Add hex drivers

hw/fpga/addr_decode.sv

@@ -2,11 +2,11 @@ module addr_decode(
     input logic [15:0] addr,
     output logic ram_cs,
     output logic rom_cs,
-    output logic io_cs
+    output logic hex_cs
 );
 
 assign rom_cs = addr[15];
 assign ram_cs = ~addr[15] && addr < 16'h7ff0;
-assign io_cs = addr >= 16'h7ff0 && addr < 16'h8000;
+assign hex_cs = addr >= 16'h7ff0 && addr < 16'h7ff2;
 
 endmodule