22.214.171.124. Dynamic On-Die Termination (ODT) in DDR4
Rtt_nom and Rtt_wr work the same as in DDR3, which is described in Dynamic ODT for DDR3.
Refer to the DDR4 JEDEC* specification or your memory vendor data sheet for details about available termination values and functional description for dynamic ODT in DDR4 devices.
For DDR4 LRDIMM, if SPD byte 152 calls for different values of Rtt_Park to be used for package ranks 0 and 1 versus package ranks 2 and 3, set the value to the larger of the two impedance settings.