source: trunk/FirmwareFX2/fx2/delay.c@ 191

/* -*- c++ -*- */
/*-----------------------------------------------------------------------------
 * Delay routines
 *-----------------------------------------------------------------------------
 * 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
 *-----------------------------------------------------------------------------
 */

/*
 * Delay approximately 1 microsecond (including overhead in udelay).
 */
static void
udelay1 (void) _naked
{
  _asm                          ; lcall that got us here took 4 bus cycles
        ret                     ; 4 bus cycles
  _endasm;
}

/*
 * delay for approximately usecs microseconds
 */
void
udelay (unsigned char usecs)
{
  do {
    udelay1 ();
  } while (--usecs != 0);
}


/*
 * Delay approximately 1 millisecond.
 * We're running at 48 MHz, so we need 48,000 clock cycles.
 *
 * Note however, that each bus cycle takes 4 clock cycles (not obvious,
 * but explains the factor of 4 problem below).
 */
static void
mdelay1 (void) _naked
{
  _asm
        mov     dptr,#(-1200 & 0xffff)
002$:   
        inc     dptr            ; 3 bus cycles
        mov     a, dpl          ; 2 bus cycles
        orl     a, dph          ; 2 bus cycles
        jnz     002$            ; 3 bus cycles

        ret
  _endasm;
}

void
mdelay (unsigned int msecs)
{
  do {
    mdelay1 ();
  } while (--msecs != 0);
}