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https://github.com/bradgrantham/apple2a.git
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55 lines
1.7 KiB
ArmAsm
55 lines
1.7 KiB
ArmAsm
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; ---------------------------------------------------------------------------
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; crt0.s
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; ---------------------------------------------------------------------------
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;
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; Startup code for cc65 (Single Board Computer version)
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.export _init, _exit
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.import _main
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.export __STARTUP__ : absolute = 1 ; Mark as startup
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.import __RAM_START__, __RAM_SIZE__ ; Linker generated
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.import copydata, zerobss, initlib, donelib
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.include "zeropage.inc"
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; ---------------------------------------------------------------------------
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; Place the startup code in a special segment
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.segment "STARTUP"
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; ---------------------------------------------------------------------------
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; A little light 6502 housekeeping
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_init: LDX #$FF ; Initialize stack pointer to $01FF
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TXS
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CLD ; Clear decimal mode
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; ---------------------------------------------------------------------------
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; Set cc65 argument stack pointer
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LDA #<(__RAM_START__ + __RAM_SIZE__)
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STA sp
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LDA #>(__RAM_START__ + __RAM_SIZE__)
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STA sp+1
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; ---------------------------------------------------------------------------
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; Initialize memory storage
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JSR zerobss ; Clear BSS segment
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JSR copydata ; Initialize DATA segment
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JSR initlib ; Run constructors
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; ---------------------------------------------------------------------------
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; Call main()
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JSR _main
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; ---------------------------------------------------------------------------
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; Back from main (this is also the _exit entry): force a software break
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_exit: JSR donelib ; Run destructors
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BRK
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