92 lines
2.2 KiB
ArmAsm
92 lines
2.2 KiB
ArmAsm
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//
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// Set pointer (PNT) to current screen line , described in:
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//
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// - [CM64] Computes Mapping the Commodore 64 - page 216
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//
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screen_calculate_PNT:
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// YYY implement this!
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rts
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// Variables: (http://sta.c64.org/cbm64mem.html)
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// - $C7 - RVS - reverse mode switch
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// - $C8 - INDX - length of line minus 1 during screen input. Values: $27, 39; $4F, 79.
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// - $C9 - LXSP+0 - cursor row during screen input. Values: $00-$18, 0-24.
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// - $CA - LXSP+1 - cursor column during screen input. Values: $00-$27, 0-39.
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// - $CC - BLNSW - cursor visibility switch. Values: $01-$FF: Cursor is off.
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// - $CD - BLNCT - delay counter for changing cursor phase. Values:
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// - $CE - GDBLN - screen code of character under cursor
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// - $CF - BLNON - cursor phase switch
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// - $D0 - CRSW - end of line switch during screen input
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// - $D1-$D2 - PNT - pointer to current line in screen memory.
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// - $D3 - PNTR - current cursor column. Values: $00-$27, 0-39.
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// - $D4 - QTSW - quotation mode switch
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// - $D5 - LNMX - length of current screen line minus 1. Values: $27, 39; $4F, 79.
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// - $D6 - TBLX - current cursor row. Values: $00-$18, 0-24.
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// - $D8 - INSRT - number of insertions
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// - $D9-$F1 - LDTBL - link table
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// - $F2 - temporary value for screen scroll
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// - $F3-$F4 - USER - pointer to current line in Color RAM.
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// - $02A5 - TLNIDX - number of line currently being scrolled during scrolling the screen
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/* YYY disabled for rework
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screen_calculate_line_pointer:
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jsr screen_normalize_xy
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// Reset pointer to start of screen
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lda HIBASE
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sta PNT+1
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lda #0
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sta PNT+0
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// Add 40 for every line, or 80 if the lines are linked
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ldx TBLX
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!:
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// Stop if we have counted enough lines
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beq !+
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// Add 40 or 80 based on whether the line is linked
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// or not.
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ldy #40
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// -1 offset is because we count down from N to 1, not
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// N-1 to 0.
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lda LDTBL-1,x
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bpl sclp_l1
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ldy #80
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sclp_l1:
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// Add computed line length to pointer value
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tya
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clc
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adc PNT+0
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sta PNT+0
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lda PNT+1
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adc #0
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sta PNT+1
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// Loop back to next line
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dex
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jmp !-
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!:
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// FALLTHROUGH
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update_colour_line_pointer:
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// Now setup pointer to colour RAM
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lda PNT+0
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sta USER+0
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lda PNT+1
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sec
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sbc HIBASE
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clc
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adc #>$d800
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sta USER+1
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rts
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*/ |