Various failsafe CPUs with graduated levels of performance are available for the SIMATIC S7-1500:

• CPU 1511F-1 PN:
  the cost-effective entry-level CPU for standard and fail-safe applications with medium requirements in terms of processing performance and response speed in discrete production technology.
• CPU 1513F-1 PN:
  the CPU with a medium to large program and data memory for standard and fail-safe applications that also include distributed automation structures alongside central I/O.
• CPU 1515F-2 PN:
  for standard and failsafe applications with medium/high requirements for program scope and processing speed, for distributed setup via PROFINET IO with PROFIsafe.
• CPU 1516F-3 PN/DP:
  for applications with medium/high requirements for program scope and processing speed, for distributed configuration via PROFINET IO and PROFIBUS DP with PROFIsafe.
• CPU  1517F-3 PN/DP:
  for standard and failsafe applications with very high requirements for program scope networking, and for very high requirements regarding processing speed, for distributed setup via PROFINET IO and PROFIBUS DP with PROFIsafe. The additional integrated PROFINET interface with separate IP address can be used for network separation, for example.
• CPU 1518F-4 PN/DP:
  for standard and failsafe applications with high requirements for program scope and processing speed, for distributed setup via PROFINET IO and PROFIBUS DP with PROFIsafe. The additional integrated PROFINET interface with separate IP address can be used, for example, for network separation.