The use of the -mmcu switch is of course NOT mandatory. It is simply a convenient way to use the pre-existing linker scripts provided with the MSPGCC4 toolchain. However, if the peripheral address space is larger than the standard 512B of the original MSP430 (see the Advanced System Configuration section), a customized linker script MUST be provided.
To create a custom linker script, the simplest way is to start from an existing one:
• The MSPGCC(4) toolchain provides a wide range of examples for all supported MSP430 models (see “msp430/lib/ldscripts/” sub-directory in the MSPGCC(4) installation directory).
• The openMSP430 project also provide a simple linker script example:
ldscript_example.x
From there, the script can be modified to match YOUR openMSP430 configuration:
• In the text (rx) section definition, update the ORIGIN and LENGTH fields to match the PROGRAM MEMORY configuration.
• In the data (rwx) section definition, update the ORIGIN field to match the PERIPHERAL SPACE configuration and the LENGTH field to match the DATA MEMORY configuration.
ldscript_example.x
1 /* Default linker script, for normal executables */ 2 OUTPUT_FORMAT("elf32-msp430") 3 OUTPUT_ARCH("msp430") 4 MEMORY 5 { 6 data (rwx) : ORIGIN = 0x0200, LENGTH = 0x0080 7 text (rx) : ORIGIN = 0xf800, LENGTH = 0x0800-0x20 8 vectors (rw) : ORIGIN = 0xffe0, LENGTH = 0x20 9 } 10 REGION_ALIAS("REGION_TEXT", text); 11 REGION_ALIAS("REGION_DATA", data); 12 __WDTCTL = 0x0120; 13 __MPY = 0x0130; 14 __MPYS = 0x0132; 15 __MAC = 0x0134; 16 __MACS = 0x0136; 17 __OP2 = 0x0138; 18 __RESLO = 0x013A; 19 __RESHI = 0x013C; 20 __SUMEXT = 0x013E; 21 22 SECTIONS 23 { 24 /* Read-only sections, merged into text segment. */ 25 .hash : { *(.hash) } 26 .dynsym : { *(.dynsym) } 27 .dynstr : { *(.dynstr) } 28 .gnu.version : { *(.gnu.version) } 29 .gnu.version_d : { *(.gnu.version_d) } 30 .gnu.version_r : { *(.gnu.version_r) } 31 .rel.init : { *(.rel.init) } 32 .rela.init : { *(.rela.init) } 33 .rel.text : 34 { 35 *(.rel.text) 36 *(.rel.text.*) 37 *(.rel.gnu.linkonce.t*) 38 } 39 .rela.text : 40 { 41 *(.rela.text) 42 *(.rela.text.*) 43 *(.rela.gnu.linkonce.t*) 44 } 45 .rel.fini : { *(.rel.fini) } 46 .rela.fini : { *(.rela.fini) } 47 .rel.rodata : 48 { 49 *(.rel.rodata) 50 *(.rel.rodata.*) 51 *(.rel.gnu.linkonce.r*) 52 } 53 .rela.rodata : 54 { 55 *(.rela.rodata) 56 *(.rela.rodata.*) 57 *(.rela.gnu.linkonce.r*) 58 } 59 .rel.data : 60 { 61 *(.rel.data) 62 *(.rel.data.*) 63 *(.rel.gnu.linkonce.d*) 64 } 65 .rela.data : 66 { 67 *(.rela.data) 68 *(.rela.data.*) 69 *(.rela.gnu.linkonce.d*) 70 } 71 .rel.ctors : { *(.rel.ctors) } 72 .rela.ctors : { *(.rela.ctors) } 73 .rel.dtors : { *(.rel.dtors) } 74 .rela.dtors : { *(.rela.dtors) } 75 .rel.got : { *(.rel.got) } 76 .rela.got : { *(.rela.got) } 77 .rel.bss : { *(.rel.bss) } 78 .rela.bss : { *(.rela.bss) } 79 .rel.plt : { *(.rel.plt) } 80 .rela.plt : { *(.rela.plt) } 81 /* Internal text space. */ 82 .text : 83 { 84 . = ALIGN(2); 85 *(.init) 86 *(.init0) /* Start here after reset. */ 87 *(.init1) 88 *(.init2) /* Copy data loop */ 89 *(.init3) 90 *(.init4) /* Clear bss */ 91 *(.init5) 92 *(.init6) /* C++ constructors. */ 93 *(.init7) 94 *(.init8) 95 *(.init9) /* Call main(). */ 96 __ctors_start = . ; 97 *(.ctors) 98 __ctors_end = . ; 99 __dtors_start = . ; 100 *(.dtors) 101 __dtors_end = . ; 102 . = ALIGN(2); 103 *(.text) 104 . = ALIGN(2); 105 *(.text.*) 106 . = ALIGN(2); 107 *(.fini9) /* */ 108 *(.fini8) 109 *(.fini7) 110 *(.fini6) /* C++ destructors. */ 111 *(.fini5) 112 *(.fini4) 113 *(.fini3) 114 *(.fini2) 115 *(.fini1) 116 *(.fini0) /* Infinite loop after program termination. */ 117 *(.fini) 118 } > text 119 .rodata : 120 { 121 . = ALIGN(2); 122 *(.rodata .rodata.* .gnu.linkonce.r.*) 123 . = ALIGN(2); 124 } > text 125 _etext = .; /* Past last read-only (loadable) segment */ 126 .data : AT (ADDR (.text) + SIZEOF (.text) + SIZEOF (.rodata) ) 127 { 128 PROVIDE (__data_start = .) ; 129 . = ALIGN(2); 130 *(.data) 131 . = ALIGN(2); 132 *(.gnu.linkonce.d*) 133 . = ALIGN(2); 134 _edata = . ; 135 } > data 136 PROVIDE (__data_load_start = LOADADDR(.data) ); 137 PROVIDE (__data_size = SIZEOF(.data) ); 138 .bss SIZEOF(.data) + ADDR(.data) : 139 { 140 PROVIDE (__bss_start = .) ; 141 *(.bss) 142 *(COMMON) 143 PROVIDE (__bss_end = .) ; 144 _end = . ; 145 } > data 146 PROVIDE (__bss_size = SIZEOF(.bss) ); 147 .noinit SIZEOF(.bss) + ADDR(.bss) : 148 { 149 PROVIDE (__noinit_start = .) ; 150 *(.noinit) 151 *(COMMON) 152 PROVIDE (__noinit_end = .) ; 153 _end = . ; 154 } > data 155 .vectors : 156 { 157 PROVIDE (__vectors_start = .) ; 158 *(.vectors*) 159 _vectors_end = . ; 160 } > vectors 161 /* Stabs for profiling information*/ 162 .profiler 0 : { *(.profiler) } 163 /* Stabs debugging sections. */ 164 .stab 0 : { *(.stab) } 165 .stabstr 0 : { *(.stabstr) } 166 .stab.excl 0 : { *(.stab.excl) } 167 .stab.exclstr 0 : { *(.stab.exclstr) } 168 .stab.index 0 : { *(.stab.index) } 169 .stab.indexstr 0 : { *(.stab.indexstr) } 170 .comment 0 : { *(.comment) } 171 /* DWARF debug sections. 172 Symbols in the DWARF debugging sections are relative to the beginning 173 of the section so we begin them at 0. */ 174 /* DWARF 1 */ 175 .debug 0 : { *(.debug) } 176 .line 0 : { *(.line) } 177 /* GNU DWARF 1 extensions */ 178 .debug_srcinfo 0 : { *(.debug_srcinfo) } 179 .debug_sfnames 0 : { *(.debug_sfnames) } 180 /* DWARF 1.1 and DWARF 2 */ 181 .debug_aranges 0 : { *(.debug_aranges) } 182 .debug_pubnames 0 : { *(.debug_pubnames) } 183 /* DWARF 2 */ 184 .debug_info 0 : { *(.debug_info) *(.gnu.linkonce.wi.*) } 185 .debug_abbrev 0 : { *(.debug_abbrev) } 186 .debug_line 0 : { *(.debug_line) } 187 .debug_frame 0 : { *(.debug_frame) } 188 .debug_str 0 : { *(.debug_str) } 189 .debug_loc 0 : { *(.debug_loc) } 190 .debug_macinfo 0 : { *(.debug_macinfo) } 191 PROVIDE (__stack = ORIGIN(data) + LENGTH(data)); 192 PROVIDE (__data_start_rom = _etext) ; 193 PROVIDE (__data_end_rom = _etext + SIZEOF (.data)) ; 194 }