adn_common_cdc_fifo.md

adn_common_cdc_fifo (module)

Author: Ahasan Ullah Khalid (aukhalid02@gmail.com)

Source: adn_common_cdc_fifo.sv

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Parameters

Name	Type	Dimension	Default	Description
DATA_WIDTH	int		8	Width of the data bus
FIFO_SIZE	int		2	Log2 of the FIFO depth
SYNC_STAGES	int		2	Number of synchronization stages

Ports

Name	Direction	Type	Dimension	Description
data_in_i	input	logic [DATA_WIDTH-1:0]		Data input bus
data_in_valid_i	input	logic		Valid signal for input data
data_in_ready_o	output	logic		Ready signal for input data
data_in_arst_ni	input	logic		Asynchronous reset, active low (input domain)
data_in_clk_i	input	logic		Clock signal for the input domain
data_in_count_o	output	logic [ FIFO_SIZE:0]		Current occupancy count (input domain)
data_out_o	output	logic [DATA_WIDTH-1:0]		Data output bus
data_out_valid_o	output	logic		Valid signal for output data
data_out_ready_i	input	logic		Ready signal for output data
data_out_arst_ni	input	logic		Asynchronous reset, active low (output domain)
data_out_clk_i	input	logic		Clock signal for the output domain
data_out_count_o	output	logic [ FIFO_SIZE:0]		Current occupancy count (output domain)

Description

Purpose

This module implements a Clock Domain Crossing (CDC) FIFO, designed to safely transfer data between two independent clock domains using Gray-coded pointers and multi-stage synchronizers to prevent metastability.

Use Case

The adn_common_cdc_fifo is primarily used in digital systems where data must be passed between modules operating on different, asynchronous clock frequencies. By utilizing Gray-coded pointers, it ensures that only one bit changes at a time during pointer synchronization, effectively mitigating the risk of metastability that typically occurs when sampling signals across clock boundaries. It is ideal for streaming data interfaces, buffer management in high-speed communication protocols, and decoupling producer-consumer throughput variations.

REVISION	DATE	AUTHOR	DESCRIPTION
0.1	2026-07-27	Ahasan Ullah Khalid	Initial version
1.0	2026-07-29	Ahasan Ullah Khalid	Stable release
1.1	2026-08-02	Foez Ahmed	Ratified
1.2	2026-08-19	Ahasan Ullah Khalid	Stable release

Author : Ahasan Ullah Khalid (aukhalid02@gmail.com)