I have to do a instantation of several components

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I suppose the code for this instantation would be something like this:

componentA: componentB port map(
output_ca => input_cb
componentA: componentC port map(
output_ca => input_cc

But I know that part of the code before is wrong, because 'ouput_ca' has 6 bits and input_cb, and input_cc has only 3 bits every one of them. How would be written this code in a good way? Thank you so much for your help.


1 Answer 1


You must use some signals, you can't map straight from one pin to another (I'm also using direct instantiation to avoid creating component declarations - see also my answer here):

signal aout : std_logic_vector(5 downto 0);

A: entity work.componentA port map(
    output_pin => aout
B: entity work.componentB port map(
    input_pin => aout(5 downto 3)
C: entity work.componentC port map(
    input_pin => aout(2 downto 0)


You seem to be confused in your instantiation syntax. You wrote:

componentA:componentB port map (...

implying that componentA connects to component B.

What is actually being said is

individual_name_of_component: name_of_entity

So you pick an entity which you are instantiating on the right of the : and give it a name on the left.

  • \$\begingroup\$ Cool, I didn't know about direct instantiation. I always hated keeping component declarations in sync. \$\endgroup\$
    – ajs410
    Jul 12, 2011 at 18:09

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