1. A method for transmitting data in messages which are transmitted cyclically in specifiable time windows via a communication link of a communication system, the method comprising: initially storing, temporarily, messages sent and to be sent via the communication link, in a message memory of a communication module, the message to be sent or to be received in a current time window being taken from the message memory and sent, or received, and stored in the message memory; searching, to determine positions of the messages in the message memory, in advance at regular intervals, each interval being greater than one time window, for, in each instance, a plurality of time windows still following; and storing, as a result of a search run, the positions of the messages to be sent or to be received in the plurality of time windows still following in a buffer assigned to the message memory.