Xilinx V-4 BRAM

Hello group,

I have used the new ISE 8.i simulator (nice propeller) to simulate
a 9 bit read-only-memory using a BRAM primitive. The code
is shown below but I have a number of new questions arise:

1) Is the code around the "begin" keyword, which maps the inputs
to the primitive RAMB16 (BRAM or Block RAM) acceptable or
is there a more concise/better method?

2) I initially went to the V4 library guide and found this primitive.
I did not see there the RAMB_Sx_Sy primitives of Spartan yore,
which lead me to believe that they are abandoned in Virtex-4.
The Xilinx Virtex-4 User Guide ( ug070.pdf ) page 133 would
lead one to believe that they are available. What is the story here?

3) Generally, I would like to transport my future designs between
Spartan3s and Virtex-4 effortlessly. Are their any tips, ap notes,
or other information out there on how to do this?

4) The INIT_xx => sytax is clumsy. Especially if I choose
to use the ninth bit. What alternatives do I have?

5) I have been searching Google for code examples with the words
RAMB16 and std_logic. Is there any primitive or keyword
specific to Virtex-4 that would further refine my search?

6) I did not see the INIT value on the ISE 8.1 simulation which
I expect to see at time 0. Is this a glitch in the 8.1 simulator?

Regards,

Brad Smallridge
aivision dot com

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

library UNISIM;
use UNISIM.VComponents.all;

entity bram9p is
port (
clkb : IN std_logic;
enb : IN std_logic;
ssrb : IN std_logic;
regceb : IN std_logic;
addrb : IN std_logic_VECTOR(11 downto 0);
web : IN std_logic;
doutb : OUT std_logic_VECTOR( 8 downto 0) );
end bram9p;

architecture Behavioral of bram9p is

signal addrb15 : std_logic_vector(14 downto 0);
signal dob32 : std_logic_vector(31 downto 0);
signal dopb4 : std_logic_vector( 3 downto 0);
signal web4 : std_logic_vector( 3 downto 0);

begin

addrb15(14 downto 3) <= addrb;
addrb15( 2 downto 0) <= "000";
doutb(7 downto 0) <= dob32(7 downto 0);
doutb( <= dopb4(0);

-- Update all web bits,
-- otherwise only some addresses will be written.
web4(0) <= web;
web4(1) <= web;
web4(2) <= web;
web4(3) <= web;

-- RAMB16: Virtex-4 16k+2k Parity Paramatizable BlockRAM
-- Xilinx HDL Language Template version 8.1i
RAMB16_inst : RAMB16
generic map (
DOA_REG => 0, -- Optional output registers on the A port (0 or 1)
DOB_REG => 0, -- Optional output registers on the B port (0 or 1)
INIT_A => X"000000000", -- Initial values on A output port
INIT_B => X"000000001", -- Initial values on B output port
INVERT_CLK_DOA_REG => FALSE, -- TRUE or FALSE
INVERT_CLK_DOB_REG => FALSE, -- TRUE or FALSE
RAM_EXTENSION_A => "NONE", -- "UPPER", "LOWER" or "NONE" when cascaded
RAM_EXTENSION_B => "NONE", -- "UPPER", "LOWER" or "NONE" when cascaded
READ_WIDTH_A => 9, -- Valid values are 1,2,4,9,18 or 36
READ_WIDTH_B => 9, -- Valid values are 1,2,4,9,18 or 36
SIM_COLLISION_CHECK => "NONE", --
"ALL","WARNING_ONLY","GENERATE_X_ONLY,"NONE
SRVAL_A => X"000000000", -- Port A ouput value upon SSR assertion
SRVAL_B => X"000000002", -- Port B ouput value upon SSR assertion
WRITE_MODE_A => "READ_FIRST", -- WRITE_FIRST, READ_FIRST or NO_CHANGE
WRITE_MODE_B => "READ_FIRST", -- WRITE_FIRST, READ_FIRST or NO_CHANGE
WRITE_WIDTH_A => 9, -- 1,2,4,9,18 or 36
WRITE_WIDTH_B => 9, -- 1,2,4,9,18 or 36
-- The following INIT_xx declarations specify the initial contents of
the RAM
INIT_00 =>
X"1F1E1D1C1B1A191817161514131211100F0E0D0C0B0A0908 0706050403020100",
INIT_01 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_02 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_03 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_04 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_05 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_06 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_07 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_08 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_09 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_0A =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_0B =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_0C =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_0D =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_0E =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_0F =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_10 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_11 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_12 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_13 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_14 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_15 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_16 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_17 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_18 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_19 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_1A =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_1B =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_1C =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_1D =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_1E =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_1F =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_20 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_21 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_22 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_23 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_24 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_25 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_26 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_27 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_28 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_29 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_2A =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_2B =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_2C =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_2D =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_2E =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_2F =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_30 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_31 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_32 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_33 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_34 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_35 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_36 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_37 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_38 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_39 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_3A =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_3B =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_3C =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_3D =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_3E =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INIT_3F =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
-- The next set of INITP_xx are for the parity bits
INITP_00 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INITP_01 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INITP_02 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INITP_03 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INITP_04 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INITP_05 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INITP_06 =>
X"000000000000000000000000000000000000000000000000 0000000000000000",
INITP_07 =>
X"000000000000000000000000000000000000000000000000 0000000000000000")
port map (
CASCADEOUTA => open, -- 1-bit cascade output
CASCADEOUTB => open, -- 1-bit cascade output
DOA => open, -- 32-bit A port Data Output
DOB => dob32, -- 32-bit B port Data Output
DOPA => open, -- 4-bit A port Parity Output
DOPB => dopb4, -- 4-bit B port Parity Output
ADDRA => (others=>'0'), -- 15-bit A port Address Input
ADDRB => addrb15, -- 15-bit B port Address Input
CASCADEINA => '0', -- 1-bit cascade A input
CASCADEINB => '0', -- 1-bit cascade B input
CLKA => '0', -- Port A Clock
CLKB => clkb, -- Port B Clock
DIA => (others=>'0'), -- 32-bit A port Data Input
DIB => (others=>'0'), -- 32-bit B port Data Input
DIPA => (others=>'0'), -- 4-bit A port parity Input
DIPB => (others=>'0'), -- 4-bit B port parity Input
ENA => '0', -- 1-bit A port Enable Input
ENB => enb, -- 1-bit B port Enable Input
REGCEA => '0', -- 1-bit A port register enable input
REGCEB => regceb, -- 1-bit B port register enable input
SSRA => '0', -- 1-bit A port Synchronous Set/Reset
Input
SSRB => ssrb, -- 1-bit B port Synchronous Set/Reset Input
WEA => "0000", -- 4-bit A port Write Enable Input
WEB => web4 ); -- 4-bit B port Write Enable
Input

end Behavioral;

Brad Smallridge