Verilog卷积输出的寄存与复位技术问题求助

Alright, let's work through your convolution module issue step by step. I see two core problems here: your top-level module can't access the output results, and the timing for saving results/resetting the accumulator is risking data loss. Let's fix both with clear, actionable changes.

First, Let's Diagnose Your Current Code's Issues #

1. UnExposed Outputs: Your out_top is an internal register, not a module port—so the top-level can't read it at all.
2. Timing Conflict: When counter == 4'h8, you're assigning sum <= mult immediately after outputting sum. This mixes the final accumulator value with the next cycle's input, which can cause data loss or incorrect sums.
3. No Validity Signal: The top-level has no way to know when a convolution result is ready to read, making it impossible to safely build an output array.

Fixed Convolution Submodule #

This version fixes the timing, exposes clear outputs, and adds a validity signal for the top-level to use:

module mult_conv(
    input clk,
    input rst,
    input signed [4:0] a,        // Input data sample
    input signed [2:0] b,        // Input filter coefficient
    output reg signed [7:0] conv_result,  // Final convolution sum
    output reg conv_result_valid          // High when conv_result is valid
);

wire signed [7:0] mult;
reg signed [7:0] sum;
reg [3:0] counter;

// Sign-extended multiplication (matches your original logic)
assign mult = {{3{a[4]}}, a} * {{5{b[2]}}, b};

always @(posedge clk or posedge rst) begin
    if (rst) begin
        counter <= 4'h0;
        sum <= 8'sh00;
        conv_result <= 8'sh00;
        conv_result_valid <= 1'b0;
    end else begin
        conv_result_valid <= 1'b0;  // Default to invalid unless triggered
        
        if (counter == 4'h8) begin
            // 9th iteration: complete the accumulator and output result
            conv_result <= sum + mult;  // Add the 9th product to the sum
            conv_result_valid <= 1'b1;  // Tell top-level the result is ready
            counter <= 4'h0;            // Reset counter for next batch
            sum <= 8'sh00;              // Reset accumulator immediately
        end else begin
            // First 8 iterations: accumulate products
            sum <= sum + mult;
            counter <= counter + 4'h1;
        end
    end
end

endmodule

Key Improvements Explained #

• Validity Signal: conv_result_valid goes high only for one clock cycle when a full 9-sample convolution sum is ready. The top-level uses this as a "write enable" to safely capture results.
• Clean Timing: When the 9th iteration finishes, we immediately reset the accumulator and counter. The next clock cycle's input will start a new accumulator cycle without any overlap or data loss.
• Exposed Ports: All critical inputs/outputs are module ports, so the top-level can access everything it needs.

How to Use This in Your Top-Level Module #

To build an output array, the top-level will capture each valid conv_result and store it in a register array. Here's a simplified example:

module top_module(
    input clk,
    input rst,
    input signed [4:0] a,
    input signed [2:0] b,
    output signed [7:0] conv_array [8:0]  // Output array of 9 convolution results
);

reg [3:0] array_addr;
reg signed [7:0] conv_array_reg [8:0];

// Instantiate the convolution submodule
mult_conv u_mult_conv(
    .clk(clk),
    .rst(rst),
    .a(a),
    .b(b),
    .conv_result(conv_result),
    .conv_result_valid(conv_result_valid)
);

// Store valid results into the top-level array
always @(posedge clk or posedge rst) begin
    if (rst) begin
        array_addr <= 4'h0;
        foreach(conv_array_reg[i]) conv_array_reg[i] <= 8'sh00;
    end else begin
        if (conv_result_valid) begin
            conv_array_reg[array_addr] <= conv_result;
            // Wrap around the array address when full
            array_addr <= (array_addr == 4'h8) ? 4'h0 : array_addr + 4'h1;
        end
    end
end

// Connect internal register array to top-level output port
assign conv_array = conv_array_reg;

endmodule

This top-level module uses conv_result_valid to know exactly when to write a new result to the array, ensuring no data is lost and all results are captured correctly.

内容的提问来源于stack exchange，提问作者ViniLL