Siemens 6GK1543-1AA01 Brand Introduction 6GK1543-1AA01 (CP5431) is SIMATIC S5 series PROFIBUS communication processor, designed for S5-155U PLC rack. It specializes in PROFIBUS DP/FMS bus communication, supporting DP distributed I/O cyclic refresh and FMS symbolic message exchange, connecting S5 CPU to remote I/O, drives, HMI and other PROFIBUS nodes.