External Memory Interfaces Intel® Agilex™ FPGA IP User Guide

ID 683216
Date 10/04/2021

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5.2.1. Calibration Modes

Calibration occurs shortly after the memory device is initialized, to compensate for uncertainties in 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, resulting in two simulatable calibration modes: 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 entered during EMIF IP generation, resulting in reduced simulation time. 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.

If you enable Skip Calibration Mode, the interface still performs some memory initialization, sending DRAM Mode Register Set (MRS) commands, or commands to program register code words for RDIMM/LRDIMM, before starting normal operation. These initialization commands are necessary to set up the memory model operation and latencies.

Full Calibration Mode

Full Calibration mode simulates every stage of the calibration algorithm immediately after memory device initialization. The calibration algorithm processes each data group sequentially and each pin in each group individually, causing simulation time to increase with the number of 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 QuestaSim - Intel FPGA Edition simulator, which is supplied with the Intel® Quartus® Prime software. Submodules normally provided as clear text SystemVerilog files are encrypted using IEEE Verilog HDL encryption for QuestaSim - Intel FPGA Edition.