text: /*
   * Copyright (c) 2018, Marcelo Samsoniuk
   * 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 holder 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 HOLDER 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 <io.h>
  #include <stdio.h>
  
  extern int banner(void);
  extern int main  (void);
  
  void boot(void)
  {
      int tmp = 1&threads++;
  
      io.irq = IRQ_TIMR; // clear interrupt
  
      // thread #0
  
      if(tmp==0)
      {
          putchar('0'+tmp);
      
          while(1)
          {
              banner();
  
              printf("boot0: text@%d data@%d stack@%d\n",
                  (unsigned int)boot,
                  (unsigned int)&utimers,
                  (unsigned int)&tmp);
          
              main();
          }
      }
  
      // thread #1
  
      putchar('0'+tmp);
  
      while(1)
      {
          utimers++;
          //io.led  ^= 1; // change led
          io.gpio ^= 1; // change gpio
          io.irq  = IRQ_TIMR;  // clear interrupts and switch context
      }
  }
  