124 lines
2.7 KiB
ArmAsm
124 lines
2.7 KiB
ArmAsm
;
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; Startup code for cc65 (MEGA65 version)
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;
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.export _exit
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.export __STARTUP__ : absolute = 1 ; Mark as startup
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.import initlib, donelib
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.import zerobss, callmain
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.import BSOUT
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.import __MAIN_START__, __MAIN_SIZE__ ; Linker generated
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.import __STACKSIZE__ ; from configure file
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.include "zeropage.inc"
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.include "mega65.inc"
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; ------------------------------------------------------------------------
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; Startup code
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.segment "STARTUP"
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Start:
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; Switch off the BASIC ROM.
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; FIXME
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; lda $01
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; sta mmusave ; Save the memory configuration
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; and #$F8
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; ora #$06 ; Enable Kernal+I/O, disable BASIC
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; sta $01
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; sei
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; lda #%00000000 ; lower offset 15-8
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; ldx #%00000000 ; map blk3-1 | lower offset 19-6
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; ldy #%00000000 ; upper offset 15-8
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; ldz #%00000000 ; map blk7-4 | upper offset 19-6
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; map
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; eom
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tsx
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stx spsave ; Save the system stack ptr
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; Save space by putting some of the start-up code in the ONCE segment,
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; which can be re-used by the BSS segment, the heap and the C stack.
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jsr init
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; Clear the BSS data.
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jsr zerobss
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; Push the command-line arguments; and, call main().
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jsr callmain
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; Back from main() [this is also the exit() entry]. Run the module destructors.
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_exit: pha ; Save the return code on stack
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jsr donelib
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; Copy back the zero-page stuff.
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ldx #zpspace-1
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L2: lda zpsave,x
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sta c_sp,x
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dex
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bpl L2
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; Place the program return code into BASIC's status variable.
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pla
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sta STATUS
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; Restore the system stuff.
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ldx spsave
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txs ; Restore stack pointer
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; Back to BASIC.
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rts
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; ------------------------------------------------------------------------
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.segment "ONCE"
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init:
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; Save the zero-page locations that we need.
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ldx #zpspace-1
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L1: lda c_sp,x
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sta zpsave,x
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dex
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bpl L1
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; Set up the stack.
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lda #<(__MAIN_START__ + __MAIN_SIZE__)
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ldx #>(__MAIN_START__ + __MAIN_SIZE__)
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sta c_sp
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stx c_sp+1 ; Set argument stack ptr
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; Switch to the second charset.
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lda #14
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jsr BSOUT
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; Call the module constructors.
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jmp initlib
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; ------------------------------------------------------------------------
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; Data
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.segment "INIT"
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mmusave:.res 1
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spsave: .res 1
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zpsave: .res zpspace
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