Anything wrong with this code for using CRC generator

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first time to use CRC generator from plugin 

 1. i am not sure whether assign 0 to reset_n  2. when payload more than 32 , does it mean to set endofpacket 0, until final 32 in payload , set it 1  3. i am not sure that i understand empty this input attribute, i guess it used when endofpacket is '1' and count number of 0 in data. is it correct? if not, when and how to do? any example?  constant preamble : STD_LOGIC_VECTOR (7 DOWNTO 0) := '5555555555555555';  constant dest_mac_addr : STD_LOGIC_VETOR (5 DOWNTO 0) := '1078D2AD90CB';  constant src_mac_addr : STD_LOGIC_VECTOR (5 DOWNTO 0) := '001234567890';  constant payload : STD_LOGIC_VECTOR (7 DOWNTO 0) := '0001020304050607';  constant wholepacketlength : STD_LOGIC_VECTOR (1 DOWNTO 0) := '22';    variable tx_data : STD_LOGIC_VECTOR(31 DOWNTO 0);  variable CheckSumResult : STD_LOGIC_VECTOR (31 DOWNTO 0);  variable CheckSumValid : STD_LOGIC;    constant enableit : STD_LOGIC := '1';  constant disableit : STD_LOGIC := '0'; begin    tx_data <= preamble;  tx_data <= dest_mac_addr;  tx_data <= src_mac_addr;  tx_data <= payload;    H2:crcgen port map(  clk => CLOCK_50, --: IN STD_LOGIC;  data => payload, -- : IN STD_LOGIC_VECTOR (7 DOWNTO 0);  datavalid => enableit, --: IN STD_LOGIC;  empty => disableit : IN STD_LOGIC_VECTOR (1 DOWNTO 0);  endofpacket => enableit, --: IN STD_LOGIC;  reset_n => disableit, --: IN STD_LOGIC;  checksum => CheckSumResult, --: OUT STD_LOGIC_VECTOR (31 DOWNTO 0);  crcvalid => CheckSumValid --: OUT STD_LOGIC  &nbsp;);    tx_data <= CheckSumResult;