Routines
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7217: Play Warble
Used by the routine at PlayExplosionSound.
Makes a warble of four beeps that alternate between two notes. Nothing is played if the stage is 10 or more or is 07 or 08.
Input
A Stage
PlayWarble 7217 CP $10 Return if A is 10 or more.
7219 RET NC
721A CP $07 Jump to PlayWarble_Play if A is less than 07.
721C JR C,PlayWarble_Play
721E CP $09 Return if A is less than 09.
7220 RET C
PlayWarble_Play 7221 AND %00001111 Keep the bits of A that are set in 0F.
7223 ADD A,A Double the stage to spread the two notes.
7224 ADD A,$48 Add the base pitch of the warble.
7226 LD B,A That is the first half-period.
7227 LD C,$04 The warble is four beeps.
PlayWarble_Loop 7229 LD A,B Start from the current half-period.
722A XOR %00101010 Flip the bits of A that are set in 2A.
722C LD B,A Keep the note for the next beep.
722D CALL PlaySquareWave Call PlaySquareWave.
7230 DEC C One beep of the warble has been played.
7231 JR NZ,PlayWarble_Loop Jump to PlayWarble_Loop if the zero flag is clear.
7233 RET Return.
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