Add TXD and RXD labels to t412

fab.lib

@@ -2310,8 +2310,8 @@ $ENDFPLIST
 DRAW
 S -500 -600 500 600 0 1 10 f
 X VCC 1 0 700 100 D 50 50 1 1 W
-X PA6 2 600 -200 100 L 50 50 1 1 B
-X PA7 3 600 -300 100 L 50 50 1 1 B
+X TXD/PA6 2 600 -200 100 L 50 50 1 1 B
+X RXD/PA7 3 600 -300 100 L 50 50 1 1 B
 X PA1 4 600 200 100 L 50 50 1 1 B
 X PA2 5 600 100 100 L 50 50 1 1 B
 X ~RESET~/UPDI/PA0 6 600 300 100 L 50 50 1 1 B