dimension of an integer

[Max]

How can I obtain the dimension in bit of an integer?

I have a generic, and I need to store its value in a std_logic_vector,
but I don't know the dimansion of this vector.

thanks

 

[Johan Wouters]

Max wrote:

How can I obtain the dimension in bit of an integer?

I have a generic, and I need to store its value in a std_logic_vector,
but I don't know the dimansion of this vector.

thanks

Maybe you can use attributes such as 'high and 'low etc?
--
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Johan Wouters === Easics NV
Senior ASIC designer === a TranSwitch Company
Tel: +32-16-395 616 === System-on-Chip Design
Fax: +32-16-395 619 Interleuvenlaan 86, B-3001 Leuven, BELGIUM
mailto:johanw@easics.be http://www.easics.com

 

[Jim Lewis]

Assignments to unconstrained integer signals typically
result in 32 bit signed hardware.

For synthesis, I only recommend using integers
as literal values numeric expressions:
Y <= '1' when A > 12 else '0' ;
Count <= Count + 1 ;

In this case you don't need any conversions, it
works because of the overloading.


For a quick tutorial on VHDL overloading, conversions, ... see my
MAPLD paper, VHDL Math Tricks of the Trade. It is available
at http://www.synthworks.com/papers

Cheers,
Jim Lewis
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jim Lewis
Director of Training mailto:Jim@SynthWorks.com
SynthWorks Design Inc. http://www.SynthWorks.com
1-503-590-4787

Expert VHDL Training for Hardware Design and Verification
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Max wrote:

How can I obtain the dimension in bit of an integer?

I have a generic, and I need to store its value in a std_logic_vector,
but I don't know the dimansion of this vector.

thanks

 

[Allan Herriman]

On Fri, 19 Sep 2003 09:03:13 -0700, Jim Lewis <Jim@SynthWorks.com>
wrote:

Assignments to unconstrained integer signals typically
result in 32 bit signed hardware.

Max was asking how to determine the range for an slv that would hold
an integer of a particular value.

http://groups.google.com/groups?as_q=log2&as_ugroup=comp.lang.vhdl

Regards,
Allan.

 

[sean]

cialdi@firenze.net (Max) wrote in message

How can I obtain the dimension in bit of an integer?

I have a generic, and I need to store its value in a std_logic_vector,
but I don't know the dimansion of this vector.

If you use the CONV_STD_LOGIC_VECTOR function in std_logic_arith you
specify the number of bits for the resulting vector, eg

CONV_STD_LOGIC_VECTOR(5, 4) returns a 4-bit vector "0101"

Other conversion functions have the same arguments.

If you want an integer-type signal to be synthesised with a certain
number of bits, you define the range when you declare the signal, eg

signal blahblah : integer range 0 to 15; will synthesise to a 4 bit
signal.

Sean