Atmel CAVR-4 Manual De Usuario

CAVR-4

Part1. Using the compiler

Similar to the 

printf

 and 

sprintf

 functions, 

scanf

 and 

sscanf

 use a common 

formatter, called 

_formatted_read

. The full version of 

_formatted_read

 is very 

large, and provides facilities that are not required in many embedded applications. To 
reduce the memory consumption, an alternative smaller version is also provided.

The 

_medium_read

 formatter has the same functions as the full version, except that 

floating-point numbers are not supported. 

_medium_read

 is considerably smaller than 

the full version.

Choose Project>Options and select the General Options category. Click the Library 
options tab.

Select the appropriate Scanf formatter option, which can be either Medium or Large.

To use the 

_medium_read

 formatter, add the following line in the linker command file:

-e_medium_read=_formatted_read

To use the full version, remove the line.

This section describes the actions the runtime environment performs during startup and 
termination of applications.

The code for handling startup and termination is located in the source files 

cstartup.s90

 and 

_exit.s90

, and 

low_level_init.c

 located in the 

avr\src\lib

 directory.

When an application is initialized, a number of steps are performed:

●

The custom function 

_ _low_level_init

 is called, giving the application a chance 

to perform early initializations

●

Enables the external data and address buses if needed

●

Initializes the stack pointers to the end of 

CSTACK

 and 

RSTACK

, respectively