SPRU513Y August   2001  – June 2022 SM320F28335-EP

 

  1.   Read This First
    1.     About This Manual
    2.     How to Use This Manual
    3.     Notational Conventions
    4.     Related Documentation From Texas Instruments
    5.     Trademarks
  2. 1 Introduction to the Software Development Tools
    1. 1.1 Software Development Tools Overview
    2. 1.2 Tools Descriptions
  3. 2 Introduction to Object Modules
    1. 2.1 Object File Format Specifications
    2. 2.2 Executable Object Files
    3. 2.3 Introduction to Sections
      1. 2.3.1 Special Section Names
    4. 2.4 How the Assembler Handles Sections
      1. 2.4.1 Uninitialized Sections
      2. 2.4.2 Initialized Sections
      3. 2.4.3 User-Named Sections
      4. 2.4.4 Current Section
      5. 2.4.5 Section Program Counters
      6. 2.4.6 Subsections
      7. 2.4.7 Using Sections Directives
    5. 2.5 How the Linker Handles Sections
      1. 2.5.1 Combining Input Sections
      2. 2.5.2 Placing Sections
    6. 2.6 Symbols
      1. 2.6.1 Global (External) Symbols
      2. 2.6.2 Local Symbols
      3. 2.6.3 Weak Symbols
      4. 2.6.4 The Symbol Table
    7. 2.7 Symbolic Relocations
      1. 2.7.1 Expressions With Multiple Relocatable Symbols (COFF Only)
    8. 2.8 Loading a Program
  4. 3 Program Loading and Running
    1. 3.1 Loading
      1. 3.1.1 Load and Run Addresses
      2. 3.1.2 Bootstrap Loading
        1. 3.1.2.1 Boot, Load, and Run Addresses
        2. 3.1.2.2 Primary Bootloader
        3. 3.1.2.3 Secondary Bootloader
        4. 3.1.2.4 Boot Table
        5. 3.1.2.5 Bootloader Routine
          1. 3.1.2.5.1 Sample Secondary Bootloader Routine
    2. 3.2 Entry Point
    3. 3.3 Run-Time Initialization
      1. 3.3.1 The _c_int00 Function
      2. 3.3.2 RAM Model vs. ROM Model
        1. 3.3.2.1 Autoinitializing Variables at Run Time (--rom_model)
        2. 3.3.2.2 Initializing Variables at Load Time (--ram_model)
        3. 3.3.2.3 The --rom_model and --ram_model Linker Options
      3. 3.3.3 About Linker-Generated Copy Tables
        1. 3.3.3.1 BINIT
        2. 3.3.3.2 CINIT
    4. 3.4 Arguments to main
    5. 3.5 Run-Time Relocation
    6. 3.6 Additional Information
  5. 4 Assembler Description
    1. 4.1  Assembler Overview
    2. 4.2  The Assembler's Role in the Software Development Flow
    3. 4.3  Invoking the Assembler
    4. 4.4  Controlling Application Binary Interface
    5. 4.5  Naming Alternate Directories for Assembler Input
      1. 4.5.1 Using the --include_path Assembler Option
      2. 4.5.2 Using the C2000_A_DIR Environment Variable
    6. 4.6  Source Statement Format
      1. 4.6.1 Label Field
      2. 4.6.2 Mnemonic Field
      3. 4.6.3 Operand Field
      4. 4.6.4 Comment Field
    7. 4.7  Literal Constants
      1. 4.7.1 Integer Literals
        1. 4.7.1.1 Binary Integer Literals
        2. 4.7.1.2 Octal Integer Literals
        3. 4.7.1.3 Decimal Integer Literals
        4. 4.7.1.4 Hexadecimal Integer Literals
        5. 4.7.1.5 Character Literals
      2. 4.7.2 Character String Literals
      3. 4.7.3 Floating-Point Literals
    8. 4.8  Assembler Symbols
      1. 4.8.1 Identifiers
      2. 4.8.2 Labels
      3. 4.8.3 Local Labels
        1. 4.8.3.1 Local Labels of the Form $n
        2.       84
        3. 4.8.3.2 Local Labels of the Form name?
        4.       86
      4. 4.8.4 Symbolic Constants
      5. 4.8.5 Defining Symbolic Constants (--asm_define Option)
      6. 4.8.6 Predefined Symbolic Constants
      7. 4.8.7 Registers
      8. 4.8.8 Substitution Symbols
    9. 4.9  Expressions
      1. 4.9.1 Mathematical and Logical Operators
      2. 4.9.2 Relational Operators and Conditional Expressions
      3. 4.9.3 Well-Defined Expressions
      4. 4.9.4 Legal Expressions
    10. 4.10 Built-in Functions and Operators
      1. 4.10.1 Built-In Math and Trigonometric Functions
    11. 4.11 TMS320C28x Assembler Extensions
      1. 4.11.1 C28x Support
      2. 4.11.2 C28x FPU32 and FPU64 Extensions
      3. 4.11.3 C28x CLA Extensions
    12. 4.12 Source Listings
    13. 4.13 Debugging Assembly Source
    14. 4.14 Cross-Reference Listings
    15. 4.15 Smart Encoding
    16. 4.16 Pipeline Conflict Detection
      1. 4.16.1 Protected and Unprotected Pipeline Instructions
      2. 4.16.2 Pipeline Conflict Prevention and Detection
      3. 4.16.3 Pipeline Conflicts Detected
  6. 5 Assembler Directives
    1. 5.1  Directives Summary
    2. 5.2  Directives that Define Sections
    3. 5.3  Directives that Initialize Values
    4. 5.4  Directives that Perform Alignment and Reserve Space
    5. 5.5  Directives that Format the Output Listings
    6. 5.6  Directives that Reference Other Files
    7. 5.7  Directives that Enable Conditional Assembly
    8. 5.8  Directives that Define Union or Structure Types
    9. 5.9  Directives that Define Enumerated Types
    10. 5.10 Directives that Define Symbols at Assembly Time
    11. 5.11 Miscellaneous Directives
    12. 5.12 Directives Reference
      1.      .align
      2.      .asg/.define/.eval
      3.      .asmfunc/.endasmfunc
      4.      .bits
      5.      .bss
      6.      .byte/.ubyte/.char/.uchar
      7.      .cdecls
      8.      .clink
      9.      .common
      10.      .copy/.include
      11.      .cstruct/.cunion/.endstruct/.endunion/.tag
      12.      .data
      13.      .drlist/.drnolist
      14.      .elfsym
      15.      .emsg/.mmsg/.wmsg
      16.      .end
      17.      .fclist/.fcnolist
      18.      .field
      19.      .float/.xfloat/.xldouble
      20.      .global/.def/.ref
      21.      .group/.gmember/.endgroup
      22.      .if/.elseif/.else/.endif
      23.      .int/.unint/.word/.uword
      24.      .label
      25.      .length/.width
      26.      .list/.nolist
      27.      .long/.ulong/.xlong
      28.      .loop/.endloop/.break
      29.      .macro/.endm
      30.      .mlib
      31.      .mlist/.mnolist
      32.      .newblock
      33.      .option
      34.      .page
      35.      .preserve
      36.      .retain / .retainrefs
      37.      .sblock
      38.      .sect
      39.      .set
      40.      .space/.bes
      41.      .sslist/.ssnolist
      42.      .string/.cstring/.pstring
      43.      .struct/.endstruct/.tag
      44.      .symdepend
      45.      .tab
      46.      .text
      47.      .title
      48.      .unasg/.undefine
      49.      .union/.endunion/.tag
      50.      .usect
      51.      .var
      52.      .weak
  7. 6 Macro Language Description
    1. 6.1  Using Macros
    2. 6.2  Defining Macros
    3. 6.3  Macro Parameters/Substitution Symbols
      1. 6.3.1 Directives That Define Substitution Symbols
      2. 6.3.2 Built-In Substitution Symbol Functions
      3. 6.3.3 Recursive Substitution Symbols
      4. 6.3.4 Forced Substitution
      5. 6.3.5 Accessing Individual Characters of Subscripted Substitution Symbols
      6. 6.3.6 Substitution Symbols as Local Variables in Macros
    4. 6.4  Macro Libraries
    5. 6.5  Using Conditional Assembly in Macros
    6. 6.6  Using Labels in Macros
    7. 6.7  Producing Messages in Macros
    8. 6.8  Using Directives to Format the Output Listing
    9. 6.9  Using Recursive and Nested Macros
    10. 6.10 Macro Directives Summary
  8. 7 Archiver Description
    1. 7.1 Archiver Overview
    2. 7.2 The Archiver's Role in the Software Development Flow
    3. 7.3 Invoking the Archiver
    4. 7.4 Archiver Examples
    5. 7.5 Library Information Archiver Description
      1. 7.5.1 Invoking the Library Information Archiver
      2. 7.5.2 Library Information Archiver Example
      3. 7.5.3 Listing the Contents of an Index Library
      4. 7.5.4 Requirements
  9. 8 Linker Description
    1. 8.1  Linker Overview
    2. 8.2  The Linker's Role in the Software Development Flow
    3. 8.3  Invoking the Linker
    4. 8.4  Linker Options
      1. 8.4.1  Wildcards in File, Section, and Symbol Patterns
      2. 8.4.2  Specifying C/C++ Symbols with Linker Options
      3. 8.4.3  Relocation Capabilities (--absolute_exe and --relocatable Options)
        1. 8.4.3.1 Producing an Absolute Output Module (--absolute_exe option)
        2. 8.4.3.2 Producing a Relocatable Output Module (--relocatable option)
      4. 8.4.4  Allocate Memory for Use by the Loader to Pass Arguments (--arg_size Option)
      5. 8.4.5  Compression (--cinit_compression and --copy_compression Option)
      6. 8.4.6  Compress DWARF Information (--compress_dwarf Option)
      7. 8.4.7  Control Linker Diagnostics
      8. 8.4.8  Automatic Library Selection (--disable_auto_rts Option)
      9. 8.4.9  Disable Conditional Linking (--disable_clink Option)
      10. 8.4.10 Do Not Remove Unused Sections (--unused_section_elimination Option)
      11. 8.4.11 Linker Command File Preprocessing (--disable_pp, --define and --undefine Options)
      12. 8.4.12 Error Correcting Code Testing (--ecc Options)
      13. 8.4.13 Define an Entry Point (--entry_point Option)
      14. 8.4.14 Set Default Fill Value (--fill_value Option)
      15. 8.4.15 Define Heap Size (--heap_size Option)
      16. 8.4.16 Hiding Symbols
      17. 8.4.17 Alter the Library Search Algorithm (--library, --search_path, and C2000_C_DIR )
        1. 8.4.17.1 Name an Alternate Library Directory (--search_path Option)
        2. 8.4.17.2 Name an Alternate Library Directory ( C2000_C_DIR Environment Variable)
        3. 8.4.17.3 Exhaustively Read and Search Libraries (--reread_libs and --priority Options)
      18. 8.4.18 Change Symbol Localization
        1. 8.4.18.1 Make All Global Symbols Static (--make_static Option)
      19. 8.4.19 Create a Map File (--map_file Option)
      20. 8.4.20 Managing Map File Contents (--mapfile_contents Option)
      21. 8.4.21 Disable Name Demangling (--no_demangle)
      22. 8.4.22 Disable Merging of Symbolic Debugging Information (--no_sym_merge Option)
      23. 8.4.23 Strip Symbolic Information (--no_symtable Option)
      24. 8.4.24 Name an Output Module (--output_file Option)
      25. 8.4.25 Prioritizing Function Placement (--preferred_order Option)
      26. 8.4.26 C Language Options (--ram_model and --rom_model Options)
      27. 8.4.27 Retain Discarded Sections (--retain Option)
      28. 8.4.28 Create an Absolute Listing File (--run_abs Option)
      29. 8.4.29 Scan All Libraries for Duplicate Symbol Definitions (--scan_libraries)
      30. 8.4.30 Define Stack Size (--stack_size Option)
      31. 8.4.31 Mapping of Symbols (--symbol_map Option)
      32. 8.4.32 Introduce an Unresolved Symbol (--undef_sym Option)
      33. 8.4.33 Display a Message When an Undefined Output Section Is Created (--warn_sections)
      34. 8.4.34 Generate XML Link Information File (--xml_link_info Option)
      35. 8.4.35 Zero Initialization (--zero_init Option)
    5. 8.5  Linker Command Files
      1. 8.5.1  Reserved Names in Linker Command Files
      2. 8.5.2  Constants in Linker Command Files
      3. 8.5.3  Accessing Files and Libraries from a Linker Command File
      4. 8.5.4  The MEMORY Directive
        1. 8.5.4.1 Default Memory Model
        2. 8.5.4.2 MEMORY Directive Syntax
        3. 8.5.4.3 Expressions and Address Operators
      5. 8.5.5  The SECTIONS Directive
        1. 8.5.5.1 SECTIONS Directive Syntax
        2. 8.5.5.2 Section Allocation and Placement
          1. 8.5.5.2.1 Example: Placing Functions in RAM
          2. 8.5.5.2.2 Binding
          3. 8.5.5.2.3 Named Memory
          4. 8.5.5.2.4 Controlling Placement Using The HIGH Location Specifier
            1. 8.5.5.2.4.1 Linker Placement With the HIGH Specifier
            2.         265
            3. 8.5.5.2.4.2 Linker Placement Without HIGH Specifier
          5. 8.5.5.2.5 Alignment and Blocking
          6. 8.5.5.2.6 Alignment With Padding
          7. 8.5.5.2.7 Using the Page Method
        3. 8.5.5.3 Specifying Input Sections
          1. 8.5.5.3.1 The Most Common Method of Specifying Section Contents
          2.        272
        4. 8.5.5.4 Using Multi-Level Subsections
        5. 8.5.5.5 Specifying Library or Archive Members as Input to Output Sections
          1. 8.5.5.5.1 Archive Members to Output Sections
          2.        276
        6. 8.5.5.6 Allocation Using Multiple Memory Ranges
        7. 8.5.5.7 Automatic Splitting of Output Sections Among Non-Contiguous Memory Ranges
      6. 8.5.6  Placing a Section at Different Load and Run Addresses
        1. 8.5.6.1 Specifying Load and Run Addresses
        2.       281
        3. 8.5.6.2 Referring to the Load Address by Using the .label Directive
      7. 8.5.7  Using GROUP and UNION Statements
        1. 8.5.7.1 Grouping Output Sections Together
        2. 8.5.7.2 Overlaying Sections With the UNION Statement
        3. 8.5.7.3 Using Memory for Multiple Purposes
        4. 8.5.7.4 Nesting UNIONs and GROUPs
        5. 8.5.7.5 Checking the Consistency of Allocators
        6. 8.5.7.6 Naming UNIONs and GROUPs
      8. 8.5.8  Overlaying Pages
        1. 8.5.8.1 Using the MEMORY Directive to Define Overlay Pages
        2. 8.5.8.2 Example of Overlay Pages
          1. 8.5.8.2.1 MEMORY Directive With Overlay Pages
          2.        294
        3. 8.5.8.3 Using Overlay Pages With the SECTIONS Directive
          1. 8.5.8.3.1 SECTIONS Directive Definition for Overlays
          2.        297
        4. 8.5.8.4 Memory Allocation for Overlaid Pages
      9. 8.5.9  Special Section Types (DSECT, COPY, NOLOAD, and NOINIT)
      10. 8.5.10 Configuring Error Correcting Code (ECC) with the Linker
        1. 8.5.10.1 Using the ECC Specifier in the Memory Map
        2. 8.5.10.2 Using the ECC Directive
        3. 8.5.10.3 Using the VFILL Specifier in the Memory Map
      11. 8.5.11 Assigning Symbols at Link Time
        1. 8.5.11.1 Syntax of Assignment Statements
        2. 8.5.11.2 Assigning the SPC to a Symbol
        3. 8.5.11.3 Assignment Expressions
        4. 8.5.11.4 Symbols Automatically Defined by the Linker
        5. 8.5.11.5 Assigning Exact Start, End, and Size Values of a Section to a Symbol
        6. 8.5.11.6 Why the Dot Operator Does Not Always Work
        7. 8.5.11.7 Address and Dimension Operators
          1. 8.5.11.7.1 Input Items
          2. 8.5.11.7.2 Output Section
          3. 8.5.11.7.3 GROUPs
          4. 8.5.11.7.4 UNIONs
        8. 8.5.11.8 LAST Operator
      12. 8.5.12 Creating and Filling Holes
        1. 8.5.12.1 Initialized and Uninitialized Sections
        2. 8.5.12.2 Creating Holes
        3. 8.5.12.3 Filling Holes
        4. 8.5.12.4 Explicit Initialization of Uninitialized Sections
    6. 8.6  Linker Symbols
      1. 8.6.1 Using Linker Symbols in C/C++ Applications
      2. 8.6.2 Declaring Weak Symbols
      3. 8.6.3 Resolving Symbols with Object Libraries
    7. 8.7  Default Placement Algorithm
      1. 8.7.1 How the Allocation Algorithm Creates Output Sections
      2. 8.7.2 Reducing Memory Fragmentation
    8. 8.8  Using Linker-Generated Copy Tables
      1. 8.8.1 Using Copy Tables for Boot Loading
      2. 8.8.2 Using Built-in Link Operators in Copy Tables
      3. 8.8.3 Overlay Management Example
      4. 8.8.4 Generating Copy Tables With the table() Operator
        1. 8.8.4.1 The table() Operator
        2. 8.8.4.2 Boot-Time Copy Tables
        3. 8.8.4.3 Using the table() Operator to Manage Object Components
        4. 8.8.4.4 Linker-Generated Copy Table Sections and Symbols
        5. 8.8.4.5 Splitting Object Components and Overlay Management
      5. 8.8.5 Compression
        1. 8.8.5.1 Compressed Copy Table Format
        2. 8.8.5.2 Compressed Section Representation in the Object File
        3. 8.8.5.3 Compressed Data Layout
        4. 8.8.5.4 Run-Time Decompression
        5. 8.8.5.5 Compression Algorithms
        6.       345
      6. 8.8.6 Copy Table Contents
      7. 8.8.7 General Purpose Copy Routine
    9. 8.9  Linker-Generated CRC Tables and CRC Over Memory Ranges
      1. 8.9.1 Using the crc_table() Operator in the SECTIONS Directive
        1. 8.9.1.1 Restrictions when using the crc_table() Operator
        2. 8.9.1.2 Examples
          1. 8.9.1.2.1 Using crc_table() Operator to Compute the CRC Value for .text Data
          2.        353
          3. 8.9.1.2.2 Specifying an Algorithm in the crc_table() Operator
          4.        355
          5. 8.9.1.2.3 Using a Single Table for Multiple Sections
          6.        357
          7. 8.9.1.2.4 Applying the crc_table() Operator to a GROUP or UNION
          8.        359
        3. 8.9.1.3 Interface When Using the crc_table() Operator
          1. 8.9.1.3.1 The CRC Table Header, crc_tbl.h
      2. 8.9.2 Using the crc() Operator in the MEMORY Directive
        1. 8.9.2.1 Restrictions when Using the crc() Operator
        2. 8.9.2.2 Using the VFILL Specifier within a GROUP
        3. 8.9.2.3 Generate CRC for Most or All of Flash Memory
        4. 8.9.2.4 Computing CRCs for Both Memory Ranges and Sections
        5. 8.9.2.5 Example Specifying Memory Range CRCs
        6. 8.9.2.6 Interface When Using the crc() Operator
      3. 8.9.3 A Special Note Regarding 16-Bit char
    10. 8.10 Partial (Incremental) Linking
    11. 8.11 Linking C/C++ Code
      1. 8.11.1 Run-Time Initialization
      2. 8.11.2 Object Libraries and Run-Time Support
      3. 8.11.3 Setting the Size of the Stack and Heap Sections
      4. 8.11.4 Initializing and AutoInitialzing Variables at Run Time
    12. 8.12 Linker Example
  10. 9 Absolute Lister Description
    1. 9.1 Producing an Absolute Listing
    2. 9.2 Invoking the Absolute Lister
    3. 9.3 Absolute Lister Example
  11. 10Cross-Reference Lister Description
    1. 10.1 Producing a Cross-Reference Listing
    2. 10.2 Invoking the Cross-Reference Lister
    3. 10.3 Cross-Reference Listing Example
  12. 11Object File Utilities
    1. 11.1 Invoking the Object File Display Utility
    2. 11.2 Invoking the Disassembler
    3. 11.3 Invoking the Name Utility
    4. 11.4 Invoking the Strip Utility
  13. 12Hex Conversion Utility Description
    1. 12.1  The Hex Conversion Utility's Role in the Software Development Flow
    2. 12.2  Invoking the Hex Conversion Utility
      1. 12.2.1 Invoking the Hex Conversion Utility From the Command Line
      2. 12.2.2 Invoking the Hex Conversion Utility With a Command File
    3. 12.3  Understanding Memory Widths
      1. 12.3.1 Target Width
      2. 12.3.2 Specifying the Memory Width
      3. 12.3.3 Partitioning Data Into Output Files
      4. 12.3.4 Specifying Word Order for Output Words
    4. 12.4  The ROMS Directive
      1. 12.4.1 When to Use the ROMS Directive
      2. 12.4.2 An Example of the ROMS Directive
    5. 12.5  The SECTIONS Directive
    6. 12.6  The Load Image Format (--load_image Option)
      1. 12.6.1 Load Image Section Formation
      2. 12.6.2 Load Image Characteristics
    7. 12.7  Excluding a Specified Section
    8. 12.8  Assigning Output Filenames
    9. 12.9  Image Mode and the --fill Option
      1. 12.9.1 Generating a Memory Image
      2. 12.9.2 Specifying a Fill Value
      3. 12.9.3 Steps to Follow in Using Image Mode
    10. 12.10 Array Output Format
    11. 12.11 Building a Table for an On-Chip Boot Loader
      1. 12.11.1 Description of the Boot Table
      2. 12.11.2 The Boot Table Format
      3. 12.11.3 How to Build the Boot Table
        1. 12.11.3.1 Building the Boot Table
        2. 12.11.3.2 Leaving Room for the Boot Table
      4. 12.11.4 Booting From a Device Peripheral
      5. 12.11.5 Setting the Entry Point for the Boot Table
      6. 12.11.6 Using the C28x Boot Loader
        1. 12.11.6.1 Sample Command File for Booting From 8-Bit SPI Boot
        2.       424
        3. 12.11.6.2 Sample Command File for C28x 16-Bit Parallel Boot GP I/O
        4.       426
        5. 12.11.6.3 Sample Command File for Booting From 8-Bit SCI Boot
        6.       428
    12. 12.12 Using Secure Flash Boot on TMS320F2838x Devices
    13. 12.13 Controlling the ROM Device Address
    14. 12.14 Control Hex Conversion Utility Diagnostics
    15. 12.15 Description of the Object Formats
      1. 12.15.1 ASCII-Hex Object Format (--ascii Option)
      2. 12.15.2 Intel MCS-86 Object Format (--intel Option)
      3. 12.15.3 Motorola Exorciser Object Format (--motorola Option)
      4. 12.15.4 Extended Tektronix Object Format (--tektronix Option)
      5. 12.15.5 Texas Instruments SDSMAC (TI-Tagged) Object Format (--ti_tagged Option)
      6. 12.15.6 TI-TXT Hex Format (--ti_txt Option)
        1. 12.15.6.1 TI-TXT Object Format
    16. 12.16 Hex Conversion Utility Error Messages
  14. 13Sharing C/C++ Header Files With Assembly Source
    1. 13.1 Overview of the .cdecls Directive
    2. 13.2 Notes on C/C++ Conversions
      1. 13.2.1  Comments
      2. 13.2.2  Conditional Compilation (#if/#else/#ifdef/etc.)
      3. 13.2.3  Pragmas
      4. 13.2.4  The #error and #warning Directives
      5. 13.2.5  Predefined symbol __ASM_HEADER__
      6. 13.2.6  Usage Within C/C++ asm( ) Statements
      7. 13.2.7  The #include Directive
      8. 13.2.8  Conversion of #define Macros
      9. 13.2.9  The #undef Directive
      10. 13.2.10 Enumerations
      11. 13.2.11 C Strings
      12. 13.2.12 C/C++ Built-In Functions
      13. 13.2.13 Structures and Unions
      14. 13.2.14 Function/Variable Prototypes
      15. 13.2.15 C Constant Suffixes
      16. 13.2.16 Basic C/C++ Types
    3. 13.3 Notes on C++ Specific Conversions
      1. 13.3.1 Name Mangling
      2. 13.3.2 Derived Classes
      3. 13.3.3 Templates
      4. 13.3.4 Virtual Functions
    4. 13.4 Special Assembler Support
      1. 13.4.1 Enumerations (.enum/.emember/.endenum)
      2. 13.4.2 The .define Directive
      3. 13.4.3 The .undefine/.unasg Directives
      4. 13.4.4 The $defined( ) Built-In Function
      5. 13.4.5 The $sizeof Built-In Function
      6. 13.4.6 Structure/Union Alignment and $alignof( )
      7. 13.4.7 The .cstring Directive
  15.   A Symbolic Debugging Directives
    1.     A.1 DWARF Debugging Format
    2.     A.2 Debug Directive Syntax
  16.   B XML Link Information File Description
    1.     B.1 XML Information File Element Types
    2.     B.2 Document Elements
      1.      B.2.1 Header Elements
      2.      B.2.2 Input File List
      3.      B.2.3 Object Component List
      4.      B.2.4 Logical Group List
      5.      B.2.5 Placement Map
      6.      B.2.6 Symbol Table
  17.   C CRC Reference Implementation
    1.     C.1 Compilation Instructions
    2.     C.2 Reference CRC Calculation Routine
      1.      C.2.1 Reference Implementation of a CRC Calculation Function: ref_crc.c
    3.     C.3 Linker-Generated Copy Tables and CRC Tables
      1.      C.3.1 Main Routine for Example Application: main.c
      2.      C.3.2 Checking CRC Values: check_crc.c
      3.      C.3.3 Task1 Routine: task1.c
      4.      C.3.4 Task2 Routine: task2.c
      5.      C.3.5 Task3 Routine: task3.c
      6.      C.3.6 Example 1 Command File: ex1.cmd (for COFF)
  18.   D Glossary
    1.     D.1 Terminology
  19.   E Revision History
  20.   499
  21.   500
  22.   501
  23.   502
  24.   E Earlier Revisions

2.3 Introduction to Sections

The smallest unit of an object file is a section. A section is a block of code or data that occupies contiguous space in the memory map. Each section of an object file is separate and distinct.

COFF format executable object files contain sections.

ELF format executable object files contain segments. An ELF segment is a meta-section. It represents a contiguous region of target memory. It is a collection of sections that have the same property, such as writeable or readable. An ELF loader needs the segment information, but does not need the section information. The ELF standard allows the linker to omit ELF section information entirely from the executable object file.

Object files usually contain three default sections:

.text sectionContains executable code (1)
.data sectionUsually contains initialized data
.ebss section (for COFF)
.bss section (for EABI)		Usually reserves space for uninitialized variables

Note that the .data section is used mainly for EABI. For COFF, the compiler generates .cinit sections that are used to initialize the .ebss section. The assembler can be used to place initialized data in the .data section for both COFF and EABI.

The assembler and linker allow you to create, name, and link other kinds of sections. The .text, .data, and .ebss or .bss sections are archetypes for how sections are handled.

There are two basic types of sections:

Initialized sectionsContain data or code. The .text and .data sections are initialized; user-named sections created with the .sect assembler directive are also initialized.
Uninitialized sectionsReserve space in the memory map for uninitialized data. The .ebss or .bss section is uninitialized; user-named sections created with the .usect assembler directive are also uninitialized.

Several assembler directives allow you to associate various portions of code and data with the appropriate sections. The assembler builds these sections during the assembly process, creating an object file organized as shown in Figure 3-1.

One of the linker's functions is to relocate sections into the target system's memory map; this function is called placement. Because most systems contain several types of memory, using sections can help you use target memory more efficiently. All sections are independently relocatable; you can place any section into any allocated block of target memory. For example, you can define a section that contains an initialization routine and then allocate the routine in a portion of the memory map that contains ROM. For information on section placement, see the "Specifying Where to Allocate Sections in Memory" section of the TMS320C28x Optimizing C/C++ Compiler User's Guide.

Figure 3-1 shows the relationship between sections in an object file and a hypothetical target memory. (This figure shows COFF sections. For EABI, the .ebss section would be .bss.) ROM may be EEPROM, FLASH or some other type of physical memory in an actual system.

GUID-0E0C7C53-3FE8-46B7-8AC0-C594B6DC7094-low.pngFigure 2-1 Partitioning Memory Into Logical Blocks
1. Some targets allow content other than text, such as constants, in .text sections.
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