Asynchronous Signal Message
You define a Message as an asynchronous signal message by displaying the Properties window for the Message and setting the 'Synch' field to 'Asynchronous', and the 'Kind' field to 'Signal'. A synchronous message cannot be used to convey signals, so setting the 'Synch' field to 'Synchronous' disables the 'Kind' field.
'Return Value', 'Assign To' and the, which are not applicable to asynchronous signals, are disabled.
The Operations button changes to a, which you click on to associate the asynchronous signal message with a Signal element in the model. You can type the arguments corresponding to the Signal attributes into the 'Argument(s)' field.
When you click on the Signal button, the 'Select Signal' dialog displays, through which you locate and select the required Signal element.