Zilog ZUSBOPTS Manual do Utilizador descarregar pdf (Página 185)

100

101

UM017105-0511 Language Extensions

Zilog Developer Studio II – ZNEO™

User Manual

157

The enumeration data type is defined as int as per ANSI C. The C-Compiler provides

language extension to specify the enumeration data type to be other than

int.

•

Setting Flash Option Bytes in C – see page 168

The ZNEO CPU has four Flash option bytes. The C-Compiler provides language

extension to define these Flash option bytes.

•

Supported New Features from the 1999 Standard – see page 169

The ZNEO C-Compiler is based on the 1989 ANSI C standard. Some new features

from the 1999 standard are supported in this compiler for ease of use.

Additional Keywords for Storage Specification

The _Near, _Far, _Rom, and _Erom keywords are storage class specifiers and are used to

control the allocation of data objects by the compiler. They can be used on individual data

objects similar to

const and volatile keywords in the ANSI C standard. The storage

specifiers can only be used to control the allocation of global and static data. The alloca-

tion of local data (nonstatic local) and function parameters is decided by the compiler and

is described in later sections. Any storage specifier used on local and parameter data is

ignored by the compiler.

The Zilog header file <

zneo.h> defines macros to permit the use of the more familiar

keywords:

near, far, rom, and erom. The reason for not using these keywords directly is

to avoid conflict with C identifiers in a preexisting C program. (To avoid conflicts, current

ANSI recommendations are that keywords for vendor extensions to the C language begin

with an underscore and capital letter.)

The data allocation for various storage class specifiers is shown in Figure 126 and

described in the following sections:

•

_Near – see page 158

•

_Rom – see page 158

•

_Erom – see page 159

•

_Far – see page 159

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