Controller 3 Jump Op

Controller 3 Jump Op

We can generate an arbitrary jump to any address within RDRAM by pressing the following buttons:

//This sets J op
0800 = D-Up button

//Combinations of these sets J range between 0x00_0000 and 0x7C_0000
0010 = R Button
0008 = C-Up
0004 = C-Down
0002 = C-Left
0001 = C-Right

//Joystick input adds between 0000000 and 03FFFC to J
//with an adapter, any value is possible, but physically there's an approx. limitation of +- 81 units
02: s8 = X axis, right is positive, left is negative
03: s8 = Y axis, up is positive, down is negative


However, the delay slot is InputLast. If we hold Controller 3 input, the following are generated:

Input   J       Delay Slot Op
0800    000000  sll at, r0, 0
0801    040000  (Special)   //undefined
0802    080000  srl at, r0, 0
0803    0C0000  sra at, r0, 0
0804    100000  sllv at, r0, r0
0805    140000  (Special)   //undefined
0806    180000  srlv at, r0, r0
0807    1C0000  srav at, r0, r0
0808    200000  jr r0       //crash due to jump in delay slot
0809    240000  jalr at, r0 //crash due to jump in delay slot
080A    280000  (Special)   //undefined
080B    2C0000  (Special)   //undefined
080C    300000  SYSCALL     //not sure what this does
080D    340000  BREAK       //makes no sense in a delay slot, might have undefined behavior?
080E    380000  (Special)   //undefined
080F    3C0000  SYNC        //not sure what this does
0810    400000  mfhi at
0811    440000  mthi r0
0812    480000  mflo at
0813    4C0000  mtlo r0
0814    500000  dsllv at, r0, r0
0815    540000  (Special)   //undefined
0816    580000  dsrlv at, r0, r0
0817    5C0000  dsrav at, r0, r0
0818    600000  mult r0, r0
0819    640000  multu r0, r0
081A    680000  div r0, r0
081B    6C0000  divu r0, r0
081C    700000  dmult r0, r0
081D    740000  dmultu r0, r0
081E    780000  ddiv r0, r0
081F    7C0000  ddivu r0, r0