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

5.2.3 Making Large Programs Fit Across Upper and Lower Memory

For MSP430X devices that have an “upper” memory region (memory above the 0xFFFF boundary), the large memory model (-mlarge) is supported.

If a program built for one of these MSP430X devices is too large to fit exclusively in the lower memory region using the small memory model, rebuilding the program for the large memory model (-mlarge) with -mcode-region=either and possibly -mdata-region=either can help it to fit.

There is a code size and performance penalty when using -mdata-region=either. MSP430X instructions must be generated to address data, even in cases where an MSP430 instruction would suffice, since the compiler must assume that data might be placed in the upper memory region. Therefore, -mdata-region=either should be used only if it is necessary—that is, if the program would not otherwise fit on the device.

Note that the -mlarge option alone forces the compiler to generate CALLA and RETA instructions for all subroutine calls and returns. While there is no code size penalty for using these instructions instead of CALL and RET, there is some performance overhead. There is no additional penalty to using -mcode-region=either if -mlarge is in use.

See Table 4-2 for details on how the "either" options shuffle code and data sections between upper and lower memory. For best results, use these options with the -ffunction-sections and -fdata-sections options, so that the sections available to be shuffled are smaller.