In this paper, we are interested to control applications designed using the component based standard IEC61499. In this standard, a function block is de- fined as an event trigger component containing its own data. Two versions of the standard have been proposed. In the first version, function block selects only one event among simultaneous input event occurrences. In the second one, it contains a limited buffer to store them. In the two cases, some occurrences may be lost due the buffer limitation leading to non predictable behavior. We propose a schedulability condition to avoid any loosing phenomena in blocks.