Zilog EZ80F916 - Manual (Page 163)

UM014423-0607 Using the ANSI C-Compiler
ZiLOG Developer Studio II
eZ80Acclaim! ® User Manual
143
Placement of Consecutive Variables
The compiler also provides syntax to place several variables at consecutive addresses. For
example:
char ch1 _At 0xB7E000;
char ch2 _At ...;
char ch3 _At ...;
This places
ch1
at address
0xB7E000
,
ch2
at the next address (
0xB7E001
) after
ch1
, and
ch3
at the next address (
0xB7E002
) after
ch2
. The
_At ...
directive can only be used
after a previous
_At
or
_Align
directive.
Alignment of a Variable
The following syntax can be used to declare a global or static variable aligned at a speci-
fied alignment:
char ch2 _Align 2; // ch2 is aligned at even boundary
char ch4 _Align 4; // ch4 is aligned at a four byte boundary
NOTE: Only aligned variables with the
const
qualifier can be initialized. Non-
const
aligned variables would not be re-initialized correctly upon program reset. The
uninitialized aligned variables are not initialized to zero by the compiler startup
routine.
Inline Assembly
There are two methods of inserting assembly language within C code:
•
“Inline Assembly Using the Pragma Directive” on page 143
•
“Inline Assembly Using the asm Statement” on page 143
Inline Assembly Using the Pragma Directive
The first method uses the
#pragma feature of ANSI C with the following syntax:
#pragma asm " <assembly line> "
#pragma can be inserted anywhere within the C source file. The contents of
<assembly line> must be legal assembly language syntax. The usual C escape sequences
(such as
\n , \t , and \r ) are properly translated. Currently, the compiler does not process
the <assembly line>. Except for escape sequences, it is passed through the compiler to the
assembler verbatim.
Inline Assembly Using the asm Statement
The second method of inserting assembly language uses the
asm statement: