EmbDev.net

Forum: FPGA, VHDL & Verilog Bitwise OR of std_logic_vector


Author: Hamidreza Ahmadian (Company: Uni Siegen) (ahmadian)
Posted on:

Rate this post
0 useful
not useful
Hello,

Suppose we have 4 buffer, each has a single bit which indicates if the 
buffer is empty and we connect this pin to the bellow signal.

signal buffer_empty       : std_logic_vector (3 downto 0);

Each bit of the above signal indicates whether the corresponding buffer 
is empty or not and the below signal indicates whether we have an empty 
buffer al all.

signal any_buffer_empty   : std_logic;

The second signal can be assigned as follows:

any_buffer_empty <= buffer_empty (0) and buffer_empty (1) and 
buffer_empty (2) and buffer_empty (3);

Now the problem gets difficult for me if the number of buffers is 
parameterized (by a generic or constant like NR_BUFF) and I cannot 
figure out how to calculate the second signal in this case.

Thanks in advance,
Hamid

Author: Lothar Miller (lkmiller) (Moderator)
Posted on:

Rate this post
0 useful
not useful
Hamidreza A. wrote:
> and I cannot figure out how to calculate the second signal in this case.
Check out the package reduce_pack and in there the functions or_reduce() 
as well as and_reduce().

See this also:
http://www.edaboard.com/thread253196.html

: Edited by Moderator
Author: Stefan Weide (Guest)
Posted on:

Rate this post
1 useful
not useful
You can also use the following
  -- bit-wise or
  any_buffer_empty <= '0' when buffer_empty=(buffer_empty'range=>'0') else
                      '1';
  --bit-wise and
  all_buffer_empty <= '1' when buffer_empty=(buffer_empty'range=>'1') else
                      '0';

Reply

Entering an e-mail address is optional. If you want to receive reply notifications by e-mail, please log in.

Rules — please read before posting

  • Post long source code as attachment, not in the text
  • Posting advertisements is forbidden.

Formatting options

  • [c]C code[/c]
  • [avrasm]AVR assembler code[/avrasm]
  • [vhdl]VHDL code[/vhdl]
  • [code]code in other languages, ASCII drawings[/code]
  • [math]formula (LaTeX syntax)[/math]




Bild automatisch verkleinern, falls nötig
Note: the original post is older than 6 months. Please don't ask any new questions in this thread, but start a new one.