Controller Interface

The transceiver is connected via the microcontroller’s integrated serial interface. This is known as the SCI. Originally, a UART was used as a serial interface. However, since it is difficult to achieve a fault-free interface via UART, there is now also microcontroller with Enhanced SCI (ESCI) or LIN SCI.

Data Transmission

Serial data transmission in a cluster is byte-oriented. The SCI transmits the least significant bit (lsb) of each byte first, which is framed by a start bit and a stop bit. This combination of ten bits is referred to as an SCI frame. A message is composed of multiple SCI frames (see figure: Frame).

SCI Frame

Each SCI Frame begins with a dominant Start bit, which causes a falling edge that is used by all receivers for resynchronization. Nodes can delay the transmission of SCI frames. This can lead to pauses in the transmission. These pauses are known as Interbyte Spaces.