mirror of
https://github.com/cc65/cc65.git
synced 2024-12-21 20:29:24 +00:00
133 lines
2.4 KiB
ArmAsm
133 lines
2.4 KiB
ArmAsm
;
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; Startup code for cc65 (Apple2 version)
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;
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; This must be the *first* file on the linker command line
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;
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.export _exit, __Exit
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.import initlib, donelib
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.import zerobss
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.import __STARTUP_LOAD__, __BSS_LOAD__ ; Linker generated
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.import callmain
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.include "zeropage.inc"
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.include "apple2.inc"
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; ------------------------------------------------------------------------
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; The executable header
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.segment "EXEHDR"
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.word __STARTUP_LOAD__ ; Start address
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.word __BSS_LOAD__ - __STARTUP_LOAD__ ; Size
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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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; ProDOS TechRefMan, chapter 5.2.1:
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; "For maximum interrupt efficiency, a system program should not use more
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; than the upper 3/4 of the stack."
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ldx #$FF
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txs ; Init stack pointer
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; Save the zero page locations we need
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ldx #zpspace-1
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: lda sp,x
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sta zpsave,x
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dex
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bpl :-
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; Save the original RESET vector
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ldx #$02
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: lda SOFTEV,x
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sta rvsave,x
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dex
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bpl :-
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; ProDOS TechRefMan, chapter 5.3.5:
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; "Your system program should place in the RESET vector the address of a
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; routine that ... closes the files."
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ldx #<_exit
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lda #>_exit
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jsr reset ; Setup RESET vector
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; Clear the BSS data
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jsr zerobss
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; Setup the stack
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lda HIMEM
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sta sp
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lda HIMEM+1
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sta sp+1 ; Set argument stack ptr
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; Call module constructors
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jsr initlib
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; Push arguments and call main()
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jsr callmain
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; Avoid re-entrance of donelib. This is also the _exit entry
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_exit: ldx #<__Exit
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lda #>__Exit
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jsr reset ; Setup RESET vector
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; Call module destructors
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jsr donelib
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; Restore the original RESET vector. This is also the __Exit entry
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__Exit: ldx #$02
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: lda rvsave,x
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sta SOFTEV,x
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dex
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bpl :-
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; Copy back the zero page stuff
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ldx #zpspace-1
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: lda zpsave,x
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sta sp,x
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dex
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bpl :-
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; ProDOS TechRefMan, chapter 5.2.1:
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; "System programs should set the stack pointer to $FF at the warm-start
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; entry point."
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ldx #$FF
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txs ; Re-init stack pointer
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; Back to DOS
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jmp DOSWARM
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; ------------------------------------------------------------------------
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; Setup RESET vector
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reset: stx SOFTEV
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sta SOFTEV+1
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eor #$A5
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sta PWREDUP
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rts
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; ------------------------------------------------------------------------
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; Data
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.data
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zpsave: .res zpspace
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rvsave: .res 3
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