Honored ContributorHello,
I'm need to load a ROM with a cos and sin lookup table. I know Quartus have an auto fill cell function built in but does it support sin and cos? Or does I need a 3d-party program to do that? Also, how do I convert the cos answer to HEX/BIN? For example cos(25)= 0,9063 how do I translate that to HEX? Thanks for your answer :)
Honored ContributorI suspect you'll need to write a program (probably in C) for your host to generate the hex data in the required format.
Honored ContributorWhere is your source from? in VHDL, you can infer a rom from a constant, and you can populate the constant from a sin/cos function.
Honored ContributorI'm using Quartus MegaWizard to generate a ROM in VHDL. I doesn't really understand what you want me to do, could you be a little more specific and explain a bit more?
Honored ContributorHave a read of this document, page 13-13: http://www.altera.co.uk/literature/hb/qts/qts_qii51007.pdf
It explains how to write your VHDL code so that quartus can infer a rom without having to use the megawizard. This way you can use a custom initialisation function to populate the rom contents.Honored ContributorIf you prefer to use a RAM MegaFunction with an external initialization file, it's probably convenient to use a *.mif instead of *.hex file. It's formatted text and can be easily generated in a spreadsheet calculator.
Honored ContributorHonored ContributorHonored ContributorI looked at the function and I found this:
TYPE ROM IS ARRAY(0 TO 511) OF UNSIGNED(8 DOWNTO 0);
FUNCTION INIT_ROM RETURN ROM IS
VARIABLE romvar: ROM;
VARIABLE x: REAL;
begin
for I in 0 TO 511 loop
x:= SIN(real(i)*MATH_PI/real(511));
romvar(i):=CONV_UNSIGNED(INTEGER(x*real(511)),9);
end loop;
return romvar;
end;
have a look at the coding guidelines, as I mentioned in post# 5
Honored ContributorI have understand how the ROM works and how to interface it. Now it is the SIN function that gives me trouble.
I have this code:
-- Quartus II VHDL Template
-- Dual-Port ROM
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
USE ieee.std_logic_arith.all;
USE ieee.math_real.all;
entity dual_port_rom is
generic
(
DATA_WIDTH : natural := 14;
ADDR_WIDTH : natural := 4096
);
port
(
clk : in std_logic;
addr_a : in integer range 0 to 2**ADDR_WIDTH - 1;
q_a : out std_logic_vector((DATA_WIDTH -1) downto 0)
);
end entity;
architecture rtl of dual_port_rom is
subtype word_t is std_logic_vector((DATA_WIDTH-1) downto 0);
TYPE ROM IS ARRAY((ADDR_WIDTH-1) downto 0) OF word_t;
FUNCTION INIT_ROM RETURN ROM IS
VARIABLE romvar: ROM;
VARIABLE x: REAL;
begin
for I in 0 TO 2**ADDR_WIDTH-1 loop
x:= SIN(real(i)*MATH_PI/real(ADDR_WIDTH-1));
romvar(i):= std_logic_vector(to_unsigned(x*real(ADDR_WIDTH-1),DATA_WIDTH));
end loop;
return romvar;
end;
-- Declare the ROM signal and specify a default value. Quartus II
-- will create a memory initialization file (.mif) based on the
-- default value.
signal rom : memory_t := romvar;
begin
process(clk)
begin
if(rising_edge(clk)) then
q_a <= rom(addr_a);
end if;
end process;
end rtl;
