The MC33199D is a serial interface circuit used in diagnostic applications. It is the interface between the microcontroller and the special K and L Lines of the ISO diagnostic port. The MC33199D has been designed to meet the "Diagnosis System ISO 9141" specification. The device has a bidirectional bus K Line driver, fully protected against short circuits and over temperature. It also includes the L Line receiver, used during the wake up sequence in the ISO transmission. The MC33199 has a unique feature which allows transmission baud rate up to 200 k baud.