PICC Define a variable

[Kasun Ganganath]

I want to define a variable which value cannot be change even power off the micro controller. So i think the variable must stored in flash memory or EEPROM.
How can I define it?

[Banfa]

My memory of PIC programming is that there is a

rom

keyword added to C that allows you to define a variable that resides in the flash (program) memory of the device and would be read-only.

Check your compiler documentation.

[donbock]

Do you seek a constant whose value is set when you write the source code and that never changes after that ... or do you seek a variable that your program can alter at run-time, but whose value is retained while power is off?

The first case can usually be accomplished like this:

static const int variable = 10;

The C Standard doesn't require it, but most compilers for embedded systems will store a variable such as this in the same place that the program instructions go; and that is usually some sort of read-only memory.

The second case is more idiosyncratic. Your hardware needs to have some sort of NVRAM. You need to study your compiler and linker documentation to learn the compiler-specific method of making use of special memory like that.