1
0
mirror of https://github.com/cc65/cc65.git synced 2024-06-15 02:29:32 +00:00
cc65/libsrc/cx16/crt0.s

131 lines
2.8 KiB
ArmAsm

;
; Start-up code for cc65 (CX16 r35 version)
;
.export _exit
.export __STARTUP__ : absolute = 1 ; Mark as start-up
.import initlib, donelib
.import zerobss, callmain
.import CHROUT
.import __MAIN_START__, __MAIN_SIZE__ ; Linker-generated
.include "zeropage.inc"
.include "cx16.inc"
; ------------------------------------------------------------------------
; Start-up code
.segment "STARTUP"
Start: tsx
stx spsave ; Save the system stack ptr
; Save space by putting some of the start-up code in the ONCE segment,
; which will 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].
_exit:
; Put the program return code into BASIC's status variable.
sta STATUS
; Run the module destructors.
jsr donelib
.if 0 ; We don't need to preserve zero-page space for cc65's variables.
; Copy back the zero-page stuff.
ldx #zpspace-1
L2: lda zpsave,x
sta sp,x
dex
bpl L2
.endif
; Restore the system stuff.
ldx spsave
txs ; Restore stack pointer
ldx ramsave
stx VIA1::PRA ; Restore former RAM bank
lda VIA1::PRB
and #<~$07
ora #$04
sta VIA1::PRB ; Change back to BASIC ROM
; Back to BASIC.
rts
; ------------------------------------------------------------------------
.segment "ONCE"
init:
; Change from BASIC's ROM to Kernal's ROM.
lda VIA1::PRB
and #<~$07
sta VIA1::PRB
; Change to the second RAM bank.
lda VIA1::PRA
sta ramsave ; Save the current RAM bank number
lda #$01
sta VIA1::PRA
.if 0 ; We don't need to preserve zero-page space for cc65's variables.
; Save the zero-page locations that we need.
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x
dex
bpl L1
.endif
; 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 lower/UPPER PetSCII charset.
lda #$0E
jsr CHROUT
; Call the module constructors.
jmp initlib
; ------------------------------------------------------------------------
; Data
.segment "INIT"
ramsave:
.res 1
spsave: .res 1
.if 0
zpsave: .res zpspace
.endif