160 |
Chapter 5. Assembler Macros |
|
|
Predefined C Macro Constants
Ax51 provides you with predefined constants to use in preprocessor directives and C code for more portable programs. The following table lists and describes each one.
Constant |
Description |
_ _A51_ _ |
Allows you to identify the A51 assembler and returns the version number (for |
|
example, 600 for version 6.00). Only defined when using A51. |
_ _AX51_ _ |
Allows you to identify the AX51 assembler and returns the version number |
|
(for example, 100 for version 1.00). Only defined when using AX51. |
_ _A251_ _ |
Allows you to identify the A251 assembler and returns the version number |
|
(for example, 300 for version 3.00). Only defined when using A251. |
_ _DATE_ _ |
Date when the compilation was started. |
_ _FILE_ _ |
Name of the file being compiled. |
_ _KEIL_ _ |
Defined to 1 to indicate that you are using a development tool from Keil |
|
Software. |
_ _LINE_ _ |
Current line number in the file being compiled. |
_ _TIME_ _ |
Time when the compilation was started. |
_ _STDC_ _ |
Defined to 1 to indicate full conformance with the ANSI C Standard. |
5
Keil Software — A51/AX51/A251 Macro Assembler and Utilities |
161 |
|
|
Examples with C Macros
The following assembler source file shows the usage of C Macros.
#if !defined (__A51__) || __A51__ < 600
#error "This source file requires A51 V6.00 or higher" #endif
#pragma NOLIST
#include <reg52.h> // register definition file for 80C52 #pragma LIST
#define TEST1 10
#define MYTEXT "Hello World"
#if TEST1 == 10 DB MYTEXT
#endif
DB "GENERATED: ", __DATE__
MOV R0,#TEST1 * 10
END
The listing file generated by A51 shows the text replacements performed by the C preprocessor:
|
|
|
|
|
|
5 |
LOC |
OBJ |
LINE |
SOURCE |
|
|
|
|
|
|
||||
|
|
1 |
|
|
|
|
|
|
4 |
|
|
|
|
|
|
|
|
|
|
|
|
|
117 |
$LIST |
|
|
|
|
|
118 |
|
|
|
|
|
|
119 |
|
|
|
|
|
|
120 |
|
|
|
|
|
|
121 |
|
|
|
|
|
|
122 |
|
|
|
|
0000 |
48656C6C |
123 |
DB |
"Hello World" |
|
|
0004 |
6F20576F |
|
|
|
|
|
0008 |
726C64 |
|
|
|
|
|
|
|
124 |
|
|
|
|
000B |
47454E45 |
125 |
DB |
"GENERATED: ", "Jul 28 2000" |
|
|
000F |
52415445 |
|
|
|
|
|
0013 |
443A204A |
|
|
|
|
|
0017 |
756C2032 |
|
|
|
|
|
001B |
38203230 |
|
|
|
|
|
001F |
3030 |
|
|
|
|
|
|
|
126 |
|
|
|
|
0021 |
7864 |
127 |
MOV |
R0,#10 * 10 |
|
|
|
|
128 |
|
|
|
|
|
|
129 |
END |
|
|
|
162 |
Chapter 5. Assembler Macros |
|
|
C Preprocessor Side Effects
The integrated C preprocessor in Ax51 has two side effects. This might cause problems when you translate programs that are written for previous Ax51 versions.
1.If you are using the backslash character at the end of a comment line, the next line will be a comment too.
; THIS IS A COMMENT ENDING WITH \
MOV A,#0 DUE TO THE \ IN THE PREVIOUS LINE THE LINES A CONCATINATED
;AND THE MOV INSTRUCTION WILL NOT BE TRANSLATED
2.If you are using $INCLUDE in conditional assembly blocks, the file must exist even when the block will not be assembled.
$IF 0 |
|
$INCLUDE (MYFILE.INC) |
; this file must exist, even when the block |
|
; is not translated, since the C preprocessor |
$ENDIF |
; interprets the file first. |
#if 0 |
// with C preprocessor statements |
#include (myfile.inc) |
// the file needs not to exist |
#endif |
|
5