diff --git a/elab_expr.cc b/elab_expr.cc
index 384216a03..f9b95a4e2 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: elab_expr.cc,v 1.107 2006/07/31 03:50:17 steve Exp $"
+#ident "$Id: elab_expr.cc,v 1.108 2006/08/09 05:19:08 steve Exp $"
 #endif
 
 # include "config.h"
@@ -111,8 +111,19 @@ NetEBinary* PEBinary::elaborate_expr_base_(Design*des,
 	    tmp->set_line(*this);
 	    break;
 
-	  case '/':
 	  case '%':
+	      /* The % operator does not support real arguments in
+		 baseline Verilog. But we allow it in our extended
+		 form of verilog. */
+	    if (generation_flag < GN_VER2001X) {
+		  if (lp->expr_type()==IVL_VT_REAL || rp->expr_type()==IVL_VT_REAL) {
+			cerr << get_line() << ": error: Modulus operator may not "
+			      "have REAL operands." << endl;
+			des->errors += 1;
+		  }
+	    }
+	      /* Fall through to handle the % with the / operator. */
+	  case '/':
 	    tmp = new NetEBDiv(op_, lp, rp);
 	    tmp->set_line(*this);
 	    break;
@@ -1387,6 +1398,9 @@ NetExpr* PEUnary::elaborate_expr(Design*des, NetScope*scope,
 
 /*
  * $Log: elab_expr.cc,v $
+ * Revision 1.108  2006/08/09 05:19:08  steve
+ *  Add support for real valued modulus.
+ *
  * Revision 1.107  2006/07/31 03:50:17  steve
  *  Add support for power in constant expressions.
  *
diff --git a/tgt-vvp/eval_real.c b/tgt-vvp/eval_real.c
index 279c3e824..99d1a847e 100644
--- a/tgt-vvp/eval_real.c
+++ b/tgt-vvp/eval_real.c
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: eval_real.c,v 1.14 2005/07/13 04:52:31 steve Exp $"
+#ident "$Id: eval_real.c,v 1.15 2006/08/09 05:19:08 steve Exp $"
 #endif
 
 /*
@@ -80,6 +80,10 @@ static int draw_binary_real(ivl_expr_t exp)
 	    fprintf(vvp_out, "    %%div/wr %d, %d;\n", l, r);
 	    break;
 
+	  case '%':
+	    fprintf(vvp_out, "    %%mod/wr %d, %d;\n", l, r);
+	    break;
+#if 0
 	  case '%':
 	      { struct vector_info res = draw_eval_expr(exp, STUFF_OK_XZ);
 		l = allocate_word();
@@ -89,7 +93,7 @@ static int draw_binary_real(ivl_expr_t exp)
 	        clr_vector(res);
 	      }
 	      break;
-
+#endif
 	  default:
 	    fprintf(stderr, "XXXX draw_binary_real(%c)\n",
 		    ivl_expr_opcode(exp));
@@ -312,6 +316,9 @@ int draw_eval_real(ivl_expr_t exp)
 
 /*
  * $Log: eval_real.c,v $
+ * Revision 1.15  2006/08/09 05:19:08  steve
+ *  Add support for real valued modulus.
+ *
  * Revision 1.14  2005/07/13 04:52:31  steve
  *  Handle functions with real values.
  *
diff --git a/vvp/codes.h b/vvp/codes.h
index fac20c9aa..d226f7f9f 100644
--- a/vvp/codes.h
+++ b/vvp/codes.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: codes.h,v 1.78 2006/02/02 02:44:00 steve Exp $"
+#ident "$Id: codes.h,v 1.79 2006/08/09 05:19:08 steve Exp $"
 #endif
 
 
@@ -95,6 +95,7 @@ extern bool of_LOAD_XP(vthread_t thr, vvp_code_t code);
 extern bool of_LOADI_WR(vthread_t thr, vvp_code_t code);
 extern bool of_MOD(vthread_t thr, vvp_code_t code);
 extern bool of_MOD_S(vthread_t thr, vvp_code_t code);
+extern bool of_MOD_WR(vthread_t thr, vvp_code_t code);
 extern bool of_MOV(vthread_t thr, vvp_code_t code);
 extern bool of_MUL(vthread_t thr, vvp_code_t code);
 extern bool of_MUL_WR(vthread_t thr, vvp_code_t code);
@@ -178,6 +179,9 @@ extern vvp_code_t codespace_null(void);
 
 /*
  * $Log: codes.h,v $
+ * Revision 1.79  2006/08/09 05:19:08  steve
+ *  Add support for real valued modulus.
+ *
  * Revision 1.78  2006/02/02 02:44:00  steve
  *  Allow part selects of memory words in l-values.
  *
diff --git a/vvp/compile.cc b/vvp/compile.cc
index 2d090a99f..fec45c245 100644
--- a/vvp/compile.cc
+++ b/vvp/compile.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: compile.cc,v 1.222 2006/08/08 05:11:37 steve Exp $"
+#ident "$Id: compile.cc,v 1.223 2006/08/09 05:19:08 steve Exp $"
 #endif
 
 # include  "arith.h"
@@ -139,6 +139,7 @@ const static struct opcode_table_s opcode_table[] = {
       { "%loadi/wr",of_LOADI_WR,3,{OA_BIT1,     OA_NUMBER,   OA_BIT2} },
       { "%mod",    of_MOD,    3,  {OA_BIT1,     OA_BIT2,     OA_NUMBER} },
       { "%mod/s",  of_MOD_S,  3,  {OA_BIT1,     OA_BIT2,     OA_NUMBER} },
+      { "%mod/wr", of_MOD_WR, 2,  {OA_BIT1,     OA_BIT2,     OA_NONE} },
       { "%mov",    of_MOV,    3,  {OA_BIT1,     OA_BIT2,     OA_NUMBER} },
       { "%mul",    of_MUL,    3,  {OA_BIT1,     OA_BIT2,     OA_NUMBER} },
       { "%mul/wr", of_MUL_WR, 2,  {OA_BIT1,     OA_BIT2,     OA_NONE} },
@@ -1496,6 +1497,9 @@ void compile_param_string(char*label, char*name, char*value)
 
 /*
  * $Log: compile.cc,v $
+ * Revision 1.223  2006/08/09 05:19:08  steve
+ *  Add support for real valued modulus.
+ *
  * Revision 1.222  2006/08/08 05:11:37  steve
  *  Handle 64bit delay constants.
  *
diff --git a/vvp/opcodes.txt b/vvp/opcodes.txt
index 9c58061b1..627875f20 100644
--- a/vvp/opcodes.txt
+++ b/vvp/opcodes.txt
@@ -1,7 +1,7 @@
 /*
  * Copyright (c) 2001-2003 Stephen Williams (steve@icarus.com)
  *
- *  $Id: opcodes.txt,v 1.70 2006/02/02 02:44:00 steve Exp $
+ *  $Id: opcodes.txt,v 1.71 2006/08/09 05:19:08 steve Exp $
  */
 
 
@@ -424,6 +424,10 @@ replaced with the result.
 
 The /s form does signed %.
 
+* %mod/wr <bit-l>, <bit-r>
+
+This opcode is the real-valued modulus of the two real values.
+
 * %mov <dst>, <src>, <wid>
 
 This instruction copies a vector from one place in register space to
diff --git a/vvp/vthread.cc b/vvp/vthread.cc
index 50a2e3f04..a977e558a 100644
--- a/vvp/vthread.cc
+++ b/vvp/vthread.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: vthread.cc,v 1.155 2006/08/08 05:11:37 steve Exp $"
+#ident "$Id: vthread.cc,v 1.156 2006/08/09 05:19:08 steve Exp $"
 #endif
 
 # include  "config.h"
@@ -2279,6 +2279,18 @@ bool of_MOD_S(vthread_t thr, vvp_code_t cp)
       return true;
 }
 
+/*
+ * %mod/wr <dest>, <src>
+ */
+bool of_MOD_WR(vthread_t thr, vvp_code_t cp)
+{
+      double l = thr->words[cp->bit_idx[0]].w_real;
+      double r = thr->words[cp->bit_idx[1]].w_real;
+      thr->words[cp->bit_idx[0]].w_real = fmod(l,r);
+
+      return true;
+}
+
 /*
  * %mov <dest>, <src>, <wid>
  *   This instruction is implemented by the of_MOV function
@@ -3272,6 +3284,9 @@ bool of_JOIN_UFUNC(vthread_t thr, vvp_code_t cp)
 
 /*
  * $Log: vthread.cc,v $
+ * Revision 1.156  2006/08/09 05:19:08  steve
+ *  Add support for real valued modulus.
+ *
  * Revision 1.155  2006/08/08 05:11:37  steve
  *  Handle 64bit delay constants.
  *