109 lines
2.1 KiB
ArmAsm
109 lines
2.1 KiB
ArmAsm
; Startup code for cc65 and Shiru's NES library
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; based on code by Groepaz/Hitmen <groepaz@gmx.net>, Ullrich von Bassewitz <uz@cc65.org>
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; edited by Steven Hugg (remove integrated Famitone2 library, add NMICallback)
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.export _exit,__STARTUP__:absolute=1
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.export _HandyRTI
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.export NMI,IRQ,START
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.import initlib,push0,popa,popax,_main,zerobss,copydata
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; Linker generated symbols
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.import __RAM_START__ ,__RAM_SIZE__
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.import __ROM0_START__ ,__ROM0_SIZE__
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.import __STARTUP_LOAD__,__STARTUP_RUN__,__STARTUP_SIZE__
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.import __CODE_LOAD__ ,__CODE_RUN__ ,__CODE_SIZE__
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.import __RODATA_LOAD__ ,__RODATA_RUN__ ,__RODATA_SIZE__
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.include "atari7800.inc"
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.segment "ZEROPAGE"
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INTVEC: .res 2
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.segment "HEADER"
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.byte $4e,$45,$53,$1a
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.res 8,0
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.segment "STARTUP"
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START:
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_exit:
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sei ;Disable interrupts
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cld ;Clear decimal mode
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;******** Atari recommended startup procedure
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lda #$07
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sta INPTCTRL ;Lock into 7800 mode
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lda #$7F
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sta CTRL ;Disable DMA
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lda #$00
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sta OFFSET
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sta INPTCTRL
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ldx #$FF ;Reset stack pointer
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txs
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;************** Clear zero page and hardware ******
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ldx #$40
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lda #$00
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@1:
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sta $00,x ;Clear zero page
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sta $100,x ;Clear page 1
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inx
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bne @1
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ldy #$00 ;Clear Ram
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@2:
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sta $1800,y
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sta $1900,y
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sta $1a00,y
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sta $1b00,y
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sta $1c00,y
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sta $1d00,y
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sta $1e00,y
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sta $1f00,y
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sta $2200,y
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sta $2300,y
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sta $2400,y
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sta $2500,y
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sta $2600,y
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sta $2700,y
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iny
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bne @2
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ldx #$00
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@3: ;Clear 2100-213F
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sta $2100,x
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inx
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cpx #$40
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bne @3
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; set interrupt vector in ZP
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lda #<_HandyRTI
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sta INTVEC
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lda #>_HandyRTI
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sta INTVEC+1
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; start main()
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jmp _main ;no parameters
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; interrupt handler
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NMI:
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IRQ:
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jmp (INTVEC)
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_HandyRTI:
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rti
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; CPU vectors
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.segment "VECTORS"
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.word NMI ;$fffa vblank nmi
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.word START ;$fffc reset
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.word IRQ ;$fffe irq / brk
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