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The Little Mermaid/ROM map: Difference between revisions
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| Line 4: | Line 4: | ||
0x8000 | 0x8000 | ||
Runs the action scripts of every object slot | Runs the action scripts of every object slot from lowest to highest and checks for collisions each frame. | ||
06:8000:A5 B1 LDA $00B1 ; Check Ariel's health | 06:8000:A5 B1 LDA $00B1 ; Check Ariel's health | ||
06:8002:F0 3A BEQ $803E ; Exit if zero | 06:8002:F0 3A BEQ $803E ; Exit if zero | ||
| Line 38: | Line 38: | ||
06:803C:D0 CA BNE $8008 | 06:803C:D0 CA BNE $8008 | ||
06:803E:60 RTS ----------------------------------------- | 06:803E:60 RTS ----------------------------------------- | ||
Page 07 (0xC000-0xFFFF) | |||
Location in ROM: 0x1C010-0x2000F | |||
0xC250 | |||
Advance random number generator each frame | |||
07:C250:A2 00 LDX #$00 | |||
07:C252:A0 04 LDY #$04 | |||
07:C254:B5 E4 LDA $E4,X | |||
07:C256:29 02 AND #$02 | |||
07:C258:85 00 STA $0000 | |||
07:C25A:B5 E5 LDA $E5,X | |||
07:C25C:29 02 AND #$02 | |||
07:C25E:45 00 EOR $0000 ; If 0x02 bits of 0xE4 and 0xE5 | |||
07:C260:18 CLC ; are the same, highest bit of | |||
07:C261:F0 01 BEQ $C264 ; new RNG value will be zero. | |||
07:C263:38 SEC ; Otherwise, it will be one. | |||
07:C264:76 E4 ROR $E4,X ; Then shift all previous bits right. | |||
07:C266:E8 INX | |||
07:C267:88 DEY | |||
07:C268:D0 FA BNE $C264 | |||
07:C26A:60 RTS ----------------------------------------- | |||
Revision as of 22:15, 27 December 2018
Page 06 (0x8000-0xBFFF)
Address in ROM: 0x18010-0x1C00F
0x8000 Runs the action scripts of every object slot from lowest to highest and checks for collisions each frame. 06:8000:A5 B1 LDA $00B1 ; Check Ariel's health 06:8002:F0 3A BEQ $803E ; Exit if zero 06:8004:A2 01 LDX #$01 06:8006:86 EF STX $00EF ; Current slot # 06:8008:A9 06 LDA #$06 06:800A:85 99 STA $0099 ; ? 06:800C:BD 00 03 LDA $0300,X 06:800F:10 25 BPL $8036 ; Skip ahead if slot is empty 06:8011:BD A0 04 LDA $04A0,X ; Check if object is stunned 06:8014:D0 16 BNE $802C ; If so, skip action script 06:8016:BC 10 03 LDY $0310,X 06:8019:B9 20 85 LDA $8520,Y ; Obtain address of action script 06:801C:85 00 STA $0000 ; from jump table located 06:801E:B9 80 85 LDA $8580,Y ; at 0x8520,0x8580 06:8021:85 01 STA $0001 06:8023:A9 80 LDA #$80 ; Set return address 06:8025:48 PHA 06:8026:A9 2B LDA #$2B 06:8028:48 PHA 06:8029:6C 00 00 JMP ($0000) ; Run object's action script 06:802C:E0 03 CPX #$03 ; Check if object is a bubble 06:802E:90 06 BCC $8036 ; Jump ahead if so 06:8030:20 3F 80 JSR $803F ; Run action if object is colliding with Ariel 06:8033:20 FF 80 JSR $80FF ; Run action if object is colliding with a bubble 06:8036:E6 EF INC $00EF ; Tick up to next object slot 06:8038:A6 EF LDX $00EF 06:803A:E0 10 CPX #$10 ; Loop until all slots examined 06:803C:D0 CA BNE $8008 06:803E:60 RTS -----------------------------------------
Page 07 (0xC000-0xFFFF)
Location in ROM: 0x1C010-0x2000F
0xC250 Advance random number generator each frame 07:C250:A2 00 LDX #$00 07:C252:A0 04 LDY #$04 07:C254:B5 E4 LDA $E4,X 07:C256:29 02 AND #$02 07:C258:85 00 STA $0000 07:C25A:B5 E5 LDA $E5,X 07:C25C:29 02 AND #$02 07:C25E:45 00 EOR $0000 ; If 0x02 bits of 0xE4 and 0xE5 07:C260:18 CLC ; are the same, highest bit of 07:C261:F0 01 BEQ $C264 ; new RNG value will be zero. 07:C263:38 SEC ; Otherwise, it will be one. 07:C264:76 E4 ROR $E4,X ; Then shift all previous bits right. 07:C266:E8 INX 07:C267:88 DEY 07:C268:D0 FA BNE $C264 07:C26A:60 RTS -----------------------------------------