Continuous adaptive training for data interface timing calibration

A data interface circuit, comprising:

• a calibration controller circuit;
• two parallel data capture paths that capture a common data bit value, where each path includes a programmable DLL controlled by the calibration controller, said two data capture paths comprising a mission path that performs data capture for a functional circuit, and a reference path that performs data capture solely for calibration purposes;
• wherein one programmable DLL delays a capture strobe for the mission path and one DLL delays a capture strobe for the reference path;
• and
• wherein the data interface circuit is capable of performing continuous timing calibration and is operated by a method comprising:
• performing an initial calibration operation for both reference and mission paths to establish optimal delay settings, and determining a delta value between the optimal delay settings for the reference and mission paths;
• operating the functional circuit including operation of the mission path;
• from time to time and without interfering with operation of the functional circuit or the mission path, performing an additional calibration of the reference path to determine a new optimal delay setting for the reference path;
• and
• if the new optimal delay setting for the reference data path differs from a previous delay setting by an amount greater than a change threshold value, setting the delay setting for the mission path to be equal to the new optimal delay setting for the reference path adjusted by the delta value.

A circuit for implementing a continuous timing calibration function for a data interface, comprising:

• a calibration controller circuit;
• two parallel data capture circuits that capture a common data bit value, where each data capture circuit includes at least one programmable DLL controlled by the calibration controller, said two parallel data capture circuits comprising a mission path that performs data capture for a functional circuit, and a reference path that performs data capture solely for calibration purposes;
• and
• wherein an initial calibration is performed for both reference and mission paths to establish optimal initial delay settings, and a delta value between the optimal delay settings of the reference and mission paths is determined;
• wherein the functional circuit operates including operation of the mission path;
• wherein from time to time during operation of the functional circuit, and without interfering with operation of the functional circuit or the mission path, an additional calibration operation is performed for the reference path to determine a new optimal delay setting;
• and
• wherein if a new optimal delay setting for the reference data path differs from a previous optimal delay setting by an amount greater than a change threshold value, the delay setting for the mission path is set to a value that is equal to the new optimal delay setting for the reference path adjusted by the delta value.