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|
;
; Startup code for cc65 (C64 version)
;
.export _exit
.export __STARTUP__ : absolute = 1 ; Mark as startup
.import initlib, donelib
.import zerobss, callmain
.import BSOUT
.import __MAIN_START__, __MAIN_SIZE__ ; Linker generated
.import __STACKSIZE__ ; from configure file
.importzp ST
.include "zeropage.inc"
.include "c64.inc"
; ------------------------------------------------------------------------
; Startup code
.segment "STARTUP"
Start:
; Switch off the BASIC ROM.
lda $01
sta mmusave ; Save the memory configuration
and #$F8
ora #$06 ; Enable Kernal+I/O, disable BASIC
sta $01
tsx
stx spsave ; Save the system stack ptr
; Save space by putting some of the start-up code in the ONCE segment,
; which can be re-used by the BSS segment, the heap and the C stack.
jsr init
; Clear the BSS data.
jsr zerobss
; Push the command-line arguments; and, call main().
jsr callmain
; Back from main() [this is also the exit() entry]. Run the module destructors.
_exit: pha ; Save the return code on stack
jsr donelib
; Copy back the zero-page stuff.
ldx #zpspace-1
L2: lda zpsave,x
sta sp,x
dex
bpl L2
; Place the program return code into BASIC's status variable.
pla
sta ST
; Restore the system stuff.
ldx spsave
txs ; Restore stack pointer
ldx mmusave
stx $01 ; Restore memory configuration
; Back to BASIC.
rts
; ------------------------------------------------------------------------
.segment "ONCE"
init:
; Save the zero-page locations that we need.
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x
dex
bpl L1
; Set up the stack.
lda #<(__MAIN_START__ + __MAIN_SIZE__)
ldx #>(__MAIN_START__ + __MAIN_SIZE__)
sta sp
stx sp+1 ; Set argument stack ptr
; Switch to the second charset.
lda #14
jsr BSOUT
; Call the module constructors.
jmp initlib
; ------------------------------------------------------------------------
; Data
.segment "INIT"
mmusave:.res 1
spsave: .res 1
zpsave: .res zpspace
|
