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Viewing Issue Advanced Details
| ID | Category [?] | Severity [?] | Reproducibility | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 01326 | DIP/Input | Minor | Have not tried | Feb 19, 2008, 15:43 | Feb 19, 2008, 15:43 |
| Tester | -Misc Reporters- | View Status | Public | Platform | |
| Assigned To | stephh | Resolution | Bugs That Aren't Bugs | OS | |
| Status [?] | Resolved | Driver | |||
| Version | N/A | Fixed in Version | Build | ||
| Fixed in Git Commit | Github Pull Request # | ||||
| Summary | 01326: madcrash: The extra lives don't fit the "Bonus Life" Dip Switch when you set the "Occurence" Dip Switch to "1st, 2nd then every 2nd". | ||||
| Description | The extra lives don't fit the "Bonus Life" Dip Switch when you set the "Occurence" Dip Switch to "1st, 2nd then every 2nd". | ||||
| Steps To Reproduce | |||||
| Additional Information |
marvins.c merged into snk.c in 0.127u2 Read the text file for more info. "Basic" Z80 knowledge needed, sorry ;) - stephh madcrash (marvins.c driver) There is an ingame bug if you set the "Occurence" Dip Switch to "1st, 2nd then every 2nd" ... Here are some useful addresses : - 0xc663-0xc666 : player score (BCD coded, MSB first) - 0xc303-0xc306 : 1st bonus life (BCD coded, MSB first) - 0xc307-0xc30a : 2nd bonus life (BCD coded, MSB first) - 0xc670-0xc673 : next bonus life in case of more than 2 occurences (MSB first) In fact, only these addresses interest us : 0xc663-0xc664, 0xc307-0xc308 and 0xc670-0xc671 ... I assume that you've set the "Bonus Lives" Dip Switch to "20k, 60k" ... When you start a game, here are the contents of the addresses : - 0xc663 = 0x00 and 0xc664 = 0x00 - 0xc307 = 0x00 and 0xc308 = 0x06 - 0xc670 = 0x00 and 0xc671 = 0x00 When you get your 1st life at 20000 points, this code is executed : [BEGIN] 1300: 21 07 C3 ld hl,$C307 1303: 11 70 C6 ld de,$C670 1306: 01 04 00 ld bc,madcrash (marvins.c driver)04 1309: ED B0 ldir [END] So the contents of the addresses are now : - 0xc663 = 0x00 and 0xc664 = 0x02 - 0xc307 = 0x00 and 0xc308 = 0x06 - 0xc670 = 0x00 and 0xc671 = 0x06 But when your score reaches 60000 points, this code is executed : [BEGIN] 1352: 11 0A C3 ld de,$C30A 1355: 21 73 C6 ld hl,$C673 1358: 06 04 ld b, 135A: 37 scf 135B: 3F ccf 135C: 1A ld a,(de) 135D: 1B dec de 135E: 8E adc a,(hl) 135F: 77 ld (hl),a 1360: 2B dec hl 1361: 10 F9 djnz 5C [END] If you watch carefully, you'll notice that there is NO 'daa' ("decimal ajust", needed when you add/sub BCD numbers) after the 'adc a,(hl)' at address 0x135e ... So the contents of the addresses are now : - 0xc663 = 0x00 and 0xc664 = 0x06 - 0xc307 = 0x00 and 0xc308 = 0x06 - 0xc670 = 0x00 and 0xc671 = 0x0c !!! When your scores reaches 100000 points, 0xc663 = 0x00 and 0xc664 = 0x10 ... And 0x0010 > 0x000c ... So you get ANOTHER life and the buggy routine is called again ! So the contents of the addresses are now : - 0xc663 = 0x00 and 0xc664 = 0x10 - 0xc307 = 0x00 and 0xc308 = 0x06 - 0xc670 = 0x00 and 0xc671 = 0x12 !!! And this means that another life will be awarded when your score reaches 120000 points (0xc663 = 0x00 and 0xc664 = 0x12) ! I could continue for ever ;) I hope that you've understood everything ... |
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| Affected Sets / Systems | madcrash | ||||
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