LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
--
LIBRARY EXEMPLAR;
USE EXEMPLAR.exemplar_1164.ALL;
USE EXEMPLAR.exemplar.ALL;
--
LIBRARY parwan_s;
USE parwan_s.ALL;
USE parwan_s.synthesis_parameters.ALL;
USE parwan_s.synthesis_utilities.ALL;
--
ENTITY parwan_memory IS
  PORT (cs : IN std_logic; rwbar : IN std_logic;
        databus : INOUT byte := "ZZZZZZZZ"; adbus : IN twelve
       );
END parwan_memory;
--
ARCHITECTURE behavioral OF parwan_memory IS
  TYPE byte_memory IS ARRAY ( INTEGER RANGE <> ) OF std_logic_vector ( 7 DOWNTO 0 );
BEGIN
  mem : PROCESS 
    VARIABLE memory : byte_memory ( 0 TO 63 ) := 
      ("00000000", "00011000", "10100000", "00011001", --00: lda 24, sta 25
       "00100000", "00011010", "01000000", "00011011", --04: and 26, add 27
       "11100010", "11101001", "01100000", "00011100", --08: cac, asr, sub 28
       "00010000", "00011101", "11000000", "00100100", --12: lda i 29, jsr 36
       "11101000", "11100000", "10000000", "00100000", --16: asl, nop, jmp 32
       "00000000", "00000000", "00000000", "00000000", --20:
       "01011100", "00000000", "01110000", "00010010", --24: (24, 25, 26, 27)
       "00001100", "00011111", "00000000", "01011010", --28: (28, 29, 30, 31)
       "10000000", "00010010", "00000000", "00000000", --32: jmp 18
       "00000000", "11100010", "10010000", "00100100", --36:    , cma, jmp i 36
       "00000000", "00000000", "00000000", "00000000",
       "00000000", "00000000", "00000000", "00000000",
       "00000000", "00000000", "00000000", "00000000",
       "00000000", "00000000", "00000000", "00000000",
       "00000000", "00000000", "00000000", "00000000",
       "00000000", "00000000", "00000000", "00000000" );
    VARIABLE ia : INTEGER;
  BEGIN
    databus <= "ZZZZZZZZ";
    IF cs = '1' THEN
      WAIT FOR 70 NS;
      ia := evec2int (adbus);
      IF rwbar = '1' THEN 
        IF ia >= 64 THEN 
          databus <= "ZZZZZZZZ";
        ELSE
          databus <= memory (ia);
        END IF;
      ELSIF rwbar = '0' THEN
        IF ia < 64 THEN
          memory (ia) := databus;
        END IF;
      END IF;
    END IF;
    WAIT ON cs, adbus;
    WAIT FOR 50 NS;
  END PROCESS mem;
END behavioral;