| Chase H.Q. | Routines |
| Prev: A955 | Up: Map | Next: A9DE |
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This seems to calculate the position of stones on the dirt track section.
Used by the routines at main_loop and cpu_driver.
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| layout_dirt_and_stones | A97E | LD A,$00 | A = <self modified> -- Self modified by A974 | |
| A980 | AND A | Return if A is zero | ||
| A981 | RET Z | |||
| A982 | LD IYh,$E3 | IY = $E361 | ||
| A985 | LD IYl,$61 | |||
| A988 | LD BC,$1400 | BC = $1400 | ||
| A98B | LD HL,$ED28 | Point HL at (something above the stack) | ||
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Scan through whatever-it-is for a non-zero byte. Move 4 bytes per iteration.
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| ldas_loop1 | A98E | LD A,(HL) | A = *HL++ | |
| A98F | AND A | Set flags | ||
| A990 | INC HL | |||
| A991 | JR NZ,layout_dirt_and_stones_0 | Jump to A9A7 if non-zero | ||
| A993 | INC HL | HL += 3 | ||
| A994 | INC HL | |||
| A995 | INC HL | |||
| ldas_loop1_continue | A996 | DEC IY | IY-- | |
| A998 | DJNZ ldas_loop1 | Loop to ldas_loop1 while B > 0 | ||
| A99A | LD A,C | A = C | ||
| A99B | AND A | Set flags | ||
| A99C | RET NZ | Return if non-zero | ||
| A99D | LD ($A97F),A | Self modify LD A @ layout_dirt_and_stones | ||
| A9A0 | LD ($C0BC),A | Self modify LD A @ rm_c0bb | ||
| A9A3 | LD ($A9DF),A | Self modify LD A @ dust_stones_stuff | ||
| A9A6 | RET | Return | ||
| layout_dirt_and_stones_0 | A9A7 | LD A,(HL) | A = *HL++ | |
| A9A8 | INC HL | |||
| A9A9 | INC C | C++ | ||
| A9AA | EXX | |||
| A9AB | EX AF,AF' | Bank A | ||
| A9AC | LD A,(IY+$01) | L = ~(IY[1] * 2) | ||
| A9AF | ADD A,A | |||
| A9B0 | CPL | |||
| A9B1 | LD L,A | |||
| A9B2 | LD H,$E8 | H = $E8 -- road drawing (left) | ||
| A9B4 | LD D,(HL) | D = *HL | ||
| A9B5 | DEC L | L-- | ||
| A9B6 | LD E,(HL) | E = *HL | ||
| A9B7 | LD H,$EC | H = $EC | ||
| A9B9 | LD A,(HL) | A = *HL | ||
| A9BA | INC L | L++ | ||
| A9BB | LD H,(HL) | H = *HL | ||
| A9BC | LD L,A | L = A | ||
| A9BD | AND A | Set flags | ||
| A9BE | PUSH DE | |||
| A9BF | SBC HL,DE | HL -= DE | ||
| A9C1 | EX DE,HL | |||
| A9C2 | LD HL,$0000 | HL = $0000 [not self modified] | ||
| A9C5 | EX AF,AF' | Unbank A | ||
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Multiplier.
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| A9C6 | LD B,$08 | B = 8 | ||
| ldas_loop2 | A9C8 | RLA | ||
| A9C9 | JR NC,layout_dirt_and_stones_1 | If carry HL += DE | ||
| A9CB | ADD HL,DE | |||
| layout_dirt_and_stones_1 | A9CC | ADD HL,HL | HL <<= 1 | |
| A9CD | DJNZ ldas_loop2 | Loop to ldas_loop2 while B > 0 | ||
| A9CF | LD A,H | A = H | ||
| A9D0 | RRA | |||
| A9D1 | LD C,A | C = A | ||
| A9D2 | POP HL | |||
| A9D3 | ADD HL,BC | HL += BC | ||
| A9D4 | PUSH HL | |||
| A9D5 | EXX | |||
| A9D6 | POP DE | |||
| A9D7 | LD (HL),E | DE = wordat(HL); HL += 2 | ||
| A9D8 | INC HL | |||
| A9D9 | LD (HL),D | |||
| A9DA | INC HL | |||
| A9DB | JP ldas_loop1_continue | Jump to ldas_loop1_continue | ||
| Prev: A955 | Up: Map | Next: A9DE |