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cc65/libsrc/c16/crt0.s
cuz bbbf2ac45a Move the startup code into its own segment
git-svn-id: svn://svn.cc65.org/cc65/trunk@1581 b7a2c559-68d2-44c3-8de9-860c34a00d81
2002-11-22 17:43:30 +00:00

115 lines
2.1 KiB
ArmAsm

;
; Startup code for cc65 (C16 version)
;
; This must be the *first* file on the linker command line
;
; Note: The C16 is actually the Plus/4 with just 16KB of memory. So many
; things are similar here, and we even use the plus4.inc include file.
;
.export _exit
.import initlib, donelib
.import push0, _main, zerobss
.import MEMTOP, RESTOR, BSOUT, CLRCH
.include "zeropage.inc"
.include "../plus4/plus4.inc"
; ------------------------------------------------------------------------
; Create an empty LOWCODE segment to avoid linker warnings
.segment "LOWCODE"
; ------------------------------------------------------------------------
; Place the startup code in a special segment.
.segment "STARTUP"
; BASIC header with a SYS call
.word Head ; Load address
Head: .word @Next
.word 1000 ; Line number
.byte $9E,"4109" ; SYS 4109
.byte $00 ; End of BASIC line
@Next: .word 0 ; BASIC end marker
; ------------------------------------------------------------------------
; Actual code
ldx #zpspace-1
L1: lda sp,x
sta zpsave,x ; save the zero page locations we need
dex
bpl L1
; Close open files
jsr CLRCH
; Switch to second charset
lda #14
jsr BSOUT
; Clear the BSS data
jsr zerobss
; Save system stuff and setup the stack
tsx
stx spsave ; save system stk ptr
sec
jsr MEMTOP ; Get top memory
cpy #$80 ; We can only use the low 32K :-(
bcc MemOk
ldy #$80
ldx #$00
MemOk: stx sp
sty sp+1 ; set argument stack ptr
; Call module constructors
jsr initlib
; Pass an empty command line
jsr push0 ; argc
jsr push0 ; argv
ldy #4 ; Argument size
jsr _main ; call the users code
; Call module destructors. This is also the _exit entry.
_exit: jsr donelib ; Run module destructors
; Restore system stuff
ldx spsave
txs
; Copy back the zero page stuff
ldx #zpspace-1
L2: lda zpsave,x
sta sp,x
dex
bpl L2
; Reset changed vectors
jmp RESTOR
.data
zpsave: .res zpspace
.bss
spsave: .res 1