Machine builders ask for “locked PLC code”; end customers ask for “open code”. Both have a point, and Siemens provides several distinct mechanisms that get mixed up in contracts.
The three mechanisms
Know-how protection encrypts block source: the block runs and can be called, but its logic is not viewable without the password. Copy protection binds a block to a serial number (CPU or memory card) so the program will not run when copied to other hardware. Access levels (read/write/HMI protection with passwords) control who can connect to the CPU at all — this one belongs to security, not IP.
Our honest recommendations
- Protect library function blocks that embody real technology — your winding algorithm, your patented sequence. Leave the machine-specific coordination code open: the customer’s maintenance team must diagnose at 3 a.m. without you.
- Fully-locked machines age badly. Businesses close, passwords get lost, and we regularly meet ten-year-old machines that cannot be modified — the eventual result is a rip-out retrofit that erases the builder’s IP anyway.
- Put the protection agreement in the contract explicitly: which blocks, who holds passwords, what happens on insolvency (escrow).
FAQ
Can protection be cracked? Assume any determined attacker with physical access eventually wins. Protection raises the cost of casual copying; it is not a substitute for commercial trust.
Does protection survive upgrades? Protected blocks migrate between Portal versions, but keep the original sources safe — you cannot edit what you cannot open, including your own blocks after a personnel change.
Zone Otomasyon writes machine software with a documented open/protected split both sides can live with. Discuss your policy.