Routines
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68B1: Play Square Wave
Used by the routines at PlayChirp, PlayRisingTone, LevelStartJingle and Handler_RisingSweep.
Plays one cycle of a square wave; the speaker is switched on for a period of time and then switched off for the same amount of time.
Input
D Duration of wave
PlaySquareWave 68B1 LD A,$10 Play square wave sound.
68B3 OUT ($FE),A
68B5 LD B,D
PlaySquareWave_Loop 68B6 DJNZ PlaySquareWave_Loop
68B8 XOR A Play "silence".
68B9 OUT ($FE),A
68BB LD B,D
Silence_Loop 68BC DJNZ Silence_Loop
68BE RET Return.
View the equivalent code in;
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