Zilog ZUSBOPTS Manual de usuario descargar pdf (Pagina 184)

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Language Extensions UM017105-0511

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Zilog Developer Studio II – ZNEO™

User Manual

Language Extensions

To give you additional control over the way the ZNEO C-Compiler allocates storage and

to enhance its ability to handle common real-time constructs, the compiler implements the

following extensions to the ANSI C standard:

•

Additional Keywords for Storage Specification

The compiler divides the ZNEO CPU memory into four memory spaces: Near ROM,

Extended ROM, Near RAM, and Extended (Far) RAM. It provides the following key-

words with which you can control the storage location of data in these memory

spaces:

–

_Near (near)

–

_Far (far)

–

_Rom (rom)

–

_Erom (erom)

These keywords can also be used to specify the memory space to which a pointer is

pointing to.

•

Memory Models – see page 161

The compiler supports two memory models: small and large. These models allow you

to control where data are stored by default. Each application can only use one model.

The model can affect the efficiency of your application. Some of the memory alloca-

tion defaults associated with a memory model can be overridden using the keywords

for storage specification.

•

Interrupt Support – see page 162

The ZNEO CPU supports various interrupts. The C-Compiler provides language

extensions to designate a function as interrupt service routine and provides features to

set each interrupt vector.

•

Placement Directives – see page 164

The placement directives allow users to place objects at specific hardware addresses

and align objects at a given alignment.

•

String Placement – see page 165

Because the ZNEO CPU has multiple address spaces, the C-Compiler provides lan-

guage extensions to specify the storage for string constants.

•

Inline Assembly – see page 166

The C-Compiler provides directives for embedding assembly instructions and direc-

tives into the C program.

•

Char and Short Enumerations – see page 167

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