Rex: Routine at D473

D473: Configure note for current channel

Used by the routine at D424.

Input
IX	address pointer to channel data buffer

D473

LD A,(IX+$00)

Return if channel is not active

D476

CP $FF

D478

RET Z

D479

CALL $D4DC

Send channel volume command

D47C

CALL $D4F1

Send channel volume command

D47F

LD L,(IX+$02)

Set IY to the address pointer for the sound da

D482

LD H,(IX+$03)

D485

PUSH HL

D486

POP IY

D488

DEC (IX+$01)

Decrement variation counter

D48B

JP Z,$D4AD

If counter is 0 jump to configure next note

D48E

LD E,(IY+$01)

Set BC value of pitch and coarse delta

D491

LD C,E

D492

RL E

D494

SBC A,A

D495

LD B,A

D496

LD L,(IX+$04)

Increment pitch and coarse data for tone/noise

D499

LD H,(IX+$05)

D49C

ADD HL,BC

D49D

LD (IX+$04),L

D4A0

LD (IX+$05),H

D4A3

LD A,(IX+$07)

Increment/decrement volume

D4A6

ADD A,(IY+$02)

D4A9

LD (IX+$07),A

D4AC

RET

check if there are more tones

D4AD

DEC (IX+$00)

Decrement tones number?

D4B0

JP Z,$D4CB

if zero jump to disable channel

D4B3

INC IY

Point IY to the next tone data

D4B5

INC IY

D4B7

INC IY

D4B9

PUSH IY

Update address pointer to tone data

D4BB

POP HL

D4BC

LD (IX+$02),L

D4BF

LD (IX+$03),H

D4C2

LD A,(IY+$00)

Set new variation counter

D4C5

LD (IX+$01),A

D4C8

JP $D473

Configure next tone

disable channel

D4CB

LD A,($D5EF)

Set volume to zero for current channel

D4CE

ADD A,$07

D4D0

LD D,A

D4D1

LD E,$00

D4D3

CALL $D4F1

Send volume command

D4D6

LD A,$FF

Disable current channel

D4D8

LD (IX+$00),A

D4DB

RET