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dilbert57 |
-- FILE NAME: bootrom.vhdl
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-- ENTITY NAME: boot_rom
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-- ARCHITECTURE NAME: behave
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-- REVISION: A
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--
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-- DESCRIPTION: 64 byte x 8 bit ROM to down a Monitor
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-- program on reset
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--
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--Written by John Kent for the micro8 processor
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_arith.all;
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use ieee.std_logic_unsigned.all;
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library work;
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-- use work.memory.all;
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entity boot_rom is
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port (
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addr : in std_logic_vector(5 downto 0);
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data : out std_logic_vector(7 downto 0)
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);
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end entity boot_rom;
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architecture basic of boot_rom is
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constant width : integer := 8;
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constant memsize : integer := 64;
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type rom_array is array(0 to memsize-1) of std_logic_vector(width-1 downto 0);
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constant rom_data : rom_array :=
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( "10011100", -- $FFC0 - 9C RESET RSP
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"10100110", "00010001", -- $FFC1 - A6 11 LDA #$11
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"10110111", "00010000", -- $FFC3 - B7 10 STA ACIACS
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"10101110", "00000000", -- $FFC5 - AE 00 LDX #$00
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"11010110", "11111111", "11100010", -- $FFC7 - D6 FFE2 LOOP0 LDA $FFE0,X
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"00100111", "00001000", -- $FFCA - 27 08 BEQ INPUT
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"00000011", "00010000", "11111101", -- $FFCC - 03 10 FD LOOP1 BRCLR 1,$10,LOOP1
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"10110111", "00010001", -- $FFCF - B7 11 STA ACIADA
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"01011100", -- $FFD1 - 5C INCX
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"00100000", "11110011", -- $FFD3 - 20 F3 BRA LOOP0
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"00000001", "00010000", "11111101", -- $FFD5 - 01 10 FD INPUT BRCLR 0,$10,INPUT
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"10110110", "00010001", -- $FFD7 - B6 11 LDA ACIADA
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"11001101", "11111111", "11011111", -- $FFD9 - CD FFDF JSR SUBR
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"11001100", "11111111", "11000000", -- $FFDC - CC FFC0 JMP RESET
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"10110111", "00010001", -- $FFDF - B7 11 SUBR STA ACIADA
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"10000001", -- $FFE1 - 81 RTS
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"01001000", "01100101", "01101100", -- $FFE2 - 48 65 6c MSG FCC "Hel"
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"01101100", "01101111", "00100000", -- $FFE5 - 6c 6f 20 FCC "lo "
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"01010111", "01101111", "01110010", -- $FFE8 - 57 6f 72 FCC "Wor"
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"01101100", "01100100", -- $FFEB - 6c 64 FCC "ld"
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"00001010", "00001101", "00000000", -- $FFED - 0a 0d 00 FCB LF,CR,NULL
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"11111111", "11000000", -- $FFF0 - FF C0 FDB RESET
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"11111111", "11000000", -- $FFF2 - FF C0 FDB RESET
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"11111111", "11000000", -- $FFF4 - FF C0 FDB RESET
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"11111111", "11000000", -- $FFF6 - FF C0 FDB RESET
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"11111111", "11000000", -- $FFF8 - FF C0 FDB RESET
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"11111111", "11000000", -- $FFFA - FF C0 FDB RESET
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"11111111", "11000000", -- $FFFC - FF C0 FDB RESET
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"11111111", "11000000" -- $FFFE - FF C0 FDB RESET
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);
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begin
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data <= rom_data(conv_integer(addr));
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end architecture basic;
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