Hardware and software

• Inventory of every CPU, I/O module, drive and HMI, with firmware versions

• Current program backups, verified to match what is running

• Source code with comments, or confirmation that none exists

• Licences for current engineering software

• List of networked devices and addresses

• Spare-parts stock and supplier status for each component

Documentation

• Electrical drawings checked against the installed panel

• Safety function list and most recent risk assessment

• Interface list to upstream and downstream machines

• Recipe and format data, with owner

Operations

• Available shutdown windows for the next 12 months

• Acceptable restart rate after cutover

• Operators and technicians available for training

• Known faults and workarounds collected from operators

• Current downtime and MTTR baseline

Migration plan

• Target platform agreed with maintenance and IT

• Coding standard agreed

• Simulation approach for logic testing

• Panel pre-wiring and FAT plan

• Cutover sequence with go/no-go points

• Fallback plan if cutover fails

• Safety reassessment scope

• Documentation deliverables agreed

• Support arrangement after go-live