US Patent 7649855 Alternative 1000BASE-T scrambler

A physical coding sublayer (PCS) device includes a first data scrambler, a second data scrambler, and a selector. The first data scrambler scrambles first data and implements a first scrambling cycle. The second data scrambler scrambles second data and implements a second scrambling cycle. The second data is different than the first data. The second scrambling cycle is shorter than the first scrambling cycle. The selector selects the first data scrambler to scramble the first data during normal operations. The selector selects the second data scrambler to scramble the second data during testing. The first data scrambler does not scramble the second data. The second data scrambler does not scramble the first data.