stream_queue.md

stream_queue

Property	Value
Kind	module
RTL source	rtl/stream/stream_advanced.sv
Availability	Synthesizable RTL

Summary

Parameterized valid/ready queue with optional fall-through.

Functional Behavior

Parameterized valid/ready queue with optional fall-through. It follows the repository valid/ready rule: a payload transfers only when both signals are high in the same cycle, and a stalled valid payload remains stable.

Suitable Applications

Use for elastic pipelines, stream routing, arbitration, backpressure, and response handling.

Parameters

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

Parameter	Declaration
DATA_WIDTH	parameter int DATA_WIDTH = 32
DEPTH	parameter int DEPTH = 4
FALL_THROUGH	parameter bit FALL_THROUGH = 1'b1
PTR_WIDTH	parameter int PTR_WIDTH = (DEPTH > 1) ? $clog2(DEPTH) : 1
COUNT_WIDTH	parameter int COUNT_WIDTH = $clog2(DEPTH + 1)

Interface Definition

module stream_queue #(
    parameter int DATA_WIDTH   = 32,
    parameter int DEPTH        = 4,
    parameter bit FALL_THROUGH = 1'b1,
    parameter int PTR_WIDTH    = (DEPTH > 1) ? $clog2(DEPTH) : 1,
    parameter int COUNT_WIDTH  = $clog2(DEPTH + 1)
) (
    input  logic                   clk_i,
    input  logic                   rst_n_i,
    input  logic                   flush_i,
    input  logic                   in_valid_i,
    output logic                   in_ready_o,
    input  logic [ DATA_WIDTH-1:0] in_data_i,
    output logic                   out_valid_o,
    input  logic                   out_ready_i,
    output logic [ DATA_WIDTH-1:0] out_data_o,
    output logic [COUNT_WIDTH-1:0] usage_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
in_valid_i	input	input logic in_valid_i
in_ready_o	output	output logic in_ready_o
in_data_i	input	input logic [ DATA_WIDTH-1:0] in_data_i
out_valid_o	output	output logic out_valid_o
out_ready_i	input	input logic out_ready_i
out_data_o	output	output logic [ DATA_WIDTH-1:0] out_data_o
usage_o	output	output logic [COUNT_WIDTH-1:0] usage_o

Integration and Use

Observe vector sizing, selection encoding, and flush semantics in the declaration. Do not modify a valid payload while its corresponding ready is low.

stream_queue #(
    .DATA_WIDTH(DATA_WIDTH),
    .DEPTH(DEPTH),
    .FALL_THROUGH(FALL_THROUGH),
    .PTR_WIDTH(PTR_WIDTH),
    .COUNT_WIDTH(COUNT_WIDTH)
) u_stream_queue (
    .clk_i(clk_i),
    .rst_n_i(rst_n_i),
    .flush_i(flush_i),
    .in_valid_i(in_valid_i),
    .in_ready_o(in_ready_o),
    .in_data_i(in_data_i),
    .out_valid_o(out_valid_o),
    .out_ready_i(out_ready_i),
    .out_data_o(out_data_o),
    .usage_o(usage_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.