1bpp to whatever bpp

ChrPointer = 10
TilesLeft = 12
  lda #$00
  sta PPUADDR
  sta PPUADDR
  lda #<CHR
  sta ChrPointer+0
  lda #>CHR
  sta ChrPointer+1
  lda #48
  sta TilesLeft

CharLoop:
  .repeat 2
    ldy #0
  : lda (ChrPointer),y
    sta PPUDATA
    iny
    cpy #8
    bne :-
  .endrep

  ; alternatively make all but the first plane empty with a loop here

  lda ChrPointer+0
  add #8
  sta ChrPointer+0
  bcc :+
    inc ChrPointer+1
  :

  dec TilesLeft
  bne CharLoop