The use of analysis techniques for improving quality of software for industrial controllers is widely used. Mainly Simulation and Formal Verification can be used as complementary techniques improving dependability of mechatronic systems behavior. In this paper there are used Simulation and Formal Verification for guaranteeing safe software for Programmable Logic Controllers, mainly related with using Function blocks of IEC 61131-3 standard. For studying, simulating and verifying behavior of those blocks are used timed automata, as modeling formalism, and UPPAAL, as tool for simulation and Formal Verification purposes.