thx for all.
I have implemented the IEEE 754 std and it works fun.
I have an other question: I have implemented a concurrency project (using IRQ and sw event).
in this project, I checks the status of IRQ3 if it is not activated I try to active it using this code:
NVIC_DisableIRQ(EINT3_IRQn); // Enable IRQ3
NVIC_EnableIRQ(EINT3_IRQn); // Enable IRQ3
but it still already not activated.