;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-

;; Sets memory in 'A'-registry to all addresses from 'A_start' until 'A_start' + 'length'
;; Modifies A, X and A_start
.proc clear_screen
        .include "mem.inc"
        VIC_bank = $4000
        length_ = $1f40
        low_length_3 = $C0 + $03 ;; we need one more.
        Mov_16 A_start, A_start + 1, #<VIC_bank, #>VIC_bank
        LDA #$00
        ;; big_set sets the memory in $ff chunks.
        ;; skipp if length >= $ff
        LDX #>length_
        BNE big_set
        JMP small_set
big_set: ;sets $ff of memory
        ;; Y value do not matter, will go through all anyway!
        .repeat $ff
        STA (A_start), Y
        DEY
        .endrepeat
        STA (A_start), Y ; dont forget Y =0
big_set_end:
        ;;set all hole $ff memory chunks!
        INC A_start + 1
        DEX ;; length +1 --
        BEQ small_set
        JMP big_set

small_set:
        LDX big_set + low_length_3
        LDY #$60
        STY big_set + low_length_3
        LDY #<length_
        JSR big_set
        STX big_set + low_length_3
        RTS
.endproc