parallel scrambler implementation

[T. Irmen]

Hi,

my poly is G(x)= 1 + x^39 + x^58
and my databuswith ist 64bit.

And that´s my implementation:
( scramble_1s is the history of the scrambler, data_0 the data input, and
scrambled_s is current scrambling result )

scramble: process(scrambled_s,data_0,scrambled1_s)
variable scrambled_v : std_logic_vector(63 downto 0);
begin
if CLK'event and CLK = '1' then
for i in 0 to 17 loop
scrambled_v(i) := scrambled_v(7+i) XOR scrambled_v(46+i) XOR data_0(i);
end loop;
for i in 18 to 56 loop
scrambled_v(i) := scrambled_v(7+i) XOR scrambled1_s(i-18) XOR data_0(i);
end loop;
for i in 57 to 63 loop
scrambled_v(i) := scrambled1_s(i-57) XOR scrambled1_s(i-18) XOR
data_0(i);
end loop;
scrambled_s <= scrambled_v;
end if;
end process scramble;

Something goes wrong here, don´t know what

any suggestions?

thanks,
thomas

 

[T. Irmen]

Problem solved!

I used a generic prbs generator!

now it works fine

Thomas

 

[jussi l]

Hi,

Just wanted to show, how to do these LFSRs in somewhat more readable. I dont
remember what was the polynominal for the register below, but I think you
get the picture...

Regards and happy new year,
juza

process (CLK1, Reset)
begin
if Reset = '1' then
LFSR_1 <= S1;
elsif CLK1'event and CLK1 = '1' then
if ena_falling = '1' then
LFSR_1(0) <= LFSR_1(1) xor LFSR_1(2) xor LFSR_1(4) xor
LFSR_1(15);
LFSR_1(15 downto 1) <= LFSR_1(14 downto 0);
end if;
end if;
end process;

 

[T. Irmen]

mmmh, thats a serial implementation and not readable also

Happy new year!

Thomas

 

[OutputLogic]

Online Parallel Scrambler generator tool

There is an online tool that generates a Verilog code for parallel scramblers with different polynomial sizes and coefficients. It's on "http OutputLogic dot com" [sorry, this site doesn't let me post a link in a regular way]

Hope that helps