1
0
mirror of https://github.com/cc65/cc65.git synced 2024-12-25 17:29:50 +00:00
cc65/libsrc/atmos/crt0.s
2015-01-09 22:19:35 -05:00

109 lines
2.5 KiB
ArmAsm

;
; Startup code for cc65 (Oric version)
;
; By Debrune Jérôme <jede@oric.org> and Ullrich von Bassewitz <uz@cc65.org>
; 2015-01-09, Greg King
;
.export _exit
.export __STARTUP__ : absolute = 1 ; Mark as startup
.import initlib, donelib
.import callmain, zerobss
.import __RAM_START__, __RAM_SIZE__, __STACKSIZE__
.include "zeropage.inc"
.include "atmos.inc"
; ------------------------------------------------------------------------
; Place the startup code in a special segment.
.segment "STARTUP"
; Save the zero-page area that we're about to use.
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x
dex
bpl L1
; Clear the BSS data.
jsr zerobss
; 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
; Save some system stuff; and, set up the stack.
tsx
stx spsave ; Save system stk ptr
lda #<(__RAM_START__ + __RAM_SIZE__ + __STACKSIZE__)
sta sp
lda #>(__RAM_START__ + __RAM_SIZE__ + __STACKSIZE__)
sta sp+1 ; Set argument stack ptr
; Call the module constructors.
jsr initlib
; 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
; ------------------------------------------------------------------------
.segment "ZPSAVE1"
zpsave:
; This padding is needed by a bug in the ROM.
; (The CLOAD command starts BASIC's variables table on top of the last byte
; that was loaded [instead of at the next address].)
; This is overlaid on a buffer, so that it doesn't use extra space in RAM.
.byte 0
; The segments "ZPSAVE1" and "ZPSAVE2" always must be together.
; They create a single object (the zpsave buffer).
.segment "ZPSAVE2"
.res zpspace - 1
; ------------------------------------------------------------------------
.bss
spsave: .res 1
stsave: .res 1