196 lines
2.7 KiB
ArmAsm
196 lines
2.7 KiB
ArmAsm
.ifndef scroll_row1
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scroll_row1 EQU $8A00
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scroll_row2 EQU $8B00
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scroll_row3 EQU $8C00
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scroll_row4 EQU $8D00
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.endif
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SCROLL_LENGTH EQU $61
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OFFSET EQU $62
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;========================
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; scroll some text
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;========================
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; RLE compressed data in INL/INH
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; CV is Y position to display at
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gr_scroll:
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lda #0
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sta OFFSET
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;=======================
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; decompress scroll text
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;=======================
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jsr decompress_scroll
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scroll_loop:
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ldx #0
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ldy CV
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lsr
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lda gr_offsets,Y ; get position
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sta sm1+1
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lda gr_offsets+2,Y ; get position
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sta sm2+1
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lda gr_offsets+4,Y ; get position
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sta sm3+1
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lda gr_offsets+6,Y ; get position
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sta sm4+1
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iny
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clc
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lda gr_offsets,Y ; get position
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adc DRAW_PAGE
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sta sm1+2
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lda gr_offsets+2,Y ; get position
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adc DRAW_PAGE
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sta sm2+2
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lda gr_offsets+4,Y ; get position
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adc DRAW_PAGE
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sta sm3+2
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lda gr_offsets+6,Y ; get position
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adc DRAW_PAGE
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sta sm4+2
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ldy OFFSET
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draw_loop:
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lda scroll_row1,Y
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sm1:
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sta $400,X
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lda scroll_row2,Y
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sm2:
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sta $480,X
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lda scroll_row3,Y
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sm3:
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sta $500,X
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lda scroll_row4,Y
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sm4:
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sta $580,X
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iny
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inx
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cpx #40
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bne draw_loop
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;==================
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; flip pages
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;==================
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jsr page_flip ; 6
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;==================
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; delay
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;==================
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lda #125
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jsr WAIT
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;==================
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; loop forever
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;==================
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clc
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lda OFFSET
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adc #40
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cmp SCROLL_LENGTH
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beq done_scrolling
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inc OFFSET
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jmp scroll_loop ; 3
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done_scrolling:
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rts
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;=======================
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; decompress scroll
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;=======================
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decompress_scroll:
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ldy #0
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jsr scroll_load_and_increment
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sta SCROLL_LENGTH
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lda #<scroll_row1
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sta OUTL
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lda #>scroll_row1
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sta OUTH
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decompress_scroll_loop:
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jsr scroll_load_and_increment ; load compressed value
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cmp #$A1 ; EOF marker
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beq done_decompress_scroll ; if EOF, exit
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pha ; save
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and #$f0 ; mask
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cmp #$a0 ; see if special AX
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beq decompress_scroll_special
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pla ; note, PLA sets flags!
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ldx #$1 ; only want to print 1
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bne decompress_scroll_run
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decompress_scroll_special:
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pla
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and #$0f ; check if was A0
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bne decompress_scroll_color ; if A0 need to read run, color
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decompress_scroll_large:
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jsr scroll_load_and_increment ; get run length
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decompress_scroll_color:
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tax ; put runlen into X
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jsr scroll_load_and_increment ; get color
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decompress_scroll_run:
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sta (OUTL),Y
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pha
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clc ; increment 16-bit pointer
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lda OUTL
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adc #$1
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sta OUTL
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lda OUTH
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adc #$0
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sta OUTH
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pla
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dex ; repeat for X times
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bne decompress_scroll_run
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beq decompress_scroll_loop ; get next run
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done_decompress_scroll:
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rts
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scroll_load_and_increment:
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lda (INL),Y ; load and increment 16-bit pointer
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pha
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clc
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lda INL
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adc #$1
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sta INL
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lda INH
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adc #$0
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sta INH
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pla
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rts
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