54 lines
1.1 KiB
ArmAsm
54 lines
1.1 KiB
ArmAsm
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//
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// Well-known Kernal routine, described in:
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//
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// - [CM64] Compute's Mapping the Commodore 64 - page 215
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//
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setup_vicii:
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// XXX it should also set default devices
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// Clear everything - turn off sprites (observed hanging around after
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// running programs and resetting), etc.
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lda #$00
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ldx #$2E
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!:
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sta __VIC_BASE, x
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dex
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bpl !-
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// Disable C128 extra keys - just to be sure they won't interfere with anything
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stx VIC_XSCAN
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// Disable the C128 2MHz mode, it prevents VIC-II display from working correctly
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stx VIC_CLKRATE
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// Set up default IO values
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// - [CM64] page 129 - VIC_SCROLY
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// - [CM64] pages 140-144 - VIC_SCROLX
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// - [CM64] pages 145-146 - VIC_YMCSB
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lda #$1B // according to [CM64] page 137 some software assumes oldest bit is 0
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sta VIC_SCROLY
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lda #$C8
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sta VIC_SCROLX // 40 column etc
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lda #$14
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sta VIC_YMCSB
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lda #$0F
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sta VIC_IRQ // clear all interrupts
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// We use a different colour scheme of white text on all blue
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lda #$06
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sta VIC_EXTCOL
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sta VIC_BGCOL0
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// Setup default I/O devices
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jmp clrchn_reset
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