Patent ID: 8941423
Filing Date: 2015-01-27
Classification: G06F,G11C,H03K,H03L

Abstract:
1. A method for operating a data interface circuit for capturing received data bits including a frequently executed timing calibration function, the method comprising: operating a calibration controller circuit during functional operation of the data interface circuit, whereby at least two parallel data capture paths capture a common data bit value; wherein a first data capture path comprises a mission path that performs data capture for a functional circuit, and a second data capture path comprises a reference path that frequently performs data capture solely for calibration purposes without interfering with operation of the functional circuit or the mission path; wherein the mission path includes a programmable delay element controlled by the calibration controller circuit; wherein the reference path includes a plurality of parallel delay elements controlled by the calibration controller, and wherein each of the plurality of parallel delay elements in the reference path is connected to a capture flip-flop, thus producing a plurality of captured reference data bit values; wherein one or more of the plurality of parallel delay elements in the reference path provides a delay value that enables detection of an optimal calibration condition for the data bit value captured by the reference path, resulting in determination of an optimal delay setting for the reference path, the method further comprising: performing a first calibration operation for both reference and mission paths to establish optimal delay settings, wherein a delta value between the optimal delay settings of the reference and mission paths is determined; 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; and if the new optimal delay setting for the reference data path differs from the previous optimal delay setting by an amount greater than a change threshold value, setting the delay setting for the mission path to be equal to be the new optimal delay setting for the reference path adjusted by the delta value.