Texas Instruments MSP50C6xx manual Compiler, Foreword

C– – Compiler

label RESW expression: This directive is used to reserve the number of words indicated by expression, starting at the current RAM address. label is given the value of the current RAM address. If the current RAM address is not EVEN, the assembler increments it by 1 before allocating the desired amount. (Note that RAM locations are accessed by their BYTE address in MSP50C6xx assembly language, i.e., word 1 is at address 2, etc...)

RORG expression: Marks the start of a RELATIVE segment code, i.e., a segment that can be relocated by the linker. Expression is an arbitrary number, but it must be present or an assembly error will occur.

STRING text_string: Equivalent to the TEXT directive, but the text is terminated by a 0. (automatically done by the assembler)

TEXT text_string: Equivalent to the BYTE directive, but the data is a text string enclosed in double quotes.

UNLIST: The lines following this directive are not included in the listing file (extension

.lst) created by the assembler.

5.5 C– – Compiler

The C– – compiler generates an assembly language file of the same name, with extension .opt. It also generates a file with extension .glb where global variable initialization is taken care of, if the routine main was encountered in the current file. A file with extension .ext is also generated to take care of global and external declarations that will be used by the assembler. These two files are included in the .opt file generated by the C– – compiler. Note that all symbols defined in C– – source code are changed before being written to assembly language: an underscore character is put in front of the first character of each symbol. Also note that local labels created by the C– – compiler are built using the current source file name followed by an ordinal number. Consequently, to avoid problems at link time due to symbols bearing the same name, never use symbol names starting with an underscore in assembly language files. It is imperative to use file names that are different for C– – files (extension .cmm) and assembly language files (extension .asm).

5.5.1Foreword

C–– is a high level language to be used with the MSP50C6xx microprocessors. Although it looks a lot like C, it has some limitations/restrictions which will be highlighted throughout the remainder of this chapter. This language is compiled into MSP50C6xx assembly language.

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