MSP430 Embedded Application Binary Interface Application Report Literature Number: SLAA534A June 2013–Revised June 2020 Contents 1 Introduction......................................................................................................................... 7 1.1 ABIs for the MSP430 .................................................................................................... 7 1.2 Scope ...................................................................................................................... 8 1.3 ABI Variants............................................................................................................... 9 1.4 Toolchains and Interoperability......................................................................................... 9 1.5 Libraries ................................................................................................................... 9 1.6 Types of Object Files................................................................................................... 10 1.7 Segments ................................................................................................................ 10 1.8 MSP430 Architecture Overview....................................................................................... 10 1.9 MSP430 Memory Models.............................................................................................. 10 1.10 Reference Documents ................................................................................................. 11 1.11 Code Fragment Notation............................................................................................... 11 2 Data Representation ........................................................................................................... 12 2.1 Basic Types ............................................................................................................. 12 2.2 Data in Registers ....................................................................................................... 13 2.3 Data in Memory ......................................................................................................... 13 2.4 Pointer Types ........................................................................................................... 13 2.5 Complex Types ......................................................................................................... 14 2.6 Structures and Unions ................................................................................................. 14 2.7 Arrays .................................................................................................................... 14 2.8 Bit Fields ................................................................................................................. 15 2.8.1 Volatile Bit Fields............................................................................................ 15 2.9 Enumeration Types..................................................................................................... 16 3 Calling Conventions ........................................................................................................... 17 3.1 Call and Return ......................................................................................................... 17 3.1.1 Call Instructions ............................................................................................. 17 3.1.2 Return Instruction ........................................................................................... 17 3.1.3 Pipeline Conventions ....................................................................................... 17 3.1.4 Weak Functions ............................................................................................. 17 3.2 Register Conventions .................................................................................................. 18 3.2.1 Argument Registers......................................................................................... 19 3.2.2 Callee-Saved Registers .................................................................................... 19 3.3 Argument Passing ...................................................................................................... 19 3.3.1 Register Singles............................................................................................. 19 3.3.2 Register Pairs ............................................................................................... 20 3.3.3 Split Pairs .................................................................................................... 21 3.3.4 Quads (Four-Register Arguments)........................................................................ 21 3.3.5 Special Convention for Compiler Helper Functions .................................................... 23 3.3.6 C++ Argument Passing .................................................................................... 23 3.3.7 Passing Structs and Unions ............................................................................... 24 3.3.8 Stack Layout of Arguments Not Passed in Registers .................................................. 24 3.3.9 Frame Pointer ............................................................................................... 24 3.4 Return Values ........................................................................................................... 25 2 Table of Contents SLAA534A–June 2013–Revised June 2020 Submit Documentation Feedback Copyright © 2013–2020, Texas Instruments Incorporated www.ti.com 3.5 Structures and Unions Passed and Returned by Reference ..................................................... 25 3.6 Conventions for Compiler Helper Functions ........................................................................ 26 3.7 Scratch Registers for Functions Already Seen ..................................................................... 26 3.8 _ _mspabi_func_epilog Helper Functions ........................................................................... 26 3.9 Interrupt Functions...................................................................................................... 26 4 Data Allocation and Addressing ........................................................................................... 27 4.1 Data Sections and Segments ......................................................................................... 27 4.2 Addressing Modes...................................................................................................... 28 4.3 Allocation and Addressing of Static Data ........................................................................... 28 4.3.1 Addressing Methods for Static Data...................................................................... 28 4.3.2 Placement Conventions for Static Data.................................................................. 29 4.3.3 Initialization of Static Data ................................................................................. 30 4.4 Automatic Variables .................................................................................................... 30 4.5 Frame Layout ........................................................................................................... 31 4.5.1 Stack Alignment ............................................................................................. 32 4.5.2 Register Save Order........................................................................................ 32 4.6 Heap-Allocated Objects................................................................................................ 32 5 Code Allocation and Addressing .......................................................................................... 33 5.1 Computing the Address of a Code Label............................................................................ 33 5.1.1 Absolute Addressing for Code ............................................................................ 33 5.1.2 Symbolic Addressing ....................................................................................... 33 5.1.3 Immediate Addressing...................................................................................... 34 5.2 Branching ................................................................................................................ 34 5.3 Calls ...................................................................................................................... 34 5.3.1 Direct Call .................................................................................................... 34 5.3.2 Far Call Trampoline......................................................................................... 34 5.3.3 Indirect Calls................................................................................................. 34 6 Helper Function API............................................................................................................ 35 6.1 Floating-Point Behavior ................................................................................................ 35 6.2 C Helper Function API ................................................................................................. 35 6.3 Special Register Conventions for Helper Functions ............................................................... 39 6.4 Floating-Point Helper Functions for C99............................................................................. 40 7 Standard C Library API ......................................................................................................