Routines
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6568: Play Music
Used by the routines at StartGame, HandleCake and HandleFallingCharlie.
Plays a tune using the BEEPER routine. Each byte of the tune is a note number, in bits 0-4, which chooses the pitch and length of the note from the table at MusicNotes. The tune ends at the byte FF.
Input
DE Address of the tune
PlayMusic 6568 LD A,(DE) Fetch the next note of the tune.
6569 CP $FF Return if the end of the tune (FF) has been reached.
656B RET Z
656C AND %00011111 Keep only bits 0-4 (the note number).
656E DEC A Decrease the note number by one (note numbers start from 01).
656F SLA A Double the note number, as there are two bytes for each note.
6571 LD C,A Use the result as an offset into the table of notes.
6572 LD B,$00
6574 LD HL,$6594 Find the entry for the note in MusicNotes.
6577 ADD HL,BC
6578 PUSH DE Stash the pointer to the tune on the stack.
6579 LD A,(HL) Fetch the pitch of the note.
657A INC HL Increment HL by one.
657B LD E,(HL) Fetch the length of the note into E.
657C LD D,$00 Set the high byte of the length to 00.
657E LD L,A Put the pitch in L.
657F LD H,$00 Set the high byte of the pitch to 00.
6581 SLA L Multiply the pitch by 04 for the BEEPER routine.
6583 RL H
6585 SLA L
6587 RL H
6589 PUSH IX Stash IX on the stack.
658B CALL $03B5 Play the note using BEEPER.
658E POP IX Restore IX from the stack.
6590 POP DE Restore the pointer to the tune from the stack.
6591 INC DE Move on to the next note of the tune.
6592 JR PlayMusic Jump back to PlayMusic to play the next note (the tune only ends when the terminator is reached).
View the equivalent code in;
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