Shift registers

[gervaz]

Hi all, I'm using shift registers in order to instantiate multiple
cores in my system. I'm a newbie and I would like to know if my
approach is correct. Every instance of the core have a shift reg that
provide the data input and another sifth reg that takes the data
output. I use the generate statement to connect all my instances to
the various shft registers.

This is the code (I want to instantiate multiple Aquarius cores --
found on opencores.org). Can you please provide me feedback? Thanks

-------------------------------------------------------------------------------------------------------------------
--- multi_instance_aquarius
-------------------------------------------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;


entity multi_instance is
generic (
NINSTANCES : integer := 1;
NINPUT : integer := 15;
NOUTPUT : integer := 18
);

port (
CLK: in std_logic;
RST: in std_logic;
SHIFTIN: in std_logic_vector (0 to NINSTANCES-1);
SHIFTOUT: out std_logic_vector (0 to NINSTANCES-1);
ALOAD: in std_logic
);
end multi_instance;

architecture arch of multi_instance is

component shiftregINCOMP is
generic (
NINPUT : integer := 15
);
port (CLK, RST: in std_logic;
DATAin: in std_logic;
DATAout: out std_logic_vector (NINPUT-1 downto 0)
);
end component;

component shiftregOUTCOMP is
generic (
NOUTPUT : integer := 18
);
port (CLK, RST: in std_logic;
DATAin: in std_logic_vector (NOUTPUT-1 downto 0);
DATAout: out std_logic;
ALOAD : in std_logic
);
end component;

component top is port (

CLK_SRC : in std_logic;
RST_n : in std_logic;
LCDDBI : in std_logic_vector (7 downto 0);
KEYXI : in std_logic_vector (4 downto 0);
RXD : in std_logic;
CTS : in std_logic;
LCDRS : out std_logic;
LCDRW : out std_logic;
LCDE : out std_logic;
LCDDBO : out std_logic_vector (7 downto 0);
KEYYO : out std_logic_vector (4 downto 0);
TXD : out std_logic;
RTS : out std_logic
);
end component;

type shiftregIN is array (NINSTANCES-1 downto 0) of std_logic_vector
(NINPUT-1 downto 0);
type shiftregOUT is array (NINSTANCES-1 downto 0) of std_logic_vector
(NOUTPUT-1 downto 0);
signal DATAin : shiftregIN;
signal DATAout : shiftregOUT;

begin

generate_inst: for I in 0 to NINSTANCES-1 generate

top_inst : top
port map (
CLK_SRC => CLK,
RST_n => RST,
--------------------------------------------------------
LCDDBI => DATAin(I) (NINPUT-1 downto NINPUT-8),
KEYXI => DATAin(I) (NINPUT-9 downto NINPUT-13),
RXD => DATAin(I) (NINPUT-14),
CTS => DATAin(I) (NINPUT-15),
--------------------------------------------------------
LCDRS => DATAout(I) (NOUTPUT-1),
LCDRW => DATAout(I) (NOUTPUT-2),
LCDE => DATAout(I) (NOUTPUT-3),
LCDDBO => DATAout(I) (NOUTPUT-4 downto NOUTPUT-11),
KEYYO => DATAout(I) (NOUTPUT-12 downto NOUTPUT-16),
TXD =>DATAout(I) (NOUTPUT-17),
RTS => DATAout(I) (NOUTPUT-18)
);

shiftregIN_inst : shiftregINCOMP
generic map (NINPUT => NINPUT)

port map (
CLK => CLK,
RST => RST,
DATAin => SHIFTIN(I),
DATAout => DATAin(I)
);

shiftregOUT_inst : shiftregOUTCOMP
generic map (NOUTPUT => NOUTPUT)

port map (
CLK => CLK,
RST => RST,
ALOAD => ALOAD,
DATAin => DATAout(I),
DATAout => SHIFTOUT(I)
);

end generate;

end arch;

-------------------------------------------------------------------------------------------------------------------
-- shiftregin
-------------------------------------------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity shiftregINCOMP is
generic (
NINPUT : integer := 15
);
port (CLK, RST: in std_logic;
DATAin: in std_logic;
DATAout: out std_logic_vector (NINPUT-1 downto 0)
);
end entity;

architecture arch of shiftregINCOMP is
signal tmp : std_logic_vector(NINPUT-1 downto 0);
begin
process (CLK, RST)
begin
if RST = '0' then
tmp <= (others => '0');
elsif CLK'event and CLK = '1' then
tmp <= tmp(NINPUT-2 downto 0) & DATAin;
end if;
end process;
DATAout <= tmp;
end arch;

-------------------------------------------------------------------------------------------------------------------
-- shiftregout
-------------------------------------------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity shiftregOUTCOMP is
generic (
NOUTPUT : integer := 18
);
port (CLK, RST: in std_logic;
DATAin: in std_logic_vector (NOUTPUT-1 downto 0);
DATAout: out std_logic;
ALOAD : in std_logic
);
end entity;

architecture arch of shiftregOUTCOMP is
signal tmp : std_logic_vector(NOUTPUT-1 downto 0);
begin
process (CLK, RST, ALOAD)
begin
if RST = '1' then
tmp <= (others => '0');
else
if ALOAD = '1' then
tmp <= DATAin;
elsif CLK'event and CLK = '1' then
tmp <= tmp(NOUTPUT-2 downto 0) & '0';
end if;
end if;
end process;
DATAout <= tmp(NOUTPUT-1);
end arch;

 

[Tricky]

The warning it's giving is because you assign tmp from DATAin when
ALOAD = '1', so DATAin also needs to be in the sensitivity list.

Also, try not to use the ALOAD signal. It will be too prone to meta-
stability. Try and synchronise it if you can and put it inside the
clock.

You have also included packages when you dont need to: std_logic_arith
and unsigned. They are unnessasry in your design.