 C166 User's Guide | |
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C166 User's Guide
C166 Introduction Compiling Programs Language Extensions Preprocessor Advanced Programming Sections, Classes, and Groups
Special Sections Locating Sections Customization Files Startup Code STARTUP.A66 START167.A66 Basic I/O Memory Allocation TRAPS.C Optimizer Optimizer Options General Optimizations 80C166-Specific Optimizations Global Register Coloring DPP Registers Stacks System Stack User Stack Stack Sizes System Stack Size User Stack Size XBUS Memory and Peripherals On-chip XRAM XBUS Peripherals Interfacing C to Assembler Function Parameters Function Return Values Using the SRC Directive Register Usage Example Routines TINY Model SMALL Model COMPACT Model MEDIUM Model LARGE Model Data Storage Formats Bit Variables 1-byte Scalars 2-byte Scalars 4-byte Scalars float Scalars float Errors double Scalars double Errors near Pointers far Pointers huge Pointers xhuge Pointers Absolute Memory Access Absolute Access Macros Linker Location Controls Debugging Error Messages Library Reference Appendixfar Pointers
Pointers to far objects are stored using four bytes (32 bits). The bytes are stored little endian or low to high order. The first word contains the 14-bit memory offset (bits 14 and 15 are always 0). The second word contains the page number (or segment number for function pointers). The memory address is calculated as follows:
Variable Address = (Page * 0x4000L) + Offset
Function Address = (Segment * 0x10000L) + Offset
A far pointer is stored in memory at a word boundary as follows:
| Address+0 | Address+1 | Address+2 | Address+3 | |
|---|---|---|---|---|
| Contents | Offset (LSB) | Offset (MSB) | Page (LSB) or Segment (LSB) | Page (MSB) or Segment (MSB) |
A far pointer can access objects up to 16K in size in any memory area. Objects larger than 16K must be accessed using huge or xhuge pointers.
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