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Forum: FPGA, VHDL & Verilog vhdl equivalent of verilog


Author: Hareesh Mohanan (Company: Mindteck) (hareeshp)
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hi,

can anyone tell me the vhld equivalent of below number
 20'h08000 

Author: Lothar Miller (lkmiller) (Moderator)
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It's x"08000" or 16#08000#

Author: C. A. Rotwang (Guest)
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Lothar M. wrote:
> It's x"08000" or 16#08000#

Depends on type. 16#*# works for integer; x"*" for std_logic_vector and 
alike. The later is restricted to vectors with width 
4,8,12,16,20,..,4*n.

https://stackoverflow.com/questions/38777859/vhdl-...

Author: Hareesh Mohanan (Company: Mindteck) (hareeshp)
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Lothar M. wrote:
> It's x"08000" or 16#08000#

but for hex, decimal and binary all have x kind of representation?

Author: C. A. Rotwang (Guest)
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Hareesh M. wrote:
> Lothar M. wrote:
>> It's x"08000" or 16#08000#
>
> but for hex, decimal and binary all have x kind of representation?

No.

Author: Hareesh Mohanan (Company: Mindteck) (hareeshp)
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C. A. Rotwang wrote:
> Hareesh M. wrote:
>> Lothar M. wrote:
>>> It's x"08000" or 16#08000#
>>
>> but for hex, decimal and binary all have x kind of representation?
>
> No.

could you suggest any document for this?

Author: C. A. Rotwang (Guest)
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Hareesh M. wrote:
> C. A. Rotwang wrote:
>> Hareesh M. wrote:
>>> Lothar M. wrote:
>>>> It's x"08000" or 16#08000#
>>>
>>> but for hex, decimal and binary all have x kind of representation?
>>
>> No.
>
> could you suggest any document for this?

See the stackoverflow-link above.
For Details about the x" representation at std_logic_vector and so see 
the source Code of the according libraries:
https://standards.ieee.org/downloads/1076/1076.2-1996/
For uses of literals written as 16#* alike, see 
http://vhdl.renerta.com/mobile/source/vhd00041.htm

Over and Out,

Author: C. A. Rotwang (Guest)
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Supplement:

You must disitinct between "numeric literals" and "bit vector literals".

See reference guide 
http://www.ics.uci.edu/~jmoorkan/vhdlref/literals.html.
Note the reference to the VHDL Language Reference Manual (LRM) sections 
in the head of the page.

Author: Markus F. (mfro)
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Author: Hareesh Mohanan (Company: Mindteck) (hareeshp)
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Lothar M. wrote:
> It's x"08000" or 16#08000#

but how can i represent the no: of bits

Author: Vancouver (Guest)
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You cant't. Number of bits is always number of digits*4. If you need 
another number of bits, you need to create a subvector:

y <= X"1200";        --  16bit vector
z <= y(12 downto 0); --  13bit subvector

Author: Hareesh Mohanan (Company: Mindteck) (hareeshp)
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Vancouver wrote:
> You cant't. Number of bits is always number of digits*4. If you need
> another number of bits, you need to create a subvector:
>
> y <= X"1200";        --  16bit vector
> z <= y(12 downto 0); --  13bit subvector

actually i want to initialize as constant and need to call in a case 
statement.

Author: Markus F. (mfro)
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Hareesh M. wrote:
> Lothar M. wrote:
>> It's x"08000" or 16#08000#
>
> but how can i represent the no: of bits

If your toolset supports VHDL 2008, you can define literals with a 
leading length indicator:
17x"08000"

will create a 17 bit wide constant.

Author: Vancouver (Guest)
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Anyway, afaik there is no way in VHDL to specify the exact number of 
bits in a hexadecimal constant.

You could say something like "00"&x"1200" for 18bit. Or you can use the 
to_unsigned conversion function of numeric.std which takes the number of 
bits as parameter. See p.17 in

http://www.synthworks.com/papers/vhdl_math_tricks_...


But there is no nice shortcut like in Verilog.

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