For each configuration ("Debug" or "Release") the toolchain maintains two options for the target processor hardware, the processor type and its clock speed. The processor type is passed as a command line option to all tools requiring the processor type. The clock speed is only passed onto the compiler as a #define F_CPU xxxxxxxx. Its up to the application to do anything with this value, e.g. adjust its internal timings.
Having the options separate for each configuration means that for the Debug configuration a target processor different from the Release configuration can be selected. This can be used to - for example - debug on a simulator with a processor having an UART connected to virtual terminal, even if the final target processor used for the release does not have an UART. The default settings for both configurations are the ones selected when the project was created.
Note: This may change in future versions of the plugin to have only a single entry valid for all configurations. Your feedback about this is welcome.
The options can be changed via the project properties.
To change the target processor select the project properties, expand C/C++ Build and select the Tool Settings tab. Then select the Target Hardware item and change the settings as required.
Note: The list of available processors is hand made, so if a processor is missing which is supported by the compiler, file a bug report to get the processor included into the list.
Note: There is currently no checking done on the MCU Clock Frequency field. The value is passed as is to the compiler.
Add / Remove AVR specific Tools from the Toolchain