common/docs/reference/utils/fifo.md

fifo

Property	Value
Kind	module
RTL source	rtl/utils/fifo.sv
Availability	Synthesizable RTL

Summary

Power-of-two synchronous FIFO with combinational head read.

Functional Behavior

Power-of-two synchronous FIFO with combinational head read. Its exact parameters and ports are reproduced below from the implementation declaration.

Suitable Applications

Use as a small reusable datapath, state, coding, delay, or verification primitive.

Parameters

The declaration below is canonical; retain the RTL-enforced parameter range.

Parameter	Declaration
DATA_WIDTH	parameter int DATA_WIDTH = 32
BUFFER_DEPTH	parameter int BUFFER_DEPTH = 8
LOG_BUFFER_DEPTH	parameter int LOG_BUFFER_DEPTH = (BUFFER_DEPTH > 1) ? $clog2(BUFFER_DEPTH) : 1

Interface Definition

module fifo #(
    parameter int DATA_WIDTH       = 32,
    parameter int BUFFER_DEPTH     = 8,
    parameter int LOG_BUFFER_DEPTH = (BUFFER_DEPTH > 1) ? $clog2(BUFFER_DEPTH) : 1
) (
    input  logic                      clk_i,
    input  logic                      rst_n_i,
    input  logic                      flush_i,
    input  logic                      push_i,
    output logic                      full_o,
    input  logic [    DATA_WIDTH-1:0] dat_i,
    input  logic                      pop_i,
    output logic                      empty_o,
    output logic [    DATA_WIDTH-1:0] dat_o,
    output logic [LOG_BUFFER_DEPTH:0] cnt_o
);

Port Summary

Signal	Direction	Declaration
clk_i	input	input logic clk_i
rst_n_i	input	input logic rst_n_i
flush_i	input	input logic flush_i
push_i	input	input logic push_i
full_o	output	output logic full_o
dat_i	input	input logic [ DATA_WIDTH-1:0] dat_i
pop_i	input	input logic pop_i
empty_o	output	output logic empty_o
dat_o	output	output logic [ DATA_WIDTH-1:0] dat_o
cnt_o	output	output logic [LOG_BUFFER_DEPTH:0] cnt_o

Integration and Use

Keep parameter values within RTL assertions and add required clocking, reset, or CDC protection at the caller boundary.

fifo #(
    .DATA_WIDTH(DATA_WIDTH),
    .BUFFER_DEPTH(BUFFER_DEPTH),
    .LOG_BUFFER_DEPTH(LOG_BUFFER_DEPTH)
) u_fifo (
    .clk_i(clk_i),
    .rst_n_i(rst_n_i),
    .flush_i(flush_i),
    .push_i(push_i),
    .full_o(full_o),
    .dat_i(dat_i),
    .pop_i(pop_i),
    .empty_o(empty_o),
    .dat_o(dat_o),
    .cnt_o(cnt_o)
);

Dependencies and Verification

The linked RTL source is the implementation authority and contains local assertions for unsupported parameter combinations. See docs/design.md for repository-wide CDC, reset, stream, and storage contracts, and docs/verification.md for the verification matrix.