5 files changed, 108 insertions, 4 deletions
diff --git a/nandgame/Makefile b/nandgame/Makefile
index 5e16703..8a6e6ea 100644
--- a/nandgame/Makefile
+++ b/nandgame/Makefile
@@ -51,10 +51,10 @@ clean:
 	rm -rf *.json *.fs *.svg *.log *.dep *.vvp *.lxt2
 
 simu: $(PROGRAM).lxt2
-	gtkwave $< >/dev/null 2>&1
+# 	gtkwave $< >/dev/null 2>&1
 
 simu2: verilator.$(PROGRAM)/dump.vvp
-	gtkwave $< >/dev/null 2>&1
+# 	gtkwave $< >/dev/null 2>&1
 
 lint: $(PROGRAM).sv
 	verilator --quiet --lint-only -Wall -Wno-PROCASSINIT $(PROGRAM).sv
diff --git a/nandgame/arith_unit.sv b/nandgame/arith_unit.sv
new file mode 100644
index 0000000..ebbaaf8
--- /dev/null
+++ b/nandgame/arith_unit.sv
@@ -0,0 +1,27 @@
+// nandgame logic unit
+
+`timescale 1us/1us
+
+`include "nandgame_types.v"
+
+module  arith_unit #(
+  parameter DATA_WIDTH = 16
+) (
+  input [(DATA_WIDTH-1):0] X,
+  input [(DATA_WIDTH-1):0] Y,
+  input ArithCode operation,
+
+  output logic [(DATA_WIDTH-1):0] RES
+);
+
+always_comb begin
+    case (operation)
+        ARITH_PLUS: RES = X + Y;
+        ARITH_MINUS:  RES = X - Y;
+        ARITH_INC: RES = X + 1;
+        ARITH_DEC: RES = X - 1;
+        default: RES = 0;
+    endcase
+end
+
+endmodule
diff --git a/nandgame/arith_unit_tb.sv b/nandgame/arith_unit_tb.sv
new file mode 100644
index 0000000..054e484
--- /dev/null
+++ b/nandgame/arith_unit_tb.sv
@@ -0,0 +1,71 @@
+`timescale 1us/1us
+
+// `include "nandgame_types.v"
+
+module  arith_unit_tb (
+);
+
+logic [15:0] in1;
+logic [15:0] in2;
+ArithCode opcode;
+logic [15:0] result;
+
+ arith_unit uut (
+  .X(in1),
+  .Y(in2),
+  .operation(opcode),
+  .RES(result)
+);
+
+string filename;
+initial begin
+`ifdef DUMP_FILE_NAME
+  filename=`DUMP_FILE_NAME;
+`else
+  filename=" arith_unit.lxt2";
+`endif
+  $dumpfile(filename); $dumpvars();
+
+end
+
+initial begin
+  in1 = 13;
+  in2 = 17;
+  opcode = ARITH_PLUS;
+  #1
+  assert(result == 30);
+  #1
+  in1 = 12;
+  in2 = 4;
+  opcode = ARITH_MINUS;
+  #1
+  assert(result == 8);
+  #1
+  in1 = 12;
+  in2 = 13;
+  opcode = ARITH_MINUS;
+  #1
+  assert(result == 16'hffff);
+  #1
+  in1 = 13;
+  in2 = 17;
+  opcode = ARITH_INC;
+  #1
+  assert(result == 14);
+  #1
+  in1 = 13;
+  in2 = 17;
+  opcode = ARITH_DEC;
+  #1
+  assert(result == 12);
+  #1
+  in1 = 0;
+  in2 = 17;
+  opcode = ARITH_DEC;
+  #1
+  assert(result == 16'hffff);
+  #1
+  $finish();
+end
+
+endmodule
diff --git a/nandgame/logic_unit_tb.sv b/nandgame/logic_unit_tb.sv
index c1495c3..be5366e 100644
--- a/nandgame/logic_unit_tb.sv
+++ b/nandgame/logic_unit_tb.sv
@@ -1,7 +1,6 @@
 `timescale 1us/1us
 
-`include "nandgame_types.v"
-
+//`include "nandgame_types.v"
 module logic_unit_tb (
 );
 
diff --git a/nandgame/nandgame_types.v b/nandgame/nandgame_types.v
index 2104d37..80e9375 100644
--- a/nandgame/nandgame_types.v
+++ b/nandgame/nandgame_types.v
@@ -4,3 +4,10 @@ typedef enum logic [1:0] {
     LOGIC_XOR  = 2'b10,
     LOGIC_NEGT = 2'b11
 } LogicCode;
+
+typedef enum logic [1:0] {
+    ARITH_PLUS  = 2'b00,
+    ARITH_INC   = 2'b01,
+    ARITH_MINUS = 2'b10,
+    ARITH_DEC   = 2'b11
+} ArithCode;