arch_a.s

picoos源码。The RTOS and the TCP/IP stack will be built automatically.

/*
   Copyright (c) 2003, Swen Moczarski
   All rights reserved.

   Redistribution and use in source and binary forms, with or without 
   modification, are permitted provided that the following conditions are met:

   * Redistributions of source code must retain the above copyright notice, 
     this list of conditions and the following disclaimer.
  
   * Redistributions in binary form must reproduce the above copyright notice, 
     this list of conditions and the following disclaimer in the documentation 
     and/or other materials provided with the distribution.
  
   * Neither the name of the copyright holders nor the names of its contributors 
     may be used to endorse or promote products derived from this software 
     without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
   AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
   ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
   LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
   POSSIBILITY OF SUCH DAMAGE.
*/

#include <avr/io.h>


//  EXPORTS - Functions
    .global  p_pos_findbit


// r24 = bitfield
// r22 = rrOffset
p_pos_findbit:
         mov    r18, r24
         mov    r19, r22

         inc    r19
         clc
offsetLoop:
         ror    r18
         dec    r19
         brne   offsetLoop
         
         mov    r19, r22
nextBitLoop:
         brcs   bitFound
         ror    r18
         inc    r19
         rjmp   nextBitLoop
         
bitFound:
         mov    r24, r19
         subi   r24, 0x08
         
         brpl   correctOffset
         mov    r24, r19
         ret
         
correctOffset:  
         dec    r24
         ret