知识点

    always @(*)
        case(sel)
            2'b00:   begin      
                    sout_t = p0 ;
                end
            2'b01:       sout_t = p1 ;
            2'b10:       sout_t = p2 ;
            default:     sout_t = p3 ;
        endcase

第一次

回答

module top_module( 
    input [15:0] a, b, c, d, e, f, g, h, i,
    input [3:0] sel,
    output [15:0] out );
    
    always @(*)
        case(sel)
            3'd0:  out[15:0] = a[15:0];
            3'd1:  out[15:0] = b[15:0];
            3'd2:  out[15:0] = c[15:0];
            3'd3:  out[15:0] = d[15:0];
            3'd4:  out[15:0] = e[15:0];
            3'd5:  out[15:0] = f[15:0];
            3'd6:  out[15:0] = g[15:0];
            3'd7:  out[15:0] = h[15:0];
            3'd8:  out[15:0] = i[15:0];
            default:out[15:0] = 16'hffff;
        endcase
    
endmodule

结果

Warning (15610): No output dependent on input pin "i[0]" File: /home/h/work/hdlbits.8402616/top_module.v Line: 2
Warning (15610): No output dependent on input pin "i[1]" File: /home/h/work/hdlbits.8402616/top_module.v Line: 2
Warning (15610): No output dependent on input pin "i[2]" File: /home/h/work/hdlbits.8402616/top_module.v Line: 2
[13 more]

第二次

回答

module top_module( 
    input [15:0] a, b, c, d, e, f, g, h, i,
    input [3:0] sel,
    output [15:0] out );
    
    always @(*)
        case(sel)
            4'd0:  out[15:0] = a[15:0];
            4'd1:  out[15:0] = b[15:0];
            4'd2:  out[15:0] = c[15:0];
            4'd3:  out[15:0] = d[15:0];
            4'd4:  out[15:0] = e[15:0];
            4'd5:  out[15:0] = f[15:0];
            4'd6:  out[15:0] = g[15:0];
            4'd7:  out[15:0] = h[15:0];
            4'd8:  out[15:0] = i[15:0];
            default:out[15:0] = 16'hffff;
        endcase
    
endmodule

结果

Status: Success!