HDLbits:Dff16e

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. byteena1 controls the upper byte d15:8, while byteena0 controls the lower byte d7:0.

resetn is a synchronous, active-low reset.

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

创建 16 D flip-flops。有时只修改一组触发器的一部分很有用。使能字节的输入控制是否应在该周期内写入 16 个寄存器中的每个字节。byteena1 控制上字节 d15：8，而 byteena0 控制下字节 d7：0。

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)
                q <= 0;
            else if(byteena[0])     //从这里开始错误！！！
                q[7:0] <= d[7:0];  
            else if(byteena[1])
                q[15:8] <= d[15:8];  
        end
endmodule