eater_alu: Use 2complneg instead of subtract

1 files changed, 36 insertions, 0 deletions

diff --git a/eater_cpu/eater_alu_tb.sv b/eater_cpu/eater_alu_tb.sv
new file mode 100644
index 0000000..c921804
--- /dev/null
+++ b/eater_cpu/eater_alu_tb.sv
@@ -0,0 +1,36 @@
+`timescale 1us/1us
+
+module eater_alu_tb;
+
+logic sub_n_add;
+logic [7:0] A, B, out;
+
+eater_alu uut(
+    .clk_in(1'b0),
+    .subtract_n_add_in(sub_n_add),
+    .A_in(A),
+    .B_in(B),
+    .en_output_in(1'b1),
+    .bus_out(out)
+);
+
+initial begin
+    $dumpfile("eater_alu.vvp");
+    $dumpvars();
+
+    sub_n_add = 0;
+    A = 10;
+    B = 5;
+    #1
+    assert(out == 15)
+    else $error("Exptected 15, got %d", out);
+    #1;
+    sub_n_add = 1;
+    #1
+    assert(out == 5)
+    else $error("Exptected 15, got %d", out);
+    #1;
+    $finish();
+end
+    
+endmodule
\ No newline at end of file