VHDL之concurrent之block

1　　Simple BLOCK

　　The simple block represents only a way of partitioning the code. It allows concurrent statements to be clustered into a BLOCK, with the

purpose of turning a set of concurrent statements to be more readable and more manageable.　　

label: BLOCK
    [declarative part]
BEGIN
    (concurrent statements)
END BLOCK label;

2　　Guarded BLOCK

　　A guarded BLOCK includes an additional expression, called guard expression. A guard statement in a guarded BLOCK is executed only when

the guard expression is TRUE.

label: BLOCK (guard expression)
    [declarative part]
BEGIN
    (concurrent guarded and unguarded statements)
END BLOCK label;