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22nd November 2006, 05:25 #1
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vhdl addition
Hi Guys
Can anyone pls tell me how to do binary addition with vectors...
i tried to do but it gives me a error as "Type error resolving infix expression "+" as type std_logic_vector."
Code VHDL  [expand] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Library IEEE; Use Ieee.std_logic_1164.all; entity add is Port( a: in std_logic_vector(3 downto 0) ; sum:out std_logic_vector(3 downto 0) ); end add; architecture behav of add is signal tmp : std_logic_vector(3 downto 0); begin tmp <= a(0) + a(1) +a(2) + a(3) when en = '1' else "0000"; sum <= tmp; end behav;
Last edited by andre_teprom; 4th March 2014 at 02:20. Reason: added VHDL syntax formatting

22nd November 2006, 05:25

22nd November 2006, 07:50 #2
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addition in vhdl
Hi!
Just add:
1. Use Ieee.std_logic_unsigned.all;
2. en: in std_logic;
3. you have to extend a(0), a(1) etc to 4bit by "000"&
Have a nice day!
Code:Library IEEE; Use Ieee.std_logic_1164.all; Use Ieee.std_logic_unsigned.all; entity add is Port( a: in std_logic_vector(3 downto 0) ; en: in std_logic; sum:out std_logic_vector(3 downto 0) ); end add; architecture behav of add is signal tmp : std_logic_vector(3 downto 0); begin tmp <= (("000"&a(0)) + ("000"&a(1))+ ("000"&a(2)) + ("000"&a(3))) when en = '1' else "0000"; sum <= tmp; end behav;

22nd November 2006, 10:51 #3
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vhdl std_logic_vector addition
Originally Posted by dunets
Thanks a lot for your help.
tama

22nd November 2006, 10:51

25th November 2006, 05:45 #4
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vhdl binary addition
Originally Posted by s3034585
include the foolowing libraries
arith and unsigned too then they will executed

26th November 2006, 07:35 #5
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addition vhdl
i prefer the numeric lib instead of arth lib, the latter is synopsys prepoerity.

26th November 2006, 07:35

2nd March 2014, 08:44 #6
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Re: how to go Binary addition in vhdl with vectors
can someone please explain to me what this does ("0000"&a(0)) in this particular line of text below. the exact code is in one of the replies on this thread
Code:tmp <= (("000"&a(0)) + ("000"&a(1))+ ("000"&a(2)) + ("000"&a(3))) when en = '1' else "0000"; sum <= tmp;

2nd March 2014, 12:42 #7
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Re: how to go Binary addition in vhdl with vectors
It creates a vector. a(0) is a single bit. Only vectors of type signed or unsigned can be added together.

2nd March 2014, 13:09 #8
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Re: how to go Binary addition in vhdl with vectors
The code calculates the number of '1' bits in input vector a. Is this what you want to achieve?
The question title might suggest that you want to add multiple vectors. But there's only one input vector.
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