mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-05-31 21:41:32 +00:00
127 lines
1.5 KiB
ArmAsm
127 lines
1.5 KiB
ArmAsm
hgr_page1_clearscreen = $7000
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hgr_page2_clearscreen = $7300
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hgr_clear_codegen:
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;========================
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; set up output pointers
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lda #<(hgr_page1_clearscreen) ; assume both start page boundary
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sta OUTL
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sta INL
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lda #>(hgr_page1_clearscreen)
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sta OUTH
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lda #>(hgr_page2_clearscreen)
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sta INH
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;=====================
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; set up prolog
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lda #$A0 ; ldy
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jsr write_both
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lda #8 ; only part of screen
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jsr write_both
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ldx #0
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hgr_clear_codegen_loop:
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lda #$99 ; STA
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jsr write_both
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lda hposn_low,X ; low is same both
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jsr write_both
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lda hposn_high,X
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ora #$20
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pha
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jsr write_p1
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pla
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eor #$60
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jsr write_p2
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inx
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cpx #192
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bne hgr_clear_codegen_loop
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;======================================
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; write epilog
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; TODO: replace with memcpy of some sort?
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lda #$C8 ; INY
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jsr write_both
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lda #$C0 ; CPY
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jsr write_both
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lda #32 ; end value
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jsr write_both
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lda #$F0 ; beq
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jsr write_both
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lda #$03 ; +3
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jsr write_both
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lda #$4C ; JMP
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jsr write_both
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lda #<(hgr_page1_clearscreen+2)
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jsr write_both
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lda #>(hgr_page1_clearscreen+2)
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jsr write_p1
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lda #>(hgr_page2_clearscreen+2)
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jsr write_p2
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lda #$60 ; RTS
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; jsr write_both
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; rts ; tail call
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; fallthrough
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;=============================
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;
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write_both:
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pha
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jsr write_p2
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pla
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; fallthrough
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write_p1:
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ldy #0
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sta (OUTL),Y
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clc
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lda OUTL
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adc #1
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sta OUTL
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lda #0
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adc OUTH
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sta OUTH
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rts
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write_p2:
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ldy #0
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sta (INL),Y
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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 #0
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adc INH
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sta INH
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rts
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