def _breakHDB2(HDB2):
 ACK = ((HDB2 & 2) / pow(2, 1))
 NAK = (HDB2 & 1)
 return (ACK, NAK)

def _breakHDB2 ( HDB2 ) : ACK = ( ( HDB2 & 2 ) / pow ( 2 , 1 ) ) NAK = ( HDB2 & 1 ) return ( ACK , NAK )
decode header byte 2 .