PoC.fifo.shift

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This FIFO implementation is based on an internal shift register. This is especially useful for smaller FIFO sizes, which can be implemented in LUT storage on some devices (e.g. Xilinx’ SRLs). Only a single read pointer is maintained, which determines the number of valid entries within the underlying shift register.

The specified depth (MIN_DEPTH) is rounded up to the next suitable value.

Entity Declaration:

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entity fifo_shift is
  generic (
    D_BITS    : positive;               -- Data Width
    MIN_DEPTH : positive                -- Minimum FIFO Size in Words
  );
  port (
    -- Global Control
    clk : in std_logic;
    rst : in std_logic;

    -- Writing Interface
    put : in  std_logic;                            -- Write Request
    din : in  std_logic_vector(D_BITS-1 downto 0);  -- Input Data
    ful : out std_logic;                            -- Capacity Exhausted

    -- Reading Interface
    got  : in  std_logic;                            -- Read Done Strobe
    dout : out std_logic_vector(D_BITS-1 downto 0);  -- Output Data
    vld  : out std_logic                             -- Data Valid
  );
end entity fifo_shift;