AVR Assembler

Preface
1 AVR Assembler Known Issues
2 AVR Assembler Command Line Options
3 Assembler Source
4 AVR Assembler Syntax
5 Assembler Directives
- 5.1 BYTE
  Reserves bytes for a variable.
- 5.2 CSEG
  Code segment.
- 5.3 CSEGSIZE
  Program Memory Size.
- 5.4 DB
  Define constant byte(s) in program memory and EEPROM.
- 5.5 DD
  Define constant double-word(s) in program memory and EEPROM.
- 5.6 DEF
  Set a symbolic name on a register.
- 5.7 DQ
  Define constant quad-word(s) in program memory and EEPROM.
- 5.8 DSEG
  Data Segment.
- 5.9 DW
  Define constant word(s) in program memory and EEPROM.
- 5.10 ELIF and ELSE
  Conditional assembly.
- 5.11 ENDIF
  Conditional assembly.
- 5.12 ENDM and ENDMACRO
  End macro.
- 5.13 EQU
  Set a symbol equal to an expression.
- 5.14 ERROR
  Outputs an error message string.
- 5.15 ESEG
  EEPROM Segment.
- 5.16 EXIT
  Exit this file.
- 5.17 IF, IFDEF, and IFNDEF
  Conditional assembly.
- 5.18 INCLUDE
  Include another file.
- 5.19 LIST
  Turn the listfile generation on.
- 5.20 LISTMAC
  Turn macro expansion on.
- 5.21 MACRO
  Begin macro.
- 5.22 MESSAGE
  Output a message string.
- 5.23 NOLIST
  Turn listfile generation OFF.
- 5.24 ORG
  Set program origin.
- 5.25 OVERLAP and NOOVERLAP
  Set up overlapping section.
- 5.26 SET
  Set a symbol equal to an expression.
- 5.27 UNDEF
  Undefine a register symbolic name.
- 5.28 WARNING
  Outputs a warning message string.
6 Preprocessor
7 Expressions
The Assembler incorporates constant expressions.
8 AVR Instruction Set
9 Revision History
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5.25 OVERLAP and NOOVERLAP

Set up overlapping section.

Introduced in AVRASM 2.1. These directives are for projects with special needs and should normally not be used.

These directives only affect the currently active segment (CSEG, DSEG, and ESEG).

The .overlap/nooverlap directives mark a section that will be allowed to overlap code/data with code/data defined elsewhere, without any error or warning messages being generated. This is totally independent of what is set using the #pragma, General Purpose directives. The overlap-allowed attribute will stay in effect across .org directives, but will not follow across .cseg/.eseg/.dseg directives (each segment marked separately).

The typical use of this is to set up some form of default code or data that may or may not later be modified by overlapping code or data, without having to disable assembler overlap detection altogether.

Syntax

.OVERLAP
.NOOVERLAP

Example

.overlap 
.org 0 ; section #1 
rjmp default 
.nooverlap 
.org 0 ; section #2 
rjmp RESET ; No error given here 
.org 0 ; section #3 
rjmp RESET ; Error here because overlap with #2

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