FadeToBlackZ80_V2

.model Spectrum128
.org #8000

; Fade to black
;
; Syntax for SpecNet IDE
; https://dotneteer.github.io/spectnetide/

SCREEN_START .equ 0x4000
SCREEN_COLS  .equ 32
SCREEN_ROWS  .equ 24
SCREEN_ATTRIBUTES_COUNT .equ SCREEN_COLS * SCREEN_ROWS
SCREEN_BITMAP_COUNT     .equ SCREEN_ATTRIBUTES_COUNT * 8
SCREEN_ATTRIBUTES_START .equ SCREEN_START + SCREEN_BITMAP_COUNT
INK_MASK    .equ %00000111
PAPER_MASK  .equ %00111000
BRIGHT_MASK .equ %01000000
FLASH_MASK  .equ %10000000
BRIGHT_FLASH_MASK .equ (BRIGHT_MASK | FLASH_MASK)
BRIGHT_INK_MASK   .equ (BRIGHT_MASK | INK_MASK )
BRIGHT_PAPER_MASK .equ (BRIGHT_MASK |PAPER_MASK )

; Put some stuff on the screen to fade
    ld hl, SCREEN_START
    ld bc, SCREEN_BITMAP_COUNT / 2

Bitmap1:
    ld a, %10101010
    ld (hl), a
    inc hl
    ld a, %00111100
    ld (hl), a
    inc hl

    ; if bc != 0
    dec bc
    dec bc
    xor a
    or b
    jr nz, Bitmap1
    xor a
    or c
    jr nz, Bitmap1

    ld bc, SCREEN_BITMAP_COUNT / 2
Bitmap2:
    ld a, %01010101
    ld (hl), a
    inc hl
    ld a, %11000011
    ld (hl), a
    inc hl

    ; if bc != 0
    dec bc
    dec bc
    xor a
    cp b
    jr nz, Bitmap2
    xor a
    cp c
    jr nz, Bitmap2

    ld hl, SCREEN_ATTRIBUTES_START
    xor a
    ld b, SCREEN_ATTRIBUTES_COUNT / 4
Attr1:
    dec a
    ld d, a
    and PAPER_MASK
    ld (hl), a
    inc hl
    ld a, d
    and INK_MASK
    ld (hl), a
    inc hl
    ld a, d
    and BRIGHT_PAPER_MASK
    ld (hl), a
    inc hl
    ld a, d
    and BRIGHT_INK_MASK
    ld (hl), a
    inc hl

    ; if b != 0
    dec b
    xor a
    cp b
    ld a, d
    jr nz, Attr1

; Fade to Black
    ld d, 7
FadeStart:
    ld hl, SCREEN_ATTRIBUTES_START
    ld bc, SCREEN_ATTRIBUTES_COUNT
.loop 50 ; change to adjust rate
    halt
.endl

FadeScreen:
    ld a, (HL)
    exx

    ld b, a
    ld c, a
    ld e, a

;   and BRIGHT_FLASH_MASK
    and BRIGHT_MASK ; change to exclude flash attribute
    ld b, a
    ld a, c
    and INK_MASK
    jr z, ZeroInk
    dec a
ZeroInk:
    ld e, a
    ld a, c
    and PAPER_MASK
    jr z, ZeroPaper
    sra a
    sra a
    sra a
    jr z, ZeroPaper
    dec a
    sla a
    sla a
    sla a
ZeroPaper:
    or e
    or b

    exx
    ld (hl), a
    inc hl

; if bc != 0

    dec bc
    xor a
    cp b
    jr nz, FadeScreen
    xor a
    cp c
    jr nz, FadeScreen

; if d == 0 end
    dec d
    xor a
    cp d
    jr nz, FadeStart

    ret
s