sdcc/device/lib/r800/crt0.s

   1 ;--------------------------------------------------------------------------
   2 ;  crt0.s - Generic crt0.s for a Z80
   3 ;
   4 ;  Copyright (C) 2000, Michael Hope
   5 ;
   6 ;  This library is free software; you can redistribute it and/or modify it
   7 ;  under the terms of the GNU General Public License as published by the
   8 ;  Free Software Foundation; either version 2, or (at your option) any
   9 ;  later version.
  10 ;
  11 ;  This library is distributed in the hope that it will be useful,
  12 ;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 ;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 ;  GNU General Public License for more details.
  15 ;
  16 ;  You should have received a copy of the GNU General Public License
  17 ;  along with this library; see the file COPYING. If not, write to the
  18 ;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  19 ;   MA 02110-1301, USA.
  20 ;
  21 ;  As a special exception, if you link this library with other files,
  22 ;  some of which are compiled with SDCC, to produce an executable,
  23 ;  this library does not by itself cause the resulting executable to
  24 ;  be covered by the GNU General Public License. This exception does
  25 ;  not however invalidate any other reasons why the executable file
  26 ;   might be covered by the GNU General Public License.
  27 ;--------------------------------------------------------------------------
  28
  29         .module crt0
  30         .globl  _main
  31
  32         .area   _HEADER (ABS)
  33         ;; Reset vector
  34         .org    0
  35         jp      init
  36
  37         .org    0x08
  38         ei
  39         reti
  40         .org    0x10
  41         ei
  42         reti
  43         .org    0x18
  44         ei
  45         reti
  46         .org    0x20
  47         ei
  48         reti
  49         .org    0x28
  50         ei
  51         reti
  52         .org    0x30
  53         ei
  54         reti
  55         .org    0x38
  56         ei
  57         reti
  58
  59         .org    0x100
  60 init:
  61         ;; Set stack pointer directly above top of memory.
  62         ld      sp,#0x0000
  63
  64         call    ___sdcc_external_startup
  65
  66         ;; Initialise global variables. Skip if __sdcc_external_startup returned
  67         ;; non-zero value. Note: calling convention version 1 only.
  68         or      a, a
  69         call    Z, gsinit
  70
  71         call    _main
  72         jp      _exit
  73
  74         ;; Ordering of segments for the linker.
  75         .area   _HOME
  76         .area   _CODE
  77         .area   _INITIALIZER
  78         .area   _GSINIT
  79         .area   _GSFINAL
  80
  81         .area   _DATA
  82         .area   _INITIALIZED
  83         .area   _BSEG
  84         .area   _BSS
  85         .area   _HEAP
  86
  87         .area   _CODE
  88 __clock::
  89         ld      a,#2
  90         rst     0x08
  91         ret
  92
  93 _exit::
  94         ;; Exit - special code to the emulator
  95         ld      a,#0
  96         rst     0x08
  97 1$:
  98         halt
  99         jr      1$
 100
 101         .area   _GSINIT
 102 gsinit::
 103
 104         ; Default-initialized global variables.
 105         ld      bc, #l__DATA
 106         ld      a, b
 107         or      a, c
 108         jr      Z, zeroed_data
 109         ld      hl, #s__DATA
 110         ld      (hl), #0x00
 111         dec     bc
 112         ld      a, b
 113         or      a, c
 114         jr      Z, zeroed_data
 115         ld      e, l
 116         ld      d, h
 117         inc     de
 118         ldir
 119 zeroed_data:
 120
 121         ; Explicitly initialized global variables.
 122         ld      bc, #l__INITIALIZER
 123         ld      a, b
 124         or      a, c
 125         jr      Z, gsinit_next
 126         ld      de, #s__INITIALIZED
 127         ld      hl, #s__INITIALIZER
 128         ldir
 129
 130 gsinit_next:
 131
 132         .area   _GSFINAL
 133         ret
 134