A data processor system is described comprising a first and a second data processor unit (PU1, PU2). The first data processor unit (PU1) has a data source (SW1, IP11, IP 12) for providing data units for transmission to the second data processor unit (PU2) and a retry buffer (RBUF) for temporarily storing transmitted data units. It is provided with a data selector (RSEL) for selecting data units from the data source or from the retry buffer, and a controller (RCTRL) for controlling the data selector, as well as an output (T1x) for providing data selected for transmissions. The second data processor unit (PU2) has an input (R1x) for receiving the transmitted data and an output (PU20) for further transmitting the received data to a third data processor unit. It also has an input buffer (IBUF) coupled to the input, for temporarily storing the received data. The second data processing unit further comprises an error detector (ED) for detecting an error in the received data and a message generating unit (EF) coupled to the error detector for generating an error message for the first data processor unit in case the error detector detects an error. The controller (RCTRL) of the first data processor unit causes the data selector to select data from the retry buffer (RBUF) if it receives an error message, and causes the data selector to select the data source (SW1, IP11, IP 12) otherwise. The first data processor unit (PU1) limits retransmission of a data unit to a predetermined maximum number of times irrespective of whether the data unit is correctly received or not. This allows for an undisturbed flow of streaming data with an increased reliability.