Loading data from CharPad Pro in Kick Assembler (https://subchristsoftware.itch.io/charpad-pro)

charpad-background.asm

.filenamespace background
// Render Background

.var background_data   = LoadBinary("gfx/background.bin")
.var background_colors = LoadBinary("gfx/background-colors.bin")

.label color_memory       = 55296
.label screen_memory      = 1024

 // Zero Page segment, don't include in prg
.segment ZP "Background"
char_position: .word 0
color_position: .word 0
background_pointer: .word 0

.segment BACKGROUND "CODE"

draw:
    ldx #0
    lda #<color_memory
    sta color_position
    lda #>color_memory
    sta color_position+1

    lda #<screen_memory
    sta char_position
    lda #>screen_memory
    sta char_position+1,X

    lda #<background
    sta background_pointer
    lda #>background
    sta background_pointer+1

    ldy #0
!:
    lda (background_pointer),Y
    sta (char_position),Y
    tax

    lda charset_attrib_L1_data, X
    sta (color_position),Y
    iny
    bne !-

    // next page
    inc  char_position+1
    inc  background_pointer+1
    inc  color_position+1
    lda char_position+1
    // End of screen high byte will be 8
    cmp #8
    bne !-

    rts


.segment BACKGROUND "Background"
// Background and Color data imported from Charpad
.align $100
background:
.fill background_data.getSize(), background_data.get(i)


// CHARSET IMAGE ATTRIBUTE DATA (L1)...
// 256 attributes, 1 attribute per image, 8 bits per attribute, total size is 256 ($100) bytes.
// nb. Upper nybbles = material (unused here), lower nybbles = colour (colour matrix low).
charset_attrib_L1_data:
.fill background_colors.getSize(), background_colors.get(i)