52 lines
1.1 KiB
ArmAsm
52 lines
1.1 KiB
ArmAsm
; Atari VCS 2600 startup code for cc65
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; Florent Flament (contact@florentflament.com), 2017
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.export _exit
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.export __STARTUP__ : absolute = 1
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.import __RAM_START__, __RAM_SIZE__
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.import copydata
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.import _main
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.include "zeropage.inc"
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.segment "STARTUP"
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start:
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; Clear decimal mode
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cld
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; Initialization Loop:
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; * Clears Atari 2600 whole memory (128 bytes) including BSS segment
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; * Clears TIA registers
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; * Sets system stack pointer to $ff (i.e top of zero-page)
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; * Sets ROM bank 0 for mapper 3E/3F
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ldx #0
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stx $3F
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txa
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clearLoop:
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dex
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txs
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pha
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bne clearLoop
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; Initialize data
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jsr copydata
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; Initialize C stack pointer
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lda #<(__RAM_START__ + __RAM_SIZE__)
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ldx #>(__RAM_START__ + __RAM_SIZE__)
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sta sp
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stx sp+1
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; Call main
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_exit:
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jmp _main
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.segment "VECTORS"
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.word start ; NMI
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.word start ; Reset
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.word start ; IRQ
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