Running from Flash or ROM

Lightfoot applications can be run from ROM/Flash or run from RAM. During development, almost all of your applications will be run from RAM and downloaded from your development PC to the development board using the lfdownload tool and the monitor on the development board.
When you are ready to deploy the system, you will not have a development PC to download from, now will you have a monitor running on your target system to initiaite a download.

Converting to a Flash/ROM based application

Running from ROM or Flash is a simple matter of changing a configuration value in config.xml, rebuilding your application, storing in Flash or blowing into a PROM.
Edit config.xml and add the following entry into the target section.
<bootconstants mode="ROM"/>

When you remake your application, the end result is no longer a .bin file, but is a .raw file. This raw file is an exact image of how your application will be in Flash can be downloaded using the flash downloading tool.

Behind the scenes

The simple adding of the bootconstants line to the XML configuration file causes the linker to read in a different command file. This command file causes the linker to work with 3 memory areas, ROM, Program RAM and Data RAM.

ROM memory area

The ROM memory area stores the following information:

Bootstrap code used to boot the system and setup the board.
All application code, library code and the majority of runtime code.
All constant pools.
All readonly data structures.

Program RAM memory area

The program RAM memory area stores the following information:

interrupt handlers
trap handlers
soft byte codes
flash-writing code

Data RAM memory area

The data RAM memory area stores the following information:

constants accessible via cnsti instructions
All mutable data structures.

Raw memory image

The raw memory image is basically the ROM memory area followed by the two the two RAM areas with relocation information. When the system is booted, the relocatable RAM areas are copied into the correct location, memory areas to be initialised are initialised and the application starts running normally.