3.17.29 MSP430 Options

These options are defined for the MSP430:

-masm-hex

Force assembly output to always use hex constants. Normally such constants are signed decimals, but this option is available for testsuite and/or aesthetic purposes.

-mmcu=

Select the MCU to target. This is used to create a C preprocessor symbol based upon the MCU name, converted to upper case and pre- and post-fixed with ‘__’. This in turn is used by the msp430.h header file to select an MCU-specific supplementary header file.

The option also sets the ISA to use. If the MCU name is one that is known to only support the 430 ISA then that is selected, otherwise the 430X ISA is selected. A generic MCU name of ‘msp430’ can also be used to select the 430 ISA. Similarly the generic ‘msp430x’ MCU name selects the 430X ISA.

In addition an MCU-specific linker script is added to the linker command line. The script's name is the name of the MCU with .ld appended. Thus specifying -mmcu=xxx on the gcc command line defines the C preprocessor symbol __XXX__ and cause the linker to search for a script called xxx.ld.

This option is also passed on to the assembler.

-mcpu=

Specifies the ISA to use. Accepted values are ‘msp430’, ‘msp430x’ and ‘msp430xv2’. This option is deprecated. The -mmcu= option should be used to select the ISA.

-msim

Link to the simulator runtime libraries and linker script. Overrides any scripts that would be selected by the -mmcu= option.

-mlarge

Use large-model addressing (20-bit pointers, 32-bit size_t).

-msmall

Use small-model addressing (16-bit pointers, 16-bit size_t).

-mrelax

This option is passed to the assembler and linker, and allows the linker to perform certain optimizations that cannot be done until the final link.

mhwmult=

Describes the type of hardware multiply supported by the target. Accepted values are ‘none’ for no hardware multiply, ‘16bit’ for the original 16-bit-only multiply supported by early MCUs. ‘32bit’ for the 16/32-bit multiply supported by later MCUs and ‘f5series’ for the 16/32-bit multiply supported by F5-series MCUs. A value of ‘auto’ can also be given. This tells GCC to deduce the hardware multiply support based upon the MCU name provided by the -mmcu option. If no -mmcu option is specified then ‘32bit’ hardware multiply support is assumed. ‘auto’ is the default setting.

Hardware multiplies are normally performed by calling a library routine. This saves space in the generated code. When compiling at -O3 or higher however the hardware multiplier is invoked inline. This makes for bigger, but faster code.

The hardware multiply routines disable interrupts whilst running and restore the previous interrupt state when they finish. This makes them safe to use inside interrupt handlers as well as in normal code.

-minrt

Enable the use of a minimum runtime environment - no static initializers or constructors. This is intended for memory-constrained devices. The compiler includes special symbols in some objects that tell the linker and runtime which code fragments are required.