i86/mtx-16-bit/mtx/samples/LAB3/s.s

   1 .globl begtext, begdata, begbss                      ! needed by linker
   2
   3 .globl _tswitch,_getc,_putc                          ! EXPORT these
   4 .globl _main,_running,_scheduler,_proc,_procSize     ! IMPORT these
   5
   6 .text                                                ! these tell as:
   7 begtext:                                             ! text,data,bss segments
   8 .data                                                ! are all the same.
   9 begdata:
  10 .bss
  11 begbss:
  12 .text
  13
  14 start:
  15         mov     ax,cs                   ! establish segments
  16         mov     ds,ax                   ! Let DS,SS,ES = CS=0x1000.
  17         mov     ss,ax
  18         mov     es,ax
  19
  20         mov     sp,#_proc               ! sp -> proc[0]
  21         add     sp,_procSize            ! sp -> proc[0]'s HIGH END
  22
  23         call _main                      ! call main() in C
  24
  25 dead:   jmp dead                        ! loop if main() ever returns
  26
  27
  28 _tswitch:
  29 SAVE:   push ax
  30         push bx
  31         push cx
  32         push dx
  33         push bp
  34         push si
  35         push di
  36         pushf
  37         mov   bx, _running
  38         mov   2[bx], sp
  39
  40 FIND:   call _scheduler
  41
  42 RESUME: mov   bx, _running
  43         mov   sp, 2[bx]
  44         popf
  45         pop  di
  46         pop  si
  47         pop  bp
  48         pop  dx
  49         pop  cx
  50         pop  bx
  51         pop  ax
  52         ret
  53
  54
  55 _getc:
  56         xorb   ah,ah
  57         int    0x16
  58         ret
  59
  60 _putc:
  61         push   bp
  62         mov    bp,sp
  63         movb   al,4[bp]
  64         movb   ah,#14
  65         mov    bx,#0x000B   ! CYAN color
  66         int    0x10
  67         pop    bp
  68         ret