Test bench

[john]

Hi,

I am using ISE10.1 and simulating the code using its own behavioral
simulator. It generated the VDHL test code for me which I modified and
developed later. The Spartan is reading an 8 bit parallel data bus and
write it to a RAM. I assigned the 8 bit parallel data bus with some
numbers in the VHDL test bench and can see them in the simulator.

Now, What I want to know is

1. How can I make the VHDL test bench file to read my made text file
and write the output results in the some text file too. Using ISE and
Modelsim? How can I define the location where I want o store the file?
Thanks
John

 

[Mike Treseler]

Now, What I want to know is

1. How can I make the VHDL test bench file to read my made text file
and write the output results in the some text file too.

I would write a stimulus process and a checking process in vhdl,
and an assert statement to check values.
I would use the text as a comment.

Using ISE and Modelsim?

Just modelsim and an editor.

How can I define the location where I want o store the file?

Text from assert and report statements goes to the modelsim terminal.
I can redirect it to a file if need be,
but I only really need one bit of data: pass or fail.

-- Mike Treseler

testbench example here:
http://mysite.verizon.net/miketreseler/

 

[KJ]

Hi,

1. How can I make the VHDL test bench file to read my made text file
and write the output results in the some text file too.

For some basics on reading and writing files refer to
http://www.eda.org/comp.lang.vhdl/FAQ1.html#files

Likely you'll want to be able to read and write std_logic_vector types since
that is likely the data type for your RAM I/O. Google for something like
"convert std_logic_vector to string" and you will probably be able to find a
package of functions that someone has put together that you can use. Things
like std_logic, integer, time (i.e. basic types that aren't vectors) can be
easily converted to strings like this
std_logic'image(xyz)
integer'image(xyz)
time'image(xyz)

But std_logic_vector'image(xyz) is not valid. It's not too difficult to
write your own function that loops through the elements of a
std_logic_vector assembling the string bit at a time...but then you'll be
asking for how to do this in hex...so like I said, Google a bit to see how
others have done it and you'll be moving up the learning curve as you do so.
Once you have such a package of your own you can reuse it on anything in the
future as well and will be part of your own personal toolkit of "things that
I wish I didn't have to create from scratch, but I did".

Using ISE and
Modelsim?
Modelsim

How can I define the location where I want o store the file?

That is part of the file_open function that is part of the VHDL language.
One of the parameters is the file/path name.

Also consider Mike's suggestion. Many times the reason people have for
wanting file I/O is for the purposes of verifying that their designs are
working correctly. But this can be done without any file I/O by creating a
testbench for your design that generates known stimulus and checks that the
outputs are correct using VHDL asserts.
Kevin Jennings