All CPUs have a rugged, compact plastic housing. The following components are located on the front panel:

• LEDs to indicate status and errors
• Mode selector
• Connection for MPI

The CPUs also include:

• Slot for SIMATIC Micro Memory Cards (MMC);
  MMCs replace the integrated load memory and are therefore an absolute requirement for operation.
• Connection for integrated inputs/outputs via the front connector (compact CPUs only)
• Connection for PROFIBUS (DP CPUs only)
• Connection for RS 422/485 (PtP CPUs only)
• Connection for PROFINET (PN CPUs only)