All CPUs have a rugged, compact plastic enclosure with a display integrated in the front flap of the control.

The front of the controller contains:

• LEDs to indicate status and errors

The CPUs also include:

• a slot for the SIMATIC memory card;
  these memory cards are required for operation.
• Mode switch
• Connection for PROFINET IO IRT (2-port switch)
• Connection for PROFIBUS (CPU 1516-3 PN/DP and higher)
• Connection for PROFINET (CPU 1515-2 PN and higher)