A method for maintaining the states of a receiver during the silent line
state of a network device operating in a low power link suspend mode is
presented. Accordingly, a method of freezing the states of the equalizer
and keeping the receiver clock locked to a frequency that is
approximately equal to that of the input data while providing for rapid
adjustment to the phase and thus recovery of the input data is presented.
During Silent Line State (SLS), the receiver states are frozen using
methods that avoid parasitic decay. Also, the receive clock phase lock
loop is locked onto the local transmit clock since the local transmit
clock has a frequency approximating the incoming data frequency. During
the SLS, the transmitter of the remote network device may have been
turned off to conserve power therefore the receiver has no way of
immediately knowing the phase of an incoming data. Thus, in order to
prevent loss of data, the receiver loops of the receiving network device
are trained to the frequency of the transmitting remote network device
using periodic Link Suspend packets. Thus, in most cases, only the phase
of the incoming signal need be acquired when data arrives. The phase may
be quickly acquired using loop bandwidth shift methods whereby the
receive clock phase lock loop bandwidth is increased to a value that aids
rapid acquisition of the input clock and then, after acquisition, the
bandwidth is shifted to a low value to enhance noise rejection during
tracking.