Routines
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41896: Sounds: Click
Used by the routines at FallThroughTrapdoor, SoundsAxeThrow, SoundsSword, SoundsFireball and SoundsWeaponPop.
Plays a tone on the speaker by switching it on and off. Each cycle is a wait of the half period with the speaker on and the same wait with the speaker off.
This entry plays one cycle (a click). The entry at SoundsBeep plays the number of cycles that is in C, and the routines which follow play other tones by loading BC and jumping to it.
Writing 16 to port 254 sets the speaker bit and leaves the border black.
A single click is too short to be heard on its own, so there is no sample for it here. It is heard in the run of clicks played by SoundsWeaponPop (which has a sample), and in those played by SoundsAxeThrow, SoundsSword and SoundsFireball, and when the player falls through a trapdoor in FallThroughTrapdoor.
Input
B The half period of the tone (0 is 256)
SoundsClick 41896 LD C,1 C=1 (one cycle).
This entry point is used by the routines at SoundsInventory, SoundsDropItem, SoundsWalking, SoundsWalkLow, SoundsStart, SoundEffect, SoundEffectNext, SoundsAppear, SoundEffectEating and SoundsBounce.
Play C cycles of the tone.
SoundsBeep 41898 LD A,16 A=16 (the speaker bit).
41900 OUT (254),A Switch the speaker on.
41902 PUSH BC Stash the cycle counter and the half period on the stack, as the wait counts B down to zero.
SoundsClick_OnDelay 41903 DJNZ SoundsClick_OnDelay Wait for the half period.
41905 POP BC Restore the cycle counter and the half period from the stack.
41906 PUSH BC Stash them on the stack again.
41907 XOR A A=0 (clear the speaker bit).
41908 OUT (254),A Switch the speaker off.
SoundsClick_OffDelay 41910 DJNZ SoundsClick_OffDelay Wait for the half period.
41912 POP BC Restore the cycle counter and the half period from the stack.
41913 DEC C Decrease the cycle counter by one.
41914 JR NZ,SoundsBeep Jump back to SoundsBeep until all of the cycles have been played.
41916 RET Return.
View the equivalent code in;
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