Routines
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63E1: Play Tune
Used by the routine at LevelComplete.
Plays a tune one note at a time until the terminator is reached. The low five bits of each byte in the tune data are a note number from 01 to 08 which is used to look up the pitch and the duration of the note in the table at NoteTable for the ROM BEEPER routine.
Input
DE Pointer to the tune data
PlayMusic 63E1 LD A,(DE) Fetch the next note of the tune.
63E2 CP $FF Return if the terminator (FF) has been reached.
63E4 RET Z
63E5 AND %00011111 Keep only bits 0-4 (the note number).
63E7 DEC A Decrease the note number by one (the notes are numbered from one).
63E8 SLA A Double it, as there are two bytes for each note in the table.
63EA LD C,A Make this the offset into the note table in BC.
63EB LD B,$00
63ED LD HL,$640D HL=NoteTable (the note table).
63F0 ADD HL,BC Add the offset to find the note.
63F1 PUSH DE Stash the tune pointer on the stack.
63F2 LD A,(HL) Fetch the pitch of the note.
63F3 INC HL Move onto the duration of the note.
63F4 LD E,(HL) E=the duration of the note.
63F5 LD D,$00 Set the high byte of the duration (D) to 00.
63F7 LD L,A HL=the pitch of the note.
63F8 LD H,$00
63FA SLA L Multiply HL by four to make the pitch for the beeper.
63FC RL H
63FE SLA L
6400 RL H
6402 PUSH IX Stash IX on the stack, as the beeper routine overwrites it.
6404 CALL $03B5 Call BEEPER.
6407 POP IX Restore IX and the tune pointer from the stack.
6409 POP DE
640A INC DE Move onto the next note of the tune.
640B JR PlayMusic Loop back round to PlayMusic to play the next note (the tune only ends when the terminator is reached).
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