Martianoids: Routine at 49293

49293: Make Noise If Visible

Used by the routines at AnimateSmoke and EndSmoke.

Makes a burst of noise, if the entity is visible. It is made of sixteen short tones with pitches that come from bytes of the ROM picked at random.

Input
IX	Entity

MakeNoiseIfVisible

49293

BIT 0,(IX+15)

Return if the entity cannot be seen.

49297

RET Z

49298

LD A,R

Pick a random page of the ROM...

49300

AND 31

49302

LD H,A

49303

LD A,(38423)

...and a random place in it.

49306

LD L,A

49307

LD E,16

There are sixteen tones.

MakeNoiseIfVisible_Loop

49309

LD A,(HL)

Fetch a byte of the ROM, and move on to the next one.

49310

INC HL

49311

AND 127

Keep the lower seven bits of it.

49313

LD B,A

Use it as the pitch.

49314

LD C,1

Each tone is made of one cycle.

49316

CALL PlayWaveSequence

Make the tone using PlayWaveSequence.

49319

DEC E

Loop back until all sixteen tones have been made.

49320

JR NZ,MakeNoiseIfVisible_Loop

49322

RET

Return.