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ECE 447: Lecture 16

ECE 447: Lecture 16. Assembler Directives. ECE 447: Constants. C. assembly. decimal 23 23 o r 23D hexadecimal 0xf9 $f9 or 0f9H binary — %1011 or 1011B octal 067 @67 or 67O character ’w’ ’w’. Special constants. $0A $09 $07.

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ECE 447: Lecture 16

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  1. ECE 447: Lecture 16 Assembler Directives

  2. ECE 447: Constants C assembly decimal 23 23 or 23D hexadecimal 0xf9 $f9 or 0f9H binary — %1011 or 1011B octal 067 @67 or 67O character ’w’ ’w’ Special constants $0A $09 $07 ‘\n’ - new line ‘\t’ - horizontal tab ‘\a’ - alert (bell)

  3. ECE 447: Defining a Constant assembler C #define PORTB 0x1004 PORTB EQU $1004 DELAY SET 100 ……. DELAY SET 200 #define DELAY 100 ………. #undef DELAY #define DELAY 200

  4. ECE 447: Assembler Directives Declaration of global uninitialized variables rmb - reserve memory bytes assembler C c: rmb 1 char c; or unsigned char c; int k; or unsigned int k; or char * k; k: rmb 2 m: rmb 4 long m; or float m; array1: rmb 20*2 int array1[20]; unsigned char array2 [5][4]; array2: rmb 5*4

  5. ECE 447: Assembler Directives Declaration of global initialized variables fcb - form constant byte fdb - form double byte C assembler char c = -1; or unsigned char c = 255; c: fcb $ff int k=-1; or unsigned int k=0xffff; k: fdb $ffff m: fdb $0010, $0000 long m = 0x00100000; array1: fdb 3, 12, 87 int array1[3] = {3, 12, 87};

  6. ECE447: Assembler Directives Declaration of global initialized character arrays (strings) fcc - form constant character assembler C char string1[] = “ECE447” string1: fcc “ECE447” fcb 0 string2: fcc 3, ABC fcb 0 char string2 [4] = “ABC”;

  7. ECE447: Assembler Directives Defining external variables and functions assembler C int a; int func1() { ……. } .global a a: rmb 2 (outside of any function) .global func1 func1: ……… or func1 …………

  8. ECE 447: Assembler Directives Defining static variables and functions C assembler static int a; static int func1() { ……. } a rmb 2 (outside of any function) func1 ………

  9. ECE 447: Assembler Directives assembler C int a = 3; int * b; a fcb 3 b rmb 2 a &a a #a LDX #a STX b LDX #b LDD #4 STD 0,X b = & a; *b = 4;

  10. ECE 447: Assembler Directives Defining a macro #define MAX(a, b) ((a>=b)?a:b) MAX %MACRO a , b, cont LDD a CPD b BGE cont LDD b cont %ENDM

  11. ECE 447: Assembler Directives Including a file #include <stdio.h> %INCLUDE “stdio.h” %INCLUDE “mydefs.h” #include “mydefs.h” Conditional compilation/assembly #if SYSTEM == MSDOS …….. #else ……. #endif %if SYSTEM == MSDOS ………. %else …….. %endif

  12. ECE 447: Linker Oriented Directives Putting Code in Specific Sections section .text section .data section .bss Manually Placing Code in Memory org $C000 Indicating GMU assembly .mri 1 Telling Assembler where the end of ASM file is end

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