SLAU646F September   2015  – June 2020

 

  1.   Read This First
    1.     How to Use This User's Guide
    2.     Related Documentation
    3.     If You Need Assistance
    4.     Trademarks
  2. 1Introduction
  3. 2Installing MSP430 GCC Toolchain
    1. 2.1 Installing MSP430 GCC in CCS Releases Before v7.2
    2. 2.2 Installing MSP430 GCC as Stand-Alone Package
  4. 3Using MSP430 GCC Within CCS
    1. 3.1 Create New Project
    2. 3.2 Debug Using MSP-FET, MSPFET430UIF, eZ-FET, eZ430
    3. 3.3 Build Options for MSP430 GCC
      1. 3.3.1  GNU Compiler
      2. 3.3.2  GNU Compiler: Runtime
      3. 3.3.3  GNU Compiler: Symbols
      4. 3.3.4  GNU Compiler: Directories
      5. 3.3.5  GNU Compiler: Optimization
      6. 3.3.6  GNU Compiler: Preprocessor
      7. 3.3.7  GNU Compiler: Assembler
      8. 3.3.8  GNU Compiler: Debugging
      9. 3.3.9  GNU Compiler: Diagnostic Options
      10. 3.3.10 GNU Compiler: Miscellaneous
      11. 3.3.11 GNU Linker
      12. 3.3.12 GNU Linker: Basic
      13. 3.3.13 GNU Linker: Libraries
      14. 3.3.14 GNU Linker: Symbols
      15. 3.3.15 GNU Linker: Miscellaneous
      16. 3.3.16 GNU Objcopy Utility
    4. 3.4 CCS Compared to MSP430 GCC
  5. 4MSP430 GCC Stand-Alone Package
    1. 4.1 MSP430 GCC Stand-Alone Package Folder Structure
    2. 4.2 Package Content
    3. 4.3 MSP430 GCC Options
    4. 4.4 MSP430 Built-in Functions
    5. 4.5 Using MSP430 GCC Support Files
    6. 4.6 Quick Start: Blink the LED
      1. 4.6.1 Building with a Makefile
      2. 4.6.2 Building Manually with gcc
      3. 4.6.3 Debugging
        1. 4.6.3.1 Starting GDB Agent
          1. 4.6.3.1.1 Using the GUI
          2. 4.6.3.1.2 Using the Command Line
        2. 4.6.3.2 Debugging With GDB
          1. 4.6.3.2.1 Running a Program in the Debugger
          2. 4.6.3.2.2 Setting a Breakpoint
          3. 4.6.3.2.3 Single Stepping
          4. 4.6.3.2.4 Stopping or Interrupting a Running Program
      4. 4.6.4 Creating a New Project
    7. 4.7 GDB Settings
      1. 4.7.1 Console Application
      2. 4.7.2 Optional Parameters for msp430.dat
      3. 4.7.3 GUI Application
      4. 4.7.4 Attaching the Debugger
      5. 4.7.5 Configuring the Target Voltage
      6. 4.7.6 Resetting the Target
      7. 4.7.7 Halting the Target
  6. 5MSP430 GCC Features
    1. 5.1 C/C++ Attributes
      1. 5.1.1 GCC Function Attribute Support
      2. 5.1.2 GCC Data Attribute Support
      3. 5.1.3 GCC Section Attribute Support
    2. 5.2 Hints for Reducing the Size of MSP430 GCC Programs
      1. 5.2.1 The -mtiny-printf Option
      2. 5.2.2 The -ffunction-sections and -fdata-sections Options
      3. 5.2.3 Making Large Programs Fit Across Upper and Lower Memory
      4. 5.2.4 NOP Instructions Surrounding Interrupt State Changes
    3. 5.3 C Runtime Library (CRT) Startup Behavior
    4. 5.4 Using printf with MSP430 GCC
    5. 5.5 Link-time Optimization (LTO)
    6. 5.6 The __int20 Type and Pointers in the Large Memory Model
  7. 6Building MSP430 GCC From Sources
    1. 6.1 Required Tools
    2. 6.2 Building MSP430 GCC (Mitto Systems Limited)
      1. 6.2.1 Building a Native MSP430 GCC Toolchain
      2. 6.2.2 Building the MSP430 GCC Toolchain for Windows
    3. 6.3 Building MSP430 GCC Stand-Alone Full Package
  8. 7MSP430 GCC and MSPGCC
    1. 7.1 Calling Convention
    2. 7.2 Other Portions of the ABI
  9. 8Appendix
    1. 8.1 GCC Intrinsic Support
    2. 8.2 NOP Instructions Required Between Interrupt State Changes
  10. 9References
  11.   Revision History

5.6 The __int20 Type and Pointers in the Large Memory Model

For MSP430X devices in the large memory model, pointers and size_t are 20 bits in size. To handle this, GCC defines the __int20 type, which uses 20 bits of space in registers, and 32 bits of space in memory.

This type is built into the compiler, so it can be used like any other type in source code. Using unsigned __int20 designates the unsigned version of the type.

The __int20 type is not part of the ISO C specification, so using this type in any program compiled with flags that check for standards compliance may cause a warning or error to be emitted. A variation of the type that will not trigger these standards compliance messages is defined as __int20__ (using a trailing double underscore).