Ax51 User's Guide

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Ax51 User's Guide

Ax51 Introduction

Assembling Programs

Writing Assembly Programs

Assembly Statements

Symbols and Symbol Names

Using Operands and Expressions

Special Assembler Symbols

CODE

Program Addresses

Expressions and Operators

Character Strings

Location Counter

*

+

-

/

<

<=

<>

==

>

>=

EQ

GT

LT

NE

OR

Class Operators

Expression Classes

Relocatable Expressions

Simple Relocatable Expressions

Extended Relocatable Expressions

Expressions Example

Control Statements

Macro Processor

CODE

CODE memory can be accessed with the instruction MOVC via the DPTR register.

Example for all 8051 variants

?CO?my_seg SEGMENT CODE                ; define a SEGMENT of class CODE
           RSEG    ?CO?my_seg
TABLE:     DB      1,2,4,8,0x10        ; a table with constant values

?PR?myprog SEGMENT CODE                ; define a segment for program code
           RSEG    ?PR?myprog
           MOV     DPTR,#TABLE         ; load address of table
           MOV     A,#3                ; load offset into table
           MOVC    A,@A+DPTR           ; access via MOVC instruction