| Chase H.Q. | Routines |
| Prev: C2E7 | Up: Map | Next: C57C |
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| main_loop_13 | C452 | LD ($C8A4),SP | Self modify SP restore instruction | |
| C456 | XOR A | |||
| C457 | LD ($A248),A | var_a248 = 0 | ||
| C45A | LD ($C161),A | Self modify 'LD A,x' @ C160 to be zero (tunnel drawing code) | ||
| C45D | LD ($C890),A | Self modify 'LD A,x' @ C88F to be zero | ||
| C460 | LD A,$03 | Self modify 'LD A,x' @ C6D8 to be 3 | ||
| C462 | LD ($C6D9),A | |||
| C465 | LD IY,$E301 | IY = $E301 | ||
| C469 | LD A,$60 | C = $60 - IY[0] | ||
| C46B | SUB (IY+$00) | |||
| C46E | LD C,A | |||
| C46F | LD A,($A240) | Load road_buffer_offset into A | ||
| C472 | ADD A,$40 | Add 64 so it's the lanes data offset | ||
| C474 | LD IXl,A | IX = $EE00 + A | ||
| C476 | LD IXh,$EE | |||
| C479 | LD B,A | B = A | ||
| C47A | AND $01 | |||
| C47C | LD ($C6B3),A | $C6B3 = A & 1 | ||
| C47F | RR B | RR B twice | ||
| C481 | RR B | |||
| C483 | LD HL,$D010 | HL = $D010 doubtful that this is a pointer | ||
| C486 | LD A,H | A = $D0 | ||
| C487 | LD B,$55 | B = $55 -- Set this to $00 and the landscape goes blank - but only half the time | ||
| C489 | JR C,j_c48f | If B carried out earlier then jump | ||
| C48B | LD HL,$0030 | HL = $0030 | ||
| C48E | LD B,H | B = $00 | ||
| j_c48f | C48F | LD ($C6D4),A | Self modify 'XOR x' @ C6D3 to be zero [OR $D0 -- check other code again] | |
| C492 | LD A,H | A = $00 | ||
| C493 | LD ($C678),A | Self modify 'ADD A,x' @ C677 | ||
| C496 | LD A,L | A = $30 | ||
| C497 | LD ($C652),A | Self modify 'ADD A,x' @ C651 to be $30 | ||
| C49A | INC A | A = $31 | ||
| C49B | LD ($C699),A | Self modify 'ADD A,x' @ C698 to be $31 | ||
| C49E | LD HL,$C534 | HL = $C534 | ||
| C4A1 | LD ($C4B3),HL | Self modify 'JP Z,x' @ C4B2 to be main_loop_13_9 | ||
| C4A4 | LD L,$FF | L = $FF | ||
| C4A6 | LD DE,$0100 | DE = $0100 | ||
| C4A9 | LD A,B | A = B | ||
| C4AA | LD ($C6BD),A | Self modify 'LD A,x' @ C6BC to be zero? | ||
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This entry point is used by the routine at C598.
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| main_loop_13_0 | C4AD | LD A,(IX+$00) | A = IX[0] & 3 | |
| C4B0 | AND $03 | |||
| C4B2 | JP Z,main_loop_13_9 | Jump to <self modified> if zero | ||
| C4B5 | EXX | Bank | ||
| C4B6 | LD L,(IX+$00) | L = IX[0] -- sampled IX=$EEFD $EEFE $EEFF $EE00 .. etc. | ||
| C4B9 | ADD A,$E7 | A += $E7 | ||
| C4BB | LD ($C643),A | Self modify 'LD H,x' @ C642 | ||
| C4BE | LD ($C5B4),A | Self modify 'LD H,x' @ C5B3 | ||
| C4C1 | LD H,A | H = A | ||
| C4C2 | SLA L | L <<= 1 | ||
| C4C4 | BIT 7,L | New bit 7 set? | ||
| C4C6 | JR NZ,main_loop_13_3 | Jump if set -- Split road plotting path | ||
| C4C8 | JR NC,main_loop_13_1 | |||
| C4CA | ADD A,$03 | A &= 3 | ||
| C4CC | LD C,$FD | C = $FD | ||
| C4CE | JP main_loop_13_2 | Jump | ||
| main_loop_13_1 | C4D1 | ADD A,$02 | A += 2 | |
| C4D3 | LD C,$FE | C = $FE | ||
| main_loop_13_2 | C4D5 | LD ($C5DA),A | Self modify 'LD H,x' @ C5D9 | |
| C4D8 | LD ($C68B),A | Self modify 'LD H,x' @ C68A | ||
| C4DB | LD A,C | A = C | ||
| C4DC | LD ($C5AD),A | Self modify 'LD B,x' @ C5AC | ||
| C4DF | JP $C2E7 | Jump | ||
| main_loop_13_3 | C4E2 | JR C,main_loop_13_7 | -- Split road plotting path | |
| C4E4 | LD C,$FF | C = $FF | ||
| C4E6 | LD H,$01 | H = $01 | ||
| C4E8 | BIT 4,L | Bit 4 set? | ||
| C4EA | JR NZ,main_loop_13_4 | Jump if set | ||
| C4EC | BIT 3,L | Bit 3 set? | ||
| C4EE | JR Z,main_loop_13_6 | Jump if clear | ||
| main_loop_13_4 | C4F0 | LD A,IYl | A = IY.low | |
| C4F2 | LD ($C15E),A | Self modify 'CP x' @ C15D | ||
| C4F5 | LD A,$01 | A = 1 | ||
| C4F7 | INC C | C++ | ||
| C4F8 | BIT 5,L | Bit 5 set? | ||
| C4FA | JR Z,main_loop_13_5 | Jump if clear | ||
| C4FC | DEC C | C-- | ||
| C4FD | INC A | A++ | ||
| C4FE | DEC H | H-- | ||
| main_loop_13_5 | C4FF | LD ($C161),A | Self modify 'LD A,x' @ C160 | |
| main_loop_13_6 | C502 | LD A,H | A = H | |
| C503 | LD ($C890),A | Self modify 'LD A,x' @ C88F | ||
| C506 | LD A,$EB | A = $EB | ||
| C508 | LD ($C5DA),A | Self modify 'LD H,x' @ C5D9 | ||
| C50B | LD ($C68B),A | Self modify 'LD H,x' @ C68A | ||
| C50E | LD A,$FF | A = $FF | ||
| C510 | LD ($C5AD),A | Self modify 'LD B,x' @ C5AC | ||
| C513 | LD A,C | A = C | ||
| C514 | EXX | Bank/unbank | ||
| C515 | LD B,A | B = A | ||
| C516 | JP main_loop_13_11 | Jump | ||
| main_loop_13_7 | C519 | BIT 6,L | Bit 6 set? | |
| C51B | JP NZ,$C8E3 | Jump if set -- Split road plotting path | ||
| C51E | LD A,L | A = L | ||
| C51F | AND $18 | A &= 24 | ||
| C521 | LD A,$00 | A = 0 | ||
| C523 | JR NZ,main_loop_13_8 | Jump if non-zero | ||
| C525 | INC A | A++ | ||
| main_loop_13_8 | C526 | LD ($A248),A | var_a248 = A | |
| C529 | LD A,$FF | A = $FF | ||
| C52B | LD ($C5AD),A | Self modify 'LD B,x' @ C5AC | ||
| C52E | LD HL,$C534 | |||
| C531 | JP main_loop_13_10 | Jump forward | ||
| main_loop_13_9 | C534 | EXX | Bank/unbank | |
| C535 | LD A,$E8 | A = $E8 | ||
| C537 | LD ($C643),A | Self modify 'LD H,x' @ C642 | ||
| C53A | LD ($C5B4),A | Self modify 'LD H,x' @ C5B3 | ||
| C53D | ADD A,$04 | A += 4 | ||
| C53F | LD ($C68B),A | Self modify 'LD H,x' @ C68A | ||
| C542 | LD ($C5DA),A | Self modify 'LD H,x' @ C5D9 | ||
| C545 | LD A,$FC | A = $FC | ||
| C547 | LD ($C5AD),A | Self modify 'LD B,x' @ C5AC | ||
| C54A | LD HL,$C551 | |||
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This entry point is used by the routine at C2E7.
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| main_loop_13_10 | C54D | LD ($C4B3),HL | Self modify 'JP Z,x' @ C4B2 | |
| C550 | EXX | Bank/unbank | ||
| main_loop_13_11 | C551 | LD A,B | A = B | |
| C552 | AND A | Set flags | ||
| C553 | JP NZ,$C598 | Jump if non-zero | ||
| C556 | EXX | Bank/unbank | ||
| C557 | LD HL,$C55F | Self modify 'JP NZ,x' @ C6AD to be C55F | ||
| C55A | LD ($C6AE),HL | |||
| C55D | EXX | Bank/unbank | ||
| C55E | EX AF,AF' | |||
| C55F | LD A,D | A = D | ||
| C560 | DEC D | D-- | ||
| C561 | AND $0F | A &= 15 | ||
| C563 | JR Z,$C58A | Jump if zero | ||
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This entry point is used by the routine at C58A.
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| main_loop_13_12 | C565 | LD ($C56D),DE | Self modify 'LD DE,x' @ C56C (below) | |
| C569 | LD B,$FF | B = $FF | ||
| C56B | EXX | Bank/unbank | ||
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Calculate address of next bitmap scanline ??
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| C56C | LD DE,$0000 | DE = <self modified> | ||
| C56F | LD A,E | L = E + 31 | ||
| C570 | ADD A,$1F | |||
| C572 | LD L,A | |||
| C573 | LD H,D | H = D | ||
| C574 | LD SP,HL | Put it in SP (so we can use PUSH for speed) | ||
| C575 | LD HL,$0000 | HL = 0 [not self modified apparently] | ||
| C578 | LD C,L | C = L | ||
| C579 | JP $C62E | Jump into a sequence of 15 PUSH HLs | ||
| Prev: C2E7 | Up: Map | Next: C57C |