Drift tracking feedback for communication channels

An apparatus coupled with a communication channel, the channel including a first component, a second component, and a communication link coupling the first and second components, the communication channel having a parameter with an operation value;

• comprising:
• memory in one of the first and second components to store the operation value of the parameter of the communication channel;
• a reference clock;
• monitor logic in one of the first and second components to monitor a signal outside the communication channel, that has a characteristic which drifts relative to the reference clock by amounts that correlate with drift of the parameter of the communication channel relative to the reference clock, to track the amounts of drift in the characteristic;
• and
• logic, responsive to the monitoring, to update the operation value based on the amounts of drift.

An interface for a communication bus, comprising:

• a plurality of input/output drivers coupled with respective bi-directional links in the communication bus, the input/output drivers including
• a transmitter, responsive to a transmit clock, which drives a signal on a corresponding link in the communication bus;
• a receiver, responsive to a receive clock, which samples a signal on the corresponding link;
• a transmit clock generator coupled to the transmitter and to a reference clock having a frequency over 100 MegaHertz, which generates the transmit clock;
• a receive clock generator coupled to the receiver and to the reference clock, which generates the receive clock, wherein at least one of the transmit clock generator and the receive clock generator is adjustable in response to a phase control signal;
• and
• a drift tracking circuit, coupled to a link carrying a monitored signal that is characterized by drift relative to the reference clock that correlates with drift of parameters in the communication bus relative to the reference clock, the drift tracking circuit including
• a phase detector to track changes in phase between the reference clock and the monitored signal, and
• logic to monitor the changes in phase, and issue an indication that the phase control signal, for said at least one of the transmit clock generator and the receive clock generator, be updated to account for the changes in phase.

A method for calibrating a communication channel, including a first component, a second component, and a communication link coupling the first and second components, the communication channel having a parameter with an operation value determined by calibration, comprising:

• setting the operation value of the parameter of the communication channel in one of the first and second components;
• supplying from the first component, a monitor signal on a channel which loops back to the first component;
• monitoring, using monitor circuits in the first component, a signal from a medium outside the communication channel, the signal having a characteristic which drifts relative to the reference clock signal at said monitor circuits by amounts that correlate with drift of the parameter of the communication channel, to track the amounts of drift in the characteristic;
• and
• in response to the monitoring, updating the operation value based on the amounts of drift in the characteristic of the signal.

A method for calibrating a communication channel, including a first component, a second component, and a communication link coupling the first and second components, the communication channel having a drive timing point with an operation value determined by calibration, comprising:

• setting the operation value of the drive timing point of the communication channel;
• monitoring a signal from a medium outside the communication channel, the signal having a characteristic which drifts by amounts that correlate with drift of the drive timing point of the communication channel, to track the amounts of drift in the characteristic;
• and
• in response to the monitoring, updating the operation value based on the amounts of drift in the characteristic of the signal.

A method for calibrating a communication channel, including a first component, a second component, and a communication link coupling the first and second components, the communication channel having a drive timing point with an operation value determined by calibration, comprising:

• setting the operation values of the drive timing point and sample timing point of the communication channel;
• monitoring a signal from a medium outside the communication channel, the signal having a characteristic which drifts by amounts that correlate with drift of the drive timing point and sample timing point of the communication channel, to track the amounts of drift in the characteristic;
• and
• in response to the monitoring, updating the operation values of the drive timing point and sample timing point based on the amounts of drift in the characteristic of the signal.