full adder example using fpga

[Amit]

Hello group,

Does anybody know about an online resource that I can find some
samples on how to implement a full adder using LUT? either using
Flex10k or any other classical methods?

I've started learning FPGA and have done something but need to compare
it.

Regards,
Amit

 

[KJ]

Hello group,

Does anybody know about an online resource that I can find some
samples on how to implement a full adder using LUT?

Google lists about 19000

http://www.google.com/search?hl=en&q=VHDL+full+adder

KJ

 

[Ralf Hildebrandt]

Does anybody know about an online resource that I can find some
samples on how to implement a full adder using LUT? either using
Flex10k or any other classical methods?

Usually you don't need to think about every single fulladder. Just use
result<=a+b; -- all signals are vectors of type signed or unsigned

For a single fulladder you could use:

signal result : unsigned(1 downto 0);
signal a,b,c_in : std_ulogic;
signal sum,c_out : std_ulogic;

result<=unsigned('0' & a) + unsigned('0' & b) + unsigned('0' & c_in);
sum<=result(0);
c_out<=result(1);


Ralf

 

[Andy]

Usually you don't need to think about every single fulladder. Just use
result<=a+b; -- all signals are vectors of type signed or unsigned

For a single fulladder you could use:

signal result : unsigned(1 downto 0);
signal a,b,c_in : std_ulogic;
signal sum,c_out : std_ulogic;

result<=unsigned('0' & a) + unsigned('0' & b) + unsigned('0' & c_in);
sum<=result(0);
c_out<=result(1);

Ralf

It's even easier with integers:

signal a,b,sum,c_in,c_out : integer range 0 to 1;

sum <= (a + b + c_in) mod 2;
c_out <= (a + b + c_in) / 2;

Andy

 

[Mike Treseler]

It's even easier with integers:

Easier still, if I let synthesis wire up the carries

-- Mike Treseler

 

[Amit]

Easier still, if I let synthesis wire up the carries

-- Mike Treseler

Thanks to all,

But maybe I didn't ask the question properly or I had to post in a
different group (I'm sure doesn't exist). My concern is not regarding
VHDL sytnax but trying to understand how to tacking the flow on a
Flex10K diagram.

I apologize all for this.

However, if somebody knows this I will be more than happy to have your
help.

Regards,
Amit