cpu/tests/common/skidbuffer.sv

module skidbuffer #(
    parameter WIDTH = 1
)(
    input logic clk,
    input logic reset,

    input logic [WIDTH-1:0] in,
    input logic in_valid,
    output logic in_ready,

    output logic [WIDTH-1:0] out,
    output logic out_valid,
    input logic out_ready
);

logic buffer_filled = 0;
logic [WIDTH-1:0] buffer_val;

always_ff @(posedge clk) begin
    if (reset) begin
        buffer_filled <= 0;
    end else begin
        if (in_valid && in_ready) begin
            // input always gets stored whether it needs to be or not
            buffer_val <= in;
        end

        if (buffer_filled) begin
            if (out_ready && !(in_valid && in_ready)) begin
                // out_valid = 1 since buffer is full
                buffer_filled <= 0;
            end
        end else begin
            if (in_valid && !(out_valid && out_ready)) begin
                // in_ready = 1 since buffer is empty
                buffer_val = in;
                buffer_filled <= 1;
            end
        end
    end
end

always_comb begin
    if (buffer_filled) begin
        in_ready = out_ready;
        out_valid = 1;
        out = buffer_val;
    end else begin
        in_ready = 1;
        out_valid = in_valid;
        out = in;
    end
end

endmodule