DMA

I tested with an Altera FIFO (with show-ahead option activated) and it&#39;s ok. http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/biggrin.gif

The thing is that now I need another RAM but it can&#39;t be a FIFO: a control unit gives it the address for writing and RAM gets out the data sequentially if "NiosRead" is high. The problem is reading data from my module again: the first time is just fine, but the second time I run the program the first datum is repeated and the value# 8 is lost. Here is the VHDL code:

LIBRARY ieee;

USE ieee.std_logic_1164.all;

USE ieee.std_logic_arith.all;

USE ieee.std_logic_unsigned.all;

ENTITY ram_idct_out IS

PORT(

NiosCS : IN std_logic;

NiosRead : IN std_logic;

NiosReset : IN std_logic;

clk : IN std_logic;

data_in : IN std_logic_vector (8 DOWNTO 0);

dir_w : IN std_logic_vector (5 DOWNTO 0);

write : IN std_logic;

data_out : OUT std_logic_vector (8 DOWNTO 0)

);

-- Declarations

END ram_idct_out ;

ARCHITECTURE flow OF ram_idct_out IS

-- Architecture declarations

TYPE memory_type is array (63 DOWNTO 0) of

std_logic_vector(8 DOWNTO 0);

SIGNAL memory : memory_type;

SIGNAL rd_addr : integer range 63 DOWNTO 0;

SIGNAL wr_addr: integer range 63 DOWNTO 0;

BEGIN

-----------------------------------------------------------------

process0 : PROCESS (clk, NiosReset)

-----------------------------------------------------------------

BEGIN

-- Asynchronous Reset

IF (NiosReset = &#39;1&#39;) THEN

-- Reset Actions

rd_addr <= 0;

data_out <= (OTHERS => &#39;0&#39;);

ELSIF (clk&#39;EVENT AND clk = &#39;1&#39;) THEN

data_out <= memory(rd_addr);

IF NiosRead = &#39;1&#39; AND NiosCS = &#39;1&#39; THEN

IF rd_addr = 63 THEN

rd_addr <= 0;

ELSE

rd_addr <= rd_addr + 1;

END IF;

END IF;

IF write = &#39;1&#39; THEN

memory(wr_addr) <= data_in;

END IF;

END IF;

END PROCESS process0;

-- Architecture concurrent statements

wr_addr <= conv_integer(unsigned(dir_w));

END flow;

Could you please help me? http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/unsure.gif Thanks!!!!

By the way, I have to add another DMA for reading, I thought that it could work out with only one (for writing and reading).