diff --git a/des/sim/tb_des.tcl b/des/sim/tb_des.tcl
new file mode 100644
index 0000000..ffdeba8
--- /dev/null
+++ b/des/sim/tb_des.tcl
@@ -0,0 +1,10 @@
+set signals [list]
+lappend signals "top.tb_des.s_reset"
+lappend signals "top.tb_des.s_clk"
+lappend signals "top.tb_des.s_validin"
+lappend signals "top.tb_des.s_mode"
+lappend signals "top.tb_des.s_key"
+lappend signals "top.tb_des.s_datain"
+lappend signals "top.tb_des.s_validout"
+lappend signals "top.tb_des.s_dataout"
+set num_added [ gtkwave::addSignalsFromList $signals ]