http://blogs.yahoo.co.jp/jun_constellation/29353615.html

http://www.picfun.com/pic18/app18x02.html

http://www.it.lth.se/digp/Avr-libc-1.4.3/group__avr__watchdog.htmlhttp://arms22.blog91.fc2.com/blog-date-200901.html

http://juen-cs.dl.juen.ac.jp/html/hp/13/02/explanation.html