volatile的用法

使用前提: 如果一個global變數宣告再某個地方, 但有可能又被另一個program作修改, 而compiler不知道的話, 那就需要加上volatile


Use

A variable should be declared volatile whenever its value could change unexpectedly. In practice, only three types of variables could change:

• Memory-mapped peripheral registers
• Global variables modified by an interrupt service routine
• Global variables within a multi-threaded application

http://www.embedded.com/electronics-blogs/beginner-s-corner/4023801/Introduction-to-the-Volatile-Keyword