Patent ID: 8111785

Claim:
In a clock and data recovery (CDR) device, a method for automatic frequency acquisition maintenance, the method comprising: in an automatic frequency acquisition (AFA) mode, using a phase detector (PHD) to acquire the phase of a non-synchronous input communication signal having an initial first frequency; in response to acquiring the phase of the input communication signal, dividing a synthesized signal by a selected frequency ratio value, creating a frequency detection signal having a frequency equal to a reference signal frequency; saving the frequency ratio value in a tangible memory medium; in response to a loss of lock/loss of signal (LOL/LOS) signal being asserted, retrieving the frequency ratio value from memory; using a phase-frequency detector (PFD), the reference signal, and the frequency ratio value, generating a synthesized signal with the first frequency; in response to using the PFD to generate the synthesized signal and the LOL/LOS signal being deasserted, using a rotational frequency detector (RFD) to generate a synthesized signal having a frequency equal to the frequency of the input communication signal; and, in response to using the RFD to generate the synthesized signal and the LOL/LOS signal being asserted, initiating the AFA mode.