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[/] [w11/] [tags/] [w11a_V0.6/] [tools/] [fx2/] [src/] [startup.a51] - Rev 36
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;;; -*- asm -*-
;;; $Id: startup.a51 395 2011-07-17 22:02:55Z mueller $
;;;
;;;-----------------------------------------------------------------------------
;;; Startup code
;;;-----------------------------------------------------------------------------
;;; Code taken from USRP2 firmware (GNU Radio Project), version 3.0.2,
;;; Copyright 2003 Free Software Foundation, Inc.
;;;-----------------------------------------------------------------------------
;;; This code is part of usbjtag. usbjtag 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 of the License,
;;; or (at your option) any later version. usbjtag 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 this program in the file
;;; COPYING; if not, write to the Free Software Foundation, Inc., 51 Franklin
;;; St, Fifth Floor, Boston, MA 02110-1301 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
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