Block-ram FIFO in Xilinx

[zlotawy]

Hello,
I have generated a block-ram based FIFO queue (2 independent clocks, 2
inputs, 1 output) with the use of Core Generator. In the creator I used the
36 bit data bus. Is it possible to parameterize this variable?
I think, that the Xilinx doesn't give such possibility. The generated code:

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
-- synthesis translate_off
Library XilinxCoreLib;
-- synthesis translate_on
ENTITY fifa IS
port (
din: IN std_logic_VECTOR(35 downto 0);
rd_clk: IN std_logic;
rd_en: IN std_logic;
rst: IN std_logic;
wr_clk: IN std_logic;
wr_en: IN std_logic;
dout: OUT std_logic_VECTOR(35 downto 0);
empty: OUT std_logic;
full: OUT std_logic);
END fifa;

ARCHITECTURE fifa_a OF fifa IS
-- synthesis translate_off
component wrapped_fifa
port (
din: IN std_logic_VECTOR(35 downto 0);
rd_clk: IN std_logic;
rd_en: IN std_logic;
rst: IN std_logic;
wr_clk: IN std_logic;
wr_en: IN std_logic;
dout: OUT std_logic_VECTOR(35 downto 0);
empty: OUT std_logic;
full: OUT std_logic);
end component;

-- Configuration specification
for all : wrapped_fifa use entity
XilinxCoreLib.fifo_generator_v4_1(behavioral)
generic map(
c_has_int_clk => 0,
c_rd_freq => 1,
c_wr_response_latency => 1,
c_has_srst => 0,
c_has_rd_data_count => 0,
c_din_width => 36,
c_has_wr_data_count => 0,
c_full_flags_rst_val => 1,
c_implementation_type => 2,
c_family => "virtex2p",
c_use_embedded_reg => 0,
c_has_wr_rst => 0,
c_wr_freq => 1,
c_underflow_low => 0,
c_has_meminit_file => 0,
c_has_overflow => 0,
c_preload_latency => 1,
c_dout_width => 36,
c_rd_depth => 1024,
c_default_value => "BlankString",
c_mif_file_name => "BlankString",
c_has_underflow => 0,
c_has_rd_rst => 0,
c_has_almost_full => 0,
c_has_rst => 1,
c_data_count_width => 10,
c_has_wr_ack => 0,
c_use_ecc => 0,
c_wr_ack_low => 0,
c_common_clock => 0,
c_rd_pntr_width => 10,
c_use_fwft_data_count => 0,
c_has_almost_empty => 0,
c_rd_data_count_width => 10,
c_enable_rlocs => 0,
c_wr_pntr_width => 10,
c_overflow_low => 0,
c_prog_empty_type => 0,
c_optimization_mode => 0,
c_wr_data_count_width => 10,
c_preload_regs => 0,
c_dout_rst_val => "0",
c_has_data_count => 0,
c_prog_full_thresh_negate_val => 1020,
c_wr_depth => 1024,
c_prog_empty_thresh_negate_val => 3,
c_prog_empty_thresh_assert_val => 2,
c_has_valid => 0,
c_init_wr_pntr_val => 0,
c_prog_full_thresh_assert_val => 1021,
c_use_fifo16_flags => 0,
c_has_backup => 0,
c_valid_low => 0,
c_prim_fifo_type => "1kx36",
c_count_type => 0,
c_prog_full_type => 0,
c_memory_type => 1);
-- synthesis translate_on
BEGIN
-- synthesis translate_off
U0 : wrapped_fifa
port map (
din => din,
rd_clk => rd_clk,
rd_en => rd_en,
rst => rst,
wr_clk => wr_clk,
wr_en => wr_en,
dout => dout,
empty => empty,
full => full);
-- synthesis translate_on

END fifa_a;


There are 2 parameters: c_din_width =>36 and c_dout_width => 36. I can't
use here values greater than 36. What is the use of this parameters? Can I
change this parameters values to i.e. 20?
I would like to use the queue with different sizes of the data bus. Is it a
good solution to create a maximum size data bus and use it to write there
smaller data?
Or maybe it is better to create a 1bit queue, and with the use of GENERATE
command generate N 1 bit queues to have a N-bit queue?

Device is Virtex2Pro.

Regards,
zlotawy

 

[Mike Treseler]

I have generated a block-ram based FIFO queue (2 independent clocks, 2
inputs, 1 output) with the use of Core Generator. In the creator I used the
36 bit data bus. Is it possible to parameterize this variable?

The core generator does not make synthesis code,
so this is a xilinx question, not a vhdl question.
I can't see into that black box any better than you can.

-- Mike Treseler

 

[paragon.john]

Hello,
I have generated a block-ram based FIFO queue (2 independent clocks, 2
inputs, 1 output) with the use of Core Generator. In the creator I used the
36 bit data bus. Is it possible to parameterize this variable?
I think, that the Xilinx doesn't give such possibility. The generated code:

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
-- synthesis translate_off
Library XilinxCoreLib;
-- synthesis translate_on
ENTITY fifa IS
port (
din: IN std_logic_VECTOR(35 downto 0);
rd_clk: IN std_logic;
rd_en: IN std_logic;
rst: IN std_logic;
wr_clk: IN std_logic;
wr_en: IN std_logic;
dout: OUT std_logic_VECTOR(35 downto 0);
empty: OUT std_logic;
full: OUT std_logic);
END fifa;

ARCHITECTURE fifa_a OF fifa IS
-- synthesis translate_off
component wrapped_fifa
port (
din: IN std_logic_VECTOR(35 downto 0);
rd_clk: IN std_logic;
rd_en: IN std_logic;
rst: IN std_logic;
wr_clk: IN std_logic;
wr_en: IN std_logic;
dout: OUT std_logic_VECTOR(35 downto 0);
empty: OUT std_logic;
full: OUT std_logic);
end component;

-- Configuration specification
for all : wrapped_fifa use entity
XilinxCoreLib.fifo_generator_v4_1(behavioral)
generic map(
c_has_int_clk => 0,
c_rd_freq => 1,
c_wr_response_latency => 1,
c_has_srst => 0,
c_has_rd_data_count => 0,
c_din_width => 36,
c_has_wr_data_count => 0,
c_full_flags_rst_val => 1,
c_implementation_type => 2,
c_family => "virtex2p",
c_use_embedded_reg => 0,
c_has_wr_rst => 0,
c_wr_freq => 1,
c_underflow_low => 0,
c_has_meminit_file => 0,
c_has_overflow => 0,
c_preload_latency => 1,
c_dout_width => 36,
c_rd_depth => 1024,
c_default_value => "BlankString",
c_mif_file_name => "BlankString",
c_has_underflow => 0,
c_has_rd_rst => 0,
c_has_almost_full => 0,
c_has_rst => 1,
c_data_count_width => 10,
c_has_wr_ack => 0,
c_use_ecc => 0,
c_wr_ack_low => 0,
c_common_clock => 0,
c_rd_pntr_width => 10,
c_use_fwft_data_count => 0,
c_has_almost_empty => 0,
c_rd_data_count_width => 10,
c_enable_rlocs => 0,
c_wr_pntr_width => 10,
c_overflow_low => 0,
c_prog_empty_type => 0,
c_optimization_mode => 0,
c_wr_data_count_width => 10,
c_preload_regs => 0,
c_dout_rst_val => "0",
c_has_data_count => 0,
c_prog_full_thresh_negate_val => 1020,
c_wr_depth => 1024,
c_prog_empty_thresh_negate_val => 3,
c_prog_empty_thresh_assert_val => 2,
c_has_valid => 0,
c_init_wr_pntr_val => 0,
c_prog_full_thresh_assert_val => 1021,
c_use_fifo16_flags => 0,
c_has_backup => 0,
c_valid_low => 0,
c_prim_fifo_type => "1kx36",
c_count_type => 0,
c_prog_full_type => 0,
c_memory_type => 1);
-- synthesis translate_on
BEGIN
-- synthesis translate_off
U0 : wrapped_fifa
port map (
din => din,
rd_clk => rd_clk,
rd_en => rd_en,
rst => rst,
wr_clk => wr_clk,
wr_en => wr_en,
dout => dout,
empty => empty,
full => full);
-- synthesis translate_on

END fifa_a;

There are 2 parameters: c_din_width =>36 and c_dout_width => 36. I can't
use here values greater than 36. What is the use of this parameters? Can I
change this parameters values to i.e. 20?
I would like to use the queue with different sizes of the data bus. Is it a
good solution to create a maximum size data bus and use it to write there
smaller data?
Or maybe it is better to create a 1bit queue, and with the use of GENERATE
command generate N 1 bit queues to have a N-bit queue?

Device is Virtex2Pro.

Regards,
zlotawy

You can directly instantiate the Block Memory Generator in your VHDL.
See the core data sheet page 34 for more info on this.
http://www.xilinx.com/bvdocs/ipcenter/data_sheet/blk_mem_gen_ds512.pdf

-John

 

[paragon.john]

You can directly instantiate the Block Memory Generator in your VHDL.
See the core data sheet page 34 for more info on this.http://www.xilinx.com/bvdocs/ipcenter/data_sheet/blk_mem_gen_ds512.pdf

-John

Forgive my error. I was looking at the Block Memory Generator. It
doesn't look like there is a way to do direct instantiation of the
FIFO Generator. One solution would be to hand-write the xco file and
add it to your ISE project.