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ST20-SWCSUN

ST20 software development and debugging tools

STMicroelectronics 

ST20–SWC

Workspace allocation by coloring reduces the amount of workspace required by using the

same word for two variables when it can be determined that they are not both required at the

same time.

The optimizing compiler also implements a pragma, IMS_nosideeffects, whereby the user can

indicate that a function does not have any side-effects on external or static variables. The optimizer

can then use this information to make assumptions about what state can be changed by a function

invocation and hence about the validity of any previously computed expressions.

2.2.5 Libraries

The full set of ANSI libraries is provided.

The standard library operates in double precision. Versions of the mathematical functions are

provided that operate on float arguments and return float values. These libraries provide improved

performance for applications where performance requirements override accuracy requirements.

A reduced C library is supplied to minimize code size for embedded systems applications. This library

is appropriate for code which does not need to access host facilities.

Collections of functions can be compiled separately with the ANSI C compiler and then combined into

a library. The linker is used to combine separately compiled functions into a program.

2.2.6 Assembler inserts

The ANSI C Toolset provides a very powerful assembler insert facility. The assembler insert facility

supports:

Access to the full instruction set of the ST20;

Symbolic access to C variables (automatic and static);

Pseudo operations to load values into registers;

Loading results of C expressions;

Labels and jumps;

Directives for instruction sizing, stack access, return address access etc.

2.3 Support for embedded applications

The toolset has been designed to support the development of embedded applications. The features

include the ability to place code and data at particular places in memory, being able to access the

ST20 instruction set efficiently from C, and to reduce the C run-time overhead to suit the application.

2.3.1 Placing code and data

At configuration level, a program consists of its code, stack, static and heap segments. The configurer

allocates each of these separate segments a place in the memory of the processor.

By default, the configurer allocates all the code and data segments to a contiguous default block of

memory. The location of this default block and the order of the segments may be defined in the

configuration description. The configuration description can also specify that any one of the code or

data segments of an application are to be allocated to particular places in memory outside the default

block.

The compiler, linker and collector each will optionally produce a listing of how the various parts of an

application are mapped into the segments and memory.A tool is provided that can read all these map

files and produce a summary of the whole application, giving the locations of all the functions and

static variables. Information is collated about code and data segments including the start address and

size.

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