This discussion has been locked.

You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Program Memory Constants

tom g over 12 years ago

Note: This was originally posted on 22nd July 2013 at http://forums.arm.com

I am using a Cortex-M0 with Keil uVision4. How are constants located in program memory and how can these program memory constants be changed by code?

Parents

Scott Douglass over 12 years ago

Note: This was originally posted on 24th July 2013 at http://forums.arm.com

What is it that you're trying to accomplish?

If they change then they are not really constants; if the code is running and you change the constants (say, from a debugger) then there's no guarantee that the code will still work. For example two functions might share part of a constant literal. It might be better to store the values in variables.

The compiler has various ways encoding constants. A constant might be part of an instruction, a piece of data in the same section as code or as a separate (read only) data section.

Changing a constant at runtime (once you've located it) might be simple if it's in RAM or tricky if it's in FLASH.
Cancel
Vote up 0 Vote down

Cancel

Reply

Scott Douglass over 12 years ago

Note: This was originally posted on 24th July 2013 at http://forums.arm.com

What is it that you're trying to accomplish?

If they change then they are not really constants; if the code is running and you change the constants (say, from a debugger) then there's no guarantee that the code will still work. For example two functions might share part of a constant literal. It might be better to store the values in variables.

The compiler has various ways encoding constants. A constant might be part of an instruction, a piece of data in the same section as code or as a separate (read only) data section.

Changing a constant at runtime (once you've located it) might be simple if it's in RAM or tricky if it's in FLASH.
Cancel
Vote up 0 Vote down

Cancel

Children

No data