Verilog刷题笔记42

题目：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.

解题：

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==0)
            q<=16'b0;
        else if(byteena[1]|byteena[0])begin
            if(byteena[0]==1)
            	q[7:0]<=d[7:0];
        	if(byteena[1]==1)
            	q[15:8]<=d[15:8];
        end
    end
            
endmodule

结果正确：

其他解题方法：

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 <= 16'd0;
	else begin
		case(byteena)
			2'b00: q <= q;
			2'b01: q[7:0] <= d[7:0];
			2'b10: q[15:8] <= d[15:8];
			2'b11: q <= d;
		endcase
	end	
end
endmodule