Bubbler: Routine at A20F

A20F: Play Rest

Used by the routine at PlayNote.

Plays a rest, which is a fixed length of silence, in a piece of music.

Input
DE	The address of the byte of the music

Output
DE	The address of the next byte of the music

PlayRest

A20F

LD A,(DE)

Fetch the byte of the music again.

A210

INC DE

Move onto the next byte of the music.

A211

RLCA

Rotate bits 6 and 7 of the note down...

A212

RLCA

...to bits 0 and 1.

A213

AND %00000011

Keep them, but the result is not used.

A215

XOR A

Set the multiplier to zero...

A216

INC A

...and then to one.

A217

LD L,A

Store it in L.

A218

LD BC,$430B

Set the length of the delay.

PlayRest_Loop

A21B

PUSH BC

Save the length of the delay.

PlayRest_Delay

A21C

DEC BC

Count the delay down.

A21D

LD A,B

Combine the two bytes...

A21E

OR C

...to test whether it is zero.

A21F

JR NZ,PlayRest_Delay

Jump back until the delay has finished.

A221

POP BC

Restore the length of the delay.

A222

DEC L

Decrease the multiplier by one.

A223

JR NZ,PlayRest_Loop

Jump back until none remain.

A225

RET

Return.

View the equivalent code in;

Gunfright