  In this report we describe a tool framework for certifying properties of
PLCs: CERTPLC. CERTPLC can handle PLC descriptions provided in the Sequential
Function Chart (SFC) language of the IEC 61131-3 standard. It provides routines
to certify properties of systems by delivering an independently checkable
formal system description and proof (called certificate) for the desired
properties. We focus on properties that can be described as inductive
invariants. System descriptions and certificates are generated and handled
using the COQ proof assistant. Our tool framework is used to provide supporting
evidence for the safety of embedded systems in the industrial automation domain
to third-party authorities. In this document we describe the tool framework:
usage scenarios, the archi-tecture, semantics of PLCs and their realization in
COQ, proof generation and the construction of certificates.
