Global constants definition problem

[Weng Tianxiang]

Hi,
Help is needed.

I have some global constants shared among several modules, so I
set up a file to define a global package like the following:

Package MG_x_Constant is
constant DATA_BITS : integer := 16;
constant DATA_RANGE : real := (2.0**16);
-- constant DATA_BITS : integer := 64;
-- constant DATA_RANGE : real := (2.0**64);


-- used in all test bench
constant DATABITS : integer := DATA_BITS;

end MG_x_Constant;

Package body MG_x_Constant is
....
end MG_x_Constant;

In other modules, DATA_BITS, DATABITS are freely used.

This morning I found a problem:
when I changed DATA_BITS from 16 to 64, the ModelSim
sim window still shows constant DATABITS = 16 and it never changed,
even though I tried to delete the module from library and
re-compile it again. constant DATABITS = 16 doesn't change.

IN compilation order, the global package definition file is always the
first one.

I though if the global constant definition changes, all its appearance
should change, but it doesn't. Why?

What is wrong with the above statements?

Thank you.

Weng

 

[Jozsef]

Hello,
Try to recompile ALL sources which references to this package. I think
about modelsim don't check & update referenced variables under
compilation process in other sources.

Best regards

 

[Weng Tianxiang]

Hello,
Try to recompile ALL sources which references to this package. I think
about modelsim don't check & update referenced variables under
compilation process in other sources.

Best regards

Hi Jozsef,
I re-compiled every modules, but the constants in global package don't
change as if they were compiled once and never re-compiled again.

I even deleted all work directory contents, recompile every modules,
but constants in the global package still don't change.

That is what I have experienced.

Any other ideas?

Weng

 

[Mike Treseler]

I even deleted all work directory contents, recompile every modules,
but constants in the global package still don't change.

Maybe they are declared in more than one place.

-- Mike Treseler

 

[Weng Tianxiang]

Maybe they are declared in more than one place.

-- Mike Treseler

Hi MIke,
Never!

I tried to move all constant definitions from package entity module to
package body module, all constants usage are errors.

Weng

 

[Weng Tianxiang]

Hi MIke,
Never!

I tried to move all constant definitions from package entity module to
package body module, all constants usage are errors.

Weng

Hi,
Is it possible that the error happens because I have used 2 levels of
constants:

constant DATA_BITS : integer := 16; <-- I change this value,
constant DATABITS : integer := DATA_BITS; <-- this value doesn't
change

Weng

 

[Brian Drummond]

I re-compiled every modules, but the constants in global package don't
change as if they were compiled once and never re-compiled again.

I even deleted all work directory contents, recompile every modules,
but constants in the global package still don't change.

I've just been through something similar. What happened in my case was:

the package was compiled into a library, and included in my desigh via
"Library/Use" statements.

The library was mapped into a particular Modelsim directory, and this
mapping was stored in modelsim.ini, in the directory where I was working
on the package.

Later, when I worked on the design, I found it using an OLD version of
the package - because its mapping for that library was in a DIFFERENT
modelsim.ini file (because the design was in a different place from the
package).

I got into this mess because this project was a combination of two older
ones, and not a fresh start.

This may not be your problem, but it's worth checking the library
mapping paths in ALL relevant versions of modelsim.ini are what you
expect.

- Brian

 

[Weng Tianxiang]

I've just been through something similar. What happened in my case was:

the package was compiled into a library, and included in my desigh via
"Library/Use" statements.

The library was mapped into a particular Modelsim directory, and this
mapping was stored in modelsim.ini, in the directory where I was working
on the package.

Later, when I worked on the design, I found it using an OLD version of
the package - because its mapping for that library was in a DIFFERENT
modelsim.ini file (because the design was in a different place from the
package).

I got into this mess because this project was a combination of two older
ones, and not a fresh start.

This may not be your problem, but it's worth checking the library
mapping paths in ALL relevant versions of modelsim.ini are what you
expect.

- Brian

Hi,
Thank you everyone who gave me an answer.

The problem is resolved, I would like to share the lesson
I learned from this experience.

1. Original code:
DATABITS_16_32_64 <= 64 when DATABITS = 64 else
32 when DATABITS = 32 else
16; -- for data bits between 4-16

BlockRAM_A: for I in 0 to 2 generate
BlockRAM_0: BlockRAM
generic map (
DATABITS => DATABITS_16_32_64,
DEPTH => LEVEL_X)
port map (
...
);
end generate;

The problem is the following statement:
DATABITS_16_32_64 <= 64 when DATABITS = 64 else
32 when DATABITS = 32 else
16; -- for data bits between 4-16

I thought DATABITS_16_32_64 was assigned value before it was used
in generic map, but it is wrong.

Because block BlockRAM_A and DATABITS_16_32_64 assignment statement
are in concurrent area, DATABITS_16_32_64 in generate map (...)
doesn't use the value it is assigned to in the above statement.
When loading, ModelSim immediately reports
error for situation of DATABITS = 16 so that it seems to me that
global variable DATABITS doesn't change.

1. The answers everyone gave show unanimously that
the grammar I used in global file is right;
2. So I abandoned my original idea to search for other clues.
3. Luckyly, I found the error after one day rest about the problem.

The following is the right coding for the segment:

BlockRAM_A: for I in 0 to 2 generate
BlockRAM_64 : if DATABITS = 64 generate
BlockRAM_0: BlockRAM
generic map (
DATABITS => 64,
DEPTH => LEVEL_X)
port map (
...
);
end generate;

BlockRAM_64 : if DATABITS = 32 generate
BlockRAM_0: BlockRAM
generic map (
DATABITS => 32,
DEPTH => LEVEL_X)
port map (
...
);
end generate;

BlockRAM_64 : if(DATABITS /= 64 and DATABITS /= 32) generate
BlockRAM_0: BlockRAM
generic map (
DATABITS => 16,
DEPTH => LEVEL_X)
port map (
...
);
end generate;
end generate;

Thank you.

Weng

 

[jr]

Weng Tianxiang:

1. Original code:
DATABITS_16_32_64 <= 64 when DATABITS = 64 else
32 when DATABITS = 32 else
16; -- for data bits between 4-16

Why do you make DATABITS_16_32_64 a signal? All your problems derive from
that. It looks like a constant to me.

Something like this would evaluate before the generic maps:
constant DATABITS_16_32_64: integer := (((DATABITS-1)/16)+1)*16;

DATABITS 4 to 16 : DATABITS_16_32_64 is 16
DATABITS 32 : DATABITS_16_32_64 is 32
DATABITS 64 : DATABITS_16_32_64 is 64.

Other cases irrelevant, I assume.

 

[Weng Tianxiang]

Weng Tianxiang:




Why do you make DATABITS_16_32_64 a signal? All your problems derive from
that. It looks like a constant to me.

Something like this would evaluate before the generic maps:
constant DATABITS_16_32_64: integer := (((DATABITS-1)/16)+1)*16;

DATABITS 4 to 16 : DATABITS_16_32_64 is 16
DATABITS 32 : DATABITS_16_32_64 is 32
DATABITS 64 : DATABITS_16_32_64 is 64.

Other cases irrelevant, I assume.

Hi Jr,
Wow! Wonderful !!!

Your answer is very clever and absolute better than mine. I will use
your code immediately without any conditions.

I learned a trick from you.

Thank you very much.

Weng