NVRAM Howto...

Suppose I declare an XDATA variable in my program , would it be
automatically intialised as zero , for example :

   int XDATA non_vol    _at_0x0010;    //variable at 0010h
   .
   .
   .
   if(some_event_occured)
   {
      non_vol++;                    //increment var on some event
   }

Suppose I declare an XDATA variable in my program , would it be
automatically intialised as zero , for example :

   int XDATA non_vol    _at_0x0010;    //variable at 0010h
   .
   .
   .
   if(some_event_occured)
   {
      non_vol++;                    //increment var on some event
   }

Review this thread:
http://www.keil.com/forum/msgpage.asp?MsgID=4719

BTW: note that the Keil C51 xdata keyword is lowercase, and you need a space between the _at_ and the address value.
(just typos in your post?)

BTW2: note that applying bold seems to defeat the &ltpre&gt and &lt/pre&gt tags - the font is no longer monospaced :-(

Memory is not initialised by the compiler. You must explicitly initialise it. If you use the startup code, you can set it up to clear any memory area you want.

Also, unless you MUST specify addresses for RAM, why not let the linker decide where in memory to put variables? This is much easier on the developer as well as avoiding conflicts between modules.

If I just declare a variable it would not be initialised ba default ?

"If I just declare a variable it would not be initialised ba default?"

The compiler doesn't know how much XRAM you have, nor its base address.
Therefore, if you want your XRAM to be initialised, you must specify its size and base address - you do this by means of the startup code

Of course, this gives you the opportunity to specify that some areas of XRAM will be initialised, while others (eg, NVRAM) will not.

For details, refer to the thread cited earlier:
http://www.keil.com/forum/msgpage.asp?MsgID=4719

Hello,
you must declare a static variable (of course without any initialisation). Automatic variables (all variables you "just declare" are automatic) don't survive even leaving the block they was declared in, so how should they survive power off?
Have success - Peter