Method and device for serial data transmission between a base module and a first expansion module

The invention relates to a method and a device for serial data transmission between a base module (1) and an expansion module (2, 3). To allow an improved data transmission of a data packet between a base module (1) and an expansion module (2, 3) is proposed that the base module (1) and the first expansion module (2) each having a first system interface (11, 21), which four pins (7) as the Serial Peripheral interface and two pins (8) as an UART interface or as an I rweiterungsmodul (2) is transmitted, and then the data packet over the non-cyclic data transfer to the first expansion module (2) transmits.