diff --git a/common/hw-mmio_regs.adb b/common/hw-mmio_regs.adb
new file mode 100644
index 0000000..5eea563
--- /dev/null
+++ b/common/hw-mmio_regs.adb
@@ -0,0 +1,92 @@
+--
+-- Copyright (C) 2016 secunet Security Networks AG
+--
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as published by
+-- the Free Software Foundation; version 2 of the License.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU General Public License for more details.
+--
+
+package body HW.MMIO_Regs
+is
+
+   generic
+      type Word_T is mod <>;
+   procedure Read_G (Value : out Word_T; Idx : Subs_P.Index_T);
+
+   procedure Read_G (Value : out Word_T; Idx : Subs_P.Index_T)
+   is
+      Off : constant Range_P.Index_T := Range_P.Index_T
+        ((Byte_Offset + Regs (Idx).Byte_Offset) / (Range_P.Element_T'Size / 8));
+      pragma Warnings
+        (GNAT, Off, """Mask"" is not modified, could be declared constant",
+         Reason => "Ada RM forbids making it constant.");
+      Mask : Word64 := Shift_Left (1, Regs (Idx).MSB + 1 - Regs (Idx).LSB) - 1;
+      pragma Warnings
+        (GNAT, On, """Mask"" is not modified, could be declared constant");
+      Temp : Range_P.Element_T;
+   begin
+      Range_P.Read (Temp, Off);
+      Value := Word_T (Shift_Right (Word64 (Temp), Regs (Idx).LSB) and Mask);
+   end Read_G;
+
+   procedure Read_I is new Read_G (Word8);
+   procedure Read (Value : out Word8; Idx : Subs_P.Index_T) renames Read_I;
+
+   procedure Read_I is new Read_G (Word16);
+   procedure Read (Value : out Word16; Idx : Subs_P.Index_T) renames Read_I;
+
+   procedure Read_I is new Read_G (Word32);
+   procedure Read (Value : out Word32; Idx : Subs_P.Index_T) renames Read_I;
+
+   procedure Read_I is new Read_G (Word64);
+   procedure Read (Value : out Word64; Idx : Subs_P.Index_T) renames Read_I;
+
+   ----------------------------------------------------------------------------
+
+   generic
+      type Word_T is mod <>;
+   procedure Write_G (Idx : Subs_P.Index_T; Value : Word_T);
+
+   procedure Write_G (Idx : Subs_P.Index_T; Value : Word_T)
+   is
+      Off : constant Range_P.Index_T := Range_P.Index_T
+        ((Byte_Offset + Regs (Idx).Byte_Offset) / (Range_P.Element_T'Size / 8));
+      pragma Warnings
+        (GNAT, Off, """Mask"" is not modified, could be declared constant",
+         Reason => "Ada RM forbids making it constant.");
+      Mask : Word64 :=
+         Shift_Left (1, Regs (Idx).MSB + 1) - Shift_Left (1, Regs (Idx).LSB);
+      pragma Warnings
+        (GNAT, On, """Mask"" is not modified, could be declared constant");
+      Temp : Range_P.Element_T;
+   begin
+      if Regs (Idx).MSB - Regs (Idx).LSB + 1 = Range_P.Element_T'Size then
+         Range_P.Write (Off, Range_P.Element_T (Value));
+      else
+         -- read/modify/write
+         Range_P.Read (Temp, Off);
+         Temp := Range_P.Element_T
+           ((Word64 (Temp) and not Mask) or
+            (Shift_Left (Word64 (Value), Regs (Idx).LSB)));
+         Range_P.Write (Off, Temp);
+      end if;
+   end Write_G;
+
+   procedure Write_I is new Write_G (Word8);
+   procedure Write (Idx : Subs_P.Index_T; Value : Word8) renames Write_I;
+
+   procedure Write_I is new Write_G (Word16);
+   procedure Write (Idx : Subs_P.Index_T; Value : Word16) renames Write_I;
+
+   procedure Write_I is new Write_G (Word32);
+   procedure Write (Idx : Subs_P.Index_T; Value : Word32) renames Write_I;
+
+   procedure Write_I is new Write_G (Word64);
+   procedure Write (Idx : Subs_P.Index_T; Value : Word64) renames Write_I;
+
+end HW.MMIO_Regs;