Well this is not easy and there is more complication to it when the controller is in the field, extrea delays might be introduced like from heat .. Etc. The best practice is to use a controllable delay feedback circuit you can use an FSM to do it and by edge detection you can always assume your best delay, the Dqs will be your best candidate as you know how it is going to hit and then usually you have frequent 0 to one or one to zero transition from which you can predict your delay , you have to keep track always for the estimated delay so that your controller won't fail because of any extrnal parameters
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