;;; -*- asm -*- ;;; ;;;----------------------------------------------------------------------------- ;;; 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