sdcc-extra/historygraphs/whetstone-z80/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         push    af
  57         ld      a, #0x89
  58         out     (0x01), a
  59         in      a, (0x00)
  60         push    bc
  61         push    de
  62         push    hl
  63         push    iy
  64         call    _tick
  65         pop     iy
  66         pop     hl
  67         pop     de
  68         pop     bc
  69         pop     af
  70         ei
  71         reti
  72
  73         .org    0x100
  74 init:
  75         ;; Set stack pointer directly above top of memory.
  76         ld      sp,#0x0000
  77
  78         ;; Initialise global variables
  79         call    gsinit
  80         call    _main
  81         jp      _exit
  82
  83         ;; Ordering of segments for the linker.
  84         .area   _HOME
  85         .area   _CODE
  86         .area   _INITIALIZER
  87         .area   _GSINIT
  88         .area   _GSFINAL
  89
  90         .area   _DATA
  91         .area   _INITIALIZED
  92         .area   _BSEG
  93         .area   _BSS
  94         .area   _HEAP
  95
  96         .area   _CODE
  97 __clock::
  98         ld      a,#2
  99         rst     0x08
 100         ret
 101
 102 _exit::
 103         ;; Exit - special code to the emulator
 104         ld      a,#0
 105         rst     0x08
 106 1$:
 107         halt
 108         jr      1$
 109
 110         .area   _GSINIT
 111 gsinit::
 112
 113         ; Default-initialized global variables.
 114         ld      bc, #l__DATA
 115         ld      a, b
 116         or      a, c
 117         jr      Z, zeroed_data
 118         ld      hl, #s__DATA
 119         ld      (hl), #0x00
 120         dec     bc
 121         ld      a, b
 122         or      a, c
 123         jr      Z, zeroed_data
 124         ld      e, l
 125         ld      d, h
 126         inc     de
 127         ldir
 128 zeroed_data:
 129
 130         ; Explicitly initialized global variables.
 131         ld      bc, #l__INITIALIZER
 132         ld      a, b
 133         or      a, c
 134         jr      Z, gsinit_next
 135         ld      de, #s__INITIALIZED
 136         ld      hl, #s__INITIALIZER
 137         ldir
 138
 139 gsinit_next:
 140
 141         .area   _GSFINAL
 142         ret
 143