API tools faq
paste
Advertisement
retrophil

Megadrive

retrophil
Nov 19th, 2018
138
0
Never
Add comment
Not a member of Pastebin yet? Sign Up, it unlocks many cool features!
M68000 Assembler 8.11 KB | None | 0 0
raw download clone embed print report
  1. helpful: https://www.rapidtables.com/convert/number/hex-to-decimal.html
  2.  
  3. --DATA SIZES--
  4.  
  5. size                    binary                                          hexadecimal
  6.  
  7. nybble                  0010                                            2
  8. byte                    0010 1100                                       2C
  9. word                    0010 1100 1111 0101                             2C F5
  10. long-word               0010 1100 1111 0101 1001 1101 0111 0110         2C F5 9D 76
  11. ---------------------------------------------------------------------------------------------------------------------------------------
  12. If you group two nybbles together (e.g. 0100 1101), you get what is known as a “byte”.
  13. If you group two “bytes” together (e.g. 0100 1101 1011 0000), you get what is known as a “word”.
  14. If you group two “words” together (e.g. 0100 1101 1011 0000 1111 0001 0000 0110), you get what is known as a “long-word”.
  15. ---------------------------------------------------------------------------------------------------------------------------------------
  16.  
  17. --SYMBOLS--
  18.  
  19. #   Number that follows is an offset/address.
  20. $   Hex numbers will follow.
  21. %   Binary numbers will follow.
  22. " " Nothing means it'll be a decimal number that follows.
  23. ---------------------------------------------------------------------------------------------------------------------------------------
  24.  
  25. --ADDRESS REGISTERS--
  26.  
  27. move.b  #$44, (a0)          moves 44 into (not replace) a0.
  28.  
  29. ---------------------------------------------------------------------------------------------------------------------------------------
  30. scenario: (a0) contains 00000039       
  31.  
  32. move.b    #$9B,$04(a0)              =   #$9B goes into 00000039; then add 04
  33.  
  34. Answer: 0000003D
  35. ---------------------------------------------------------------------------------------------------------------------------------------
  36. movea.l   #$00000010,a0
  37. move.b    #$20,$01(a0)
  38. move.b    #$40,$02(a0)
  39. move.b    #$F0,$0F(a0)
  40. move.b    #$0E,(a0)
  41.  
  42. 00000010 is moved into a0
  43. 20 is moved to 00000010 plus 01     =   00000011
  44. 40 is moved to 00000010 plus 02     =   00000012
  45. F0 is moved to 00000010 plus 0F     =   0000001F
  46. 0E is moved to 00000010 directly    =   00000010
  47. ---------------------------------------------------------------------------------------------------------------------------------------
  48.  
  49. --AUTO INCREMENT--
  50.  
  51. movea.l   #$00000020,a0             =   00000020
  52. move.b    #$B5,(a0)+                =   00000021        (B5 moves into 00000020 then is increamented by 1)
  53. move.b    #$11,(a0)+                =   00000022
  54. ---------------------------------------------------------------------------------------------------------------------------------------
  55. movea.l   #$00000020,a0             =   00000020  (spreads over to 21 because of its size)
  56. move.w    #$A90E,(a0)+              =   00000022
  57. ---------------------------------------------------------------------------------------------------------------------------------------
  58.  
  59. --AUTO DECREMENT--
  60.  
  61. movea.l   #$00000020,a0             =   00000020
  62. move.b    #$2E,-(a0)                =   0000001F
  63. ---------------------------------------------------------------------------------------------------------------------------------------
  64. move.w    d0,d1                     =   this will copy whatevers in d0 to d1 (words worth amount)
  65. ---------------------------------------------------------------------------------------------------------------------------------------
  66. move.w    d0,$0000104E              =   If d0 contains 99004980, then 4980 is copied to memory at offsets 0000104E and 0000104F
  67. ---------------------------------------------------------------------------------------------------------------------------------------
  68.  
  69. --ADD--
  70.  
  71. addi.b    #$08,d0       =   adds 8 to whatevers in d0 (a bytes worth)
  72. ---------------------------------------------------------------------------------------------------------------------------------------
  73. addi.b    #$08,d0       =   if d0 started with 00001008, after the instruction d0 will contain 00001010 (because, 8 9 A B C D E F 10)
  74. ---------------------------------------------------------------------------------------------------------------------------------------
  75. add.w     d0,d1         =   If d0 contains FED00100, and d1 contains 00000100, after the instruction d1 will contain 00000200.
  76. ---------------------------------------------------------------------------------------------------------------------------------------
  77.  
  78. --SUB--
  79.  
  80. subi.b    #$10,d0           =   if d0 has 0000002E, after it will have 0000001E
  81. ---------------------------------------------------------------------------------------------------------------------------------------
  82.  
  83. --NOT--
  84.  
  85. not.b     d0                =   let’s say d0 contains FE800174; 74 is 0111 0100 in binary; 0111 0100 becomes 1000 1011. 74 > 8B
  86. ---------------------------------------------------------------------------------------------------------------------------------------
  87.  
  88. --SWAP--
  89.  
  90. swap      d0            =   2222EEEE changes to EEEE2222
  91. ---------------------------------------------------------------------------------------------------------------------------------------
  92.  
  93. --EXG--
  94.  
  95. exg.l     d0,d1         =   if d0 has 00000000 and d1 has 11111111; d0 will have 11111111 and d1 will have 00000000
  96. ---------------------------------------------------------------------------------------------------------------------------------------
  97.  
  98. --CLR--                 =   if d0 has 01234567, d0 will have 01234500 (wipes a bytes worth)
  99. ---------------------------------------------------------------------------------------------------------------------------------------
  100.  
  101. --AND--
  102.  
  103. Scenario: d0 contains 01234567
  104.  
  105. andi.b    #$E2,d0           =   E2 in binary is 11100010 | 67 in binary is 01100111.  Each number is compared to true or false.  1 & 1                      scores 1 anything else will score 0.
  106.  
  107. Answer: 01100010            =   E2 AND 67 = 62  (Answers 62)
  108. ---------------------------------------------------------------------------------------------------------------------------------------
  109.  
  110. --OR--
  111.  
  112. Scenario: d0 contains 01234567
  113.  
  114. ori.b     #$EC,d0           =   EC in binary is 11101100 and as we know 67 in binary is 01100111.  Each number is compared to true and false.                           Anything with a 1 in it scores 1, otherwise its 0.
  115.  
  116. Answer: 11101111            =   EC OR 67 = EF   (Answers EF)
  117. ---------------------------------------------------------------------------------------------------------------------------------------
  118. --EOR-- / --XOR--
  119.  
  120. Scenario: do contains 01234567
  121.  
  122. eori.b    #$E2,d0           =   E2 in binary is 11100010 and yet again as we know 67 in binary is 01100111.  Each number is comapred to true and                    false.  Anything with just a single 1 in it will score 1 otherwise it'll be a 0.
  123.  
  124. Answer: 10000101            =   E2 XOR 67 = 85  (Answers 85)
  125. ---------------------------------------------------------------------------------------------------------------------------------------
  126. --BSET--
  127.  
  128. Scenario: d0 is cleared, 32bits all contain 0's
  129.  
  130. bset.l    #$0E,d0           =   This puts a 1 in 0E, from which in binary is 0000 0000 0000 0000 0100 0000 0000 0000, from which in hex is 00004000
  131.  
  132. Notes:                          If what ever is being injected takes the register over 1F (1F is the highest number); the register will     wrap back round to 00 again. 20 becomes 00, 21 is 01, 22 is 02 etc... needs to be within range.
  133. ---------------------------------------------------------------------------------------------------------------------------------------
  134. --BCLR--
  135.  
  136. Notes: Does the same as BSET but instead of putting a 1 in, it puts a 0.
  137. ---------------------------------------------------------------------------------------------------------------------------------------
  138. --BCHG--
  139.  
  140. Notes: Swaps whatever the binary number is. 1 becomes 0, 0 becomes 1.
  141. ---------------------------------------------------------------------------------------------------------------------------------------
  142. --SIGNED-- / --UNSIGNED--
  143.  
  144. 00 to 7F                =   signed. (negative)
  145. 80 to FF                =   signed. (positive)
  146.  
  147. 00 to FF                =   unsigned. (positive)
  148. ---------------------------------------------------------------------------------------------------------------------------------------
  149. --NEG--
  150.  
  151. Scenario: d0 has 220002
  152.  
  153. neg.b     d0            =   002200FE (02 to FE, +2 to -2, rolls back)
  154.  
  155. Notes: This wont work with neutral numbers, 00 can't cancel out 00; 80 is the beginning of the negative, therefore it will have nothing (00).
  156. ---------------------------------------------------------------------------------------------------------------------------------------
Advertisement
Add Comment
Please, Sign In to add comment
Advertisement
Public Pastes
Advertisement
We use cookies for various purposes including analytics. By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy.  OK, I Understand
Not a member of Pastebin yet?
Sign Up, it unlocks many cool features!