US Patent No: 5,642,114

Number of patents in Portfolio can not be more than 2000

Variable length code decoder using a content addressable memory with match inhibiting gate

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Abstract

The present invention relates to a variable-length code decoding circuit for decoding an input variable-length code string and a variable-length code decoding system using the same. A typical variable-length code decoding circuit of the present invention includes a CAM cell 10 for storing a variable-length code bit and a RAM cell 20 which is paired with the CAM cell 10 for storing a mask bit so as to perform a masking operation. The variable-length code decoding circuit further includes an NMOS transistor 30 which is coupled between the CAM cell 10 and a match line ML for selectively disconnecting the CAM cell 10 from the match line ML in response to an output of the RAM cell 20. The CAM cell 10 collates a bit of the input variables-length code string with the stored code bit. When the input bit matches the stored code bit, the CAM cell 10 outputs an H level matching to the match line ML and otherwise it outputs an L level unmatching to the match line ML. If the CAM cell 10 does not relate to the collating operation that is, if it does not matter whether there is a match, the RAM cell 20 corresponding to the CAM cell 10 outputs an L level signal to turn off the NMOS transistor 30. When the NMOS 30 is turned off, the output of the CAM cell 10 is not transmitted to the match line ML.

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First Claim

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Patent Owner(s)

Patent OwnerAddressTotal Patents
OKI SEMICONDUCTOR CO., LTD.TOKYO3236

International Classification(s)

  • [Classification Symbol]
  • [Patents Count]

Inventor(s)

Inventor Name Address # of filed Patents Total Citations
Komoto, Eiji Saitama, JP 10 85
Nakamura, Takao Ibaraki, JP 222 1062

Cited Art

Patent Info (Count) # Cites Year
 
MAGNACHIP SEMICONDUCTOR, LTD. (1)
5,475,389 Adaptive variable-length coding apparatus 3 1994
 
TEKTRONIX, INC. (1)
4,670,858 High storage capacity associative memory 94 1983
 
TELCORDIA TECHNOLOGIES, INC. (1)
5,245,338 High-speed variable-length decoder 39 1992
 
TTI INVENTIONS A LLC (1)
5,173,695 High-speed flexible variable-length-code decoder 118 1990

Patent Citation Ranking

Forward Cites

Patent Info (Count) # Cites Year
 
NETLOGIC MICROSYSTEMS, INC. (13)
6,418,042 Ternary content addressable memory with compare operand selected according to mask value 33 1998
6,137,707 Method and apparatus for simultaneously performing a plurality of compare operations in content addressable memory device 101 1999
6,460,112 Method and apparatus for determining a longest prefix match in a content addressable memory device 38 1999
7,143,231 Method and apparatus for performing packet classification for policy-based packet routing 8 1999
6,539,455 Method and apparatus for determining an exact match in a ternary content addressable memory device 34 1999
6,499,081 Method and apparatus for determining a longest prefix match in a segmented content addressable memory device 50 1999
6,154,384 Ternary content addressable memory cell 113 1999
6,944,709 Content addressable memory with block-programmable mask write mode, word width and priority 34 2001
6,934,795 Content addressable memory with programmable word width and programmable priority 37 2001
6,892,272 Method and apparatus for determining a longest prefix match in a content addressable memory device 8 2002
6,574,702 Method and apparatus for determining an exact match in a content addressable memory device 22 2002
7,272,027 Priority circuit for content addressable memory 1 2004
7,246,198 Content addressable memory with programmable word width and programmable priority 9 2005
 
ALTERA CORPORATION (3)
5,940,852 Memory cells configurable as CAM or RAM in programmable logic devices 35 1997
6,058,452 Memory cells configurable as CAM or RAM in programmable logic devices 43 1999
6,263,400 Memory cells configurable as CAM or RAM in programmable logic devices 9 2000
 
SANDISK CORPORATION (3)
6,317,349 Non-volatile content addressable memory 35 1999
6,166,938 Data encoding for content addressable memories 42 1999
6,157,558 Content addressable memory cell and array architectures having low transistor counts 35 1999
 
SUN MICROSYSTEMS, INC. (2)
6,078,987 Translation look aside buffer having separate RAM arrays which are accessable with separate enable signals 17 1997
5,936,873 Single ended match sense amplifier 29 1997
 
BROADCOM CORPORATION (1)
6,809,945 Content addressable memory match line sensing techniques 0 2003
 
ESILICON CORPORATION (1)
6,134,135 Mask arrangement for scalable CAM/RAM structures 39 2000
 
GOOGLE INC. (1)
6,615,310 Lossless data compressor with all CAM words available 1 2000
 
INTERNATIONAL BUSINESS MACHINES CORPORATION (1)
6,452,822 Segmented match line arrangement for content addressable memory 18 2001
 
KAWASAKI MICROELECTRONICS, INC. (1)
6,646,900 Ternary content addressable memory with data and mask data settable therewithin by one write cycle 12 2002
 
MITSUBISHI ELECTRIC CORPORATION (1)
8,291,150 Table device, variable length coding apparatus, variable length decoding apparatus, and variable length coding and decoding apparatus 0 2007
 
NEC CORPORATION (1)
5,787,458 Content addressable memory of a simple construction capable of retrieving a variable word length data 27 1996
 
NEC ELECTRONICS CORPORATION (1)
6,404,359 Variable length decoding system having a mask circuit for improved cache hit accuracy 2 2000
 
PHILIPS ELECTRONICS NORTH AMERICA CORPORATION (1)
5,835,035 High performance variable length decoder with two-word bit stream segmentation and related method 9 1997
 
STMICROELECTRONICS S.A. (1)
6,995,997 Cache cell with masking 0 2004