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Forum: FPGA, VHDL & Verilog VHDL fill rest of the vector in assignment


VHDL fill rest of the vector in assignment
von Václav (Guest)

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Hello,
I'd like to assign a value to an std_logic_vector, and fill the rest of 
the vector with zeros. The length of the vector is defined with a 
generic or a constant.
So it would be like this (but this does not work):

signal my_signal : std_logic_vector(CONST_WIDTH downto 0);
my_signal <= (others => '0') & x"2";

It could be done with a for generate statement, but are there any 
shorter and nicer solutions?

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Re: VHDL fill rest of the vector in assignment
von Lothar M. (Company: Titel) (lkmiller) (Moderator)

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Václav wrote:
> but are there any shorter and nicer solutions?
Have a look for the resize() function in the numeric_std lib.
But keep in mind: this function only works for signed and unsigned 
vectors, not for a std_logic_vector.

: Edited by Moderator
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Re: VHDL fill rest of the vector in assignment
von Václav (Guest)

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Oh this does it, as long as DMEM_ADDR_W is 5 or greater:

1
tb_addr <= (DMEM_ADDR_W-1 downto 4 => '0') & x"2";

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Re: VHDL fill rest of the vector in assignment
von tuna (Guest)

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tb_addr <= (1 => '1', others => '0');    --bit 1 is '1' and other bits 
are '0'

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