M:/USB-BDI/USB-BDI/Firmware/MPC555-USB-BDI/src/_startup.a51

;;; -*- asm -*-
;;;
;;; Copyright 2003,2004 Free Software Foundation, Inc.
;;; 
;;; This file is part of GNU Radio
;;; 
;;; GNU Radio is free software; you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 2, or (at your option)
;;; any later version.
;;; 
;;; GNU Radio is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;; 
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Radio; see the file COPYING.  If not, write to
;;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;;; Boston, MA 02111-1307, USA.

    
;;; The default external memory initialization provided by sdcc is not
;;; appropriate to the FX2.  This is derived from the sdcc code, but uses 
;;; the FX2 specific _MPAGE sfr.


        ;; .area XISEG   (XDATA)  ; the initialized external data area
    ;; .area XINIT   (CODE)       ; the code space consts to init XISEG
        .area XSEG    (XDATA)     ; zero initialized xdata
        .area USBDESCSEG (XDATA)  ; usb descriptors

        
        .area CSEG    (CODE)

        ;; sfr that sets upper address byte of MOVX using @r0 or @r1
        _MPAGE  =       0x0092

__sdcc_external_startup::
        ;; This system is now compiled with the --no-xinit-opt 
        ;; which means that any initialized XDATA is handled
        ;; inline by code in the GSINIT segs emitted for each file.
        ;; 
        ;; We zero XSEG and all of the internal ram to ensure 
        ;; a known good state for uninitialized variables.

;       _mcs51_genRAMCLEAR() start
        mov     r0,#l_XSEG
        mov     a,r0
        orl     a,#(l_XSEG >> 8)
        jz      00002$
        mov     r1,#((l_XSEG + 255) >> 8)
        mov     dptr,#s_XSEG
        clr     a
        
00001$: movx    @dptr,a
        inc     dptr
        djnz    r0,00001$
        djnz    r1,00001$
        
        ;; We're about to clear internal memory.  This will overwrite
        ;; the stack which contains our return address.
        ;; Pop our return address into DPH, DPL
00002$: pop     dph
        pop     dpl
        
        ;; R0 and A contain 0.  This loop will execute 256 times.
        ;; 
        ;; FWIW the first iteration writes direct address 0x00,
        ;; which is the location of r0.  We get lucky, we're 
        ;; writing the correct value (0)
        
00003$: mov     @r0,a
        djnz    r0,00003$

        push    dpl             ; restore our return address
        push    dph

        mov     dpl,#0          ; indicate that data init is still required
        ret