(-1)*xn operation in FPGA

Well, that's what you have to do if you want to form the 2's complement of a number. Depending on the application, you may be able to get away with less. For example, if you're computing A minus B, you invert the bits in B, put A and B into an adder, and inject a 1 into the adder carry-in to get the increment--no need for an extra adder.

Or you could always write c = a - b and let Verilog do the work.

There's more on binary arithmetic here:

Bob Perlman Cambrian Design Works

Hi,

SunLei schrieb:

The sollution of inverting every single bit is easy in (V)HDL (unlike to C). a

-xn works the same way in VHDL as it is does in C. The signal (or variable) xn being defined to be the appropriate type:

signal xn, something: signed (15 downto 0); -- Example 1 signal xn, something: integer range -32768 to 32767; -- Example 2

....

something