diff --git a/fpga/hdl/device_models/aps6404l.vhd b/fpga/hdl/device_models/aps6404l.vhd
index e22b976..0ad48a8 100644
--- a/fpga/hdl/device_models/aps6404l.vhd
+++ b/fpga/hdl/device_models/aps6404l.vhd
@@ -130,8 +130,13 @@ begin
 							print("  Addr: " & to_hstring(bytes(1)) & to_hstring(bytes(2)) & to_hstring(bytes(3)));
 							addr := to_integer(unsigned(std_logic_vector'(bytes(1), bytes(2), bytes(3))));
 						elsif bytecnt > 4 then
-							dout := mem(addr);
-							print("  Read " & integer'image(addr) & ": " & to_hstring(mem(addr)));
+							if addr < SIZE then
+								dout := mem(addr);
+								print("  Read " & integer'image(addr) & ": " & to_hstring(mem(addr)));
+							else
+								dout := (others => 'X');
+								print("  Read " & integer'image(addr) & ": OUT-OF-BOUNDS");
+							end if;
 							addr := addr + 1;
 						end if;
 
@@ -141,8 +146,12 @@ begin
 							addr := to_integer(unsigned(std_logic_vector'(bytes(1), bytes(2), bytes(3))));
 						elsif bytecnt > 3 then
 							print("  Write " & integer'image(addr) & ": " & to_hstring(bytes(bytecnt)));
-							mem(addr) := bytes(bytecnt);
-							addr      := addr + 1;
+							if (addr < SIZE) then
+								mem(addr) := bytes(bytecnt);
+							else
+								print("    Error: OUT OF BOUNDS access! Ignoring write.");
+							end if;
+							addr := addr + 1;
 						end if;
 
 					when COMPLETE =>