Small Data Area PIC/PID Support

The basic requirement for position independent code and data in the small data area is, at runtime, maintaining the link time address relationships between the startup code ( .init ) and the .sdata and .sdata2 segments. For example, if the link time addresses are:

.init = 0x00002000
  

.sdata2 = 0x00003000
  

.sdata = 0x00004000
  

but .init somehow is executed at 0x00002500, then those link time addresses must all increment by 0x00000500 for their runtime addresses.

Any segment that does not maintain the address relationship at runtime is considered external and must be addressed with absolute addresses. Segments that do maintain their link time address relationship at runtime are considered internal and must be addressed with PC-relative and SDA-relative addressing.

• Internal and External Segments and References
  The linker determines at link time whether code and data segments are external or internal.
• PIC/PID Linker Command File Directives
  Linker command file directives override PIC/PID related linker default setting.
• Linker-defined Symbols
  The linker-generated start and end symbols that are automatically generated for loadable segments are internal if they are addresses into internal segments, and external if they are for external segments.
• Uses for SDA PIC/PID
  Scenarios where PIC/PID runtime can be used.
• Building an SDA PIC/PID Application
  Building an SDA PIC/PID application.
• Internal and External Addressing Modes
  An address mode is applied to a memory segment as a part of the ROM image or at the executing (or logical) address of the segment.