Method for protecting or securing data transmission in a data bus, involves data telegrams having variable length data field and a test sum i.e. cyclic redundancy check (CRC), which has shorter length for short data field lengths

摘要

Constant telegram overheads arising from a long test sum being transmitted with short data telegrams and resulting in the telegram overhead being independent of the number of useful data bits (data field), can be reduced without losses in transmission quality and thus reducing the bus load by the reduction of the telegram overhead. The number of test sum bits is independent of the number of data bits being protected and therefore of the telegram length, and with short data field lengths the test sum has a shorter length than with a data field of greater length. The test sum is specifically selected by the sender on the basis of a length instruction of the data field provided in the telegram.