What are the requirements for integrated SIS/BPCS systems?

Integrated SIS/BPCS requirements per IEC 61511: logical separation (SIF logic must be segregated even if same hardware platform), physical separation where required by SIL (separate I/O cards for SIL 2/3, separate processors for SIL 3), independence of utilities (separate power supplies, watchdogs), protection against BPCS faults affecting SIS (no common communication failures), access control (SIS programming protected from BPCS access), different programming environments or access rights, documented proof of separation (vendor assessment, platform certification), and clear delineation of SIS vs BPCS functions. Benefits: reduced hardware cost, common engineering tools. Risks: potential common mode failures, complexity in proving independence. Require platform-specific safety manual demonstrating separation.