AtMega32: Portc.5 liefert bei logisch1 nur 1.6V?

Hallo!

Mein Atmega32 liefert nur 1.6V an Portc.5, alle anderen funktionieren 
normal. Woran kann das liegen?

Das Programm:
$regfile = "m32def.dat"
$crystal = 1000000


Config Portd.0 = Output
Config Portd.1 = Output
Config Portc.7 = Output
Config Portc.6 = Output
Config Portc.5 = Output
Config Portc.4 = Output
Config Portc.3 = Output
Config Portc.2 = Output
Config Portc.1 = Output
Config Portc.0 = Output
Config Portd.7 = Output
Config Portd.6 = Output

Multiplex1 Alias Portd.0
Multiplex2 Alias Portd.1
B1 Alias Portc.0
B2 Alias Portc.1
B3 Alias Portc.2
B4 Alias Portc.3
B5 Alias Portc.4
B6 Alias Portc.5
B7 Alias Portc.6
B8 Alias Portc.7
B9 Alias Portd.7
B10 Alias Portd.6


Do

   Multiplex1 = 1

   B1 = 1
   B2 = 1
   B3 = 1
   B4 = 1
   B5 = 1
   B6 = 1
   B7 = 1
   B8 = 1
   B9 = 1
   B10 = 1

Loop


End