diff --git a/src/hilight.c b/src/hilight.c
index 655059c9..22db2276 100644
--- a/src/hilight.c
+++ b/src/hilight.c
@@ -875,9 +875,10 @@ void propagate_hilights(int set, int clear, int mode)
 }
 
 /* use negative values to bypass the normal hilight color enumeration */
-#define LOGIC_X -1
-#define LOGIC_0 -12
-#define LOGIC_1 -5
+#define LOGIC_0 -12  /* 0 */
+#define LOGIC_1 -5   /* 1 */
+#define LOGIC_X -1   /* 2 */
+#define LOGIC_Z -13  /* 3 */
 #define STACKMAX 200
 
 int get_logic_value(int inst, int n)
@@ -914,7 +915,7 @@ void print_stack(int  *stack, int sp)
 int eval_logic_expr(int inst, int output)
 {
   int stack[STACKMAX];
-  int pos = 0, i, sp = 0;
+  int pos = 0, i, s, sp = 0;
   char *str;
   int res = 0;
 
@@ -922,82 +923,113 @@ int eval_logic_expr(int inst, int output)
   dbg(1, "eval_logic_expr(): inst=%d pin=%d function=%s\n", inst, output, str ? str : "NULL");
   if(!str) return 2; /* no logic function defined, return LOGIC_X */
   while(str[pos]) {
-    if(str[pos] == 'd') { /* duplicate top element*/
-      if(sp > 0 && sp < STACKMAX) {
-        stack[sp] = stack[sp - 1];
-        sp++;
-      }
-    /* rotate down: bottom element goes to top */
-    } else if(str[pos] == 'r') {
-      if(sp > 1) {
-        int tmp = stack[0];
-        for(i = 0 ; i < sp - 1; i++) stack[i] = stack[i + 1];
-        stack[sp - 1] = tmp;
-      }
-    } else if(str[pos] == 'x') { /* exchange top 2 operands */
-      if(sp > 1) {
-         int tmp = stack[sp - 2];
-         stack[sp - 2] =  stack[sp - 1];
-         stack[sp - 1] = tmp;
-      }
-    } else if(str[pos] == '~') { /* negation operator */
-      if(sp > 0) {
-        sp--;
-        if(stack[sp] != 2) stack[sp] = !stack[sp];
-        ++sp;
-      }
-    } else if(str[pos] == '|') { /* or operator */
-      if(sp > 1) {
-        res = 0;
-        for(i = sp - 2; i < sp; i++) {
-          if(stack[i] == 1) {
-            res = 1;
-            break;
-          } else if(stack[i] == 2) {
-            res = 2;
-          }
+    switch(str[pos]) {
+      case 'd': /* duplicate top element*/
+        if(sp > 0 && sp < STACKMAX) {
+          stack[sp] = stack[sp - 1];
+          sp++;
         }
-        stack[sp - 2] = res;
-        sp--;
-      }
-    } else if(str[pos] == '&') { /* and operator */
-      if(sp > 1) {
-        res = 1;
-        for(i = sp - 2; i < sp; i++) {
-          if(stack[i] == 0) {
-            res = 0;
-            break;
-          } else if(stack[i] == 2) {
-            res = 2;
-          }
+        break;
+      case 'r': /* rotate down: bottom element goes to top */
+        if(sp > 1) {
+          s = stack[0];
+          for(i = 0 ; i < sp - 1; i++) stack[i] = stack[i + 1];
+          stack[sp - 1] = s;
         }
-        stack[sp - 2] = res;
-        sp--;
-      }
-    } else if(str[pos] == '^') { /* xor operator */
-      if(sp > 1) {
-        res = 0;
-        for(i = sp - 2; i < sp; i++) {
-          if(stack[i] != 2) {
-            res = res ^ stack[i];
-          }
-          else {
-            res = 2;
-            break;
-          }
+        break;
+      case 'x': /* exchange top 2 operands */
+        if(sp > 1) {
+           s = stack[sp - 2];
+           stack[sp - 2] =  stack[sp - 1];
+           stack[sp - 1] = s;
         }
-        stack[sp - 2] = res;
-        sp--;
-      }
-    } else if(str[pos] == 'L') { /* logic low (0) */
-      if(sp < STACKMAX) {
-        stack[sp++] = 0;
-      }
-    } else if(str[pos] == 'H') { /* logic high (1) */
-      if(sp < STACKMAX) {
-        stack[sp++] = 1;
-      }
-    } else if(isdigit(str[pos])) {
+        break;
+      case '~': /* negation operator */
+        if(sp > 0) {
+          sp--;
+          if(!(stack[sp] & 2)) stack[sp] = !stack[sp];
+          ++sp;
+        }
+        break;
+      case  'z': /* Tristate driver [signal,enable,'z']-> signal if z==1, Z (3) otherwise */
+        if(sp > 1) {
+          s = stack[sp - 1];
+          stack[sp - 2] = (s & 2) ? 2 : (s == 1 ) ? stack[sp - 2] : 3;
+          sp--;
+        }
+        break;
+      case 'm': /* mux operator */
+        s = stack[sp - 1];
+        if(sp > 2) {
+          stack[sp - 3] = (s & 2) ? 2 : (s == 0) ? stack[sp - 3]  : stack[sp - 2];
+          sp -=2;
+        }
+        break;
+      case '|': /* or operator */
+        if(sp > 1) {
+          res = 0;
+          for(i = sp - 2; i < sp; i++) {
+            if(stack[i] == 1) {
+              res = 1;
+              break;
+            } else if(stack[i] & 2) {
+              res = 2;
+            }
+          }
+          stack[sp - 2] = res;
+          sp--;
+        }
+        break;
+      case '&': /* and operator */
+        if(sp > 1) {
+          res = 1;
+          for(i = sp - 2; i < sp; i++) {
+            if(stack[i] == 0) {
+              res = 0;
+              break;
+            } else if(stack[i] & 2) {
+              res = 2;
+            }
+          }
+          stack[sp - 2] = res;
+          sp--;
+        }
+        break;
+      case '^': /* xor operator */
+        if(sp > 1) {
+          res = 0;
+          for(i = sp - 2; i < sp; i++) {
+            if(!(stack[i] & 2)) {
+              res = res ^ stack[i];
+            }
+            else {
+              res = 2;
+              break;
+            }
+          }
+          stack[sp - 2] = res;
+          sp--;
+        }
+        break;
+      case 'L': /* logic low (0) */
+        if(sp < STACKMAX) {
+          stack[sp++] = 0;
+        }
+        break;
+      case 'H': /* logic high (1) */
+        if(sp < STACKMAX) {
+          stack[sp++] = 1;
+        }
+        break;
+      case 'Z': /* logic Z (3) */
+        if(sp < STACKMAX) {
+          stack[sp++] = 3;
+        }
+        break;
+      default:
+        break;
+    } /* switch */
+    if(isdigit(str[pos])) {
       if(sp < STACKMAX) {
         char *num = str + pos;
         while(isdigit(str[++pos])) ;
@@ -1007,7 +1039,7 @@ int eval_logic_expr(int inst, int output)
       else dbg(0, "eval_logic_expr(): stack overflow!\n");
     }
     pos++;
-  }
+  } /* while */
   dbg(1, "eval_logic_expr(): inst %d output %d, returning %d\n", inst, output, stack[0]);
   return stack[0];
 }
@@ -1032,7 +1064,8 @@ void create_simdata(void)
       xctx->simdata.inst[i].pin[j].go_to=NULL;
       my_snprintf(function, S(function), "function%d", j);
       my_strdup(717, &xctx->simdata.inst[i].pin[j].function, get_tok_value(symbol->prop_ptr, function, 0));
-      my_strdup(963, &xctx->simdata.inst[i].pin[j].go_to, get_tok_value(symbol->rect[PINLAYER][j].prop_ptr, "goto", 0));
+      my_strdup(963, &xctx->simdata.inst[i].pin[j].go_to, 
+                get_tok_value(symbol->rect[PINLAYER][j].prop_ptr, "goto", 0));
       str = get_tok_value(symbol->rect[PINLAYER][j].prop_ptr, "clock", 0);
       xctx->simdata.inst[i].pin[j].clock = str[0] ? str[0] - '0' : -1;
     }
@@ -1065,8 +1098,8 @@ void propagate_logic()
   int i, j, npin;
   int propagate;
   struct hilight_hashentry  *entry;
-  int val, oldval;
-  static int map[] = {LOGIC_0, LOGIC_1, LOGIC_X};
+  int val, oldval, newval;
+  static int map[] = {LOGIC_0, LOGIC_1, LOGIC_X, LOGIC_Z};
 
   tclsetvar("tclstop", "0");
   prepare_netlist_structs(0);
@@ -1127,10 +1160,11 @@ void propagate_logic()
             /* no bus_hilight_lookup --> no bus expansion */
             entry = hilight_lookup(xctx->inst[i].node[propagate], 0, XLOOKUP); /* destination pin */
             oldval = (!entry) ? LOGIC_X : entry->value;
-            val =  map[eval_logic_expr(i, propagate)];
-            if(oldval != val) {
+            newval = eval_logic_expr(i, propagate);
+            val =  map[newval];
+            if(newval != 3 && oldval != val) {
                hilight_lookup(xctx->inst[i].node[propagate], val, XINSERT);
-               found=1; /* keep looping until no more nets are found. */
+               if(newval!=3) found=1; /* keep looping until no more nets are found. */
             }
           }
         }
@@ -1151,7 +1185,7 @@ void logic_set(int value, int num)
   char *type;
   xRect boundbox;
   int big =  xctx->wires> 2000 || xctx->instances > 2000 ;
-  static int map[] = {LOGIC_0, LOGIC_1, LOGIC_X};
+  static int map[] = {LOGIC_0, LOGIC_1, LOGIC_X, LOGIC_Z};
   struct hilight_hashentry  *entry;
  
   prepare_netlist_structs(0);
diff --git a/src/xschem.h b/src/xschem.h
index 5e2f1688..240c1149 100644
--- a/src/xschem.h
+++ b/src/xschem.h
@@ -299,7 +299,7 @@ extern char win_temp_dir[PATH_MAX];
 #define LINE_OUTSIDE(xa,ya,xb,yb,x1,y1,x2,y2) \
  (xa>=x2 || xb<=x1 ||  ( (ya<yb)? (ya>=y2 || yb<=y1) : (yb>=y2 || ya<=y1) ) )
 
-#define CLIP(x,a,b) (x<a?a:x>b?b:x)
+#define CLIP(x,a,b) ((x) < a ? (a) : (x) > b ? (b) : (x))
 
 #define MINOR(a,b) ( (a) <= (b) ? (a) : (b) )
 #define ROUND(a) ((a) > 0.0 ? ceil((a) - 0.5) : floor((a) + 0.5))
diff --git a/src/xschem.tcl b/src/xschem.tcl
index 8d75b6dc..fc33888d 100644
--- a/src/xschem.tcl
+++ b/src/xschem.tcl
@@ -3218,9 +3218,11 @@ global env has_x
   ###
   ### Tk event handling
   ###
-  bind . <Expose> [list raise_dialog $window_path]
-  bind . <Visibility> [list raise_dialog $window_path]
-  bind . <FocusIn> [list raise_dialog $window_path]
+  if { $window_path eq {.drw} } {
+    bind . <Expose> [list raise_dialog $window_path]
+    bind . <Visibility> [list raise_dialog $window_path]
+    bind . <FocusIn> [list raise_dialog $window_path]
+  }
   bind $window_path <Double-Button-1> {xschem callback -3 %x %y 0 %b 0 %s}
   bind $window_path <Double-Button-2> {xschem callback -3 %x %y 0 %b 0 %s}
   bind $window_path <Double-Button-3> {xschem callback -3 %x %y 0 %b 0 %s}
diff --git a/xschem_library/devices/gnd.sym b/xschem_library/devices/gnd.sym
index ef8b864d..03ecaa35 100644
--- a/xschem_library/devices/gnd.sym
+++ b/xschem_library/devices/gnd.sym
@@ -1,5 +1,7 @@
-v {xschem version=2.9.5_RC5 file_version=1.1}
-G {type=label
+v {xschem version=2.9.9 file_version=1.2 }
+G {}
+K {type=label
+function0="L"
 global=true
 format="*.alias @lab"
 template="name=l1 lab=GND"}
@@ -10,5 +12,5 @@ L 4 0 0 0 12.5 {}
 L 4 -5 12.5 5 12.5 {}
 L 4 0 17.5 5 12.5 {}
 L 4 -5 12.5 0 17.5 {}
-B 5 -2.5 -2.5 2.5 2.5 {name=p dir=inout}
+B 5 -2.5 -2.5 2.5 2.5 {name=p dir=inout goto=0}
 T {@lab} 7.5 5 0 0 0.2 0.2 {}
diff --git a/xschem_library/devices/vdd.sym b/xschem_library/devices/vdd.sym
index ebee4ecc..e98e95e5 100644
--- a/xschem_library/devices/vdd.sym
+++ b/xschem_library/devices/vdd.sym
@@ -1,5 +1,7 @@
-v {xschem version=2.9.5_RC5 file_version=1.1}
-G {type=label
+v {xschem version=2.9.9 file_version=1.2 }
+G {}
+K {type=label
+function0="H"
 global=true
 format="*.alias @lab"
 template="name=l1 lab=VDD"}
@@ -8,5 +10,5 @@ S {}
 E {}
 L 4 0 -20 0 0 {}
 L 4 -10 -20 10 -20 {}
-B 5 -2.5 -2.5 2.5 2.5 {name=p dir=inout verilog_type=wire}
+B 5 -2.5 -2.5 2.5 2.5 {name=p dir=inout verilog_type=wire goto=0}
 T {@lab} -12.5 -35 0 0 0.2 0.2 {}
diff --git a/xschem_library/xschem_simulator/dfrtp_1.sym b/xschem_library/xschem_simulator/dfrtp_1.sym
index 4d79b88d..86982927 100644
--- a/xschem_library/xschem_simulator/dfrtp_1.sym
+++ b/xschem_library/xschem_simulator/dfrtp_1.sym
@@ -1,7 +1,8 @@
 v {xschem version=2.9.9 file_version=1.2 }
 G {}
 K {type=stdcell
-function3="0 d ~ 3 & x 1 & | 2 &"
+xfunction3="0 d ~ 3 & x 1 & | 2 &"
+function3="3 1 0 m L 2 ~ m"
 format="@name @@CLK @@D @@RESET_B @VGND @VNB @VPB @VPWR @@Q @prefix\\\\dfrtp_1"
 template="name=x1 VGND=VGND VNB=VNB VPB=VPB VPWR=VPWR prefix=sky130_fd_sc_hd__ "
 extra="VGND VNB VPB VPWR prefix"
@@ -23,7 +24,7 @@ goto=3 clock=1}
 B 5 -92.5 -2.5 -87.5 2.5 {name=D dir=in }
 B 5 -92.5 17.5 -87.5 22.5 {name=RESET_B dir=in 
 goto=3
-clock=2}
+clock=0}
 B 5 87.5 -22.5 92.5 -17.5 {name=Q dir=out }
 T {@symname} 0 -6 0 0 0.3 0.3 {hcenter=true}
 T {@name} 75 -42 0 0 0.2 0.2 {}
diff --git a/xschem_library/xschem_simulator/dlrtn_1.sym b/xschem_library/xschem_simulator/dlrtn_1.sym
index b282b69f..9cc05acd 100644
--- a/xschem_library/xschem_simulator/dlrtn_1.sym
+++ b/xschem_library/xschem_simulator/dlrtn_1.sym
@@ -5,7 +5,7 @@ format="@name @@D @@GATE_N @@RESET_B @VGND @VNB @VPB @VPWR @@Q @prefix\\\\dlrtn_
 template="name=x1 VGND=VGND VNB=VNB VPB=VPB VPWR=VPWR prefix=sky130_fd_sc_hd__ "
 extra="VGND VNB VPB VPWR prefix"
 highlight=true
-function3="0 1 ~ 2 & & 1 2 3 & & |"}
+function3="0 3 1 m L 2 ~ m"}
 V {}
 S {}
 E {}
diff --git a/xschem_library/xschem_simulator/dlrtp_1.sym b/xschem_library/xschem_simulator/dlrtp_1.sym
index a160eccf..be554474 100644
--- a/xschem_library/xschem_simulator/dlrtp_1.sym
+++ b/xschem_library/xschem_simulator/dlrtp_1.sym
@@ -5,7 +5,7 @@ format="@name @@D @@GATE @@RESET_B @VGND @VNB @VPB @VPWR @@Q @prefix\\\\dlrtp_1"
 template="name=x1 VGND=VGND VNB=VNB VPB=VPB VPWR=VPWR prefix=sky130_fd_sc_hd__ "
 extra="VGND VNB VPB VPWR prefix"
 highlight=true
-function3="0 1 2 & & 1 ~ 2 3 & & |"}
+function3="3 0 1 m L 2 ~ m"}
 V {}
 S {}
 E {}