Stormbringer (48k): Routine at 47897

47897: Set parameters for and play upward scale sound

The value of A (set to zero at the start of this routine, or set to 1 before jumps from other routines into 47902) is a delay constant that determines the speed at which the sound is played.

Used by the routines at 37764, 37880, 37951, 38024, 42494, 62330, 64230 and 64926.

Input
A	(Entry at 47902 only) Delay constant

47897

XOR A

Set A to 0

47898

LD B,13

Set B to 13 (DEC C)

47900

LD H,A

Set HL to 0...

47901

LD L,A

...

This entry point is used by the routines at 47930 and 47938.

47902

LD (47916),A

Modify instruction at 47915 with value of delay constant

47905

LD A,B

Load B into A

47906

LD (47924),A

Set instruction at 47924

47909

LD (47925),HL

Set instructions at 47925 and 47926

47912

CALL 48018

Load A with current border colour

The operand of the instruction at 47915 represents the value of the delay constant. This is modified by the instruction at 47902.

47915

LD C,0

Load C with delay constant

47917

OUT (254),A

Set border colour, and reset ear/speaker

47919

XOR 16

Invert ear/speaker bit of A

47921

LD B,C

Load C (delay constant) into B...

47922

DJNZ 47922

...and delay

The instructions at 47924 - 47926 represent the manipulation of the delay constant between iterations of this routine. These instructions may decrease C by one, increase C by three or do nothing. These instructions are modified by the instructions at 47906 and 47909.

47924

DEC C

Decrease / increase delay constant for next pass, increasing / decreasing pitch of tone respectively

47925

NOP

Do nothing, or increase delay constant

47926

NOP

Do nothing, or increase delay constant

47927

JR NZ,47917

If delay constant is not zero, then loop back to continue playing tone

47929

RET

Return