 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 AppendixSystem Stack
The system stack stores return addresses and registers used for local register variables. For interrupt functions, the system stack saves the PSW, CP, and status of the MUL/DIV unit. The size of the system stack area is defined and initialized in the startup code which is executed before the C main function is called. The startup code also sets the values for the STKOV (stack overflow) and STKUN (stack underflow) registers.
The default value of the system stack is 256 words which is typically enough for most complex applications. However, if the system stack overflows, a stack overflow trap (interrupt 4) is generated. This signals that the system stack is too small.
Note
- Programs may swap the system stack area to external memory in the event of a stack overflow or underflow. However, the interrupt reaction time becomes unpredictable when this feature is used. In addition, you may encounter problems saving and restoring the MDL/MDH registers. Therefore, we recommend that you do not incorporate stack swapping features in your applications.
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