Bram for FPGA logic resource evaluation (taking Xilinx as an example)

         stay FPGA Logic design time , You need to refer to the required logical resource pair FPGA Select the type , One of them is right BRAM The evaluation of , Here we are xilinx UltraSCALE+ series FPGA For example , Yes BRAM Give a brief introduction .

        FPGA in RAM Resources are generally divided into DRAM and BRAM Two kinds of , and Xilinx UltraSCALE+ series FPGA In addition to the above two RAM outside , Some models also include UltraRAM. among DRAM by Distributed RAM, In order to FPGA in LUT（LUT in SLICEM） Resources produce , Details reference UG574：UltraScale ArchitectureConfigurable Logic Block User Guide;UltraRAM For a clock , Two ports （ Reading and writing ）, Simultaneous reading and writing , Every Block Storage capacity up to 288Kb, A clock field can contain 16 individual UltraRAM Blocks, And each Block from 4K x 7 、2 memory block form , For detailed references, see UG573：UltraScale ArchitectureMemory Resources User Guide.

         This paper mainly focuses on BRAM Give a brief introduction , And give BRAM Methods of resource evaluation .BRAM For detailed references, please refer to UG573：UltraScale ArchitectureMemory Resources User Guide.

        BRAM Belong to FPGA Embedded special RAM,RAM Blocks have large storage space , at present xilinx Typical BRAM Yes 18Kbits and 36Kbits.BRAM There must be a clock ,DRAM It can be pure combinational logic without clock , You can also add one level reg Use the clock .BRAM The read-write port can be configured , Depth can be matched , Multiple BRAM block Can be combined and cascaded , Different bit widths and depths can be set within the allowable range as required （ Storage ） Of RAM block .

         for example ： You need to save a file first RAM in , stay FPGA Read after the system starts RAM Data processing in ,coe The data stored in the file is 10230 individual 32bit Bit wide data , So in IP Nuclear RAM The set bit width of is set to 32bit Width,Depth Can be set to >10230, If set to 10230, be RAM Storage capacity is 32*10230=327360bits≈39.96KB, This is also the true data size of the data . When the configuration is complete IP Configuration item display uses 36K BRAM total 10 individual Blocks, namely 10*36*1024=368640bits=45KB, This is due to a Block The size of the block is 36Kb, according to IP Depth of configuration , what is needed RAM The number of blocks is greater than 9 Less than 10, Therefore, we need 10 individual 36K BRAM block .

         Usually in the configuration BRAM when , The setting depth can be larger than that actually used , Leave a certain margin , Generally, it can be set flexibly according to the situation .