Sample player subroutine concept for GB/C MOD player

ld a, [sample_buffer+] ;LUT for volumes integrated in buffer
ld d, a
ld a, [sample_buffer+] ;pregenerated buffer by software frequency generator, 8 bit samples for ease of use
srl a
ld e, a
ld a, [de] (to get the final amplitude)
sub $40
jr nc, nocomplement1
cpl
inc a ;because SM83 doesn't have the Z80's neg
nocomplement1:
push af
ld a, [sample_buffer+]
ld d, a
ld a, [sample_buffer+]
srl a
ld e, a
ld a, [de]
sub $40
jr nc, nocomplement2
cpl
inc a
nocomplement2:
ld b, a
pop af
add b
add $80
ld d, amplitude_LUT
ld e, a
ld a, [de]
ld b, a
or $0f
ldh [rNRx2], a
ld a, $80
ldh [rNRx4], a
ld a, b
and $f0
ld b, a
swap b
or b
ldh [rNR50], a