Knight Tyme (48k): Routine at 35690

35690: 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 35695) is a delay constant that determines the speed at which the sound is played.

Used by the routines at 26745, 26855, 26926, 26997, 30001, 32694, 55138 and 55887.

Input
A	(Entry at 35695 only) Delay constant

35690

XOR A

Set A to 0

35691

LD B,13

Set B to 13 (DEC C)

35693

LD H,A

Set HL to 0...

35694

LD L,A

...

This entry point is used by the routines at 35723 and 35731.

35695

LD (35709),A

Modify instruction at 35708 with value of delay constant

35698

LD A,B

Load B into A

35699

LD (35717),A

Set instruction at 35717

35702

LD (35718),HL

Set instructions at 35718 and 35719

35705

CALL 35819

Load A with current border colour

The operand of the instruction at 35708 represents the value of the delay constant. This is modified by the instruction at 35695.

35708

LD C,0

Load C with delay constant

35710

OUT (254),A

Set border colour, and reset ear/speaker

35712

XOR 16

Invert ear/speaker bit of A

35714

LD B,C

Load C (delay constant) into B...

35715

DJNZ 35715

...and delay

The instructions at 35717 - 35719 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 35699 and 35702.

35717

DEC C

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

35718

NOP

Do nothing, or increase delay constant (modified by instruction at 35702)

35719

NOP

Do nothing, or increase delay constant (modified by instruction at 35702)

35720

JR NZ,35710

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

35722

RET

Return