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common/docs/reference/cdc/async_reqack.md
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maksyuki 3b6a925a51 feat: add documentation for new utility components and scripts
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2026-08-04 16:35:53 +08:00

3.1 KiB

async_reqack

Property Value
Kind module
RTL source rtl/cdc/async_reqack.sv
Availability Synthesizable RTL

Summary

One-entry four-phase asynchronous data mailbox.

Functional Behavior

Captures one source payload, transfers it through a four-phase request/acknowledge protocol, and suppresses destination valid after acceptance so return-to-zero cannot create a duplicate delivery.

Suitable Applications

Use for low-throughput asynchronous control or data mailboxes.

Parameters

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

Parameter Declaration
DATA_WIDTH parameter int DATA_WIDTH = 32
SYNC_STAGES parameter int SYNC_STAGES = 2

Interface Definition

module async_reqack #(
    parameter int DATA_WIDTH  = 32,
    parameter int SYNC_STAGES = 2
) (
    input  logic                  src_clk_i,
    input  logic                  src_rst_n_i,
    input  logic                  src_valid_i,
    output logic                  src_ready_o,
    input  logic [DATA_WIDTH-1:0] src_data_i,
    input  logic                  dst_clk_i,
    input  logic                  dst_rst_n_i,
    output logic                  dst_valid_o,
    input  logic                  dst_ready_i,
    output logic [DATA_WIDTH-1:0] dst_data_o
);

Port Summary

Signal Direction Declaration
src_clk_i input input logic src_clk_i
src_rst_n_i input input logic src_rst_n_i
src_valid_i input input logic src_valid_i
src_ready_o output output logic src_ready_o
src_data_i input input logic [DATA_WIDTH-1:0] src_data_i
dst_clk_i input input logic dst_clk_i
dst_rst_n_i input input logic dst_rst_n_i
dst_valid_o output output logic dst_valid_o
dst_ready_i input input logic dst_ready_i
dst_data_o output output logic [DATA_WIDTH-1:0] dst_data_o

Integration and Use

Hold source payload only through the source valid/ready handshake. Reset at either endpoint aborts an in-flight item; this is a one-entry link.

async_reqack #(
    .DATA_WIDTH(DATA_WIDTH),
    .SYNC_STAGES(SYNC_STAGES)
) u_async_reqack (
    .src_clk_i(src_clk_i),
    .src_rst_n_i(src_rst_n_i),
    .src_valid_i(src_valid_i),
    .src_ready_o(src_ready_o),
    .src_data_i(src_data_i),
    .dst_clk_i(dst_clk_i),
    .dst_rst_n_i(dst_rst_n_i),
    .dst_valid_o(dst_valid_o),
    .dst_ready_i(dst_ready_i),
    .dst_data_o(dst_data_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.