I am almost certain that my Quartus II web 13.1 program creates RTL schematics with errors in them. (I have not upgraded the installation afterwards because my computer is offline!).

And below is another example of VHDL code that perfectly works in Xilinx ISE (not Spartan3E but with higher FPGA's only!) but never works in Quartus:

--BRAM_16x2 page194 Vaibbhav Taraate.

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

entity BRAM_16x2 is

port (q_out : out std_logic_vector (1 downto 0);

write_en : in std_logic;

clk: in std_logic;

d_in: in std_logic_vector (1 downto 0);

a_in: in std_logic_vector (3 downto 0));

end BRAM_16x2;

architecture BRAM_arch of BRAM_16x2 is

component BRAM_16x1S is

port(O : out std_logic;

D: in std_logic;

A3, A2, A1, A0: in std_logic;

WE, W_CLK: in std_logic);

end component;

begin

U0: BRAM_16x1S port map (O =>q_out(0), WE =>write_en, W_CLK =>clk, D =>d_in(0),

A0 =>a_in(0), A1 =>a_in(1), A2 =>a_in(2), A3 =>a_in(3));

U1: BRAM_16x1S port map (O =>q_out(1), WE => write_en, W_CLK => clk, D =>d_in(1),

A0 =>a_in(0), A1 =>a_in(1), A2 =>a_in(2), A3 =>a_in(3));

end BRAM_arch;

--------------Which gives following error rapport in Quartus II 13.1 but works in ISE! -------

Warning (20028): Parallel compilation is not licensed and has been disabled

Warning (12125): Using design file bram_16x2.vhd, which is not specified as a design file for the current project, but contains definitions for 2 design units and 1 entities in project

Info (12022): Found design unit 1: BRAM_16x2-BRAM_arch

Info (12023): Found entity 1: BRAM_16x2

Error (12006): Node instance "U0" instantiates undefined entity "BRAM_16x1S"

Error (12006): Node instance "U1" instantiates undefined entity "BRAM_16x1S"

Error: Quartus II 32-bit Analysis & Synthesis was unsuccessful. 2 errors, 2 warnings

Error: Peak virtual memory: 393 megabytes

Error: Processing ended: Mon May 11 17:13:47 2020

Error: Elapsed time: 00:00:02

Error: Total CPU time (on all processors): 00:00:02

Error (293001): Quartus II Full Compilation was unsuccessful. 4 errors, 2 warnings