diff --git a/Makefile.in b/Makefile.in
index ffff36e88..5a6ae894d 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -16,7 +16,7 @@
 #    59 Temple Place - Suite 330
 #    Boston, MA 02111-1307, USA
 #
-#ident "$Id: Makefile.in,v 1.172 2005/07/14 23:38:43 steve Exp $"
+#ident "$Id: Makefile.in,v 1.173 2005/08/06 17:58:16 steve Exp $"
 #
 #
 SHELL = /bin/sh
@@ -108,7 +108,7 @@ TT = t-dll.o t-dll-api.o t-dll-expr.o t-dll-proc.o
 FF = cprop.o nodangle.o synth.o synth2.o syn-rules.o
 
 O = main.o async.o design_dump.o dup_expr.o elaborate.o elab_expr.o \
-elab_lval.o elab_net.o elab_anet.o elab_pexpr.o elab_scope.o \
+elab_lval.o elab_net.o elab_pexpr.o elab_scope.o \
 elab_sig.o emit.o eval.o eval_attrib.o \
 eval_tree.o expr_synth.o functor.o lexor.o lexor_keyword.o link_const.o \
 load_module.o netlist.o netmisc.o net_assign.o \
diff --git a/PExpr.cc b/PExpr.cc
index 3640598c2..75f6dba84 100644
--- a/PExpr.cc
+++ b/PExpr.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: PExpr.cc,v 1.35 2004/10/04 01:10:51 steve Exp $"
+#ident "$Id: PExpr.cc,v 1.36 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include "config.h"
@@ -53,6 +53,14 @@ NetNet* PExpr::elaborate_lnet(Design*des, NetScope*, bool) const
       return 0;
 }
 
+NetNet* PExpr::elaborate_bi_net(Design*des, NetScope*) const
+{
+      cerr << get_line() << ": error: "
+	   << "expression not valid as argument to inout port: "
+	   << *this << endl;
+      return 0;
+}
+
 PEBinary::PEBinary(char op, PExpr*l, PExpr*r)
 : op_(op), left_(l), right_(r)
 {
@@ -262,6 +270,9 @@ bool PEUnary::is_constant(Module*m) const
 
 /*
  * $Log: PExpr.cc,v $
+ * Revision 1.36  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.35  2004/10/04 01:10:51  steve
  *  Clean up spurious trailing white space.
  *
diff --git a/PExpr.h b/PExpr.h
index 8298e1012..f518f67cc 100644
--- a/PExpr.h
+++ b/PExpr.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: PExpr.h,v 1.69 2005/07/07 16:22:49 steve Exp $"
+#ident "$Id: PExpr.h,v 1.70 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include  <string>
@@ -73,15 +73,17 @@ class PExpr : public LineInfo {
 				    Link::strength_t drive1 =Link::STRONG)
 	    const;
 
-	// This method elaborates the expression as NetNet objects. It
-	// only allows regs suitable for procedural continuous assignments.
-      virtual NetNet* elaborate_anet(Design*des, NetScope*scope) const;
-
 	// This method elaborates the expression as gates, but
 	// restricted for use as l-values of continuous assignments.
       virtual NetNet* elaborate_lnet(Design*des, NetScope*scope,
 				     bool implicit_net_ok =false) const;
 
+	// This is similar to elaborate_lnet, except that the
+	// expression is evaluated to be bi-directional. This is
+	// useful for arguments to inout ports of module instances and
+	// ports of tran primitives.
+      virtual NetNet* elaborate_bi_net(Design*des, NetScope*scope) const;
+
 	// Expressions that can be in the l-value of procedural
 	// assignments can be elaborated with this method. If the
 	// is_force flag is true, then the set of valid l-value types
@@ -122,10 +124,6 @@ class PEConcat : public PExpr {
 
       virtual void dump(ostream&) const;
 
-	// Concatenated Regs can be on the left of procedural
-	// continuous assignments.
-      virtual NetNet* elaborate_anet(Design*des, NetScope*scope) const;
-
       virtual NetNet* elaborate_lnet(Design*des, NetScope*scope,
 				     bool implicit_net_ok =false) const;
       virtual NetNet* elaborate_net(Design*des, NetScope*scope,
@@ -220,13 +218,12 @@ class PEIdent : public PExpr {
 
       virtual void dump(ostream&) const;
 
-	// Regs can be on the left of procedural continuous assignments
-      virtual NetNet* elaborate_anet(Design*des, NetScope*scope) const;
-
 	// Identifiers are allowed (with restrictions) is assign l-values.
       virtual NetNet* elaborate_lnet(Design*des, NetScope*scope,
 				     bool implicit_net_ok =false) const;
 
+      virtual NetNet* elaborate_bi_net(Design*des, NetScope*scope) const;
+
 	// Identifiers are also allowed as procedural assignment l-values.
       virtual NetAssign_* elaborate_lval(Design*des,
 					 NetScope*scope,
@@ -284,6 +281,12 @@ class PEIdent : public PExpr {
       NetAssign_* elaborate_mem_lval_(Design*des, NetScope*scope,
 				      NetMemory*mem) const;
 
+      NetNet* elaborate_lnet_common_(Design*des, NetScope*scope,
+				     bool implicit_net_ok,
+				     bool bidirectional_flag) const;
+
+      NetNet*make_implicit_net_(Design*des, NetScope*scope) const;
+
       bool eval_part_select_(Design*des, NetScope*scope, NetNet*sig,
 			     unsigned&midx, unsigned&lidx) const;
 
@@ -514,6 +517,9 @@ class PECallFunction : public PExpr {
 
 /*
  * $Log: PExpr.h,v $
+ * Revision 1.70  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.69  2005/07/07 16:22:49  steve
  *  Generalize signals to carry types.
  *
diff --git a/elab_net.cc b/elab_net.cc
index 9e7e630f9..96f41e7bc 100644
--- a/elab_net.cc
+++ b/elab_net.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: elab_net.cc,v 1.169 2005/07/15 04:13:25 steve Exp $"
+#ident "$Id: elab_net.cc,v 1.170 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include "config.h"
@@ -1815,6 +1815,36 @@ NetNet* PEFNumber::elaborate_net(Design*des, NetScope*scope,
       return net;
 }
 
+/*
+ * A private method to create an implicit net.
+ */
+NetNet* PEIdent::make_implicit_net_(Design*des, NetScope*scope) const
+{
+      NetNet::Type nettype = scope->default_nettype();
+      NetNet*sig = 0;
+
+      if (!error_implicit && nettype!=NetNet::NONE) {
+	    sig = new NetNet(scope, lex_strings.make(path_.peek_name(0)),
+			     NetNet::IMPLICIT, 1);
+	      /* Implicit nets are always scalar logic. */
+	    sig->data_type(IVL_VT_LOGIC);
+
+	    if (warn_implicit) {
+		  cerr << get_line() << ": warning: implicit "
+			"definition of wire logic " << scope->name()
+		       << "." << path_.peek_name(0) << "." << endl;
+	    }
+
+      } else {
+	    cerr << get_line() << ": error: Net " << path_
+		 << " is not defined in this context." << endl;
+	    des->errors += 1;
+	    return 0;
+      }
+
+      return sig;
+}
+
 /*
  * This private method evaluates the part selects (if any) for the
  * signal. The sig argument is the NetNet already located for the
@@ -1889,11 +1919,13 @@ bool PEIdent::eval_part_select_(Design*des, NetScope*scope, NetNet*sig,
 }
 
 /*
- * Identifiers in continuous assignment l-values are limited to wires
- * and that ilk. Detect registers and memories here and report errors.
+ * This is the common code for l-value nets and bi-directional
+ * nets. There is very little that is different between the two cases,
+ * so most of the work for both is done here.
  */
-NetNet* PEIdent::elaborate_lnet(Design*des, NetScope*scope,
-				bool implicit_net_ok) const
+NetNet* PEIdent::elaborate_lnet_common_(Design*des, NetScope*scope,
+					bool implicit_net_ok,
+					bool bidirectional_flag) const
 {
       assert(scope);
 
@@ -1921,26 +1953,16 @@ NetNet* PEIdent::elaborate_lnet(Design*des, NetScope*scope,
       }
 
       if (sig == 0) {
-	    NetNet::Type nettype = scope->default_nettype();
 
-	    if (implicit_net_ok && !error_implicit && nettype!=NetNet::NONE) {
+	    if (implicit_net_ok) {
 
-		  sig = new NetNet(scope, lex_strings.make(path_.peek_name(0)),
-				   NetNet::IMPLICIT, 1);
-		    /* Implicit nets are always scalar logic. */
-		  sig->data_type(IVL_VT_LOGIC);
-
-		  if (warn_implicit) {
-			cerr << get_line() << ": warning: implicit "
-			      "definition of wire " << scope->name()
-			     << "." << path_.peek_name(0) << "." << endl;
-		  }
+		  sig = make_implicit_net_(des, scope);
+		  if (sig == 0)
+			return 0;
 
 	    } else {
 		  cerr << get_line() << ": error: Net " << path_
 		       << " is not defined in this context." << endl;
-		  cerr << get_line() << ":      : Do you mean this? wire "
-		       << path_ << " = <expr>;" << endl;
 		  des->errors += 1;
 		  return 0;
 	    }
@@ -1978,6 +2000,15 @@ NetNet* PEIdent::elaborate_lnet(Design*des, NetScope*scope,
 	   original vector. */
 
       if (subnet_wid != sig->vector_width()) {
+	      /* If we are processing a tran or inout, then the
+		 partselect is bi-directional. Otherwise, it is a
+		 Part-to-Vector select. */
+	    NetPartSelect::dir_t part_dir;
+	    if (bidirectional_flag)
+		  part_dir = NetPartSelect::BI;
+	    else
+		  part_dir = NetPartSelect::PV;
+
 	    if (debug_elaborate)
 		  cerr << get_line() << ": debug: "
 		       << "Elaborate lnet part select "
@@ -1992,7 +2023,7 @@ NetNet* PEIdent::elaborate_lnet(Design*des, NetScope*scope,
 	    subsig->data_type( sig->data_type() );
 
 	    NetPartSelect*sub = new NetPartSelect(sig, lidx, subnet_wid,
-						  NetPartSelect::PV);
+						  part_dir);
 	    des->add_node(sub);
 	    connect(sub->pin(0), subsig->pin(0));
 
@@ -2002,6 +2033,21 @@ NetNet* PEIdent::elaborate_lnet(Design*des, NetScope*scope,
       return sig;
 }
 
+/*
+ * Identifiers in continuous assignment l-values are limited to wires
+ * and that ilk. Detect registers and memories here and report errors.
+ */
+NetNet* PEIdent::elaborate_lnet(Design*des, NetScope*scope,
+					bool implicit_net_ok) const
+{
+      return elaborate_lnet_common_(des, scope, implicit_net_ok, false);
+}
+
+NetNet* PEIdent::elaborate_bi_net(Design*des, NetScope*scope) const
+{
+      return elaborate_lnet_common_(des, scope, true, true);
+}
+
 /*
  * This method is used to elaborate identifiers that are ports to a
  * scope. The scope is presumed to be that of the module that has the
@@ -2581,6 +2627,9 @@ NetNet* PEUnary::elaborate_net(Design*des, NetScope*scope,
 
 /*
  * $Log: elab_net.cc,v $
+ * Revision 1.170  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.169  2005/07/15 04:13:25  steve
  *  Match data type of PV select input/output.
  *
diff --git a/elaborate.cc b/elaborate.cc
index f439fe487..62f70f8a0 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: elaborate.cc,v 1.327 2005/07/15 00:41:09 steve Exp $"
+#ident "$Id: elaborate.cc,v 1.328 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include "config.h"
@@ -770,13 +770,77 @@ void PGModule::elaborate_mod_(Design*des, Module*rmod, NetScope*scope) const
 	      // even multiple of the instance count.
 	    assert(prts_vector_width % instance.count() == 0);
 
+	    unsigned desired_vector_width = prts_vector_width;
+	    if (instance.count() != 1)
+		  desired_vector_width = 0;
+
 	      // Elaborate the expression that connects to the
 	      // module[s] port. sig is the thing outside the module
 	      // that connects to the port.
 
 	    NetNet*sig;
-	    if ((prts.count() >= 1)
-		&& (prts[0]->port_type() != NetNet::PINPUT)) {
+	    if ((prts.count() == 0)
+		|| (prts[0]->port_type() == NetNet::PINPUT)) {
+
+		    /* Input to module. elaborate the expression to
+		       the desired width. If this in an instance
+		       array, then let the net determine it's own
+		       width. We use that, then, to decide how to hook
+		       it up.
+
+		       NOTE that this also handles the case that the
+		       port is actually empty on the inside. We assume
+		       in that case that the port is input. */
+
+		  sig = pins[idx]->elaborate_net(des, scope,
+						 desired_vector_width,
+						 0, 0, 0);
+		  if (sig == 0) {
+			cerr << pins[idx]->get_line()
+			     << ": internal error: Port expression "
+			     << "too complicated for elaboration." << endl;
+			continue;
+		  }
+
+	    } else if (prts[0]->port_type() == NetNet::PINOUT) {
+
+		    /* Inout to/from module. This is a more
+		       complicated case, where the expression must be
+		       an lnet, but also an r-value net.
+
+		       Normally, this winds up being the same as if we
+		       just elaborated as an lnet, as passing a simple
+		       identifier elaborates to the same NetNet in
+		       both cases so the extra elaboration has no
+		       effect. But if the expression passed to the
+		       inout port is a part select, aspecial part
+		       select must be created that can paqss data in
+		       both directions.
+
+		       Use the elaborate_bi_net method to handle all
+		       the possible cases. */
+
+		  sig = pins[idx]->elaborate_bi_net(des, scope);
+		  if (sig == 0) {
+			cerr << pins[idx]->get_line() << ": error: "
+			     << "Inout port expression must support "
+			     << "continuous assignment." << endl;
+			cerr << pins[idx]->get_line() << ":      : "
+			     << "Port of " << rmod->mod_name()
+			     << " is " << rmod->ports[idx]->name << endl;
+			des->errors += 1;
+			continue;
+		  }
+
+
+	    } else {
+
+		    /* Port type must be OUTPUT here. */
+
+		    /* Output from module. Elaborate the port
+		       expression as the l-value of a continuous
+		       assignment, as the port will continuous assign
+		       into the port. */
 
 		  sig = pins[idx]->elaborate_lnet(des, scope, true);
 		  if (sig == 0) {
@@ -790,25 +854,6 @@ void PGModule::elaborate_mod_(Design*des, Module*rmod, NetScope*scope) const
 			continue;
 		  }
 
-	    } else {
-		    /* Input to module. elaborate the expression to
-		       the desired width. If this in an instance
-		       array, then let the net determine it's own
-		       width. We use that, then, to decide how to hook
-		       it up. */
-		  unsigned desired_vector_width = prts_vector_width;
-		  if (instance.count() != 1)
-			desired_vector_width = 0;
-
-		  sig = pins[idx]->elaborate_net(des, scope,
-						 desired_vector_width,
-						 0, 0, 0);
-		  if (sig == 0) {
-			cerr << pins[idx]->get_line()
-			     << ": internal error: Port expression "
-			     << "too complicated for elaboration." << endl;
-			continue;
-		  }
 	    }
 
 	    assert(sig);
@@ -955,7 +1000,7 @@ void PGModule::elaborate_mod_(Design*des, Module*rmod, NetScope*scope) const
 		  break;
 		case NetNet::PINOUT:
 		  cerr << get_line() << ": XXXX: "
-		       << "Forgot how to bind input ports!" << endl;
+		       << "Forgot how to bind inout ports!" << endl;
 		  des->errors += 1;
 		  break;
 		case NetNet::PIMPLICIT:
@@ -2974,6 +3019,9 @@ Design* elaborate(list<perm_string>roots)
 
 /*
  * $Log: elaborate.cc,v $
+ * Revision 1.328  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.327  2005/07/15 00:41:09  steve
  *  More debug information.
  *
diff --git a/ivl_target.h b/ivl_target.h
index 3efc8e7c4..5c4b883bc 100644
--- a/ivl_target.h
+++ b/ivl_target.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: ivl_target.h,v 1.158 2005/07/11 16:56:50 steve Exp $"
+#ident "$Id: ivl_target.h,v 1.159 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 #ifdef __cplusplus
@@ -234,6 +234,7 @@ typedef enum ivl_lpm_type_e {
       IVL_LPM_MOD    = 13,
       IVL_LPM_MULT   =  4,
       IVL_LPM_MUX    =  5,
+      IVL_LPM_PART_BI= 28, /* part select: bi-directional (part on 0) */
       IVL_LPM_PART_VP= 15, /* part select: vector to part */
       IVL_LPM_PART_PV= 17, /* part select: part written to vector */
       IVL_LPM_RE_AND = 20,
@@ -891,6 +892,13 @@ extern const char* ivl_udp_name(ivl_udp_t net);
  * indeed the width of the part, even though it is written to a wider
  * gate. The target will need to handle this case specially.
  *
+ * - Bi-directional Part Select (IVL_LPM_PART_BI)
+ * This is not exactly a part select but a bi-directional partial link
+ * of two nexa with different widths. This is used to implement tran
+ * devices and inout ports in certain cases. The device width is the
+ * width of the part. The ivl_lpm_q is the part end, and the
+ * ivl_lpm_data(0) is the non-part end.
+ *
  * - Comparisons (IVL_LPM_CMP_GT/GE/EQ/NE/EEQ/NEE)
  * These devices have two inputs, available by the ivl_lpm_data()
  * function, and one output available by the ivl_lpm_q function. The
@@ -1662,6 +1670,9 @@ _END_DECL
 
 /*
  * $Log: ivl_target.h,v $
+ * Revision 1.159  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.158  2005/07/11 16:56:50  steve
  *  Remove NetVariable and ivl_variable_t structures.
  *
diff --git a/netlist.cc b/netlist.cc
index 9f6772e68..85fc3e6da 100644
--- a/netlist.cc
+++ b/netlist.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: netlist.cc,v 1.246 2005/07/11 16:56:50 steve Exp $"
+#ident "$Id: netlist.cc,v 1.247 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include "config.h"
@@ -496,8 +496,8 @@ NetPartSelect::NetPartSelect(NetNet*sig, unsigned off, unsigned wid,
 	    pin(1).set_dir(Link::OUTPUT);
 	    break;
 	  case NetPartSelect::BI:
-	    pin(0).set_dir(Link::PASSIVE);
-	    pin(1).set_dir(Link::PASSIVE);
+	    pin(0).set_dir(Link::OUTPUT);
+	    pin(1).set_dir(Link::OUTPUT);
 	    break;
       }
       pin(0).set_name(perm_string::literal("Part"), 0);
@@ -2216,6 +2216,9 @@ const NetProc*NetTaskDef::proc() const
 
 /*
  * $Log: netlist.cc,v $
+ * Revision 1.247  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.246  2005/07/11 16:56:50  steve
  *  Remove NetVariable and ivl_variable_t structures.
  *
diff --git a/t-dll-api.cc b/t-dll-api.cc
index 8ba37dd36..581939c71 100644
--- a/t-dll-api.cc
+++ b/t-dll-api.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: t-dll-api.cc,v 1.130 2005/07/11 16:56:51 steve Exp $"
+#ident "$Id: t-dll-api.cc,v 1.131 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include "config.h"
@@ -713,6 +713,7 @@ extern "C" unsigned ivl_lpm_base(ivl_lpm_t net)
       switch (net->type) {
 	  case IVL_LPM_PART_VP:
 	  case IVL_LPM_PART_PV:
+	  case IVL_LPM_PART_BI:
 	    return net->u_.part.base;
 	  default:
 	    assert(0);
@@ -840,6 +841,7 @@ extern "C" ivl_nexus_t ivl_lpm_data(ivl_lpm_t net, unsigned idx)
 
 	  case IVL_LPM_PART_VP:
 	  case IVL_LPM_PART_PV:
+	  case IVL_LPM_PART_BI:
 	    assert(idx <= 1);
 	    if (idx == 0)
 		  return net->u_.part.a;
@@ -1012,6 +1014,7 @@ extern "C" ivl_nexus_t ivl_lpm_q(ivl_lpm_t net, unsigned idx)
 
 	  case IVL_LPM_PART_VP:
 	  case IVL_LPM_PART_PV:
+	  case IVL_LPM_PART_BI:
 	    assert(idx == 0);
 	    return net->u_.part.q;
 
@@ -1099,6 +1102,7 @@ extern "C" int ivl_lpm_signed(ivl_lpm_t net)
 	    return 0;
 	  case IVL_LPM_PART_VP:
 	  case IVL_LPM_PART_PV:
+	  case IVL_LPM_PART_BI:
 	    return net->u_.part.signed_flag;
 	  case IVL_LPM_REPEAT:
 	    return 0;
@@ -1167,6 +1171,8 @@ extern "C" unsigned ivl_lpm_width(ivl_lpm_t net)
 	  case IVL_LPM_PART_VP:
 	  case IVL_LPM_PART_PV:
 	    return net->u_.part.width;
+	  case IVL_LPM_PART_BI:
+	    return net->u_.part.width;
 	  case IVL_LPM_REPEAT:
 	    return net->u_.repeat.width;
 	  default:
@@ -2027,6 +2033,9 @@ extern "C" ivl_statement_t ivl_stmt_sub_stmt(ivl_statement_t net)
 
 /*
  * $Log: t-dll-api.cc,v $
+ * Revision 1.131  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.130  2005/07/11 16:56:51  steve
  *  Remove NetVariable and ivl_variable_t structures.
  *
diff --git a/t-dll.cc b/t-dll.cc
index 715ba0cc2..a3580724f 100644
--- a/t-dll.cc
+++ b/t-dll.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: t-dll.cc,v 1.153 2005/07/11 16:56:51 steve Exp $"
+#ident "$Id: t-dll.cc,v 1.154 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include "config.h"
@@ -1699,7 +1699,7 @@ bool dll_target::part_select(const NetPartSelect*net)
 	    obj->type = IVL_LPM_PART_PV;
 	    break;
 	  case NetPartSelect::BI:
-	    assert(0); // XXXX Not supported yet
+	    obj->type = IVL_LPM_PART_BI;
 	    break;
       }
       obj->name = net->name(); // NetPartSelect names are permallocated.
@@ -1707,13 +1707,14 @@ bool dll_target::part_select(const NetPartSelect*net)
       obj->scope = find_scope(des_, net->scope());
       assert(obj->scope);
 
+	/* Part selects are always unsigned. */
       obj->u_.part.signed_flag = 0;
 
 	/* Choose the width of the part select. */
       obj->u_.part.width = net->width();
       obj->u_.part.base  = net->base();
-      obj->u_.part.signed_flag = 0;
       obj->u_.part.s = 0;
+
       const Nexus*nex;
 
       switch (obj->type) {
@@ -1753,12 +1754,39 @@ bool dll_target::part_select(const NetPartSelect*net)
 	    obj->u_.part.a = (ivl_nexus_t) nex->t_cookie();
 	    break;
 
+	  case IVL_LPM_PART_BI:
+	      /* For now, handle this exactly the same as a PV */
+
+	      /* NetPartSelect:pin(0) is the output pin. */
+	    nex = net->pin(0).nexus();
+	    assert(nex->t_cookie());
+
+	    obj->u_.part.q = (ivl_nexus_t) nex->t_cookie();
+
+	      /* NetPartSelect:pin(1) is the input pin. */
+	    nex = net->pin(1).nexus();
+	    assert(nex->t_cookie());
+
+	    obj->u_.part.a = (ivl_nexus_t) nex->t_cookie();
+	    break;
+
 	  default:
 	    assert(0);
       }
 
       nexus_lpm_add(obj->u_.part.q, obj, 0, IVL_DR_STRONG, IVL_DR_STRONG);
-      nexus_lpm_add(obj->u_.part.a, obj, 0, IVL_DR_HiZ, IVL_DR_HiZ);
+
+	/* If the device is a PART_BI, then the "input" is also a
+	   strength aware output, so attach it to the nexus with
+	   strong driver. */
+      if (obj->type == IVL_LPM_PART_BI)
+	 nexus_lpm_add(obj->u_.part.a, obj, 0, IVL_DR_STRONG, IVL_DR_STRONG);
+      else
+	 nexus_lpm_add(obj->u_.part.a, obj, 0, IVL_DR_HiZ, IVL_DR_HiZ);
+
+	/* The select input is optional. */
+      if (obj->u_.part.s)
+	 nexus_lpm_add(obj->u_.part.s, obj, 0, IVL_DR_HiZ, IVL_DR_HiZ);
 
       scope_add_lpm(obj->scope, obj);
 
@@ -2103,6 +2131,9 @@ extern const struct target tgt_dll = { "dll", &dll_target_obj };
 
 /*
  * $Log: t-dll.cc,v $
+ * Revision 1.154  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.153  2005/07/11 16:56:51  steve
  *  Remove NetVariable and ivl_variable_t structures.
  *
diff --git a/tgt-stub/stub.c b/tgt-stub/stub.c
index 1a5f9bdbd..2e2188f4f 100644
--- a/tgt-stub/stub.c
+++ b/tgt-stub/stub.c
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: stub.c,v 1.131 2005/07/14 16:15:13 steve Exp $"
+#ident "$Id: stub.c,v 1.132 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include "config.h"
@@ -656,6 +656,38 @@ static void show_lpm_part(ivl_lpm_t net)
       }
 }
 
+static void show_lpm_part_bi(ivl_lpm_t net)
+{
+      unsigned width = ivl_lpm_width(net);
+      unsigned base  = ivl_lpm_base(net);
+      ivl_nexus_t port_p = ivl_lpm_q(net,0);
+      ivl_nexus_t port_v = ivl_lpm_data(net,0);
+
+      fprintf(out, "  LPM_PART_BI %s: <width=%u, base=%u, signed=%d>\n",
+	      ivl_lpm_basename(net), width, base, ivl_lpm_signed(net));
+      fprintf(out, "    P: %s\n", ivl_nexus_name(port_p));
+      fprintf(out, "    V: %s <width=%u>\n", ivl_nexus_name(port_v),
+	      width_of_nexus(port_v));
+
+
+	/* The data(0) port must be large enough for the part select. */
+      if (width_of_nexus(ivl_lpm_data(net,0)) < (width+base)) {
+	    fprintf(out, "    ERROR: Part select is out of range."
+		    " Data nexus width=%u, width+base=%u\n",
+		    width_of_nexus(ivl_lpm_data(net,0)), width+base);
+	    stub_errors += 1;
+      }
+
+	/* The Q vector must be exactly the width of the part select. */
+      if (width_of_nexus(ivl_lpm_q(net,0)) != width) {
+	    fprintf(out, "    ERROR: Part select input mistatch."
+		    " Nexus width=%u, expect width=%u\n",
+		    width_of_nexus(ivl_lpm_q(net,0)), width);
+	    stub_errors += 1;
+      }
+}
+
+
 static void show_lpm_ram(ivl_lpm_t net)
 {
       ivl_nexus_t nex;
@@ -938,6 +970,11 @@ static void show_lpm(ivl_lpm_t net)
 	    show_lpm_part(net);
 	    break;
 
+	      /* The BI part select is slightly special. */
+	  case IVL_LPM_PART_BI:
+	    show_lpm_part_bi(net);
+	    break;
+
 	  case IVL_LPM_REPEAT:
 	    show_lpm_repeat(net);
 	    break;
@@ -1490,6 +1527,9 @@ int target_design(ivl_design_t des)
 
 /*
  * $Log: stub.c,v $
+ * Revision 1.132  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.131  2005/07/14 16:15:13  steve
  *  Dump function call expression node.
  *
diff --git a/tgt-vvp/vvp_priv.h b/tgt-vvp/vvp_priv.h
index 58ac4fd69..8519dcade 100644
--- a/tgt-vvp/vvp_priv.h
+++ b/tgt-vvp/vvp_priv.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: vvp_priv.h,v 1.31 2005/07/13 04:52:31 steve Exp $"
+#ident "$Id: vvp_priv.h,v 1.32 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include  "vvp_config.h"
@@ -82,12 +82,16 @@ extern int draw_vpi_rfunc_call(ivl_expr_t exp);
  * Given a nexus, draw a string that represents the functor output
  * that feeds the nexus. This function can be used to get the input to
  * a functor, event, or even a %load in cases where I have the
- * ivl_nexus_t object.
+ * ivl_nexus_t object. The draw_net_input function will get the string
+ * cached in the nexus, if there is one, or will generate a string and
+ * cache it.
  */
-extern void draw_nexus_input(ivl_nexus_t nex);
-
 extern const char* draw_net_input(ivl_nexus_t nex);
 
+/*
+ * This is very similar to draw_net_input, but instead of returning a
+ * pointer to the string, it writes it to the output file.
+ */
 extern void draw_input_from_net(ivl_nexus_t nex);
 
 /*
@@ -194,6 +198,9 @@ extern unsigned thread_count;
 
 /*
  * $Log: vvp_priv.h,v $
+ * Revision 1.32  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.31  2005/07/13 04:52:31  steve
  *  Handle functions with real values.
  *
diff --git a/tgt-vvp/vvp_scope.c b/tgt-vvp/vvp_scope.c
index 41a7a6983..c6db082a5 100644
--- a/tgt-vvp/vvp_scope.c
+++ b/tgt-vvp/vvp_scope.c
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: vvp_scope.c,v 1.131 2005/07/11 16:56:51 steve Exp $"
+#ident "$Id: vvp_scope.c,v 1.132 2005/08/06 17:58:16 steve Exp $"
 #endif
 
 # include  "vvp_priv.h"
@@ -603,9 +603,17 @@ static const char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 		  sprintf(result, "L_%p", lpm);
 		  return result;
 	    }
-
 	    break;
 
+	  case IVL_LPM_PART_BI:
+	    if (ivl_lpm_q(lpm, 0) == nex) {
+		  sprintf(result, "L_%p/P", lpm);
+		  return result;
+	    } else if (ivl_lpm_data(lpm,0) == nex) {
+		  sprintf(result, "L_%p/V", lpm);
+		  return result;
+	    }
+	    break;
       }
 
       fprintf(stderr, "internal error: no input to nexus %s\n",
@@ -615,16 +623,18 @@ static const char* draw_net_input_drive(ivl_nexus_t nex, ivl_nexus_ptr_t nptr)
 }
 
 /*
- * This function draws the input to a net. What that means is that it
- * returns a static string that can be used to represent a resolved
- * driver to a nexus. If there are multiple drivers to the nexus, then
- * it writes out the resolver declarations needed to perform strength
- * resolution.
+ * This function draws the input to a net into a string. What that
+ * means is that it returns a static string that can be used to
+ * represent a resolved driver to a nexus. If there are multiple
+ * drivers to the nexus, then it writes out the resolver declarations
+ * needed to perform strength resolution.
  *
- * The string that this returns is bound to the nexus, so the pointer
- * remains valid.
+ * The string that this returns is malloced, and that means that the
+ * caller must free the string or store it permanently. This function
+ * does *not* check for a previously calculated string. Use the
+ * draw_net_input for the general case.
  */
-const char* draw_net_input(ivl_nexus_t nex)
+char* draw_net_input_x(ivl_nexus_t nex, ivl_nexus_ptr_t omit)
 {
       ivl_signal_type_t res;
       char result[512];
@@ -636,11 +646,7 @@ const char* draw_net_input(ivl_nexus_t nex)
 
       const char*resolv_type;
 
-	/* If this nexus already has a label, then its input is
-	   already figured out. Just return the existing label. */
-      char*nex_private = (char*)ivl_nexus_get_private(nex);
-      if (nex_private)
-	    return nex_private;
+      char*nex_private = 0;
 
       res = signal_type_of_nexus(nex);
       switch (res) {
@@ -670,6 +676,9 @@ const char* draw_net_input(ivl_nexus_t nex)
       for (idx = 0 ;  idx < ivl_nexus_ptrs(nex) ;  idx += 1) {
 	    ivl_nexus_ptr_t nptr = ivl_nexus_ptr(nex, idx);
 
+	    if (nptr == omit)
+		  continue;
+
 	      /* Skip input only pins. */
 	    if ((ivl_nexus_ptr_drive0(nptr) == IVL_DR_HiZ)
 		&& (ivl_nexus_ptr_drive1(nptr) == IVL_DR_HiZ))
@@ -711,7 +720,6 @@ const char* draw_net_input(ivl_nexus_t nex)
 	    }
 	    *tmp++ = '>';
 	    *tmp = 0;
-	    ivl_nexus_set_private(nex, nex_private);
 	    return nex_private;
       }
 
@@ -721,7 +729,6 @@ const char* draw_net_input(ivl_nexus_t nex)
 	   TRI type nexus. */
       if (ndrivers == 1 && res == IVL_SIT_TRI) {
 	    nex_private = strdup(draw_net_input_drive(nex, drivers[0]));
-	    ivl_nexus_set_private(nex, nex_private);
 	    return nex_private;
       }
 
@@ -761,22 +768,36 @@ const char* draw_net_input(ivl_nexus_t nex)
 
       sprintf(result, "RS_%p", nex);
       nex_private = strdup(result);
+      return nex_private;
+}
+
+/*
+ * Get a cached description of the nexus input, or create one if this
+ * nexus has not been cached yet. This is a wrapper for the common
+ * case call to draw_net_input_x.
+ */
+const char*draw_net_input(ivl_nexus_t nex)
+{
+	/* If this nexus already has a label, then its input is
+	   already figured out. Just return the existing label. */
+      char*nex_private = (char*)ivl_nexus_get_private(nex);
+      if (nex_private)
+	    return nex_private;
+
+      nex_private = draw_net_input_x(nex, 0);
       ivl_nexus_set_private(nex, nex_private);
       return nex_private;
 }
 
-
-
 /*
  * This function looks at the nexus in search of the net to attach
  * functor inputs to. Sort the signals in the nexus by name, and
- * choose the lexically earliest one.
+ * choose the lexically earliest one. This is different from the
+ * draw_net_input in that it also prints the result.
  */
 void draw_input_from_net(ivl_nexus_t nex)
 {
-      const char*nex_private = (const char*)ivl_nexus_get_private(nex);
-      if (nex_private == 0)
-	    nex_private = draw_net_input(nex);
+      const char*nex_private = draw_net_input(nex);
       assert(nex_private);
       fprintf(vvp_out, "%s", nex_private);
 }
@@ -1774,6 +1795,68 @@ static void draw_lpm_part_pv(ivl_lpm_t net)
       fprintf(vvp_out, ", %u, %u, %u;\n", base, width, signal_width);
 }
 
+/*
+ * Handle the drawing of a bi-directional part select. The two ports
+ * are simultaneously input and output. A simple minded connect of the
+ * input to the output causes a functor cycle which will lock into an
+ * X value, so something special is needed.
+ *
+ * NOTE: The inputs of the tran device at this point need to be from
+ * all the drivers of the nexus *except* the tran itself.
+ */
+static void draw_lpm_part_bi(ivl_lpm_t net)
+{
+      unsigned width = ivl_lpm_width(net);
+      unsigned base  = ivl_lpm_base(net);
+      unsigned signal_width = width_of_nexus(ivl_lpm_data(net,0));
+
+      unsigned idx;
+      ivl_nexus_t nex;
+      ivl_nexus_ptr_t ptr;
+
+      char*p_str;
+      char*v_str;
+
+	/* It seems implausible that the two inputs of a tran will be
+	   connected together. So assert that this is so to simplify
+	   the code to look for the nexus_ptr_t objects. */
+      assert(ivl_lpm_q(net,0) != ivl_lpm_data(net,0));
+
+      nex = ivl_lpm_q(net,0);
+      for (idx = 0 ;  idx < ivl_nexus_ptrs(nex) ;  idx += 1) {
+	    ptr = ivl_nexus_ptr(nex, idx);
+	    if (ivl_nexus_ptr_lpm(ptr) == net)
+		  break;
+      }
+      p_str = draw_net_input_x(nex, ptr);
+
+      nex = ivl_lpm_data(net,0);
+      for (idx = 0 ;  idx < ivl_nexus_ptrs(nex) ;  idx += 1) {
+	    ptr = ivl_nexus_ptr(nex, idx);
+	    if (ivl_nexus_ptr_lpm(ptr) == net)
+		  break;
+      }
+      v_str = draw_net_input_x(nex, ptr);
+
+	/* Pad the part-sized input out to a common width... */
+      fprintf(vvp_out, "L_%p/i .part/pv %s, %u, %u, %u;\n",
+	      net, p_str, base, width, signal_width);
+
+	/* Resolve together the two halves of the tran... */
+      fprintf(vvp_out, "L_%p/V .resolv tri, L_%p/i, %s;\n",
+	      net, net, v_str);
+
+	/* The full-width side is created by the tran device, all we
+	   have left to to is take a part select of that for the
+	   smaller output, and this becomes the part select output of
+	   the BI device. */
+      fprintf(vvp_out, "L_%p/P .part L_%p/V, %u, %u;\n", net,
+	      net, base, width);
+
+      free(p_str);
+      free(v_str);
+}
+
 /*
  * Draw unary reduction devices.
  */
@@ -1816,6 +1899,10 @@ static void draw_lpm_in_scope(ivl_lpm_t net)
 	    draw_lpm_add(net);
 	    return;
 
+	  case IVL_LPM_PART_BI:
+	    draw_lpm_part_bi(net);
+	    return;
+
 	  case IVL_LPM_PART_VP:
 	    draw_lpm_part(net);
 	    return;
@@ -1994,6 +2081,9 @@ int draw_scope(ivl_scope_t net, ivl_scope_t parent)
 
 /*
  * $Log: vvp_scope.c,v $
+ * Revision 1.132  2005/08/06 17:58:16  steve
+ *  Implement bi-directional part selects.
+ *
  * Revision 1.131  2005/07/11 16:56:51  steve
  *  Remove NetVariable and ivl_variable_t structures.
  *