NEWBIE TEST BENCH HELP?

Hi i'm a newbie of vhdl form italy.

I use this VHDL for an exam that i will do saturday, so is there a person
that can help me to learn in few hours how i can construct a test bench?

Thanks!

Massimiliano Bertei

Massimiliano Bertei wrote:
> Hi i'm a newbie of vhdl form italy.
>
> I use this VHDL for an exam that i will do saturday, so is there a person
> that can help me to learn in few hours how i can construct a test bench?

Hi, I'm a newbie of Italian from VHDL-land.

I use this Italian for an exam that I will do on Saturday, so is there a
person that can help me to learn Italian in a few hours so I will speak
it fluently?

Paul Uiterlinden

Paul Uiterlinden wrote:
> Massimiliano Bertei wrote:
> > Hi i'm a newbie of vhdl form italy.
> >
> > I use this VHDL for an exam that i will do saturday, so is there a
person
> > that can help me to learn in few hours how i can construct a test
bench?
>
> Hi, I'm a newbie of Italian from VHDL-land.
>
> I use this Italian for an exam that I will do on Saturday, so is
there a
> person that can help me to learn Italian in a few hours so I will
speak
> it fluently?
>
>

Paul, Isn't it better to post nothing if you have nothing to say?

Big K

Kiru:
It is true that vhdl can't be learned in a day.
It is also true that there are plenty of testbench
examples to be found here for anyone interested.
Until you have made some contribution to this group,
consider taking your own advice.

-- Mike Treseler

Mike Treseler

This is taken from a VHDL reference guide that I use for a quick
reference.

Testbench
Complete Definition:
Testbench is not defined by the VHDL Language Reference Manual and has
no
formal definition.

Simplified Syntax:
entity testbench_ent is

end entity testbench_ent;

architecture testbench_arch of testbench_ent is

signal declarations

component declarations

begin

component instantiations

stimuli (test vectors)

end architecture testbench_arch;

Description:
The testbench is a specification in VHDL that plays the role of a
complete
simulation environment for the analyzed system (unit under test, UUT).
A
testbench contains both the UUT as well as stimuli for the simulation.

The UUT is instantiated as a component of the testbench and the
architecture
of the testbench specifies stimuli for the UUT's ports, usually as
waveforms
assigned to all output and bidirectional ports of the UUT.

The entity of a testbench does not have any ports as this serves as an
environment for the UUT. All the simulation results are reported using
the
assert and report statements.

Examples:
Example 1

entity Test_Decoder_bcd is

end entity Test_Decoder_bcd;

architecture Struct_1 of Test_Decoder_bcd is

component Decoder_bcd is

port (

enable : in BIT;
led : in std_ulogic_vector(3 downto 0);
bcd : out BIT_VECTOR(1 downto 0));

end component Decoder_bcd;

signal bcd: BIT_VECTOR(1 downto 0) := "11";

signal Enable: BIT := '1';

signal led: std_ulogic_vector (3 downto 0);

begin

U1: Decoder_bcd port map (Enable,,led,bcd);

bcd <= "00" after 5 ns,
"01" after 15 ns,
"10" after 25 ns,
"11" after 35 ns;

assert bcd = "00" and led = "0001"
or bcd = "01" and led = "0010"
or bcd = "10" and led = "0100"
or bcd = "11" and led = "1000"
report "There is an incorrect value on the output led"
severity error;

end architecture Struct_1;

The design entity Test_Decoder_BCD is designed to verify correctness of
the
Decoder_BCD. This test bench applies stimuli to the bcd inputs and when
the
value of the sled signal is other than asingle '1' on the position
corresponding to the binary value of the bcd signal, with all other
bits equal
to zero, the listed error is reported.

Important notes:
Testbenches should allow automated verification of the UUT, with
reports on
success or failure of each sub-test.

In case of sequential units under test, a clock signal should be
supported in
the testbench. Typically, it is realized as a separate process in the
testbench architecture.

In order to stop the simulation with a testbench, stimuli are often
specified
inside a process which contains a non-conditional wait statement at the
end;
such statement suspends

charles.elias@wpafb.af.mil