Routines
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29152: Play Square Wave
Used by the routines at PlayArrivalSound, PlayWarble, PlayFlutterSound, PlayHitSound and PlayBumpSound.
Makes one cycle of a square wave with the speaker. The speaker is on for as long as it is off, which is set by B: the higher it is, the lower the note.
Input
B Half the length of the cycle
Output
B Unchanged
PlaySquareWave 29152 LD A,16 Turn the speaker on.
29154 OUT (254),A Send that to the speaker.
29156 LD A,B Keep the half-period.
PlaySquareWave_Delay 29157 DJNZ PlaySquareWave_Delay Hold this half of the cycle.
29159 LD B,A Restore the half-period.
29160 XOR A Turn the speaker off.
29161 OUT (254),A Send that to the speaker.
29163 LD A,B Keep the half-period again.
PlaySquareWave_Wait 29164 DJNZ PlaySquareWave_Wait Hold the other half of the cycle.
29166 LD B,A Restore the half-period.
29167 RET Return.
View the equivalent code in;
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