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https://github.com/deater/dos33fsprogs.git
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101 lines
1.3 KiB
ArmAsm
101 lines
1.3 KiB
ArmAsm
div7_table = $6800
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mod7_table = $6900
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hposn_high = $6a00
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hposn_low = $6b00
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hgr_make_tables:
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;=====================
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; make /7 %7 tables
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;=====================
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hgr_make_7_tables:
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lda #0 ; load lots of zeros
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tax
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tay
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div7_loop:
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sta div7_table,Y
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mod7_smc:
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stx mod7_table
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inx
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cpx #7
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bne div7_not7
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clc
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adc #1
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ldx #0
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div7_not7:
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inc mod7_smc+1 ; assume starts on page boundary
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iny
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bne div7_loop
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; ldy #0
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; lda #0
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;mod7_loop:
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; sta mod7_table,Y
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; clc
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; adc #1
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; cmp #7
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; bne mod7_not7
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; lda #0
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;mod7_not7:
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; iny
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; bne mod7_loop
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; Hposn table
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; hposn_low, hposn_high will each be filled with $C0 bytes
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; based on routine by John Brooks
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; posted on comp.sys.apple2 on 2018-07-11
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; https://groups.google.com/d/msg/comp.sys.apple2/v2HOfHOmeNQ/zD76fJg_BAAJ
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; clobbers A,X
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; preserves Y
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; vmw note: version I was using based on applesoft HPOSN was ~64 bytes
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; this one is 37 bytes
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build_hposn_tables:
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ldx #0
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btmi:
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txa
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and #$F8
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bpl btpl1
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ora #5
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btpl1:
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asl
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bpl btpl2
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ora #5
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btpl2:
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asl
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asl
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sta hposn_low, X
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txa
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and #7
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rol
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asl hposn_low, X
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rol
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; ora #$20
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sta hposn_high, X
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inx
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cpx #$C0
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bne btmi
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; go 16 beyond, which allows our text scrolling routine
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; ldx #16
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;extra_table_loop:
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; lda hposn_low,X
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; sta hposn_low+192,X
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; lda hposn_high,X
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; eor #$60
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; sta hposn_high+192,X
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; dex
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; bpl extra_table_loop
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rts
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