Atmel CAVR-4 Manual De Usuario

CAVR-4

Part 2. Compiler reference

The following section gives detailed reference information about each compiler option.

--char_is_signed

--char_is_signed 

By default, the compiler interprets the 

char

 type as unsigned. The 

--char_is_signed

 

option causes the compiler to interpret the 

char

 type as signed instead. This can be 

useful when you, for example, want to maintain compatibility with another compiler.

Note: The runtime library is compiled without the 

--char_is_signed

 option. If you 

use this option, you may get type mismatch warnings from the IAR XLINK Linker, 
because the library uses unsigned chars.

To set the equivalent option in IAR Embedded Workbench, select 
Project>Options>C/C++ Compiler>Language.

--cpu

--cpu=cpu

Use this option to select the processor for which the code is to be generated. 

For example, use the following command to specify the AT90S4414 derivative:

--cpu=4414

See Processor configuration, page 5, for a summary of the available processor variants.

Note that to specify the processor, you can use either the 

--cpu

 option or the 

-v

 option. 

The 

--cpu

 option is, however, more precise because it contains more information about 

the intended target than the more generic 

-v

option. For information about the implicit 

assumptions using the -v option, see -v, page 197.

This option is related to the Processor configuration option in the General Options 
category in IAR Embedded Workbench.

--zero_register

Specifies register R15 as 

zero register

--64bit_doubles

Use 64-bit doubles

--64k_flash

Specifies a maximum of 64 

Kbytes flash memory.