ESP8266 reset causes | boot mode, list? - From http://www.esp8266.com/viewtopic.php?p=2096#p2112
reset causes:
  0: 
  1: normal boot
  2: reset pin
  3: software reset
  4: watchdog reset
boot device:
  0:
  1: ram
  3: flash - See more at: http://www.esp8266.com/viewtopic.php?p=2096#p2112