Baseline Version of Max+Plus II can not use Bi-Direction?

[mountain]

I did a simulation of a sample in my Max+Plus II 10.23
the sample is:
**broken link removed**
bidir.vhd (Tri-state bus implementation)


--************************
LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

ENTITY bidir IS
PORT(
bidir : INOUT STD_LOGIC_VECTOR (7 DOWNTO 0);
oe, clk : IN STD_LOGIC;
inp : IN STD_LOGIC_VECTOR (7 DOWNTO 0);
outp : OUT STD_LOGIC_VECTOR (7 DOWNTO 0));
END bidir;

ARCHITECTURE cpld OF bidir IS
SIGNAL a : STD_LOGIC_VECTOR (7 DOWNTO 0); -- DFF that stores
-- value from input.
SIGNAL b : STD_LOGIC_VECTOR (7 DOWNTO 0); -- DFF that stores
BEGIN
-- feedback value.
PROCESS(clk)
BEGIN
IF clk = '1' AND clk'EVENT THEN -- Creates the flipflops
a <= inp;
outp <= b;
END IF;
END PROCESS;

PROCESS (oe, bidir) -- Behavioral representation
BEGIN -- of tri-states.
IF( oe = '0') THEN
bidir <= "ZZZZZZZZ";
b <= bidir;
ELSE
bidir <= a;
b <= bidir;
END IF;
END PROCESS;

END cpld;

--*****************

But the result of the simulation occured problem. So I doubt my Max+Plus
II has problem? maybe license has problem?
Is it said that the Baseline Version of Max+Plus II 10.23 can not use bi-directional port?