Patent ID: 7706297

Claim:
An apparatus that computes a variance of a histogram of a receive physical layer device, the apparatus comprising: a slicer module configured to generate a signal that represents a square of a slicer error signal; and a variance computation unit configured to use the signal that represents the square of the slicer error signal to calculate the value of variance of the histogram of the receive physical layer device, wherein the variance computation unit comprises: a variance timer logic unit having (i) a first output configured to provide an indication whether calculation of the value of variance is active and (ii) a second output configured to provide an indication whether calculation of the value of variance is starting; an adder having (i) a first input configured to receive a plurality of values of the square of the slicer error signal, (ii) a second input, and (iii) an output; an AND logic gate having (i) a first input coupled to the output of the adder, (ii) a second input coupled to the first output of the variance timer logic unit, and (iii) an output; and a variance accumulator register having (i) a first input coupled to the output of the AND logic gate, (ii) a second input coupled to the second output of the variance timer logic unit such that the variance accumulator register is reset in response to the indication that calculation of the value of variance is starting, and (iii) an output coupled to the second input of the adder.