Siemens SIPLUSS7-400CPU412H CPU Unit

LEDs indicate, for example, internal and external faults and operating statuses such as RUN, STOP, startup and "Master" operating mode as well as redundancy errors, and test functions

The PG is used to indicate signal states during program execution, to modify process variables independently of the user program, to output the contents of stack memories, to execute individual program steps, and to block program sections.

The PG can be used to obtain information about the memory capacity and operating mode of the CPU and the current loading of the work and load memory.