Adaptive filtering method and apparatus to compensate for a frequency difference between two clock sources

An adaptive filtering method usable in the transmission and receipt of data, said method comprising:

• determining an amount of frequency drift between a first clock used in transmitting data and a second clock used in receiving said data, said data comprising a plurality of data bits;
• selecting, responsive to said determining, a filtering value to be used in tracking said frequency drift;
• and
• adjusting an address of one or more data bits of said plurality of data bits to track said frequency drift, said adjusting comprising using said filtering value to determine when to adjust said address of said one or more data bits, wherein said filtering value comprises a non-symmetric filtering value, wherein said non-symmetric filtering value comprises a first value indicating when said address of said one or more data bits is to be adjusted in one direction and a second value indicating when said address of said one or more data bits is to be adjusted in another direction.

An adaptive filtering apparatus comprising:

• means for determining an amount of frequency drift between a first clock used in transmitting data and a second clock used in receiving said data, said data comprising a plurality of data bits;
• a selector coupled to said means for determining, said selector adapted to select, responsive to said determining, a filtering value to be used in tracking said frequency drift;
• and
• means for adjusting an address of one or more data bits of said plurality of data bits to track said frequency drift, said means for adjusting comprising said filtering value to be used in determining when to adjust said address of said one or more data bits, wherein said filtering value comprises a non-symmetric filtering value, wherein said non-symmetric filtering value comprises a first value indicating when said address of said one or more data bits is to be adjusted in one direction and a second value indicating when said address of said one or more data bits is to be adjusted in another direction.