Tranz Am: Routine at 24859

Used by the routine at HandlerPlayer.

Plays the next step of the sound made when a cup is collected or the car is refuelled. This is called every frame but only makes a sound on every other frame. The step counter is held at SoundCounter. For the refuel sound it counts down from 7 and bit 7 is clear; each step has a higher pitch than the one before. For the cup sound it starts at 135 (bit 7 set) and each step has a lower pitch than the one before. Each step plays 32 square waves using PlaySquareWave, and there are six of them. The cup sound:

The refuel sound:

Used by the routine at HandlerPlayer. Plays the next step of the sound made when a cup is collected or the car is refuelled. This is called every frame but only makes a sound on every other frame. The step counter is held at SoundCounter. For the refuel sound it counts down from 7 and bit 7 is clear; each step has a higher pitch than the one before. For the cup sound it starts at 135 (bit 7 set) and each step has a lower pitch than the one before. Each step plays 32 square waves using PlaySquareWave, and there are six of them. The cup sound: The refuel sound:
SoundsCupRefuel	24859	LD A,(24105)	Fetch the game timer from GameTimer.
	24862	AND %00000001	Keep only bit 0.
	24864	RET NZ	Return on every other frame.
	24865	LD HL,24134	Point HL at the step counter (SoundCounter).
	24868	LD A,(HL)	Fetch the step counter.
	24869	BIT 7,A	Jump to SoundsCup if bit 7 is set, as that is the cup sound.
	24871	JR NZ,SoundsCup
	24873	AND A	Return if the step counter is zero, as there is no sound to play.
	24874	RET Z
	24875	DEC A	Decrease the step counter by one.
	24876	LD (HL),A	Write the new step counter back to SoundCounter.
	24877	RET Z	Return if the step counter has reached zero, as the sound is over.
Work out the period of the waves from the step counter.
SoundsRefuel	24878	RLCA	Multiply the step counter by 4 by rotating it left twice.
	24879	RLCA	Multiply the step counter by 4 by rotating it left twice.
	24880	AND %00011100	Keep only bits 2-4.
	24882	OR %00100000	Set bit 5.
	24884	LD D,A	Set the period of the waves.
	24885	LD C,32	Set the wave counter to 32.
SoundsCupRefuel_Loop	24887	CALL PlaySquareWave	Play a square wave using PlaySquareWave.
	24890	DEC C	Decrease the wave counter by one and loop back to SoundsCupRefuel_Loop until all 32 waves have been played.
	24891	JR NZ,SoundsCupRefuel_Loop
	24893	RET	Return.
The cup sound keeps bit 7 set in the step counter, and inverts the step so that the pitch falls rather than rises.
SoundsCup	24894	AND %01111111	Keep only the step counter (bits 0-6).
	24896	RET Z	Return if the step counter is zero, as the sound is over.
	24897	DEC A	Decrease the step counter by one.
	24898	OR %10000000	Set bit 7 so that the sound stays the cup sound.
	24900	LD (HL),A	Write the new step counter back to SoundCounter.
	24901	AND %01111111	Keep only the step counter (bits 0-6).
	24903	RET Z	Return if the step counter has reached zero.
	24904	CPL	Flip the bits, so that the pitch falls with each step.
	24905	JR SoundsRefuel	Jump to SoundsRefuel.