Added links to number format documents.

libraries/base/common/src/vhdl/common_pkg.vhd

@@ -387,6 +387,10 @@ PACKAGE common_pkg IS
   FUNCTION func_slv_extract(                                                                   a_w, b_w, c_w                          : NATURAL; vec : STD_LOGIC_VECTOR; sel : NATURAL) RETURN STD_LOGIC_VECTOR;
   FUNCTION func_slv_extract(                                                                   a_w, b_w                               : NATURAL; vec : STD_LOGIC_VECTOR; sel : NATURAL) RETURN STD_LOGIC_VECTOR;
   
+  -- Number formats, see:
+  -- . https://support.astron.nl/confluence/display/L2M/L3+SDP+Decision%3A+Definition+of+fixed+point+numbers
+  -- . https://support.astron.nl/confluence/display/L2M/L4+SDPFW+Decision%3A+Number+representation%2C+resizing+and+rounding
+
   FUNCTION TO_UINT(vec : STD_LOGIC_VECTOR) RETURN NATURAL;  -- beware: NATURAL'HIGH = 2**31-1, not 2*32-1, use TO_SINT to avoid warning
   FUNCTION TO_SINT(vec : STD_LOGIC_VECTOR) RETURN INTEGER;
   
@@ -2073,6 +2077,9 @@ PACKAGE BODY common_pkg IS
     RETURN sel_a_b(c_pos, c_real, -c_real);
   END;
 
+  -- Fixed point format
+  -- . https://support.astron.nl/confluence/display/L2M/L3+SDP+Decision%3A+Definition+of+fixed+point+numbers
+
   FUNCTION TO_UREAL(uvec : STD_LOGIC_VECTOR; resolution_w : INTEGER) RETURN REAL IS
   BEGIN
     -- First convert as unsigned integer, then scale to real. See TO_SREAL()
@@ -2505,7 +2512,8 @@ PACKAGE BODY common_pkg IS
   END;
   
   -------------------------------------------------------------------------------------------------
-  -- Rounding schemes:
+  -- Rounding schemes
+  -- . https://support.astron.nl/confluence/display/L2M/L4+SDPFW+Decision%3A+Number+representation%2C+resizing+and+rounding
   -------------------------------------------------------------------------------------------------
   --
   -- From https://en.wikipedia.org/wiki/Rounding it follows that there are three main