Intel® Quartus® Prime Standard Edition User Guide: Design Recommendations

ID 683323
Date 9/24/2018
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2.4.1.1. Use Synchronous Memory Blocks

Memory blocks in Intel FPGA are synchronous. Therefore, RAM designs must be synchronous to map directly into dedicated memory blocks. For these devices, Intel® Quartus® Prime synthesis implements asynchronous memory logic in regular logic cells.

Synchronous memory offers several advantages over asynchronous memory, including higher frequencies and thus higher memory bandwidth, increased reliability, and less standby power. To convert asynchronous memory, move registers from the datapath into the memory block.

A memory block is synchronous if it has one of the following read behaviors:

  • Memory read occurs in a Verilog HDL always block with a clock signal or a VHDL clocked process. The recommended coding style for synchronous memories is to create your design with a registered read output.
  • Memory read occurs outside a clocked block, but there is a synchronous read address (that is, the address used in the read statement is registered). Synthesis does not always infer this logic as a memory block, or may require external bypass logic, depending on the target device architecture. Avoid this coding style for synchronous memories.
Note: The synchronous memory structures in Intel FPGA devices can differ from the structures in other vendors’ devices. For best results, match your design to the target device architecture.

This chapter provides coding recommendations for various memory types. All the examples in this document are synchronous to ensure that they can be directly mapped into the dedicated memory architecture available in Intel FPGAs.