git.sur5r.net Git - cc65/blob - libsrc/osic1p/crt0.s

   1 ; ---------------------------------------------------------------------------
   2 ; crt0.s
   3 ; ---------------------------------------------------------------------------
   4 ;
   5 ; Startup code for Ohio Scientific Challenger 1P
   6
   7 .export   _init, _exit
   8 .import   _main
   9
  10 .export   __STARTUP__ : absolute = 1    ; Mark as startup
  11 .import   __RAM_START__, __RAM_SIZE__   ; Linker generated
  12 .import   __STACKSIZE__
  13
  14 .import    zerobss, initlib, donelib
  15
  16 .include  "zeropage.inc"
  17 .include  "extzp.inc"
  18 .include  "osic1p.inc"
  19
  20 ; ---------------------------------------------------------------------------
  21 ; Place the startup code in a special segment
  22
  23 .segment  "STARTUP"
  24
  25 ; ---------------------------------------------------------------------------
  26 ; A little light 6502 housekeeping
  27
  28 _init:    ldx     #$FF          ; Initialize stack pointer to $01FF
  29           txs
  30           cld                   ; Clear decimal mode
  31
  32 ; ---------------------------------------------------------------------------
  33 ; Set cc65 argument stack pointer
  34
  35           lda     #<(__RAM_START__ + __RAM_SIZE__  + __STACKSIZE__)
  36           sta     sp
  37           lda     #>(__RAM_START__ + __RAM_SIZE__  + __STACKSIZE__)
  38           sta     sp+1
  39
  40 ; ---------------------------------------------------------------------------
  41 ; Initialize memory storage
  42
  43           jsr     zerobss       ; Clear BSS segment
  44           jsr     initlib       ; Run constructors
  45
  46 ; ---------------------------------------------------------------------------
  47 ; Call main()
  48
  49           jsr     _main
  50
  51 ; ---------------------------------------------------------------------------
  52 ; Back from main (this is also the _exit entry):
  53
  54 _exit:    jsr     donelib       ; Run destructors
  55           jmp     RESET         ; Display boot menu after program exit