Second argument of write must have a constant value.

Hello there,

I'm rather new to VHDL and find this piece of code perfectly legitimate:

architecture Behavioral of writer is
file FP: TEXT open write_mode is "output.txt";
begin
process (write) is
variable l : line;
variable data : std_logic_vector(63 downto 0);
begin
if (rising_edge(write)) then
data := DATA_in;
write(l,data);
writeline(FP,l);
end if;
end process;

end Behavioral;

But my analyzer disagrees, and says: "Second argument of write must have
a constant value." What should I do to please my analyzer?

--
"Now the storm has passed over me
I'm left to drift on a dead calm sea
And watch her forever through the cracks in the beams
Nailed across the doorways of the bedrooms of my dreams"

Nikola Skoric

Nikola Skoric <nick-> writes:

> I'm rather new to VHDL and find this piece of code perfectly legitimate:
[...]
> process (write) is

I wouldn't reuse that function name for a signal.

Cheers,
Colin

Colin Marquardt

I'm guessing that you're using textio:

write(L, VALUE, JUSTIFY, FIELD); -- Write one value to "line" L from
variable VALUE
* Data_type of VALUE can be bit, bit_vector, integer, real,
character, string, or time.
* JUSTIFY is "left" or "right" to justify within the field
* FIELD is the desired field width of the written value


You must convert the value from std_logic_vector to bit_vector before
write will accept it.

ghelbig@lycos.com

In article < .com>,
says...
> I'm guessing that you're using textio:
>
> write(L, VALUE, JUSTIFY, FIELD); -- Write one value to "line" L from
> variable VALUE
> * Data_type of VALUE can be bit, bit_vector, integer, real,
> character, string, or time.
> * JUSTIFY is "left" or "right" to justify within the field
> * FIELD is the desired field width of the written value
>
>
> You must convert the value from std_logic_vector to bit_vector before
> write will accept it.

Oh, right. Thanks. Works now.

While we're at it, can you recommend me some kind of VHDL reference? For
instance, this code I've written dumps a series of bits to the file...
and now I'd like to convert that bit_vector to string containing hex
digits. Where do I start seraching for such a function?

--
"Now the storm has passed over me
I'm left to drift on a dead calm sea
And watch her forever through the cracks in the beams
Nailed across the doorways of the bedrooms of my dreams"

Nikola Skoric

Nikola Skoric <nick-> writes:

> and now I'd like to convert that bit_vector to string containing hex
> digits. Where do I start seraching for such a function?

Check out image_pb.vhd on
http://members.aol.com/vhdlcohen/vhdl/Models.html, or the packages
on http://bear.ces.cwru.edu/vhdl/

Cheers,
Colin

Colin Marquardt