--
-- Dalton Project
-- Tony Givargis, Rilesh Patel, Deepa Varghese, Roman Lysecky
-- 12/21/98
-- Version 1.2
-- Notes: This file implements the BIOS device.  This device contains
--	  some program instructions that it loads into the main memory
--	  and asserts the ready signal.  Subsequently the processors
--	  can be activated when the ready signal is asserted and thus
--	  starting execution of the loaded program.
--	  
--

--*************************************************************************--

library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.STD_LOGIC_ARITH.all;

--*************************************************************************--

entity BIOS is
     generic (COMP_RATIO : INTEGER range 0 to 4 := 1);	
    port( clk  : in STD_LOGIC;
	      rst  : in STD_LOGIC;
	      data : out UNSIGNED(31 downto 0);
              addr : out UNSIGNED(22 downto 0);
              rd   : out STD_LOGIC;
              wr   : out STD_LOGIC;
	      rdy  : in STD_LOGIC;
	      cs   : out STD_LOGIC );
end BIOS;

--*************************************************************************--

architecture BHV_BIOS of BIOS is

	--
	-- type declarations
	--
	type STATE_TYPE is (WRITE_S, WRITE2_S, DONE_S);
	subtype MEM_CELL_TYPE is UNSIGNED(31 downto 0);


        --
	-- outputted portion
	--

	type PROG_MEM_TYPE is array(0 to 47) of MEM_CELL_TYPE;
	constant PROG_SIZE : UNSIGNED(22 downto 0) := "00000000000000000110000";

	constant PROGRAM : PROG_MEM_TYPE := (	
	    "000001111" & CONV_UNSIGNED(COMP_RATIO,23),		--LI R15 COMP_RATIO
	    "00000000100000000000000010000000",		--LI	R1 128
	    "000010010" & CONV_UNSIGNED(COMP_RATIO,23),		--LI	R18 COMP_RATIO
	    "00110000100000000000010000000111",		--STORE	R1 1031
	    "00000000100000000000000000000001",		--LI	R1 1
	    "00110000100000000000001000000001",		--STORE	R1 513
	    "000000110" & CONV_UNSIGNED(PROG_SIZE,23),		--LI	R6 PROG_SIZE
			--:L2
	    "00100001000000000000001000000000",		--LOAD	R2 512
	    "10110001100010000010000000000000",		--EQ	R3 R2 R1
	    "01010001100000000000000000001011",		--JNZ	R3 L1
	    "01110000000000000000000000000111",		--JMP	L2
			--:L1
	    "00010001000000000000000000000000",		--MOV	R2 R0		
	    "00000001100000000000000100000000",		--LI	R3 256
			--:L6
	    "00000011100000000000000000000010",		--LI	R7 2
	    "00000100000000000000000000000011",		--LI	R8 3
	    "01000010000010000110000000000000",		--GE	R4 R2 R3
	    "01010010000000000000000000101111",		--JNZ	R4 L3
	    "00110011100000000000010000000011",		--STORE	R7 1027
	    "00010111000000000000000000000000",		--MOV     R14 R0
			--:L7
	    "01001111000010000110000000000000",		--GE	R30 R2 R3
	    "01011111000000000000000000011000",		--JNZ	R30 L11	
	    "00100010100000000000001000000010",		--LOAD	R5 514
	    "00110010100000000000010000000000",		--STORE	R5 1024
	    "01110000000000000000000000011001",		--JMP	L12
			--:L11
	    "00110000000000000000010000000000",		--STORE	R0 1024
			--:L12	
	    "01100111001110000010000000000000",		--ADD	R14 R14 R1
	    "01100001000010000010000000000000",		--ADD	R2 R2 R1
	    "10111000001111011100000000000000",		--EQ      R16 R15 R14  
	    "01011000000000000000000000011110",		--JNZ     R16 L8
	    "01110000000000000000000000010011",		--JMP     L7    
			--:L8
	    "00110100000000000000010000000011",		--STORE	R8 1027
			--:L5 
	    "00100100100000000000010000000010",		--LOAD	R9 1026
	    "10110101001001000010000000000000",		--EQ	R10 R9 R1
	    "01010101000000000000000000100011",		--JNZ	R10 L4
	    "01110000000000000000000000011111",		--JMP	L5
			--:L4
	    "00100101100000000000010000000001",		--LOAD	R11 1025
	    "11000101100110000000000000000000",		--STOREI	R11 R6
	    "00011001100000000000000000000000",		--MOV	R19 R0
			--:L9
	    "00110101100000000000010000000100",		--STORE	R11 1028
	    "00110101100000000000101110111000",		--STORE	R11 3000
	    "10100101101000000000000000000000",		--SHFR	R11 8
	    "01101001110011000010000000000000",		--ADD	R19 R19 R1
	    "10111010010011100100000000000000",		--EQ	R20 R19 R18
	    "01011010000000000000000000101101",		--JNZ	R20 L10
	    "01110000000000000000000000100110",		--JMP	L9
			--:L10
	    "01100011000110000010000000000000",		--ADD	R6 R6 R1
	    "01110000000000000000000000001101",		--JMP	L6
			--:L3
	    "01110000000000000000000000101111"		--JMP	L3
	    );
	--
	-- constant 
	-- 
	constant Z_32 : UNSIGNED(31 downto 0) := 
		"ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ";

	constant Z_23 : UNSIGNED(22 downto 0) :=
		"ZZZZZZZZZZZZZZZZZZZZZZZ";

	constant C0_32 : UNSIGNED(31 downto 0) :=
		"00000000000000000000000000000000";

	constant C0_23 : UNSIGNED(22 downto 0) :=
		"00000000000000000000000";

	constant C1_23 : UNSIGNED(22 downto 0) :=
		"00000000000000000000001";


	signal loct  : UNSIGNED(22 downto 0);
	signal state : STATE_TYPE;

begin

	process(clk, rst)
	begin
		if( rst = '1' ) then

			--
			-- steady state
			--
			state <= WRITE_S;
			loct <= C0_23;
			data <= C0_32;
			addr <= C0_23;
			wr <= '0';
			rd <= '0';
			cs <= '0';

		elsif( clk'event and clk = '1' ) then

			--
			-- steady state
			--
			data <= C0_32;
			addr <= C0_23;
			rd <= '0';
			wr <= '0';
			cs <= '0';

			--
			-- otherwise
			--
			case( state ) is

				when WRITE_S =>
				
					state <= WRITE_S;
					if(loct = PROG_SIZE and rdy = '1') then

						state <= DONE_S;

					elsif( rdy = '1' ) then

						data <= 
                                                   PROGRAM(conv_integer(loct));
						addr <= loct;
						wr <= '1';
						loct <= loct + C1_23;
						state <= WRITE2_S;
					end if;
				
				when WRITE2_S =>
					state <= WRITE_S;

				when DONE_S =>
					data <= Z_32;
					addr <= Z_23;
					rd <= 'Z';
					wr <= 'Z';
					cs <= '1';
					state <= DONE_S;
			end case;
		end if;
	end process;
end BHV_BIOS;

--*************************************************************************--

--configuration CFG_BIOS of BIOS is
--	for BHV_BIOS
--	end for;
--end CFG_BIOS;

-- end of file --