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 MESSAGE COMMUNICATION PATTERN
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Two sender threads transmit information to a receiver thread  
with event data port connections.

The senders are periodic and the receiver is sporadicly dispatched 
by incomming messages.

The functional behavior of each thread is specified by a 
standard Behavior_Specification subclause. 
On the sender side, a random value is sent at complete time.
On the receiver side, if the received value is higher than 50 
the output data port is updated with the received value.

When the receiving input buffer is full, a SIZE_FIFO_ERROR 
is raised by the simulator.