This paper aims at the development of an execution model of function block networks following the IEC 61499 standard architecture for industrial measurement and control systems. Implementation of the standard requires an execution environment that is deterministic, provides real-time reactivity, and is compact to fit embedded platforms. In particular, this paper discusses the problem of function block scheduling that would be the core of such exection environment. The function blocks are modeling by Net Condition/Event Systems (NCES). It is shown that the NCES implementation provides a natural scheduling policy for function blocks that preserves concurrency and enables evaluation of the reactivity by model-checking