Coded data generation or conversion – Digital code to digital code converters – Coding by table look-up techniques
Reexamination Certificate
2001-02-05
2003-07-08
Tokar, Michael (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
Coding by table look-up techniques
C341S051000, C341S065000, C341S067000, C341S090000, C711S101000
Reexamination Certificate
active
06590511
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a retrievable memory having a variable data structure to be retrieved, and more particularly concerns a retrievable memory which eliminates the need for addresses of data to be retrieved.
2. Description of the Background Art
FIG. 8
shows a conventional data retrieve system using a CAM (Content Addressable Memory). The conventional data retrieval system has a CAM
500
and a memory
540
. The CAM
500
is constituted by a memory
510
and an address encoder
520
. The memory
510
stores a plurality of key data. The memory
540
stores a plurality of content data corresponding to the key data in the memory
510
. Upon receipt of a signal representative of key data matched with a retrieval key
530
from a memory
510
, the address encoder
520
specifies an address in the memory
540
storing the data corresponding to the matched key data.
In the conventional data retrieval system, when a retrieval key
530
is inputted to a memory
510
of the CAM
500
, the memory
510
extracts key data that is matched with the retrieval key
530
. Then, the memory
510
outputs an activation signal for activating the extracted key data to the address encoder
520
.
Then, based upon the inputted activation signal, the address encoder
520
generates an address of the content data corresponding to the key data matched with the retrieval key, and outputs the address thus generated to the memory
540
. The memory
540
outputs the content data stored in the site specified by the inputted address.
In this manner, in the conventional data retrieval system, the key data that is matched with a retrieval key
530
is extracted, and the retrieved content data is read out through generating an address for specifying the content data corresponding to the extracted key data.
Thus, in the conventional data retrieval system, a mono-directional data retrieve is carried out, that is, the content data is read out based upon the key data.
However, in the conventional data retrieval system, when the retrieval key
530
is matched with a plurality of key data, a plurality of content data are outputted from the memory
540
, resulting in a failure in obtaining a single content data.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problem, the objective of the present invention is to provide a retrievable memory which can output a single data even when a plurality of results of retrieve are obtained.
A retrievable memory in accordance with the present invention includes a first memory storing n number (n: natural number) of key data, and outputting a matching signal when inputted retrieval key information is matched with stored key data; a second memory storing n number of content data corresponding to n number of key data; and a priority encoder specifying, upon receipt of matching signal, content data stored in second memory corresponding to key data that is matched with retrieval key information, wherein priority encoder outputs a specifying signal that specifies single content data when a plurality of matching signals are inputted from first memory, and second memory outputs the content data specified by specifying signal.
In the retrievable memory of the present invention, when the retrieval key information is matched with key data stored in the first memory, the first memory outputs a matching signal to the priority encoder, and the priority encoder specifies content data stored in the second memory that corresponds to the key data matched with the retrieval key information. Moreover, upon receipt of a plurality of matching signals outputted from the first memory, the priority encoder specifies single content data. Then, the second memory outputs the content data specified by the priority encoder.
Therefore, in accordance with the present invention, single content data is outputted even when a plurality of results of retrieve are obtained.
Moreover, in accordance with the present invention, it is not necessary to generate an address for reading out content data corresponding to the key data matched with the retrieval key data, and it is possible to reduce the area of the retrievable memory.
More preferably, in a retrievable memory, the first memory stores n number of key data in an ordered manner, and the priority encoder outputs a specifying signal for specifying content data corresponding to the lowest order key data among m number (m: natural number not more than n) of key data matched with the retrieval key information when m number of matching signals are inputted from the first memory.
In the case when a plurality of matching signals are inputted from the first memory, the priority encoder specifies content data corresponding to the lowest order key data among a plurality of key data matched with the retrieval key data. Then, the second memory outputs the content data specified by the priority encoder.
Therefore, in accordance with the present invention, even when a plurality of results of retrieve are obtained, it is possible to output single content data.
More preferably, in a retrievable memory, the first memory outputs m number of first logical signals and n−m number of second logical signals when the retrieval key information matches with m number of key data, the priority encoder outputs in response to a first logical signal an activation signal for reading out content data corresponding to the lowest order key data to the second memory, and the second memory outputs content data corresponding to said lowest order key data based on said activation signal, the first logical signal is generated in accordance with the lowest order key data among said m number of first logical signals.
When the retrieval key data is matched with the key data, the first memory outputs the first logical signal, and when the data is not matched with the key data, it outputs the second logical signal. Then, the priority encoder outputs the activation signal used for reading the corresponding content data based upon the first logical signal. Moreover, upon receipt of a plurality of first logical signals from the first memory, the priority encoder outputs an activation signal used for reading content data corresponding to the lowest order key data among key data matched with the retrieval key data. Then, based upon the activation signal, the second memory outputs the content data corresponding to the key data. Therefore, in accordance with the present invention, even when a plurality of results of retrieval are obtained, single content data is outputted by the logical signal.
Moreover, the retrievable memory in accordance with the present invention includes a first memory storing n number (n: natural number) of key data, and outputting a first matching signal when inputted retrieval key information is matched with stored key data; a second memory storing n number of content data corresponding to n number of key data, and outputting a second matching signal when inputted content retrieval information is matched with stored content data; a priority encoder specifying, upon receipt of the first matching signal, the content data stored in the second memory corresponding to the key data matched with said retrieval key information, and specifying, upon receipt of the second matching signal, key data stored in the first memory corresponding to the content data matched with the content retrieval information, wherein the priority encoder outputs a first specifying signal for specifying single content data upon receipt of a plurality of first matching signals, and outputs a second specifying signal for specifying single key data upon receipt of a plurality of second matching signals, the second memory outputs the content data specified by the first specifying signal, and the first memory outputs the key data specified by the second specifying signal.
In the retrievable memory in accordance with the present invention, when retrieval key information is matched with key data stored in the first memory, the first memory outputs
Fujino Takeshi
Hayashi Isamu
Noda Hideyuki
Shimano Hiroki
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Linh V
Tokar Michael
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