alu.v

8位RISC CPU,包括alu,count,machine等等

module alu(alu_out,zero,data,accum,alu_clk,opcode);
output[7:0]alu_out;
output zero;
input[7:0] data,accum;
input[2:0] opcode;
input alu_clk;
reg[7:0]alu_out;
parameter HLT=3'b000,
          SKZ=3'b001,
          ADD=3'b010,
         ANDD=3'b011,
         XORR=3'b100,
          LDA=3'b101,
          STO=3'b110,
          JMP=3'b111;
assign zero=!accum;
always@(posedge alu_clk)
  begin
   casex(opcode)
      HLT:alu_out<=accum;
      SKZ:alu_out<=accum;
      ADD:alu_out<=data+accum;
     ANDD:alu_out<=data&accum;
     XORR:alu_out<=data^accum;
      LDA:alu_out<=data;
      STO:alu_out<=accum;
      JMP:alu_out<=accum;
  default:alu_out<=8'bxxxxxxxx;
   endcase
  end
endmodule