DM mode must be enabled for DM
calibration. The DM mode is assumed to be enabled for this description. During this
stage, DK does not move, only DQ bits and DM associated with a DK are incremented
simultaneously.
- Revert DQ and DM ODELAY taps to deskew taps so all the DQ bits and DM are edge-aligned. This might result in DK ending up near or in the right noise region.
- Increment DQ/DM ODELAY taps one tap at a time until valid data detected for 15 fine taps. The right edge is recorded as current tap value – 15.
- Increment DQ/DM ODELAY taps 10 taps at a time until left noise region is detected. Then decrement one fine tap at a time until valid data detected for 15 fine taps. Left edge is recorded as current tap – 15.
- Set DQ/DM ODELAY tap to average of right and left edges.