Some I/O standards (HSTL and SSTL) require an input termination resistance (R) to a VTT voltage of VCCO/2 (see This Figure).
Split-termination DCI creates a Thevenin equivalent circuit using two resistors of twice the resistance value (2R). One terminates to VCCO, the other to GND. Split-termination DCI provides an equivalent termination to VCCO/2 using this method. The 2R termination resistance is set by programming the ODT attribute. The resistors to VCCO and GND are equal to twice the value set by ODT. For example, to achieve the Thevenin equivalent parallel-termination circuit of approximately 50W to VCCO/2, a 240W external precision resistor is required at the VRP pin and ODT is set to RTT_48. Possible values for ODT for split-termination DCI are RTT_40, RTT_48, or RTT_60.
The DCI input standards supporting split termination are shown in Table: All DCI I/O Standards Supporting Split-Termination DCI .
This Figure illustrates split-termination DCI.