External Memory Interface Handbook Volume 2: Design Guidelines: For UniPHY-based Device Families

ID 683385
Date 3/06/2023
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3.2.3.3. Reading from Memory

During read from the memory, the ODT feature is turned off. Thus, there is no difference between using an ODT setting of 150-ohm and 75-ohm. As such, the termination scheme becomes a single parallel termination scheme (Class I) where there is an external resistor on the FPGA side and a series resistor on the memory side as shown in the following figure.
Figure 33. Single Parallel Termination Scheme (Class I) Using External Resistor and Memory-Side Series Resistor