Patent ID: 7403547

Claim:
A method for synchronizing the downstream clock of each of one or more corresponding edge QAM devices with the master clock of a remotely located CMTS, comprising: driving a first counter located at the CMTS with a first temperature compensated crystal oscillator; latching the first counter contents when a media interface transmits a time synchronization message packet; reporting the latched contents of the first counter to a first processor; generating a next time synchronization message from the latched first counter contents; transmitting the next time synchronization message from the gigabit Ethernet output of the CMTS; receiving the next time synchronization message at each of the one or more edgeQAM devices from a means for communicating clock synchronization information between the CMTS and each of the one or more edgeQAM device(s), the communicating means being coupled with the CMTS; driving a second counter located at each of the one or more edgeQAM devices with a second temperature compensated crystal oscillator; driving a third counter located at each of the one or more edgeQAM devices with a voltage controlled crystal oscillator, which is controlled with a digital to analog converter, which is in turn controlled by a second processor located at the edge QAM device, wherein the third counter is locked to the second counter; latching the contents of the second counter and the third counter when the next time synchronization message is received; reporting the latched contents of the second and third counters to the second processor; comparing the reported contents of the third counter with the contents of the received next time synchronization message packet to generate a phase error difference; adjusting the digital to analog converter by the phase error difference to cause a corresponding change in the frequency of the voltage controlled crystal oscillator; and outputting the frequency of the voltage controlled crystal oscillator to the local clock of the corresponding one or more edgeQAM devices.