diff --git a/common/hw-gfx-gma-pcode.ads b/common/hw-gfx-gma-pcode.ads
index ef2564a..595fe5b 100644
--- a/common/hw-gfx-gma-pcode.ads
+++ b/common/hw-gfx-gma-pcode.ads
@@ -57,4 +57,15 @@
    with
       Pre => Mailbox_Ready or Wait_Ready;
 
+   -- For reading data from PCode
+   procedure Mailbox_Read
+     (MBox        : in     Word32;
+      Command     : in     Word64 := 0;
+      Wait_Ready  : in     Boolean := False;
+      Reply       :    out Word64;
+      Success     :    out Boolean)
+   with
+      Pre => Mailbox_Ready or Wait_Ready,
+      Post => (if Success then Mailbox_Ready);
+
 end HW.GFX.GMA.PCode;