shiftamountreg.vhd

ARM7核在FPGA中的VHDL代码实现

--****************************************************************************************************
-- Shifter control register for ARM7TDMI-S processor
-- Designed by Ruslan Lepetenok
-- Modified 11.11.2002
--****************************************************************************************************
library	IEEE;
use IEEE.std_logic_1164.all;

entity ShiftAmountReg is port(
	                   -- Clock and reset
				       nRESET     : in  std_logic; 
					   CLK        : in  std_logic;
					   CLKEN      : in  std_logic;                      
					   -- Data signals
					   ShLenRsIn  : in   std_logic_vector(7 downto 0);  -- Shift amount for register shift (value of Rs[7..0]) 
					   ShLenRsOut : out  std_logic_vector(7 downto 0)
					   );
end ShiftAmountReg;

architecture RTL of ShiftAmountReg is
begin

ShAmRg:process(nRESET,CLK)
begin
if nRESET='0' then                -- Reset
 ShLenRsOut <= (others => '0');
 elsif CLK='1' and CLK'event then -- Clock	
  if CLKEN='1' then               -- Clock enable	 
    ShLenRsOut <= ShLenRsIn;
  end if;	  
end if;	 
end process;
	
end RTL;