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wfjm |
/* -*- c++ -*- */
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/* $Id: delay.c 395 2011-07-17 22:02:55Z mueller $ */
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/*-----------------------------------------------------------------------------
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* Delay routines
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*-----------------------------------------------------------------------------
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* Code taken from USRP2 firmware (GNU Radio Project), version 3.0.2,
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* Copyright 2003 Free Software Foundation, Inc.
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*-----------------------------------------------------------------------------
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* This code is part of usbjtag. usbjtag is free software; you can redistribute
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* it and/or modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the License,
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* or (at your option) any later version. usbjtag is distributed in the hope
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* that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
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* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details. You should have received a
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* copy of the GNU General Public License along with this program in the file
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* COPYING; if not, write to the Free Software Foundation, Inc., 51 Franklin
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* St, Fifth Floor, Boston, MA 02110-1301 USA
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*-----------------------------------------------------------------------------
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*/
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/*
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* Delay approximately 1 microsecond (including overhead in udelay).
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*/
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static void
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udelay1 (void) _naked
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{
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_asm ; lcall that got us here took 4 bus cycles
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ret ; 4 bus cycles
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_endasm;
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}
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/*
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* delay for approximately usecs microseconds
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*/
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void
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udelay (unsigned char usecs)
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{
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do {
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udelay1 ();
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} while (--usecs != 0);
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}
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/*
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* Delay approximately 1 millisecond.
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* We're running at 48 MHz, so we need 48,000 clock cycles.
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*
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* Note however, that each bus cycle takes 4 clock cycles (not obvious,
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* but explains the factor of 4 problem below).
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*/
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static void
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mdelay1 (void) _naked
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{
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_asm
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mov dptr,#(-1200 & 0xffff)
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002$:
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inc dptr ; 3 bus cycles
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mov a, dpl ; 2 bus cycles
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orl a, dph ; 2 bus cycles
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jnz 002$ ; 3 bus cycles
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ret
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_endasm;
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}
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void
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mdelay (unsigned int msecs)
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{
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do {
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mdelay1 ();
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} while (--msecs != 0);
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}
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