The following architecture is a first attempt at the register
The use of 'STABLE detects for setup violations in the data input
ARCHITECTURE first_attempt OF 8_bit_reg IS
BEGIN
PROCESS (clk)
BEGIN
IF (enable = '1') AND a'STABLE(x_setup) AND
(clk = '1') THEN
b <= a AFTER prop_delay;
END IF;
END PROCESS;
END first_attempt;
