External Memory Interface Handbook Volume 2: Design Guidelines

ID 683385
Date 5/08/2017
Document Table of Contents

8.3.1. Skip Calibration Versus Full Calibration8.4.1. Skip Calibration Versus Full Calibration

Calibration must occur shortly after the memory device is initialized, to compensate for uncertainties of the hardware system, including silicon PVT variation, circuit board trace delays, and skewed arrival times. Such variations are usually not present in an RTL simulation environment, therefore there are two options for how the calibration algorithm behaves during simulation: Skip Calibration mode (which is the default), and Full Calibration mode.

Skip Calibration Mode

In Skip Calibration mode, the calibration processor assumes an ideal hardware environment, where PVT variations, board delays, and trace skews are all zero. Instead of running the actual calibration routine, the calibration processor calculates the expected arrival time of read data based on the memory latency values that you provide, thus reducing much simulation processing. Skip calibration mode is recommended for use during system development, because it allows you to focus on interacting with the controller and optimizing your memory access patterns, thus facilitating rapid RTL development.

Full Calibration Mode

Full Calibration mode simulates every stage of the calibration algorithm immediately after memory device initialization. Because the calibration algorithm processes each data group sequentially and each pin in each group individually, simulation time increases with the number of groups and data pins in your interface. You can observe how the calibration algorithm compensates for various delays in the system by incorporating your own board delay model based on trace delays from your PCB design tools. Due to the large simulation overhead, Full Calibration simulation mode is not recommended for rapid development of IP cores.

VHDL Support

VHDL support for mixed-language simulators is implemented by generating the top-level wrapper for the core in VHDL, while all submodules are provided as clear text SystemVerilog files.

A set of precompiled device libraries is provided for use with the ModelSim* - Intel FPGA Edition single-language simulator which is supplied with the Quartus Prime software. Submodules normally provided as cleartext SystemVerilog files are encrypted using IEEE Verilog HDL encryption for ModelSim* - Intel FPGA Edition.

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