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cc65/libsrc/atmos/crt0.s

102 lines
2.3 KiB
ArmAsm

;
; Startup code for cc65 (Oric version)
;
; By Debrune Jérôme <jede@oric.org> and Ullrich von Bassewitz <uz@cc65.org>
; 2016-03-18, Greg King
;
.export _exit
.export __STARTUP__ : absolute = 1 ; Mark as startup
.import initlib, donelib
.import callmain, zerobss
.import __MAIN_START__, __MAIN_SIZE__
.include "zeropage.inc"
.include "atmos.inc"
; ------------------------------------------------------------------------
; Place the startup code in a special segment.
.segment "STARTUP"
tsx
stx spsave ; Save system stk ptr
; Save space by putting some of the start-up code in a segment
; that will be re-used.
jsr init
; Clear the BSS variables (after the constructors have been run).
jsr zerobss
; Push the command-line arguments; and, call main().
jsr callmain
; Call the module destructors. This is also the exit() entry.
_exit: jsr donelib
; Restore the system stuff.
ldx spsave
txs
lda stsave
sta STATUS
; Copy back the zero-page stuff.
ldx #zpspace - 1
L2: lda zpsave,x
sta sp,x
dex
bpl L2
; Back to BASIC.
rts
; ------------------------------------------------------------------------
; Put this code in a place that will be re-used by BSS, the heap,
; and the C stack.
.segment "ONCE"
; Save the zero-page area that we're about to use.
init: ldx #zpspace - 1
L1: lda sp,x
sta zpsave,x
dex
bpl L1
; Currently, color isn't supported on the text screen.
; Unprotect screen columns 0 and 1 (where each line's color codes would sit).
lda STATUS
sta stsave
and #%11011111
sta STATUS
; Set up the C stack.
lda #<(__MAIN_START__ + __MAIN_SIZE__)
ldx #>(__MAIN_START__ + __MAIN_SIZE__)
sta sp
stx sp+1 ; Set argument stack ptr
; Call the module constructors.
jmp initlib
; ------------------------------------------------------------------------
.segment "INIT"
spsave: .res 1
stsave: .res 1
zpsave: .res zpspace