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Routines |
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Clears the high score, the game options, the sound flag and the 1UP and 2UP scores, calculates a checksum of the ROM BEEPER routine to set the sound flag, and sets the border colour system variable.
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Blank the high score, game options, sound flag, 1UP and 2UP scores.
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| GameInitialisation | 25037 | LD HL,24064 | HL=24064 (the high score), B=11 (the byte counter) and C=0 (the value to write). | |
| 25040 | LD BC,2816 | |||
| GameInitialisation_Loop | 25043 | LD (HL),C | Clear the byte. | |
| 25044 | INC HL | Move onto the next byte. | ||
| 25045 | DJNZ GameInitialisation_Loop | Decrease the byte counter by one and loop back to GameInitialisation_Loop until all 11 bytes have been cleared. | ||
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This calculates a "checksum" of the BEEPER routine. The expected value at the end is 0 and if Sound_Enable does not contain 0 then the tunes are not played.
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| 25047 | LD HL,949 | HL=BEEPER. | ||
| 25050 | LD B,67 | Set the byte counter to 67 (the length of the routine). | ||
| 25052 | XOR A | A=0 (the start of the checksum). | ||
| Mute_Loop | 25053 | ADD A,(HL) | Add the byte of the routine to the checksum. | |
| 25054 | INC HL | Move onto the next byte of the routine. | ||
| 25055 | DJNZ Mute_Loop | Decrease the byte counter by one and loop back to Mute_Loop until the whole routine has been added. | ||
| 25057 | ADD A,104 | Add 104 to the checksum (which gives 0 if the routine is unchanged). | ||
| 25059 | LD (24068),A | Store the checksum at Sound_Enable (the sound flag). | ||
| 25062 | XOR A | Write 0 to BORDCR. | ||
| 25063 | LD (23624),A | |||
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Continue on to Game_Restart.
View the equivalent code in;
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