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topi1234 04-18-2008 11:07 AM

vhdl std_logic_vector slice access problem

I have a problem regarding slice access in a 32 bit std_logic_vector signal. Using chipscope on a virtex II pro board kit, I concluded that the value returned by 8 bit slice access operator is everytime the same and equal with the value of the least important 8 bit. This is not happen on the modelsim simlator.
in order to understand i present the vhdl source code:

-- signal declaration
signal v_RAM_OUT0 : std_logic_vector(31 downto 0);
-- rom_FRV_SBOX is a translation table that is not very important what values it contain

signal rom_FRV_SBOX : type_SBOX := (
x"63", x"7c", x"77", x"7b", x"f2", x"6b", x"6f", x"c5", x"30", x"01", x"67", x"2b", x"fe", x"d7", x"ab", x"76",
x"ca", x"82", x"c9", x"7d", x"fa", x"59", x"47", x"f0", x"ad", x"d4", x"a2", x"af", x"9c", x"a4", x"72", x"c0",
x"b7", x"fd", x"93", x"26", x"36", x"3f", x"f7", x"cc", x"34", x"a5", x"e5", x"f1", x"71", x"d8", x"31", x"15",
x"04", x"c7", x"23", x"c3", x"18", x"96", x"05", x"9a", x"07", x"12", x"80", x"e2", x"eb", x"27", x"b2", x"75",
x"09", x"83", x"2c", x"1a", x"1b", x"6e", x"5a", x"a0", x"52", x"3b", x"d6", x"b3", x"29", x"e3", x"2f", x"84",
x"53", x"d1", x"00", x"ed", x"20", x"fc", x"b1", x"5b", x"6a", x"cb", x"be", x"39", x"4a", x"4c", x"58", x"cf",
x"d0", x"ef", x"aa", x"fb", x"43", x"4d", x"33", x"85", x"45", x"f9", x"02", x"7f", x"50", x"3c", x"9f", x"a8",
x"51", x"a3", x"40", x"8f", x"92", x"9d", x"38", x"f5", x"bc", x"b6", x"da", x"21", x"10", x"ff", x"f3", x"d2",
x"cd", x"0c", x"13", x"ec", x"5f", x"97", x"44", x"17", x"c4", x"a7", x"7e", x"3d", x"64", x"5d", x"19", x"73",
x"60", x"81", x"4f", x"dc", x"22", x"2a", x"90", x"88", x"46", x"ee", x"b8", x"14", x"de", x"5e", x"0b", x"db",
x"e0", x"32", x"3a", x"0a", x"49", x"06", x"24", x"5c", x"c2", x"d3", x"ac", x"62", x"91", x"95", x"e4", x"79",
x"e7", x"c8", x"37", x"6d", x"8d", x"d5", x"4e", x"a9", x"6c", x"56", x"f4", x"ea", x"65", x"7a", x"ae", x"08",
x"ba", x"78", x"25", x"2e", x"1c", x"a6", x"b4", x"c6", x"e8", x"dd", x"74", x"1f", x"4b", x"bd", x"8b", x"8a",
x"70", x"3e", x"b5", x"66", x"48", x"03", x"f6", x"0e", x"61", x"35", x"57", x"b9", x"86", x"c1", x"1d", x"9e",
x"e1", x"f8", x"98", x"11", x"69", x"d9", x"8e", x"94", x"9b", x"1e", x"87", x"e9", x"ce", x"55", x"28", x"df",
x"8c", x"a1", x"89", x"0d", x"bf", x"e6", x"42", x"68", x"41", x"99", x"2d", x"0f", x"b0", x"54", x"bb", x"16"

process (CLK_I)
if rising_edge(CLK_I) then
if v_CALCULATION_CNTR = x"02" then
STATE_TABLE1(0) <= rom_FRV_SBOX(conv_integer(v_RAM_OUT0(7 downto 0)));
STATE_TABLE1(13) <= rom_FRV_SBOX(conv_integer(v_RAM_OUT0(15 downto 8)));
STATE_TABLE1(10) <= rom_FRV_SBOX(conv_integer(v_RAM_OUT0(23 downto 16)));
STATE_TABLE1(7) <= rom_FRV_SBOX(conv_integer(v_RAM_OUT0(31 downto 24)));

So, using chipscope I remarked that STATE_TABLE1(0) , STATE_TABLE1(13) , STATE_TABLE1(10) ,STATE_TABLE1(7) have the value calculated having as index v_RAM_OUT0(7 downto 0) and not v_RAM_OUT0(15 downto 8), v_RAM_OUT0(23 downto 16), etc. as I expect.

Please help me because I really don't know what to do.:-(

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