diff --git a/vvp/logic.cc b/vvp/logic.cc
index 3989f0583..dddafd1d0 100644
--- a/vvp/logic.cc
+++ b/vvp/logic.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: logic.cc,v 1.15 2004/12/29 23:45:13 steve Exp $"
+#ident "$Id: logic.cc,v 1.16 2004/12/31 05:56:36 steve Exp $"
 #endif
 
 # include  "logic.h"
@@ -88,6 +88,28 @@ vvp_fun_buf::~vvp_fun_buf()
 }
 
 void vvp_fun_buf::recv_vec4(vvp_net_ptr_t ptr, vvp_vector4_t bit)
+{
+      if (ptr.port() != 0)
+	    return;
+
+      for (unsigned idx = 0 ;  idx < bit.size() ;  idx += 1) {
+	    if (bit.value(idx) == BIT4_Z)
+		  bit.set_bit(idx, BIT4_X);
+      }
+
+      vvp_send_vec4(ptr.ptr()->out, bit);
+}
+
+vvp_fun_bufz::vvp_fun_bufz()
+{
+      count_functors_table += 1;
+}
+
+vvp_fun_bufz::~vvp_fun_bufz()
+{
+}
+
+void vvp_fun_bufz::recv_vec4(vvp_net_ptr_t ptr, vvp_vector4_t bit)
 {
       if (ptr.port() != 0)
 	    return;
@@ -123,7 +145,7 @@ void compile_functor(char*label, char*type,
 	    obj = new vvp_bufif_s(false,false, ostr0, ostr1);
 #endif
       } else if (strcmp(type, "BUFZ") == 0) {
-	    obj = new table_functor_s(ft_BUFZ);
+	    obj = new vvp_fun_bufz();
 #if 0
       } else if (strcmp(type, "PMOS") == 0) {
 	    obj = new vvp_pmos_s;
@@ -191,6 +213,9 @@ void compile_functor(char*label, char*type,
 
 /*
  * $Log: logic.cc,v $
+ * Revision 1.16  2004/12/31 05:56:36  steve
+ *  Add specific BUFZ functor.
+ *
  * Revision 1.15  2004/12/29 23:45:13  steve
  *  Add the part concatenation node (.concat).
  *
diff --git a/vvp/logic.h b/vvp/logic.h
index 6d114bd8a..d185c50d9 100644
--- a/vvp/logic.h
+++ b/vvp/logic.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: logic.h,v 1.9 2004/12/29 23:45:13 steve Exp $"
+#ident "$Id: logic.h,v 1.10 2004/12/31 05:56:36 steve Exp $"
 #endif
 
 # include  "vvp_net.h"
@@ -48,8 +48,8 @@ class table_functor_s: public vvp_net_fun_t {
 /*
  * The buffer functor is a very primitive functor that takes the input
  * from port-0 (and only port-0) and retransmits it as a vvp_vector4_t.
- * This is intended to model the Verilog buf(Q,D) statement. This
- * device should be useful for removing strength from vectors.
+ * The retransmitted vector has all Z values changed to X, just like
+ * the buf(Q,D) gate in Verilog.
  */
 class vvp_fun_buf: public vvp_net_fun_t {
 
@@ -62,6 +62,21 @@ class vvp_fun_buf: public vvp_net_fun_t {
     private:
 };
 
+/*
+ * The vvp_fun_bufz is like the vvp_fun_buf, but it does not change
+ * Z values to X -- it passes Z values unchanged.
+ */
+class vvp_fun_bufz: public vvp_net_fun_t {
+
+    public:
+      explicit vvp_fun_bufz();
+      virtual ~vvp_fun_bufz();
+
+      void recv_vec4(vvp_net_ptr_t p, vvp_vector4_t bit);
+
+    private:
+};
+
 // table functor types
 
 extern const unsigned char ft_AND[];
@@ -86,6 +101,9 @@ extern const unsigned char ft_var[];
 
 /*
  * $Log: logic.h,v $
+ * Revision 1.10  2004/12/31 05:56:36  steve
+ *  Add specific BUFZ functor.
+ *
  * Revision 1.9  2004/12/29 23:45:13  steve
  *  Add the part concatenation node (.concat).
  *