diff --git a/vvp/arith.cc b/vvp/arith.cc
index 6eaf6c726..aa3c0c721 100644
--- a/vvp/arith.cc
+++ b/vvp/arith.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: arith.cc,v 1.9 2001/07/07 02:57:33 steve Exp $"
+#ident "$Id: arith.cc,v 1.10 2001/07/11 02:27:21 steve Exp $"
 #endif
 
 # include  "arith.h"
@@ -110,8 +110,6 @@ vvp_arith_sum::~vvp_arith_sum()
 
 void vvp_arith_sum::set(vvp_ipoint_t i, functor_t f, bool push)
 {
-      assert(wid_ <= 8*sizeof(unsigned long));
-
       unsigned page = 0;
       unsigned pbit = 0;
       unsigned long carry = 0;
@@ -468,6 +466,9 @@ void vvp_shiftr::set(vvp_ipoint_t i, functor_t f, bool push)
 
 /*
  * $Log: arith.cc,v $
+ * Revision 1.10  2001/07/11 02:27:21  steve
+ *  Add support for REadOnlySync and monitors.
+ *
  * Revision 1.9  2001/07/07 02:57:33  steve
  *  Add the .shift/r functor.
  *
diff --git a/vvp/memory.cc b/vvp/memory.cc
index 35e4b7c43..d8051287a 100644
--- a/vvp/memory.cc
+++ b/vvp/memory.cc
@@ -18,7 +18,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: memory.cc,v 1.4 2001/06/15 03:28:31 steve Exp $"
+#ident "$Id: memory.cc,v 1.5 2001/07/11 02:27:21 steve Exp $"
 #endif
 
 #include "memory.h"
@@ -437,6 +437,8 @@ inline static struct mem_assign_s* ma_alloc()
     cur = (struct mem_assign_s*) malloc(sizeof(struct mem_assign_s));
   else
     ma_free_list = cur->next;
+
+  cur->sync_flag = false;
   return cur;
 }
 
diff --git a/vvp/schedule.cc b/vvp/schedule.cc
index 74d5830c0..486d35dbd 100644
--- a/vvp/schedule.cc
+++ b/vvp/schedule.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: schedule.cc,v 1.10 2001/05/30 03:02:35 steve Exp $"
+#ident "$Id: schedule.cc,v 1.11 2001/07/11 02:27:21 steve Exp $"
 #endif
 
 # include  "schedule.h"
@@ -27,6 +27,7 @@
 # include  <malloc.h>
 # include  <assert.h>
 
+# include  <stdio.h>
 /*
  * The event queue is arranged as a skip list, with the simulation
  * time the key to the list. The simulation time is stored in each
@@ -90,9 +91,20 @@ inline static void e_free(struct event_s* cur)
 }
 
 /*
- * This is the head of the list of pending events.
+ * This is the head of the list of pending events. This includes all
+ * the events that have not been executed yet, and reaches into the
+ * future.
  */
-static struct event_s* list = 0;
+static struct event_s* sched_list = 0;
+
+/*
+ * At the current time, events that are marked as synch events are put
+ * into this list and held off until the time step is about to
+ * advance. Then the events in this list are run and the clock is
+ * allowed to advance.
+ */
+static struct event_s* synch_list = 0;
+
 
 /*
  * This flag is true until a VPI task or function finishes the
@@ -122,20 +134,20 @@ static void schedule_event_(struct event_s*cur)
 
 	/* If the list is completely empty, then start the list with
 	   this the only event. */
-      if (list == 0) {
-	    list = cur;
+      if (sched_list == 0) {
+	    sched_list = cur;
 	    cur->next = 0;
 	    return;
       }
 
-      struct event_s*idx = list;
+      struct event_s*idx = sched_list;
       if (cur->delay < idx->delay) {
 	      /* If this new event is earlier then even the first
 		 event, then insert it in front. Adjust the delay of
 		 the next event, and set the start to me. */
 	    idx->delay -= cur->delay;
 	    cur->next = idx;
-	    list = cur;
+	    sched_list = cur;
 
       } else {
 
@@ -173,6 +185,43 @@ static void schedule_event_(struct event_s*cur)
       }
 }
 
+/*
+ * The synch_list is managed as a doubly-linked circular list. There is
+ * no need for the skip capabilities, so use the "last" member as a
+ * prev pointer. This function appends the event to the synch_list.
+ */
+static void postpone_sync_event(struct event_s*cur)
+{
+      if (synch_list == 0) {
+	    synch_list = cur;
+	    cur->next = cur;
+	    cur->last = cur;
+	    return;
+      }
+
+      cur->next = synch_list;
+      cur->last = synch_list->last;
+      cur->next->last = cur;
+      cur->last->next = cur;
+}
+
+static struct event_s* pull_sync_event(void)
+{
+      if (synch_list == 0)
+	    return 0;
+
+      struct event_s*cur = synch_list;
+      synch_list = cur->next;
+      if (cur == synch_list) {
+	    synch_list = 0;
+      } else {
+	    cur->next->last = cur->last;
+	    cur->last->next = cur->next;
+      }
+
+      return cur;
+}
+
 void schedule_vthread(vthread_t thr, unsigned delay)
 {
       struct event_s*cur = e_alloc();
@@ -228,30 +277,47 @@ void schedule_simulate(void)
 {
       schedule_time = 0;
 
-      while (schedule_runnable && list) {
+      while (schedule_runnable && sched_list) {
 
 	      /* Pull the first item off the list. Fixup the last
 		 pointer in the next cell, if necessary. */
-	    struct event_s*cur = list;
-	    list = cur->next;
+	    struct event_s*cur = sched_list;
+	    sched_list = cur->next;
 	    if (cur->last != cur) {
-		  assert(list);
-		  assert(list->delay == 0);
-		  list->last = cur->last;
+		  assert(sched_list);
+		  assert(sched_list->delay == 0);
+		  sched_list->last = cur->last;
 
 	    }
 
-	    schedule_time += cur->delay;
-	      //printf("TIME: %u\n", schedule_time);
+	      /* If the time is advancing, then first run the
+		 postponed sync events. Run them all. */
+	    if (cur->delay > 0) {
+		  struct event_s*sync_cur;
+		  while ( (sync_cur = pull_sync_event()) ) {
+			assert(sync_cur->type == TYPE_GEN);
+			if (sync_cur->obj && sync_cur->obj->run) {
+			      assert(sync_cur->obj->sync_flag);
+			      sync_cur->obj->run(sync_cur->obj, sync_cur->val);
+			}
+			e_free(sync_cur);
+		  }
+
+
+		  schedule_time += cur->delay;
+		    //printf("TIME: %u\n", schedule_time);
+	    }
 
 	    switch (cur->type) {
 		case TYPE_THREAD:
 		  vthread_run(cur->thr);
+		  e_free(cur);
 		  break;
 
 		case TYPE_PROP:
 		    //printf("Propagate %p\n", cur->fun);
 		  functor_propagate(cur->fun);
+		  e_free(cur);
 		  break;
 
 		case TYPE_ASSIGN:
@@ -269,21 +335,31 @@ void schedule_simulate(void)
 			functor_set(cur->fun, cur->val, HiZ, false);
 			break;
 		  }
+		  e_free(cur);
 		  break;
 
 		case TYPE_GEN:
-		  if (cur->obj && cur->obj->run)
-		    cur->obj->run(cur->obj, cur->val);
+		  if (cur->obj && cur->obj->run) {
+			if (cur->obj->sync_flag == false) {
+			      cur->obj->run(cur->obj, cur->val);
+			      e_free(cur);
+
+			} else {
+			      postpone_sync_event(cur);
+			}
+		  }
 		  break;
 
 	    }
 
-	    e_free(cur);
       }
 }
 
 /*
  * $Log: schedule.cc,v $
+ * Revision 1.11  2001/07/11 02:27:21  steve
+ *  Add support for REadOnlySync and monitors.
+ *
  * Revision 1.10  2001/05/30 03:02:35  steve
  *  Propagate strength-values instead of drive strengths.
  *
diff --git a/vvp/schedule.h b/vvp/schedule.h
index 14ee8e072..083e94de6 100644
--- a/vvp/schedule.h
+++ b/vvp/schedule.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: schedule.h,v 1.6 2001/05/02 01:38:13 steve Exp $"
+#ident "$Id: schedule.h,v 1.7 2001/07/11 02:27:21 steve Exp $"
 #endif
 
 # include  "vthread.h"
@@ -63,7 +63,8 @@ extern void schedule_generic(vvp_gen_event_t obj, unsigned char val,
 
 struct vvp_gen_event_s
 {
-  void (*run)(vvp_gen_event_t obj, unsigned char val);
+      void (*run)(vvp_gen_event_t obj, unsigned char val);
+      bool sync_flag;
 };
 
 /*
@@ -94,6 +95,9 @@ extern bool schedule_finished(void);
 
 /*
  * $Log: schedule.h,v $
+ * Revision 1.7  2001/07/11 02:27:21  steve
+ *  Add support for REadOnlySync and monitors.
+ *
  * Revision 1.6  2001/05/02 01:38:13  steve
  *  Describe a generic event a bit.
  *
diff --git a/vvp/vpi_callback.cc b/vvp/vpi_callback.cc
index fe2972717..18ec7cdb2 100644
--- a/vvp/vpi_callback.cc
+++ b/vvp/vpi_callback.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: vpi_callback.cc,v 1.2 2001/06/21 23:05:08 steve Exp $"
+#ident "$Id: vpi_callback.cc,v 1.3 2001/07/11 02:27:21 steve Exp $"
 #endif
 
 /*
@@ -58,7 +58,11 @@ static struct __vpiCallback* make_value_change(p_cb_data data)
       struct __vpiCallback*obj = new __vpiCallback;
       obj->base.vpi_type = &callback_rt;
       obj->cb_data = *data;
+      obj->cb_time = *(data->time);
+      obj->cb_data.time = &obj->cb_time;
 
+      assert(data->obj);
+      assert(data->obj->vpi_type);
       assert((data->obj->vpi_type->type_code == vpiReg)
 	     || (data->obj->vpi_type->type_code == vpiNet));
       struct __vpiSignal*sig = reinterpret_cast<__vpiSignal*>(data->obj);
@@ -81,6 +85,45 @@ static struct __vpiCallback* make_value_change(p_cb_data data)
       return obj;
 }
 
+struct sync_cb  : public vvp_gen_event_s {
+      struct __vpiCallback*handle;
+};
+
+static void make_sync_run(vvp_gen_event_t obj, unsigned char)
+{
+      struct sync_cb*cb = (struct sync_cb*)obj;
+      if (cb->handle == 0)
+	    return;
+
+      struct __vpiCallback*cur = cb->handle;
+      cur->cb_data.time->type = vpiSimTime;
+      cur->cb_data.time->low = schedule_simtime();
+      cur->cb_data.time->high = 0;
+      (cur->cb_data.cb_rtn)(&cur->cb_data);
+
+      delete cur;
+}
+
+static struct __vpiCallback* make_sync(p_cb_data data)
+{
+      struct __vpiCallback*obj = new __vpiCallback;
+      obj->base.vpi_type = &callback_rt;
+      obj->cb_data = *data;
+      obj->cb_time = *(data->time);
+      obj->cb_data.time = &obj->cb_time;
+
+      obj->next = 0;
+
+      struct sync_cb*cb = new sync_cb;
+      cb->sync_flag = true;
+      cb->run = &make_sync_run;
+      cb->handle = obj;
+      obj->cb_sync = cb;
+
+      schedule_generic(cb, 0, 0);
+      return obj;
+}
+
 vpiHandle vpi_register_cb(p_cb_data data)
 {
       struct __vpiCallback*obj = 0;
@@ -91,6 +134,10 @@ vpiHandle vpi_register_cb(p_cb_data data)
 	    obj = make_value_change(data);
 	    break;
 
+	  case cbReadOnlySynch:
+	    obj = make_sync(data);
+	    break;
+
 	  default:
 	    fprintf(stderr, "vpi error: vpi_register_cb invalid or "
 		    "unsupported callback reason: %d\n",
@@ -104,6 +151,8 @@ vpiHandle vpi_register_cb(p_cb_data data)
 
 int vpi_remove_cb(vpiHandle ref)
 {
+      assert(ref);
+      assert(ref->vpi_type);
       assert(ref->vpi_type->type_code == vpiCallback);
 
       struct __vpiCallback*obj = reinterpret_cast<__vpiCallback*>(ref);
@@ -150,6 +199,9 @@ void vpip_trip_monitor_callbacks(void)
 
 /*
  * $Log: vpi_callback.cc,v $
+ * Revision 1.3  2001/07/11 02:27:21  steve
+ *  Add support for REadOnlySync and monitors.
+ *
  * Revision 1.2  2001/06/21 23:05:08  steve
  *  Some documentation of callback behavior.
  *
diff --git a/vvp/vpi_priv.cc b/vvp/vpi_priv.cc
index ee33a41b5..5f6923a39 100644
--- a/vvp/vpi_priv.cc
+++ b/vvp/vpi_priv.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: vpi_priv.cc,v 1.7 2001/06/30 23:03:17 steve Exp $"
+#ident "$Id: vpi_priv.cc,v 1.8 2001/07/11 02:27:21 steve Exp $"
 #endif
 
 # include  "vpi_priv.h"
@@ -55,12 +55,12 @@ static int vpip_get_global(int property)
 
 int vpi_get(int property, vpiHandle ref)
 {
-      if (property == vpiType)
-	    return ref->vpi_type->type_code;
-
       if (ref == 0)
 	    return vpip_get_global(property);
 
+      if (property == vpiType)
+	    return ref->vpi_type->type_code;
+
       if (ref->vpi_type->vpi_get_ == 0)
 	    return -1;
 
@@ -151,6 +151,9 @@ extern "C" void vpi_sim_vcontrol(int operation, va_list ap)
 
 /*
  * $Log: vpi_priv.cc,v $
+ * Revision 1.8  2001/07/11 02:27:21  steve
+ *  Add support for REadOnlySync and monitors.
+ *
  * Revision 1.7  2001/06/30 23:03:17  steve
  *  support fast programming by only writing the bits
  *  that are listed in the input file.
diff --git a/vvp/vpi_priv.h b/vvp/vpi_priv.h
index 6151d3a28..994d387bf 100644
--- a/vvp/vpi_priv.h
+++ b/vvp/vpi_priv.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT)
-#ident "$Id: vpi_priv.h,v 1.18 2001/06/30 23:03:17 steve Exp $"
+#ident "$Id: vpi_priv.h,v 1.19 2001/07/11 02:27:21 steve Exp $"
 #endif
 
 # include  "vpi_user.h"
@@ -125,10 +125,15 @@ extern struct __vpiSignal*vpip_sig_from_ptr(vvp_ipoint_t ptr);
  * callback. The handle is stored by the run time, and it triggered
  * when the run-time thing that it is waiting for happens.
  */
+
+struct sync_cb;
 struct __vpiCallback {
       struct __vpiHandle base;
 
       struct t_cb_data cb_data;
+      struct t_vpi_time cb_time;
+
+      struct sync_cb* cb_sync;
 
       struct __vpiCallback*next;
 };
@@ -254,6 +259,9 @@ extern void vpip_set_time_precision(int pres);
 
 /*
  * $Log: vpi_priv.h,v $
+ * Revision 1.19  2001/07/11 02:27:21  steve
+ *  Add support for REadOnlySync and monitors.
+ *
  * Revision 1.18  2001/06/30 23:03:17  steve
  *  support fast programming by only writing the bits
  *  that are listed in the input file.