This solution describes the steps to remove the on-chip termination (OCT) from a design that uses UniPHY-based memory controllers. The biggest motivation to remove the OCT from the memory interface I/O is to save power. There are three things to keep in mind:
- Do not remove the FPGA (on die or on board) termination on any memory I/O operating at least 300 MHz.
- Do not remove the termination for the
- Perform the signal integrity simulations to check the signal quality after removing the OCT.
The steps below describe how to remove the OCT. These steps apply to:
- DDR3 for Stratix® V, Arria® V and Cyclone® V
- QDR II for Stratix V and Arria V
- RLDRAM II for Stratix V
Before you start making the modifications to the project, make sure your project has been compiled with no errors.
- Open the <project_name>.qsf file. Remove or comment out the termination IO assignment in the Quartus® II Settings File (.qsf) or Assignment Editor. For example, comment out the following lines:
To comment out a QSF assignment, add a pound (#) sign at the beginning of the line.
set_instance_assignment -name INPUT_TERMINATION "PARALLEL 50 OHM WITH CALIBRATION"
set_instance_assignment -name OUTPUT_TERMINATION "SERIES 50 OHM WITH CALIBRATION
- For RLDRAM II and QDRII/QDRII+ only: Remove any QSF constraint starting with
set_instance_assignment -name TERMINATION_CONTROL_BLOCK
- Start the Quartus compilation. The compilation will fail to fit the design with a bunch of errors. Double click on the first error starting with Output buffer atom and it will point to an instantiation of output buffer in altdq_dqs2_stratixv.sv. Remove following connections from that output buffer instantiation.
- For DDR2 and DDR3 only: open altdq_dqs2_stratixv.sv. Find the instance named stratixv_pseudo_diff_out. Comment out the line where dtcin is defined. Change:
Depending upon the memory protocol you are using there might be more than one instances where you need to remove the connections. Repeat step #3 until you get rid of all the errors starting with Output buffer atom