dff with byte enable

Create 16 D flip-flops. It's sometimes useful to only modify parts of a group of flip-flops. The byte-enable inputs control whether each byte of the 16 registers should be written to on that cycle. byteena[1] controls the upper byte d[15:8], while byteena[0] controls the lower byte d[7:0].

resetn is a synchronous, active-low reset.

All DFFs should be triggered by the positive edge of clk.

Dff16e - HDLBits (01xz.net)

module top_module (
    input clk,
    input resetn,
    input [1:0] byteena,
    input [15:0] d,
    output [15:0] q
);
    always @(posedge clk) begin
        if(resetn) begin
            if(byteena[1])
                q[15:8] <= d[15:8];
            else
                q[15:8] <= q[15:8];
            if(byteena[0])
                q[7:0] <= d[7:0];
            else
                q[7:0] <= q[7:0];
        end
        else begin
            q <= 16'd0;
        end
    end

endmodule

 额，当时好喜欢先写主体，后写！resetn，也不知道是怎么想的