ALU

Makefile

@@ -1,6 +1,15 @@
 clean:
 	-rm *.vcd *.vvp
 
+alu_tb: alu_tb.vcd
+	gtkwave alu_tb.vcd &
+
+alu_tb.vcd: alu_tb.vvp
+	vvp alu_tb.vvp
+
+alu_tb.vvp: alu.v alu_tb.v
+	iverilog -o alu_tb.vvp alu_tb.v
+
 inc16_tb: inc16_tb.vcd
 	gtkwave inc16_tb.vcd &
 

alu.v

@@ -0,0 +1,49 @@
+`ifndef _alu_v
+`define _alu_v
+
+`include "not16.v"
+`include "mux4way16.v"
+`include "add16.v"
+`include "and16.v"
+`include "or8way.v"
+`include "nor.v"
+
+module ALU (input [15:0] x, 
+            input [15:0] y,
+            input zx,
+            input nx,
+            input zy,
+            input ny,
+            input f,
+            input no,
+            output [15:0] out,
+            output zr,
+            output ng);
+
+    wire [15:0] x_inv, x_arg;
+    wire [15:0] y_inv, y_arg;
+    wire [15:0] sum, prod;
+    wire [15:0] sum_inv, prod_inv;
+    wire zr0, zr1;
+
+    Not16 u1 (.in(x), .out(x_inv));
+    Mux4Way16 u2 (.a(x), .b(x_inv), .c(16'h0000), .d(16'hFFFF), .sel({zx, nx}), .out(x_arg));
+
+    Not16 u3 (.in(y), .out(y_inv));
+    Mux4Way16 u4 (.a(y), .b(y_inv), .c(16'h0000), .d(16'hFFFF), .sel({zy, ny}), .out(y_arg));
+
+    Add16 u5 (.a(x_arg), .b(y_arg), .out(sum));
+    And16 u6 (.a(x_arg), .b(y_arg), .out(prod));
+    Not16 u7 (.in(sum), .out(sum_inv));
+    Not16 u8 (.in(prod), .out(prod_inv));
+    Mux4Way16 u9 (.a(prod), .b(sum), .c(prod_inv), .d(sum_inv), .sel({no, f}), .out(out));
+
+    Or8Way u10 (.in(out[15:8]), .out(zr0));
+    Or8Way u11 (.in(out[7:0]), .out(zr1));
+    Nor u12 (.a(zr0), .b(zr1), .out(zr));
+
+    assign ng=out[15];
+
+endmodule
+
+`endif

alu_tb.v

@@ -0,0 +1,79 @@
+`include "alu.v"
+
+module ALU_test;
+    reg [15:0] x, y;
+    reg zx, nx, zy, ny, f, no;
+    wire [15:0] out;
+    wire zr, ng;
+
+    integer i;
+
+    initial begin
+        $dumpfile("alu_tb.vcd");
+        $dumpvars;
+
+        x=16'hAA55;
+        y=16'h5555;
+
+        {zx, nx, zy, ny, f, no}=6'b101010;
+        #1; // should get 0
+
+        {zx, nx, zy, ny, f, no}=6'b111111;
+        #1; // should get 1
+
+        {zx, nx, zy, ny, f, no}=6'b111010;
+        #1; // should get -1
+
+        {zx, nx, zy, ny, f, no}=6'b001100;
+        #1; // should return 0xAA55
+
+        {zx, nx, zy, ny, f, no}=6'b110000;
+        #1; // should return 0x5555
+
+        {zx, nx, zy, ny, f, no}=6'b001101;
+        #1; // should return 0x55AA
+
+        {zx, nx, zy, ny, f, no}=6'b110001;
+        #1; // should return 0xAAAA
+
+        {zx, nx, zy, ny, f, no}=6'b001111;
+        #1; // should return 0x55AB
+
+        {zx, nx, zy, ny, f, no}=6'b110011;
+        #1; // should return 0xAAAB
+
+        {zx, nx, zy, ny, f, no}=6'b011111;
+        #1; // should return 0xAA56
+
+        {zx, nx, zy, ny, f, no}=6'b110111;
+        #1; // should return 0x5556
+
+        {zx, nx, zy, ny, f, no}=6'b001110;
+        #1; // should return 0xAA54
+
+        {zx, nx, zy, ny, f, no}=6'b110010;
+        #1; // should return 0x5554
+
+        {zx, nx, zy, ny, f, no}=6'b000010;
+        #1; // should return 0xFFAA
+
+        {zx, nx, zy, ny, f, no}=6'b010011;
+        #1; // should return 0x5500
+
+        {zx, nx, zy, ny, f, no}=6'b110010;
+        #1; // should return 0x5554
+
+        {zx, nx, zy, ny, f, no}=6'b000111;
+        #1; // should return 0xAB00
+
+        {zx, nx, zy, ny, f, no}=6'b000000;
+        #1; // should return 0x0055
+
+        {zx, nx, zy, ny, f, no}=6'b010101;
+        #1; // should return 0xFF55
+
+        $finish();
+    end
+
+    ALU u1(.x(x), .y(y), .zx(zx), .nx(nx), .zy(zy), .ny(ny), .f(f), .no(no), .out(out), .zr(zr), .ng(ng));
+endmodule