardware flow control may add complexity to the sending and receiving entities and the cable.
Software flow control is usually accomplished by inserting special characters into the data stream at the transmitting entity. The receiving entity is then responsible for recognizing the special character and distinguishing it from normal data that happens to be equal to a special character. Consequently, software flow control may require additional significant software complexity on the part of the receiver.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide communications systems and methods that more efficiently utilize the bandwidth normally associated with parity checking.
It is another object of the present invention to provide communications systems and methods that exchange control messages using standard asynchronous communications hardware without significant added complexity.
Moreover, it is an object of the invention to provide communications systems and methods that use standard hardware to generate the parity bit for purposes other than checking for errors in data transmission.
These and other objects, features and advantages are provided according to the present invention by communications systems and methods which use the parity generation and checking functions typically found in standard asynchronous communications hardware to signal how transmitted data should be processed. Parity errors are forced on data transmissions that contain data that is to be processed in a predetermined way by a receiver if the receiver determines that a parity error exists.
Because some communication links are highly reliable and provide a very low noise environment, parity errors caused by disturbances on such links are very unlikely. Consequently, protection offered by parity often times goes unused. The present invention uses the parity bit as a signal making better use of the otherwise wasted bandwidth allocated to the parity bit in a standard serial communication system. Moreover, the meaning of the signal can be defined by the communication system employing the invention. For example, a communication system may define the parity bit as a signal to the receiver that the associated data is part of a secondary data channel or a distinct data stream. The present invention can also be practiced using commonly available components such as UARTs.
In particular, according to the present invention, a bit stream and an associated parity bit are generated. The bit stream and an associated parity bit are communicated to a receiving entity. The receiving entity performs a parity error analysis on the communicated bit stream and associated parity bit. The receiving entity then parses the communicated bit stream according to the parity error analysis.
According to another aspect of the invention, a first parity generator is used to generate a first parity bit on the data to be communicated. The first parity and the data are transmitted in a communications medium by a data transmitter to a data receiver. A second parity generator generates a second parity bit using the communicated data. A comparator then compares the first parity bit with the second parity bit. A parser then processes the communicated data according to the results of the comparison of the first and second parity bits.
A communications system for communicating a serial bit stream and parity according to an embodiment of the resent invention includes means for generating a serial it stream and generating associated parity. Means are rovided, responsive to the parity generation means, for anipulating the generated parity. Means are provided, responsive to the manipulating means and the serial data means, for communicating the serial bit stream to the receiving entity. Means are provided, responsive to the means for communicating, for analyzing the serial bit stream and the manipulated parity for the presence of a parity error. Means are provided, responsive to the analyzing means, for parsing the communicated bit stream according to a parsing process selected based on the parity analysis. Improved data communications are thereby provided.
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International Search Report, PCT/US98/21603. Feb, 22, 1999.
Irvin David Rand
Petty Jack S.
De'cady Albert
Ericsson Inc.
Lin Samuel
Myers Bigel & Sibley & Sajovec
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