A process may contain a number of signal assignment statements for a
given signal, which together form a driver for the signal. Normally there
may only be one driver for a signal, and so the code which determines a
signals value is confined to one process.
A process is activated initially during the initialisation phase of
simulation. It executes all of the sequential statements, and then repeats,
starting again with the first statement. A process may suspended itself by
executing a wait statement. This is of the form: