Sequential circuits refer to the combinational logic circuits that consist of input variables (X) and logic gates (or Computational circuits) along with the output variable (Z). For example, flip-flops, counter, register, clocks, etc.

1. SEQUENTIAL CIRCUITS
OVERVIEW

23. Attributes
Value-type Attributes
◦ T’LEFT : Returns left bound of a type
◦ T’RIGHT : Returns right bound of a type
◦ T’HIGH, T’LOW
◦ E.g. Type my_array is (15 downto 0) of bit;
◦ Variable a:bit;
◦ a:=my_array’left; -- returns 15
◦ Variable len:integer;
◦ Len := my_array’length -- returns 16

24. Attributes
Function-type Attributes
◦ ‘pos(value)
◦ ‘val(value)
◦ ‘succ(value)
◦ ‘pred(value)
◦ Function Signal Attributes
◦ ‘event --returns true if event occurred during current delta
◦ ‘last_event -- returns time elapsed since last event occurred
◦ ‘last_value -- returns values before last event
◦ ‘stable[(time)] --returns true if reference signal has no event for specified time

25. Attributes
◦Function Signal Attributes
◦ ‘range
◦ ‘reverse_range
◦ e.g.
Signal Arr: std_logic_vector(0 10 15);
For I in Arr’range loop
Statements
End loop;