split scroll

Code:

OFFSET_BACKGROUND_HORIZONTAL:;; Clear PPU address registers (only when needed, after scroll update);LDA #$00;STA PPU_VRAM_ADDR;STA PPU_VRAM_ADDR; Set initial scroll to 0 for the static status barLDA #$00STA PPU_SCROLL           ; Horizontal scrollSTA PPU_SCROLL           ; Vertical scroll;; Wait for Sprite 0 hit to clear (from the previous frame)WaitNotSprite0:LDA PPU_STATUS           ; Read PPU status registerAND #%01000000      ; Check sprite 0 hit flag (bit 6)BNE WaitNotSprite0  ; Wait until sprite 0 hit flag is cleared;; Wait for Sprite 0 to be hitWaitSprite0:LDA PPU_STATUS          ; Read PPU status registerAND #%01000000      ; Check sprite 0 hit flag (bit 6)BEQ WaitSprite0     ; Wait until sprite 0 hit flag is set; Small delay to let the scanline finish drawingLDX #$20       ; Adjust delay for timingWaitScanline:DEXBNE WaitScanline; Increment and apply infinite horizontal scroll for the backgroundINC offset_value        ; Increment horizontal scroll variableLDA offset_valueSTA PPU_SCROLL          ; Write horizontal scroll register (horizontal scroll)LDA #$00                ; No vertical scrollingSTA PPU_SCROLL          ; Write vertical scroll register;; Check if offset_value has wrapped to $00LDA offset_valueCMP #$00              ; Compare offset_value to $00BNE SKIPNAMETABLEUPDATE ; If not $00, skip nametable update; Toggle nametable between 00 and 11LDA toggle_flagCMP #$01BNE set_nametable00; Set nametable to 11 (bits 0 and 1 = 11)set_nametable11:LDA #%10010011STA PPU_CTRL            ; Update PPU control registerLDA #$00                ; Reset toggle flagSTA toggle_flag         ; Update toggle flagRTSset_nametable00:; Set nametable to 00 (bits 0 and 1 = 00)LDA #%10010000STA PPU_CTRL            ; Update PPU control registerLDA #$01                ; Set toggle flag to 1STA toggle_flag         ; Update toggle flagRTSSKIPNAMETABLEUPDATE:    ;; Return from su