P2P Address Decoder — `p2p_address_decoder.v`

Subsystem: P2P Communication Components • Source Path: p2p/p2p_address_decoder.v

:::under-construction

🚧 Module Under Active Hardening & Verification

This module is part of the P2P Communication Components subsystem and is currently undergoing active RTL timing optimization, Quartus Platform Designer netlist verification, and testbench coverage expansion.

Target Architecture: Altera / Intel Stratix V GS FPGA (Catapult v2 hardware target)
Target Core Frequency: 250 MHz (Gen3 x8 256-bit datapath)
Verification Status: In-Progress — Structural RTL syntax validated, comprehensive gate-level simulation pending :::

1. Architectural Role & Overview

Decodes physical address windows to route DMA transfers directly to Peer GPUs or IPUs.

Key Design Principles

Deterministic Handshaking: Full ready/valid flow control preventing buffer overflows or stall deadlocks.
Synchronous Reset Protocol: Active-low reset with internal multi-stage deassertion synchronizers.
Metastability Isolation: Multi-stage flip-flop chains for any signals crossing clock domains.

2. Interface Specification (Provisional Baseline)

Module Parameters & Generics

Parameter	Type	Default	Description
`DATA_WIDTH`	Integer	`512`	Primary internal streaming datapath width
`ADDR_WIDTH`	Integer	`64`	Physical memory address bus width
`FIFO_DEPTH`	Integer	`64`	Decoupling stage FIFO buffer depth
`BURST_LIMIT`	Integer	`4096`	Maximum burst byte length per transaction

Signal Port Map

Port Name	Direction	Bit Width	Description
`clk`	Input	`1`	Subsystem Core Clock (250 MHz)
`rst_n`	Input	`1`	Active-Low Synchronous Reset
`s_axis_tdata`	Input	`DATA_WIDTH`	Ingress stream payload
`s_axis_tvalid`	Input	`1`	Ingress stream valid qualifier
`s_axis_tready`	Output	`1`	Backpressure flow-control ready
`s_axis_tlast`	Input	`1`	Ingress packet boundary delimiter
`m_axis_tdata`	Output	`DATA_WIDTH`	Egress stream payload
`m_axis_tvalid`	Output	`1`	Egress stream valid qualifier
`m_axis_tready`	Input	`1`	Downstream sink backpressure ready
`m_axis_tlast`	Output	`1`	Egress packet boundary delimiter

3. RTL Implementation Skeleton

// =============================================================================
// Module: P2P Address Decoder (p2p_address_decoder.v)
// Subsystem: P2P Communication Components
// Target: Stratix V GS FPGA / Catapult v2
// Status: Under Active Hardening
// =============================================================================

`timescale 1ns / 1ps

module p2p_address_decoder #(
    parameter DATA_WIDTH  = 512,
    parameter ADDR_WIDTH  = 64,
    parameter FIFO_DEPTH  = 64,
    parameter BURST_LIMIT = 4096
)(
    input  wire                  clk,
    input  wire                  rst_n,

    // Slave Streaming Interface (Ingress)
    input  wire [DATA_WIDTH-1:0] s_axis_tdata,
    input  wire                  s_axis_tvalid,
    output wire                  s_axis_tready,
    input  wire                  s_axis_tlast,

    // Master Streaming Interface (Egress)
    output reg  [DATA_WIDTH-1:0] m_axis_tdata,
    output reg                   m_axis_tvalid,
    input  wire                  m_axis_tready,
    output reg                   m_axis_tlast,

    // Status & Error Telemetry
    output reg  [31:0]           error_count,
    output wire                  busy_flag
);

    // -------------------------------------------------------------------------
    // Internal Registers & State Machine
    // -------------------------------------------------------------------------
    reg [31:0] cycle_count;
    reg        active_transfer;

    assign s_axis_tready = (!m_axis_tvalid || m_axis_tready);
    assign busy_flag     = active_transfer;

    always @(posedge clk or negedge rst_n) begin
        if (!rst_n) begin
            m_axis_tdata    <= {DATA_WIDTH{1'b0}};
            m_axis_tvalid   <= 1'b0;
            m_axis_tlast    <= 1'b0;
            error_count     <= 32'd0;
            cycle_count     <= 32'd0;
            active_transfer <= 1'b0;
        end else begin
            cycle_count <= cycle_count + 1'b1;

            if (m_axis_tvalid && m_axis_tready) begin
                m_axis_tvalid <= 1'b0;
                m_axis_tlast  <= 1'b0;
            end

            if (s_axis_tvalid && s_axis_tready) begin
                m_axis_tdata    <= s_axis_tdata;
                m_axis_tvalid   <= 1'b1;
                m_axis_tlast    <= s_axis_tlast;
                active_transfer <= !s_axis_tlast;
            end
        end
    end

endmodule

4. Hardware Verification & Integration Checklist

Baseline Verilog 2001 / SystemVerilog 2012 syntax compilation clean
Multi-channel backpressure assertion testbench completed
Corner-case burst alignment (unaligned offsets & 4KB boundary crossings)
Quartus Prime TimeQuest timing constraints and false-path assertions
In-system SignalTap logic analyzer capture on Catapult v2 hardware target

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P2P Address Decoder — p2p_address_decoder.v