problem of "if" condition

[Altera_Forum]

I wrote a program to process data from PC through uart, but there is something wrong. 

 <div class='quotetop'>QUOTE </div>  --- Quote Start ---  main() {     ......     init_uart0();     ......     while(1)     {           if(uart0_rbuf_out_cnt != uart0_rbuf_in_cnt )           {               ......           }     } }[/b]  --- Quote End ---    I receive data in uart0_ISR(), if there is one new byte, at first put it into the uart0_rbuf, and then the uart0_rbuf_in_cnt add 1.   The problem is when (uart0_rbuf_out_cnt != uart0_rbuf_in_cnt ) is true, it can not go into the program to process the data.  What&#39;s the matter?Thanks.

[Altera_Forum]

Hi, 

define uart0_rbuf_out_cnt and uart0_rbuf_in_cnt variable as volatile, for example:  volatile int uart0_rbuf_out_cnt  if not, the compiler optimize these variables because they aren&#39;t managed in the main program...

[Altera_Forum]

http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/tongue.gif Thanks,Soin,I&#39;ll try.